Genetic diseases of steroid metabolism

In silico characterization of the novel SDR42E1 as a potential vitamin D modulator

The short-chain dehydrogenase/reductase (SDR) superfamily encompasses enzymes that play essential roles in the metabolism of steroid hormones and lipids. Despite an enigmatic function, recent genetic studies have linked the novel SDR 42 extended-1 (SDR42E1) gene to 25-hydroxyvitamin D levels. This study investigated the potential SDR42E1 functions and interactions with vitamin D using bioinformatics and molecular docking studies. Phylogenetic analysis unveiled that the nucleotide sequences of human SDR42E1 exhibit high evolutionary conservation across nematodes and fruit flies. Molecular docking analysis identified strong binding affinities between SDR42E1 and its orthologs with vitamin D3 and essential precursors, 8-dehydrocholesterol, followed by 7-dehydrocholesterol and 25-hydroxyvitamin D. The hydrophobic interactions observed between the protein residues and vitamin D compounds supported the predicted transmembrane localization of SDR42E1. Our investigation provides valuable insights into the potential role of SDR42E1 in skin vitamin D biosynthesis throughout species. This provides the foundation for future research and development of targeted therapies for vitamin D deficiency and related health conditions.

Medicine designed to combat diseases of affluence affects the early development of fish. How do plastic microparticles contribute?

The incidence of diseases of affluence, such as diabetes mellitus, cardiovascular diseases, high blood pressure, and high cholesterol has been reported to rise. Consequently, the concentrations of residues of drugs designed to treat these diseases have been rising in water bodies. Moreover, the toxicity of these pharmaceuticals towards fish and other non-target organisms can be even enhanced by microplastic particles that are reportedly present in surface water. Therefore, the aim of this study was to describe the effects of three highly prescribed drugs, in particular metoprolol, enalapril, and metformin on fish early-life stages. Also, it was hypothesized that polystyrene microparticles will increase the toxicity of metoprolol to fish early-life stages. Embryonal acute toxicity tests on Danio rerio and Cyprinus carpio were carried out in order to describe the possible toxic effects of metoprolol, enalapril, and metformin. Also, the acute toxicity of polystyrene microparticles and the combination of metoprolol with polystyrene microparticles were tested on D. rerio embryos. Additionally, a 31-day long embryo-larval subchronic toxicity test was carried out with C. carpio in order to describe the long-term effects of low concentrations of metoprolol. The results of the study show that both metoprolol and enalapril have the potential to disrupt the early development of the heart in the embryonal stages of fish. Also, enalapril and metformin together with polystyrene microparticles seem to possibly disrupt the reproduction cycle and act as endocrine disruptors. Both pure polystyrene microparticles and the combination of them with metoprolol affect inflammatory processes in organisms. Additionally, metformin alters several metabolism pathways in fish early-life stages. The results of the study bring new evidence that even low, environmentally-relevant concentrations of pharmaceuticals have the potential to disrupt the early development of fish, particularly on a molecular level.

Classic and current concepts in adrenal steroidogenesis: a reappraisal

Adrenal steroid biosynthesis and its related pathology are constant evolving disciplines. In this paper, we review classic and current concepts of adrenal steroidogenesis, plus control mechanisms of steroid pathways, distribution of unique enzymes and cofactors, and major steroid families. We highlight the presence of a "mineralocorticoid (MC) pathway of zona fasciculata (ZF)", where most circulating corticosterone and deoxycorticosterone (DOC) originate together with 18OHDOC, under ACTH control, a claim based on functional studies in normal subjects and in patients with 11β-, and 17α-hydroxylase deficiencies. We emphasize key differences between CYP11B1 (11β-hydroxylase) and CYP11B2 (aldosterone synthase) and the onset of a hybrid enzyme - CYP11B1/CYP11B2 -, responsible for aldosterone formation in ZF under ACTH control, in "type I familial hyperaldosteronism" (dexamethasone suppressible). In "apparent MC excess syndrome", peripheral conversion of cortisol to cortisone is impaired by lack of 11β-hydroxysteroid dehydrogenase type 2, permitting free cortisol access to MC receptors resulting in severe hypertension. We discuss two novel conditions involving the synthesis of adrenal androgens: the "backdoor pathway", through which dihydrotestosterone is formed directly from androsterone, being relevant for the fetoplacental setting and sexual differentiation of male fetuses, and the rediscovery of C19 11-oxygenated steroids (11-hydroxyandrostenedione and 11-ketotestosterone), active androgens and important markers of virilization in 21-hydroxylase deficiency and polycystic ovaries syndrome. Finally, we underline two enzyme cofactor deficiencies: cytochrome P450 oxidoreductase which partially affects 21- and 17α-hydroxylation, producing a combined clinical/hormonal picture and causing typical skeletal malformations (Antley-Bixler syndrome), and PAPSS2, coupled to SULT2A1, that promotes sulfation of DHEA to DHEAS, preventing active androgens to accumulate. Its deficiency results in reduced DHEAS and elevated DHEA and androgens with virilization. Future and necessary studies will shed light on remaining issues and questions on adrenal steroidogenesis.

