Transcriptome profiling reveals differentially expressed transcripts between the human adrenal zona fasciculata and zona reticularis

Human Gonads Do Not Contribute to the Circulating Pool of 11-Oxygenated Androgens

CONTEXT

Androstenedione (A4) and testosterone (T) are produced by both the adrenal glands and the gonads. The adrenal enzyme 11β-hydroxylase (CYP11B1) executes the final step in cortisol synthesis; CYP11B1 also uses A4 and T as substrates, generating 11-hydroxyandrostenedione and 11-hydroxytestosterone, respectively. It has been suggested that CYP11B1 is expressed in the gonads, yet the circulating levels of all 11-oxygenated androgens (11-oxyandrogens) are similar in males and females of reproductive ages, despite enormous differences in T.

OBJECTIVE

To assess the gonadal contribution to the circulating pool of 11-oxyandrogens.

METHODS

We used liquid chromatography-tandem mass spectrometry to measure 13 steroids, including traditional and 11-oxyandrogens in: (i) paired gonadal and peripheral vein blood samples obtained during gonadal venograms from 11 patients (7 women), median age 37 (range, 31-51 years); and (ii) 17 women, median age 57 (range, 41-81 years) before and after bilateral salpingo-oophorectomy (BSO). We also compared CYP11B1, 17α-hydroxylase/17,20-lyase (CYP17A1), and 3β-hydroxysteroid dehydrogenase type 2 (HSD3B2) mRNA expression in adrenal, ovarian, and testicular tissue.

RESULTS

A4, T, estradiol, estrone, progesterone, 17α- and 16α-hydroxyprogesterone were all higher in gonadal veins vs periphery (P < .05 for all), while four 11-oxyandrogens were similar between matched gonadal and peripheral vein samples. Equally, in women who underwent BSO, A4 (median [interquartile range]: 59.7 [47.7-67.6] ng/dL vs 32.7 [27.4-47.8] ng/dL, P < .001) and T (24.1 [16.4-32.3] vs 15.5 [13.7-19.0] ng/dL, P < .001) declined, while 11-oxyandrogens remained stable. Gonadal tissue displayed negligible CYP11B1 mRNA.

CONCLUSION

Despite producing substantial amounts of A4 and T, human gonads are not relevant sources of 11-oxyandrogens.

Effect of Treatment on Steroidome in Women with Multiple Sclerosis

Multiple sclerosis (MS) is a chronic inflammatory neurodegenerative disease of the central nervous system. The manifestation of MS is related to steroid changes during the menstrual cycle and pregnancy. As data focusing on the effect of anti-MS drug treatment on steroidome are scarce, we evaluated steroidomic changes (79 steroids) in 61 female MS patients of reproductive age 39 (29, 47) years (median with quartiles) after treatment with anti-MS drugs on the GC-MS/MS platform and immunoassays (cortisol and estradiol). The changes were assessed using steroid levels and steroid molar ratios (SMRs) that may reflect the activities of steroidogenic enzymes (SMRs). A repeated measures ANOVA, followed by multiple comparisons and OPLS models, were used for statistical analyses. The anti-MS treatment decreased steroid levels in the follicular phase. Anti-CD20 monoclonal antibodies (mAb), such as ofatumumab and ocrelizumab; inhibitors of the sphingosine-1-phosphate receptor (S1PRI); and IFNβ-1a decreased circulating 17-hydroxy-pregnanes and shifted the CYP17A1 functioning from the hydroxylase- toward the lyase step. Decreased conjugated/unconjugated steroid ratios were found after treatment with anti-MS drugs, especially for glatiramer acetate and anti-CD20 mAb. In the luteal phase, IFN-β1a treatment increased steroidogenesis; both IFN-β1a and ocrelizumab increased AKR1D1, and S1PRI increased SRD5A functioning. Anti-CD20 mAb reduced the functioning of enzymes catalyzing the synthesis of immunomodulatory 7α/β and 16α-hydroxy-androgens, which may affect the severity of MS. The above findings may be important concerning the alterations in bioactive steroids, such as cortisol; active androgens and estrogens; and neuroactive, neuroprotective, and immunomodulatory steroids in terms of optimization of anti-MS treatment.