Glucocorticoid-induced osteoporosis in children with 21-hydroxylase deficiency

21-Hydroxylase deficiency (21-OHD) is the most common cause of congenital adrenal hyperplasia (CAH), resulting from deletions or mutations of the P450 21-hydroxylase gene (CYP21A2). Children with 21-OHD need chronic glucocorticoid (cGC) therapy, both to replace congenital deficit in cortisol synthesis and to reduce androgen secretion by adrenal cortex. GC-induced osteoporosis (GIO) is the most common form of secondary osteoporosis that results in an early, transient increase in bone resorption accompanied by a decrease in bone formation, maintained for the duration of GC therapy. Despite the conflicting results in the literature about the bone status on GC-treated patients with 21-OHD, many reports consider these subjects to be at risk for osteoporosis and fractures. In bone cells, at the molecular level, GCs regulate various functions including osteoblastogenesis, osteoclastogenesis, and the apoptosis of osteoblasts and osteocytes. In this paper, we focus on the physiology and biosynthesis of endogenous steroid hormones as well as on the effects of GCs on bone cells, highlighting the pathogenetic mechanism of GIO in children with 21-OHD.

Serum lipid profile: its relationship with osteoporotic vertebrae fractures and bone mineral density in Turkish postmenopausal women

The effect of the serum lipid levels on vertebral fractures and bone mineral density is not clear. A total of 107 postmenopausal women aged 45-79 examined by lumbar spine, hip and radius bone mineral density (BMD) measurements, lateral dorsal and lumbar spine radiographies, routine blood tests and serum lipids [total cholesterol (TC), triglyceride (TG), HDL-C, LDL-C, VLDL-C]. Demographic and lifestyle characteristics were collected. Eighty-nine radiographies with good technical properties were scored by the Kleerekoper method. Patients with vertebrae fractures had lower levels of TC, TG, LDL-C than the patients without vertebrae fractures. Total cholesterol level was the most prominent factor affecting the vertebral fracture existence. An increase of 1 mg/dl total cholesterol decreases the risk of vertebrae fracture by 2.2%. The existence of osteoporosis due to T score was not influencing the lipid values. TC and LDL-C were weakly associated with BMD at the forearm UD region after the adjustment for the possible confounders. This study shows that the serum lipids have impact on vertebrae fracture existence rather than BMD alterations.

A connection between extracellular matrix and hormonal signals during the development of the human fetal adrenal gland

The human adrenal cortex, involved in adaptive responses to stress, body homeostasis and secondary sexual characters, emerges from a tightly regulated development of a zone-specific secretion pattern during fetal life. Its development during fetal life is critical for the well being of pregnancy, the initiation of delivery, and even for an adequate adaptation to extra-uterine life. As early as from the sixth week of pregnancy, the fetal adrenal gland is characterized by a highly proliferative zone at the periphery, a concentric migration accompanied by cell differentiation (cortisol secretion) and apoptosis in the central androgen-secreting fetal zone. After birth, a strong reorganization occurs in the adrenal gland so that it better fulfills the newborn's needs, with aldosterone production in the external zona glomerulosa, cortisol secretion in the zona fasciculata and androgens in the central zona reticularis. In addition to the major hormonal stimuli provided by angiotensin II and adrenocorticotropin, we have tested for some years the hypotheses that such plasticity may be under the control of the extracellular matrix. A growing number of data have been harvested during the last years, in particular about extracellular matrix expression and its putative role in the development of the human adrenal cortex. Laminin, collagen and fibronectin have been shown to play important roles not only in the plasticity of the adrenal cortex, but also in cell responsiveness to hormones, thus clarifying some of the unexplained observations that used to feed controversies.

Deficiência da 11beta-hidroxilase

A hiperplasia congênita da adrenal devido à deficiência da enzima 11beta-hidroxilase é resultado de uma falha na conversão do 11-desoxicortisol em cortisol na última etapa da via sintética dos glicocorticóides. Em geral, esta forma da doença é responsável por cerca de 5% dos casos. A manifestação clínica do excesso de andrógenos em pacientes do sexo feminino inclui graus de ambigüidade genital que podem variar entre uma clitoromegalia até a virilização completa da genitália. Devido ao acúmulo de mineralocorticóides, aproximadamente 50% dos pacientes desenvolvem hipertensão arterial. Mutações no gene CYP11B1, que codifica a enzima 11beta-hidroxilase, são responsáveis pela doença. As características bioquímicas e moleculares da enzima e suas implicações na apresentação clínica da deficiência da 11beta-hidroxilase são abordadas no presente trabalho de revisão.