Altered Steroidome in Women with Multiple Sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) mainly afflicting young women. Various steroids can influence the onset and development of the disease or, on the contrary, mitigate its course; however, a systematic review of steroidomic changes in MS patients is lacking. Based on the gas chromatography tandem mass spectrometry (GC-MS/MS) platform and, in the case of estradiol, also using immunoassay, this study performed a comprehensive steroidomic analysis in 25 female MS patients aged 39(32, 49) years compared to 15 female age-matched controls aged 38(31, 46) years. A significant trend towards higher ratios of conjugated steroids to their unconjugated counterparts was found in patients, which is of particular interest in terms of the balance between excitatory and inhibitory steroid modulators of ionotropic receptors. Patients showed altered metabolic pathway to cortisol with decreased conversion of pregnenolone to 17-hydroxypregnenolone and 17-hydroxypregnenolone to 17-hydroxyprogesterone and increased conversion of 17-hydroxypregnenolone to dehydroepiandrosterone (DHEA), resulting in lower levels of 17-hydroxyprogesterone, as well as indications of impaired conversion of 11-deoxy-steroids to 11β-hydroxy-steroids but reduced conversion of cortisol to cortisone. Due to over-activation of hypothalamic-pituitary-adrenal axis (HPAA), however, cortisol and cortisone levels were higher in patients with indications of depleted cortisol synthesizing enzymes. Patients showed lower conversion of DHEA to androstenedione, androstenedione to testosterone, androstenedione to estradiol in the major pathway, and testosterone to estradiol in the minor pathway for estradiol synthesis at increased conversion of androstenedione to testosterone. They also showed lower conversion of immunoprotective Δ5 androstanes to their more potent 7α/β-hydroxy metabolites and had lower circulating allopregnanolone and higher ratio 3β-hydroxy-steroids to their neuroprotective 3α-hydroxy-counterparts.

Increased adrenal steroidogenesis and suppressed corticosteroid responsiveness in critical COVID-19

BACKGROUND

The effect of coronavirus disease 2019 (COVID-19) on adrenal endocrine metabolism in critically ill patients remains unclear. This study aimed to investigate the alterations in adrenal steroidogenic activity, elucidate underlying mechanisms, provide in situ histopathological evidence, and examine the clinical implications.

METHODS

The comparative analyses of the adrenal cortices from 24 patients with fatal COVID-19 and 20 matched controls were performed, excluding patients previously treated with glucocorticoids. SARS-CoV-2 and its receptors were identified and pathological alterations were examined. Furthermore, histological examinations, immunohistochemical staining and ultrastructural analyses were performed to assess corticosteroid biosynthesis. The zona glomerulosa (ZG) and zona fasciculata (ZF) were then dissected for proteomic analyses. The biological processes that affected steroidogenesis were analyzed by integrating histological, proteomic, and clinical data. Finally, the immunoreactivity and responsive genes of mineralocorticoid and glucocorticoid receptors in essential tissues were quantitatively measured to evaluate corticosteroid responsiveness.

FINDINGS

The demographic characteristics of COVID-19 patients were comparable with those of controls. SARS-CoV-2-like particles were identified in the adrenocortical cells of three patients; however, these particles did not affect cellular morphology or steroid synthesis compared with SARS-CoV-2-negative specimens. Although the adrenals exhibited focal necrosis, vacuolization, microthrombi, and inflammation, widespread degeneration was not evident. Notably, corticosteroid biosynthesis was significantly enhanced in both the ZG and ZF of COVID-19 patients. The increase in the inflammatory response and cellular differentiation in the adrenal cortices of patients with critical COVID-19 was positively correlated with heightened steroidogenic activity. Additionally, the appearance of more dual-ZG/ZF identity cells in COVID-19 adrenals was in accordance with the increased steroidogenic function. However, activated mineralocorticoid and glucocorticoid receptors and their responsive genes in vital tissues were markedly reduced in patients with critical COVID-19.

INTERPRETATION

Critical COVID-19 was characterized by potentiated adrenal steroidogenesis, associated with increased inflammation, enhanced differentiation and elevated dual-ZG/ZF identity cells, alongside suppressed corticosteroid responsiveness. These alterations implied the reduced effectiveness of conventional corticosteroid therapy and underscored the need for evaluation of the adrenal axis and corticosteroid sensitivity.

Mitochondrial dysfunction results in enhanced adrenal androgen production in H295R cells

The role of mitochondria in steroidogenesis is well established. However, the specific effects of mitochondrial dysfunction on androgen synthesis are not fully understood. In this study, we investigate the effects of various mitochondrial and metabolic inhibitors in H295R adrenal cells and perform a comprehensive analysis of steroid and metabolite profiling. We report that mitochondrial complex I inhibition by rotenone shifts cells toward anaerobic metabolism with a concomitant hyperandrogenic phenotype characterized by rapid stimulation of dehydroepiandrosterone (DHEA, 2 h) and slower accumulation of androstenedione and testosterone (24 h). Screening of metabolic inhibitors confirmed DHEA stimulation, which included mitochondrial complex III and mitochondrial pyruvate carrier inhibition. Metabolomic studies revealed truncated tricarboxylic acid cycle with an inverse correlation between citric acid and DHEA production as a common metabolic marker of hyperandrogenic inhibitors. The current study sheds light on a direct interplay between energy metabolism and androgen biosynthesis that could be further explored to identify novel molecular targets for efficient treatment of androgen excess disorders.

Steroidomics in Men with Schizophrenia

Schizophrenia is associated with numerous abnormalities, including imbalances in all hormonal axes, among which steroids play a major role. Steroidomic studies therefore represent a promising tool for early diagnosis and appropriate treatment of schizophrenia. A total of 51 adult male schizophrenics aged 27 (22, 34) years (shown as median with quartiles) and 16 healthy controls (HCs) aged 28 (25, 32) years were enrolled into this study. Our results showed the effective differentiation of men with schizophrenia from controls based on steroidomic profiles. We also found an altered metabolic pathway from pregnenolone and its sulfate (PREG/S) to cortisol in schizophrenics with several metabolic bottlenecks such as lower PREG levels due to increased PREG sulfation and/or suppressed PREGS desulfation and attenuated conversion of 17-hydroxy-PREG to 17-hydroxy-progesterone, as well as the results suggestive of suppressed CYP11B1 activity. In contrast, steroid molar ratios suggested two counterregulatory steps involving increased conversion of PREG/S to 17-hydroxy-PREG/S and decreased conversion of cortisol to cortisone, which may maintain unchanged basal cortisol levels but may not ensure a sufficient cortisol response to stress. Our data also indicated a trend to higher 7α-, 7β-, and 16α-hydroxylation that may counteract the autoimmune complications and proinflammatory processes accompanying schizophrenia. Finally, a possible suppression of HSD17B3 activity was suggested, resulting in decreased circulating testosterone levels with increased androstenedione levels.

Single-nucleus and spatial transcriptome reveal adrenal homeostasis in normal and tumoural adrenal glands

The human adrenal gland is a complex endocrine tissue. Studies on adrenal renewal have been limited to animal models or human foetuses. Enhancing our understanding of adult human adrenal homeostasis is crucial for gaining insights into the pathogenesis of adrenal diseases, such as adrenocortical tumours. Here, we present a comprehensive cellular genomics analysis of the adult human normal adrenal gland, combining single-nuclei RNA sequencing and spatial transcriptome data to reconstruct adrenal gland homeostasis. As expected, we identified primary cells of the various zones of the adrenal cortex and medulla, but we also uncovered additional cell types. They constitute the adrenal microenvironment, including immune cells, mostly composed of a large population of M2 macrophages, and new cell populations, including different subpopulations of vascular-endothelial cells and cortical-neuroendocrine cells. Utilizing spatial transcriptome and pseudotime trajectory analysis, we support evidence of the centripetal dynamics of adrenocortical cell maintenance and the essential role played by Wnt/β-catenin, sonic hedgehog, and fibroblast growth factor pathways in the adult adrenocortical homeostasis. Furthermore, we compared single-nuclei transcriptional profiles obtained from six healthy adrenal glands and twelve adrenocortical adenomas. This analysis unveiled a notable heterogeneity in cell populations within the adenoma samples. In addition, we identified six distinct adenoma-specific clusters, each with varying distributions based on steroid profiles and tumour mutational status. Overall, our results provide novel insights into adrenal homeostasis and molecular mechanisms potentially underlying early adrenocortical tumorigenesis and/or autonomous steroid secretion. Our cell atlas represents a powerful resource to investigate other adrenal-related pathologies.