Chemical synthesis of 7- and 8-dehydro derivatives of pregnane-3,17alpha,20-triols, potential steroid metabolites in Smith-Lemli-Opitz syndrome

Pregnane-3,17 alpha,20-triols bearing unsaturation at delta(7), delta(8), delta(5,7), or delta(5,8) have been tentatively identified as steroid metabolites in Smith-Lemli-Opitz syndrome (SLOS). Starting with 17 alpha-hydroxypregnenolone diacetate, we have synthesized 13 unsaturated C(21) triols by four different routes in one to four steps. These multifunctional steroids were prepared by a series of regio- and stereoselective transformations chosen to minimize facile olefin isomerization and 17-deoxygenation. The results include a study of stereoselectivity in the reduction of 17 alpha-hydroxy-20-ketosteroids, an alternative method for reducing diethyl azodicarboxylate adducts of delta(5,7) steroids, and an efficient oxidation-isomerization of a delta(5,7) steroid using cholesterol oxidase. The 13 triols and their synthetic precursors were fully characterized by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The NMR data, together with molecular modeling, indicated unanticipated conformational heterogeneity for two synthetic intermediates, 17 alpha-hydroxypregna-4,7-diene-3,20-dione and 17 alpha-hydroxy-5 beta-pregn-7-ene-3,20-dione. The unsaturated C(21) triols are useful as reference standards to study adrenal steroid production in SLOS and to develop methods for pre- and postnatal diagnosis of this congenital disorder.

Regulation of cytochrome P450 (CYP) genes by nuclear receptors

Members of the nuclear-receptor superfamily mediate crucial physiological functions by regulating the synthesis of their target genes. Nuclear receptors are usually activated by ligand binding. Cytochrome P450 (CYP) isoforms often catalyse both formation and degradation of these ligands. CYPs also metabolize many exogenous compounds, some of which may act as activators of nuclear receptors and disruptors of endocrine and cellular homoeostasis. This review summarizes recent findings that indicate that major classes of CYP genes are selectively regulated by certain ligand-activated nuclear receptors, thus creating tightly controlled networks.

Steroid 21-hydroxylase deficiency: mutational spectrum in Denmark, three novel mutations, and in vitro expression analysis

We have investigated 68 unrelated 21-hydroxylase deficient Danish patients, representing 136 alleles, and determined the mutational spectrum of the CYP21 gene. The most frequent mutations detected were deletion of CYP21 and the splice mutation in intron 2 (I2-splice). Segregation analysis showed evidence of a de novo mutation in each of two patients. Three novel mutations were detected: G64E in exon 1, Q262X in exon 7, and A362V in exon 8. G64E and A362V were introduced in the CYP21 cDNA by in vitro site-directed mutagenesis, and the two corresponding proteins were transiently expressed in COS-7 cells. The activity of 21-hydroxylase was determined using the two hormone substrates 17-hydroxyprogesterone and progesterone. The analysis showed no enzyme activity for any of the substrates, a result that correlates well with the severity of the patients' disease.

Congenital adrenal hyperplasia due to 21-hydroxylase deficiency

More than 90% of cases of congenital adrenal hyperplasia (CAH, the inherited inability to synthesize cortisol) are caused by 21-hydroxylase deficiency. Females with severe, classic 21-hydroxylase deficiency are exposed to excess androgens prenatally and are born with virilized external genitalia. Most patients cannot synthesize sufficient aldosterone to maintain sodium balance and may develop potentially fatal "salt wasting" crises if not treated. The disease is caused by mutations in the CYP21 gene encoding the steroid 21-hydroxylase enzyme. More than 90% of these mutations result from intergenic recombinations between CYP21 and the closely linked CYP21P pseudogene. Approximately 20% are gene deletions due to unequal crossing over during meiosis, whereas the remainder are gene conversions--transfers to CYP21 of deleterious mutations normally present in CYP21P. The degree to which each mutation compromises enzymatic activity is strongly correlated with the clinical severity of the disease in patients carrying it. Prenatal diagnosis by direct mutation detection permits prenatal treatment of affected females to minimize genital virilization. Neonatal screening by hormonal methods identifies affected children before salt wasting crises develop, reducing mortality from this condition. Glucocorticoid and mineralocorticoid replacement are the mainstays of treatment, but more rational dosing and additional therapies are being developed.