The Search for the Causes of Common Hyperandrogenism, 1965 to Circa 2015

From 1965 to 2015, immense strides were made into understanding the mechanisms underlying the common androgen excess disorders, premature adrenarche and polycystic ovary syndrome (PCOS). The author reviews the critical discoveries of this era from his perspective investigating these disorders, commencing with his early discoveries of the unique pattern of plasma androgens in premature adrenarche and the elevation of an index of the plasma free testosterone concentration in most hirsute women. The molecular genetic basis, though not the developmental biologic basis, for adrenarche is now known and 11-oxytestosterones shown to be major bioactive adrenal androgens. The evolution of the lines of research into the pathogenesis of PCOS is historically traced: research milestones are cited in the areas of neuroendocrinology, insulin resistance, hyperinsulinism, type 2 diabetes mellitus, folliculogenesis, androgen secretion, obesity, phenotyping, prenatal androgenization, epigenetics, and complex genetics. Large-scale genome-wide association studies led to the 2014 discovery of an unsuspected steroidogenic regulator DENND1A (differentially expressed in normal and neoplastic development). The splice variant DENND1A.V2 is constitutively overexpressed in PCOS theca cells in long-term culture and accounts for their PCOS-like phenotype. The genetics are complex, however: DENND1A intronic variant copy number is related to phenotype severity, and recent data indicate that rare variants in a DENND1A regulatory network and other genes are related to PCOS. Obesity exacerbates PCOS manifestations via insulin resistance and proinflammatory cytokine excess; excess adipose tissue also forms testosterone. Polycystic ovaries in 40 percent of apparently normal women lie on the PCOS functional spectrum. Much remains to be learned.

Update on Adrenarche-Still a Mystery

CONTEXT

Adrenarche marks the timepoint of human adrenal development when the cortex starts secreting androgens in increasing amounts, in healthy children at age 8-9 years, with premature adrenarche (PA) earlier. Because the molecular regulation and significance of adrenarche are unknown, this prepubertal event is characterized descriptively, and PA is a diagnosis by exclusion with unclear long-term consequences.

EVIDENCE ACQUISITION

We searched the literature of the past 5 years, including original articles, reviews, and meta-analyses from PubMed, ScienceDirect, Web of Science, Embase, and Scopus, using search terms adrenarche, pubarche, DHEAS, steroidogenesis, adrenal, and zona reticularis.

EVIDENCE SYNTHESIS

Numerous studies addressed different topics of adrenarche and PA. Although basic studies on human adrenal development, zonation, and zona reticularis function enhanced our knowledge, the exact mechanism leading to adrenarche remains unsolved. Many regulators seem involved. A promising marker of adrenarche (11-ketotestosterone) was found in the 11-oxy androgen pathway. By current definition, the prevalence of PA can be as high as 9% to 23% in girls and 2% to 10% in boys, but only a subset of these children might face related adverse health outcomes.

CONCLUSION

New criteria for defining adrenarche and PA are needed to identify children at risk for later disease and to spare children with a normal variation. Further research is therefore required to understand adrenarche. Prospective, long-term studies should characterize prenatal or early postnatal developmental pathways that modulate trajectories of birth size, early postnatal growth, childhood overweight/obesity, adrenarche and puberty onset, and lead to abnormal sexual maturation, fertility, and other adverse outcomes.

Steroids-producing nodules: a two-layered adrenocortical nodular structure as a precursor lesion of cortisol-producing adenoma

BACKGROUND

The human adrenal cortex consists of three functionally and structurally distinct layers; zona glomerulosa, zona fasciculata (zF), and zona reticularis (zR), and produces adrenal steroid hormones in a layer-specific manner; aldosterone, cortisol, and adrenal androgens, respectively. Cortisol-producing adenomas (CPAs) occur mostly as a result of somatic mutations associated with the protein kinase A pathway. However, how CPAs develop after adrenocortical cells acquire genetic mutations, remains poorly understood.

METHODS

We conducted integrated approaches combining the detailed histopathologic studies with genetic, RNA-sequencing, and spatially resolved transcriptome (SRT) analyses for the adrenal cortices adjacent to human adrenocortical tumours.

FINDINGS

Histopathological analysis revealed an adrenocortical nodular structure that exhibits the two-layered zF- and zR-like structure. The nodular structures harbour GNAS somatic mutations, known as a driver mutation of CPAs, and confer cell proliferative and autonomous steroidogenic capacities, which we termed steroids-producing nodules (SPNs). RNA-sequencing coupled with SRT analysis suggests that the expansion of the zF-like structure contributes to the formation of CPAs, whereas the zR-like structure is characterised by a macrophage-mediated immune response.

INTERPRETATION

We postulate that CPAs arise from a precursor lesion, SPNs, where two distinct cell populations might contribute differently to adrenocortical tumorigenesis. Our data also provide clues to the molecular mechanisms underlying the layered structures of human adrenocortical tissues.

FUNDING

KAKENHI, The Uehara Memorial Foundation, Daiwa Securities Health Foundation, Kaibara Morikazu Medical Science Promotion Foundation, Secom Science and Technology Foundation, ONO Medical Research Foundation, and Japan Foundation for Applied Enzymology.

Aging effects in adrenal cortex of male Mongolian gerbil: A model for endocrine studies

The adrenal gland produces steroid hormones that act in the homeostasis of organisms. During aging, alterations in the hormonal balance affect the adrenal glands, but these have not yet been fully described due to the lack of adequate animal models. The adrenal gland of the Mongolian gerbil has a morphology similar to the primate's adrenal gland, which makes it a possible animal model for endocrine studies. Therefore, the current study aimed to study the morphophysiology of the adrenal gland under the effect of aging. For this purpose, males Meriones unguiculatus, aged three, six, nine, twelve, and fifteen months were used. Morphometric, immunohistochemical, and hormonal analyses were performed. It was observed that during aging the adrenal gland presents hypertrophy of the fasciculata and reticularis zones. Lipofuscin accumulation was observed during aging, in addition to changes in proliferation, cell death, and cell receptors. The analyses also showed that the gerbil presents steroidogenic enzymes and the production of steroid hormones, such as DHEA, like that found in humans. The data provide the first comprehensive assessment of the morphophysiology of the Mongolian gerbil adrenal cortex during aging, indicating that this species is a possible experimental model for studies of the adrenal gland and aging.

An integrated single-cell analysis of human adrenal cortex development

The adrenal glands synthesize and release essential steroid hormones such as cortisol and aldosterone, but many aspects of human adrenal gland development are not well understood. Here, we combined single-cell and bulk RNA sequencing, spatial transcriptomics, IHC, and micro-focus computed tomography to investigate key aspects of adrenal development in the first 20 weeks of gestation. We demonstrate rapid adrenal growth and vascularization, with more cell division in the outer definitive zone (DZ). Steroidogenic pathways favored androgen synthesis in the central fetal zone, but DZ capacity to synthesize cortisol and aldosterone developed with time. Core transcriptional regulators were identified, with localized expression of HOPX (also known as Hop homeobox/homeobox-only protein) in the DZ. Potential ligand-receptor interactions between mesenchyme and adrenal cortex were seen (e.g., RSPO3/LGR4). Growth-promoting imprinted genes were enriched in the developing cortex (e.g., IGF2, PEG3). These findings reveal aspects of human adrenal development and have clinical implications for understanding primary adrenal insufficiency and related postnatal adrenal disorders, such as adrenal tumor development, steroid disorders, and neonatal stress.

Models of Congenital Adrenal Hyperplasia for Gene Therapies Testing

The adrenal glands are important endocrine organs that play a major role in the stress response. Some adrenal glands abnormalities are treated with hormone replacement therapy, which does not address physiological requirements. Modern technologies make it possible to develop gene therapy drugs that can completely cure diseases caused by mutations in specific genes. Congenital adrenal hyperplasia (CAH) is an example of such a potentially treatable monogenic disease. CAH is an autosomal recessive inherited disease with an overall incidence of 1:9500–1:20,000 newborns. To date, there are several promising drugs for CAH gene therapy. At the same time, it remains unclear how new approaches can be tested, as there are no models for this disease. The present review focuses on modern models for inherited adrenal gland insufficiency and their detailed characterization. In addition, the advantages and disadvantages of various pathological models are discussed, and ways of further development are suggested.

Transcriptome sequencing reveals two subtypes of cortisol-secreting adrenocortical tumours in dogs and identifies CYP26B1 as a potential new therapeutic target

Cushing's syndrome (CS) is a serious endocrine disorder that is relatively common in dogs, but rare in humans. In ~15%-20% of cases, CS is caused by a cortisol-secreting adrenocortical tumour (csACT). To identify differentially expressed genes that can improve prognostic predictions after surgery and represent novel treatment targets, we performed RNA sequencing on csACTs (n = 48) and normal adrenal cortices (NACs; n = 10) of dogs. A gene was declared differentially expressed when the adjusted p-value was <.05 and the log₂ fold change was >2 or < -2. Between NACs and csACTs, 98 genes were differentially expressed. Based on the principal component analysis (PCA) the csACTs were separated in two groups, of which Group 1 had significantly better survival after adrenalectomy (p = .002) than Group 2. Between csACT Group G1 and Group 2, 77 genes were differentially expressed. One of these, cytochrome P450 26B1 (CYP26B1), was significantly associated with survival in both our canine csACTs and in a publicly available data set of 33 human cortisol-secreting adrenocortical carcinomas. In the validation cohort, CYP26B1 was also expressed significantly higher (p = .012) in canine csACTs compared with NACs. In future studies it would be interesting to determine whether CYP26B1 inhibitors could inhibit csACT growth in both dogs and humans.