Regulation of cytochrome P450 (CYP) genes by nuclear receptors

Members of the nuclear-receptor superfamily mediate crucial physiological functions by regulating the synthesis of their target genes. Nuclear receptors are usually activated by ligand binding. Cytochrome P450 (CYP) isoforms often catalyse both formation and degradation of these ligands. CYPs also metabolize many exogenous compounds, some of which may act as activators of nuclear receptors and disruptors of endocrine and cellular homoeostasis. This review summarizes recent findings that indicate that major classes of CYP genes are selectively regulated by certain ligand-activated nuclear receptors, thus creating tightly controlled networks.

Development and differentiation of the interstitial and tubular compartments of fetal porcine testes

Male differentiation is initiated by fetal testicular androgen synthesis, catalyzed by the enzyme 17alpha-hydroxylase/17,20 lyase cytochrome P450 (P450c17). This study was an investigation of testicular development and differentiation in porcine fetuses recovered on Days 30-42 of gestation. The expression of P450c17 was localized in fetal gonads by in situ hybridization and immunocytochemistry and related to cellular proliferation through expression of the proliferating cell nuclear antigen (PCNA). Gonadal P450c17 expression was quantified by Western immunoblot analysis and related to testosterone secretion by cultured explants of fetal gonads. P450c17 transcripts were detected in the interstitium surrounding testicular cords preceding the appearance of the enzyme protein. The intensity of both P450c17 hybridization and staining was greater in Yorkshire fetal gonads, which also exhibited more advanced tubular development. PCNA staining was prominent within tubular primordia and was higher in testes from Yorkshire than from Meishan fetuses on all days examined. P450c17 expression paralleled testosterone secretion, which decreased by Day 42, and was generally less in cultures of Meishan than of Yorkshire fetal gonads. These data demonstrate that the expression of P450c17 in porcine fetal testes coincides with differentiation of central medullary cells and androgen secretion during gonadal development between Days 30 and 42 of gestation. This occurs as medullary cords organize and is associated with changes in cellular proliferation within the tubular compartment.

Aldosterone production despite absence or defectiveness of the CYP21 genes in two patients with salt-losing congenital adrenal hyperplasia caused by steroid 21-hydroxylase deficiency

Aldosterone and cortisol were found in plasma samples from two patients with salt-losing congenital adrenal hyperplasia caused by steroid 21-hydroxylase deficiency. One patient had a CYP21 gene deletion on one chromosome and a mutation causing erroneous mRNA splicing on the other. The other patient had a CYP21 gene deletion on one chromosome and a large scale conversion of CYP21 to CYP21P on the other. All CYP21P-like genes in these patients were defective, since they carried a deleterious 8 bp deletion in the third exon. After HPLC purification of the patients' plasma samples, cortisol was no longer detectable in the radioimmunoassay, but aldosterone levels were still within or slightly above the normal reference range. Aldosterone dropped to very low levels after steroid replacement therapy had taken effect. In at least one of these patients, the genetic defect rules out normal functioning of the adrenocortical steroid 21-hydroxylase, which implies involvement of an alternative enzyme system.

Study of a kindred with classic congenital adrenal hyperplasia: diagnostic challenge due to phenotypic variance

We sought to determine the concordance of the phenotype and genotype in a kindred with classic congenital adrenal hyperplasia due to 21-hydroxylase deficiency. The variation in phenotypic expression within this family underscores the difficulty of establishing the diagnosis in the absence of newborn screening, even with a heightened index of suspicion. Steroidogenic profiles were obtained for the three affected siblings. The available clinical history of the two affected aunts was retrieved. Genotyping was performed on several members of the kindred. Detailed sequencing of the entire CYP21 gene of two clinically dissimilar subjects in this family was undertaken to explore the possibility of other mutations or polymorphisms. PCR with ligase detection reaction analysis of CYP21 revealed that the affected family members III-2, III-3, III-4, II-3, and II-4, all were compound heterozygotes carrying the intron 2 point mutation known to interfere with splicing (nucleotide 656 A to G) and the exon 4 point mutation causing a nonconservative substitution of asparagine for isoleucine at codon 172 (I172N). Detailed sequencing of the gene was performed for the two most phenotypically dissimilar subjects. A single silent polymorphism was found in the third nucleotide for codon 248 in patient II-4, but not in patient III-4, and no additional mutations were found. Classic congenital adrenal hyperplasia remains a difficult diagnosis to make in the absence of newborn screening because of the variability of phenotypic expression. Likewise, the variable degree of genital ambiguity in affected females in this family serves to question universal advocacy of prenatal steroid treatment in pregnancies at risk for congenital adrenal hyperplasia. Extensive molecular exploration did not provide an explanation of the phenotypic heterogeneity and supports the possibility of influences other than the CYP21 gene for the observed divergence.