Ectopic localization of CYP11B1 and CYP11B2-expressing cells in the normal human adrenal gland

The sharp line of demarcation between zona glomerulosa (ZG) and zona fasciculata (ZF) has been recently challenged suggesting that this interface is no longer a compartment boundary. We have used immunohistochemical analyses to study the steroid 11β-hydroxylase (CYP11B1) and aldosterone synthase (CYP11B2) pattern of expression and investigate the remodeling of the adrenal cortex in relation to aging. We analyzed human adrenal glands prepared from 47 kidney donors. No aldosterone-producing micronodules (APMs) were detectable in the younger donors aged between 22-39 but the functional ZG depicted by positive CYP11B2 staining demonstrated a lack of continuity. In contrast, the development of APMs was found in samples from individuals aged 40-70. Importantly, the progressive replacement of CYP11B2-expressing cells in the histological ZG by CYP11B1-expressing cells highlights the remodeling capacity of the adrenal cortex. In 70% of our samples, immunofluorescence studies revealed the presence of isolated or clusters of CYP11B2 positive cells in the ZF and zona reticularis. Our data emphasize that mineralocorticoid- and glucocorticoid-producing cells are distributed throughout the cortex and the medulla making the determination of the functional status of a cell or group of cells a unique tool in deciphering the changes occurring in adrenal gland particularly during aging. They also suggest that, in humans, steroidogenic cell phenotype defined by function is a stable feature and thus, the functional zonation might be not solely maintained by cell lineage conversion/migration.

Inclusion of 11-Oxygenated Androgens in a Clinical Routine LC-MS/MS Setup for Steroid Hormone Profiling

11-Oxygenated androgens (11-OAs) are being discussed as potential biomarkers in diagnosis and therapy control of disorders with androgen excess such as congenital adrenal hyperplasia and polycystic ovary syndrome. However, quantification of 11-OAs by liquid chromatography-tandem mass spectrometry (LC-MS/MS) still relies on extensive sample preparation including liquid-liquid extraction, derivatization and partial long runtimes, which is unsuitable for high-throughput analysis under routine laboratory settings. For the first time, an established online-solid-phase extraction-LC-MS/MS (online-SPE-LC-MS/MS) method for the quantitation of seven serum steroids in daily routine use was extended and validated to include 11-ketoandrostenedione, 11-ketotestosterone, 11β-hydroxyandrostenedione and 11β-hydroxytestosterone. Combining a simple protein precipitation step with fast chromatographic separation and ammonium fluoride-modified ionization resulted in a high-throughput method (6.6 min run time) featuring lower limits of quantification well below endogenous ranges (63-320 pmol/L) with recoveries between 85% and 117% (CVs ≤ 15%). Furthermore, the ability of this method to distinguish between adrenal and gonadal androgens was shown by comparing 11-OAs in patients with hyperandrogenemia to healthy controls. Due to the single shot multiplex design of the method, potential clinically relevant ratios of 11-OAs and corresponding androgens were readily available. The fully validated method covering endogenous concentration levels is ready to investigate the diagnostic values of 11-OAs in prospective studies and clinical applications.

11-Oxygenated androgens are not secreted by the human ovary: in-vivo data from four different cases of hyperandrogenism

OBJECTIVE

Differentiation of an adrenal from an ovarian source of hyperandrogenemia can be challenging. Recent studies have highlighted the importance of 11-oxygenated C19 steroids to the androgen pool in humans. The aim of this study was to confirm the origin of 11-oxygenated androgens in females and to explore their potential use in the diagnostics of hyperandrogenic disorders.

METHODS

We measured testosterone and its precursors (dehydroepiandrosterone-sulfate and androstenedione) and 11-oxygenated androgens (11β-hydroxyandrostenedione (11-OHA4) and 11-ketotestosterone (11-KT)) in the periphery, adrenal and ovarian veins in four different cases of hyperandrogenism in females (polycystic ovary syndrome (PCOS), primary bilateral macronodular adrenal hyperplasia, Sertoli-Leydig cell tumor and ovarian steroid cell tumor).

RESULTS

Two patients demonstrate excessive testosterone secretion in neoplastic ovarian tumors which was not paralleled by a significant secretion of 11-oxygenated androgens as determined by adrenal and ovarian vein sampling. In androgen-secreting bilateral adrenal macronodular hyperplasia, steroid profiles were characterized by elevated 11-KT and 11-OHA4 concentrations in adrenal veins and the periphery. In the patient with PCOS, peripheral 11-KT concentrations were slightly elevated in comparison to the other patients, but the 11-KT and 11-OHA4 concentrations were comparable in ovarian veins and in the periphery.

CONCLUSION

This study confirms that 11-OHA4 and 11-KT are not biosynthesized by the ovary. We propose that the testosterone/11-KT ratio as well as 11-OHA4 could help identify predominant adrenal androgen excess and distinguish neoplastic and non-neoplastic ovarian androgen source.

SIGNIFICANCE STATEMENT

This study confirms that 11β-hydroxyandrostenedione (11-OHA4) and 11-ketotestosterone (11-KT) are not biosynthesized by the human ovary. We propose that the testosterone/11-KT ratio as well as 11-OHA4 could help to identify predominant adrenal androgen excess and distinguish neoplastic and non-neoplastic ovarian androgen source.

Characterization of Aldosterone-producing Cell Cluster (APCC) at Single-cell Resolution

CONTEXT

The adrenal cortex consists of zona glomerulosa (ZG), fasciculata (ZF), and reticularis. Aldosterone-producing cell clusters (APCCs) that strongly express aldosterone synthase (CYP11B2) are frequently found in adult adrenals and harbor somatic mutations that are also detected in aldosterone-producing adenomas (APAs). Primary aldosteronism is mainly caused by APAs or idiopathic hyperaldosteronism (IHA). We presume that APCCs are causing IHA and are precursors of APAs. However, the gene expression characteristics and especially the development of APCCs are not well understood.

OBJECTIVE

This study aimed to analyze the transcriptome of APCCs at single-cell resolution and infer the developmental trajectory.

METHODS

Single-cell RNA sequencing (scRNA-seq) of 2 adult adrenals was performed.

RESULTS

Immunohistochemical analyses confirmed the 2 adrenals had APCCs. scRNA-seq data of 2928 adrenal cells were obtained and 1765 adrenocortical cells were identified based on unsupervised clustering and the marker gene expression. The adrenocortical cells were divided into 6 clusters, of which 3 clusters (923 cells) were composed of APCC/ZG cells. By further subclustering, the APCC/ZG cells were divided into 3 clusters (clusters C1, C2, and C3), we finally identified APCC cluster (C3) and ZG cluster (C1). Cluster C2 seemed to be ZG-to-ZF transitional cells. RNA velocity analysis inferred the developmental direction from cluster ZG-cluster-C1 to APCC-cluster-C3. The scRNA-seq additionally revealed that many CYP11B2-positive cells were positive for CYP11B1 and/or CYP17A1, which were essential for cortisol but not for aldosterone production.

CONCLUSIONS

Our results revealed the gene expression characteristics of APCC at single-cell resolution and show that some ZG cells remodel to APCC.

Rare forms of genetic steroidogenic defects affecting the gonads and adrenals

Pathogenic variants have been found in all genes involved in the classic pathways of human adrenal and gonadal steroidogenesis. Depending on their function and severity, they cause characteristic disorders of corticosteroid and/or sex hormone deficiency, may result in atypical sex development at birth and/or puberty, and mostly lead to sexual dysfunction and infertility. Genetic disorders of steroidogenesis are all inherited in an autosomal recessive fashion. Loss of function mutations lead to typical phenotypes, while variants with partial activity may manifest with milder, non-classic, late-onset disorders that share similar phenotypes. Thus, these disorders of steroidogenesis are diagnosed by comprehensive phenotyping, steroid profiling and genetic testing using next generation sequencing techniques. Treatment comprises of steroid replacement therapies, but these are insufficient in many aspects. Therefore, studies are currently ongoing towards newer approaches such as lentiviral transmitted enzyme replacement therapy and reprogrammed stem cell-based gene therapy.

Normal and Premature Adrenarche

Adrenarche is the maturational increase in adrenal androgen production that normally begins in early childhood. It results from changes in the secretory response to adrenocorticotropin (ACTH) that are best indexed by dehydroepiandrosterone sulfate (DHEAS) rise. These changes are related to the development of the zona reticularis (ZR) and its unique gene/enzyme expression pattern of low 3ß-hydroxysteroid dehydrogenase type 2 with high cytochrome b5A, sulfotransferase 2A1, and 17ß-hydroxysteroid dehydrogenase type 5. Recently 11-ketotestosterone was identified as an important bioactive adrenarchal androgen. Birth weight, body growth, obesity, and prolactin are related to ZR development. Adrenarchal androgens normally contribute to the onset of sexual pubic hair (pubarche) and sebaceous and apocrine gland development. Premature adrenarche causes ≥90% of premature pubarche (PP). Its cause is unknown. Affected children have a significantly increased growth rate with proportionate bone age advancement that typically does not compromise growth potential. Serum DHEAS and testosterone levels increase to levels normal for early female puberty. It is associated with mildly increased risks for obesity, insulin resistance, and possibly mood disorder and polycystic ovary syndrome. Between 5% and 10% of PP is due to virilizing disorders, which are usually characterized by more rapid advancement of pubarche and compromise of adult height potential than premature adrenarche. Most cases are due to nonclassic congenital adrenal hyperplasia. Algorithms are presented for the differential diagnosis of PP. This review highlights recent advances in molecular genetic and developmental biologic understanding of ZR development and insights into adrenarche emanating from mass spectrometric steroid assays.