Adrenalectomy-induced neuronal degeneration

The binding of glucocorticoids to CNS receptors results in the modulation of many processes, ranging from neurotransmission to cell birth and death. It is of no surprise, therefore, that the removal of these steroids following adrenalectomy disrupts a variety of physiological functions throughout the brain. It is the aim of this review to briefly describe the findings of research examining some of these glucocorticoid-mediated CNS effects; however, as many of these areas have been reviewed extensively by others, this review will focus on the recently described phenomenon, adrenalectomy-induced hippocampal cell death.

CYP11B1 mutations causing non-classic adrenal hyperplasia due to 11 beta-hydroxylase deficiency

Steroid 11 beta-hydroxylase deficiency is the second most common cause of congenital adrenal hyperplasia, the inherited inability to synthesize cortisol. Severely affected patients carry mutations in the CYB11B1 gene that destroy enzymatic activity. Such patients have signs of androgen excess and usually have hypertension. Mild or non-classic 11 beta-hydroxylase deficiency has been reported previously but not studied genetically. In this study we report analysis of the CYP11B1 genes of three patients thought to suffer from non-classic 11 beta-hydroxylase deficiency. Mutations were detected in the CYP11B1 genes of two patients. One was a compound heterozygote for missense mutations N133H and T319M, whereas the other carried a nonsense mutation (Y423X) on one allele and a missense mutation (P42S) on the other. All three missense mutations affected enzymatic activity when expressed in vitro. No mutations were detected in the coding regions or intron-exon boundaries of the CYP11B1 genes of the other putative non-classic patient. In addition, we were unable to detect CYP11B1 mutations in two hirsute women with mildly elevated levels of 11 beta-hydroxylase precursors who had previously been identified in a screening study of patients in a reproductive endocrinology clinic. We conclude that nonclassic 11 beta-hydroxylase deficiency is a rare disorder. It is not a significant cause of hyperandrogenism in women and relatively stringent criteria should be used to prevent its misdiagnosis.

Gene conversions and unequal crossovers between CYP21 (steroid 21-hydroxylase gene) and CYP21P involve different mechanisms

Most cases of congenital adrenal hyperplasia, the inherited inability to synthesize cortisol, are caused by mutations in the steroid 21-hydroxylase gene (CYP21). Steroid 21-hydroxylase deficiency is unusual among genetic diseases in that approximately 95% of the mutant alleles have apparently been generated by recombination between a normally active gene (CYP21) and a linked pseudogene (CYP21P). Approximately 20% of mutant alleles carry DNA deletions of 30 kb that have presumably been generated by unequal meiotic crossing-over, whereas 75% carry one or more mutations in CYP21 that are normally found in the CYP21P pseudogene. These latter mutations are termed "gene conversions," although the mechanism by which they are generated is not well understood. To assess the frequency at which these different recombination events occur, we have used PCR to detect de novo deletions and gene conversions in matched sperm and peripheral blood leukocyte DNA samples from normal individuals. Deletions with breakpoints in a 100-bp region in intron 2 and exon 3 were detected in sperm DNA samples with frequencies of approximately 1 in 10(5)-10(6) genomes but were never detected in the matching leukocyte DNA. Gene conversions in the same region occur in approximately 1 in 10(3)-10(5) genomes in both sperm and leukocyte DNA. These data suggest that whereas deletions occur exclusively in meiosis, gene conversions occur during both meiosis and mitosis, or perhaps only during mitosis. Thus, gene conversions must occur by a mechanism distinct from unequal crossing-over.

Transcriptional regulation of the genes encoding the cytochrome P-450 steroid hydroxylases

Steroid hormone biosynthesis requires the concerted action of a related group of cytochrome P-450 steroid hydroxylases. In recent years considerable effort has been directed toward defining the molecular basis for the cell-selective expression of these genes and their transcriptional regulation by trophic hormones. The orphan nuclear receptor SF-1, acting through a conserved element found in the proximal promoter regions of all steroid hydroxylase genes, seems to be a major, but not exclusive, determinant of cell-selective gene expression. In contrast, the coordinate responses of the steroid hydroxylases to trophic hormones apparently involves an interplay of multiple proteins that collectively lead to a synchronous induction of gene expression. In some instances these interactions apparently involve transcription factors that also contribute to the cell-selective expression of these genes.