Morphologic and Molecular Characterization of Adrenals and Adrenal Rest Affected by Congenital Adrenal Hyperplasia

Introduction

Adrenocortical hyperplasia and adrenal rest tumor (ART) formation are common in congenital adrenal hyperplasia (CAH). Although driven by excessive corticotropin, much is unknown regarding the morphology and transformation of these tissues. Our study objective was to characterize CAH-affected adrenals and ART and compare with control adrenal and gonadal tissues.

Patients/Methods

CAH adrenals, ART and control tissues were analyzed by histology, immunohistochemistry, and transcriptome sequencing. We investigated protein expression of the ACTH receptor (MC2R), steroidogenic (CYP11B2, CYP11B1, CYB5A) and immune (CD20, CD3, CD68) biomarkers, and delta-like 1 homolog (DLK1), a membrane bound protein broadly expressed in fetal and many endocrine cells. RNA was isolated and gene expression was analyzed by RNA sequencing (RNA-seq) followed by principle component, and unsupervised clustering analyses.

Results

Based on immunohistochemistry, CAH adrenals and ART demonstrated increased zona reticularis (ZR)-like CYB5A expression, compared to CYP11B1, and CYP11B2, markers of zona fasciculata and zona glomerulosa respectively. CYP11B2 was mostly absent in CAH adrenals and absent in ART. DLK1 was present in CAH adrenal, ART, and also control adrenal and testis, but was absent in control ovary. Increased expression of adrenocortical marker MC2R, was observed in CAH adrenals compared to control adrenal. Unlike control tissues, significant nodular lymphocytic infiltration was observed in CAH adrenals and ART, with CD20 (B-cell), CD3 (T-cell) and CD68 (macrophage/monocyte) markers of inflammation. RNA-seq data revealed co-expression of adrenal MC2R, and testis-specific INSL3, HSD17B3 in testicular ART indicating the presence of both gonadal and adrenal features, and high expression of DLK1 in ART, CAH adrenals and control adrenal. Principal component analysis indicated that the ART transcriptome was more similar to CAH adrenals and least similar to control testis tissue.

Conclusions

CAH-affected adrenal glands and ART have similar expression profiles and morphology, demonstrating increased CYB5A with ZR characteristics and lymphocytic infiltration, suggesting a common origin that is similarly affected by the abnormal hormonal milieu. Immune system modulators may play a role in tumor formation of CAH.

Non-Canonical Effects of ACTH: Insights Into Adrenal Insufficiency

Introduction

Adrenocorticotropic hormone (ACTH) is produced from proopiomelanocortin, which is predominantly synthetized in the corticotroph and melanotroph cells of the anterior and intermediate lobes of the pituitary gland and the arcuate nucleus of the hypothalamus. Although ACTH clearly has an effect on adrenal homeostasis and maintenance of steroid hormone production, it also has extra-adrenal effects that require further elucidation.

Methods

We comprehensively reviewed English language articles, regardless of whether they reported the presence or absence of adrenal and extra-adrenal ACTH effects.

Results

In the present review, we provide an overview on the current knowledge on adrenal and extra-adrenal effects of ACTH. In the section on adrenal ACTH effects, we focused on corticosteroid rhythmicity and effects on steroidogenesis, mineralocorticoids and adrenal growth. In the section on extra-adrenal effects, we have analyzed the effects of ACTH on the osteoarticular and reproductive systems, adipocytes, immune system, brain and skin. Finally, we focused on adrenal insufficiency.

Conclusions

The role of ACTH in maintaining the function of the hypothalamic-pituitary-adrenal axis is well known. Conversely, if we broaden our vision and analyze its role as a potential treatment strategy in other conditions, it will be evident in the literature that researchers seem to have abandoned this aspect in studies conducted several years ago. We believe it is worth re-evaluating the role of ACTH considering its noncanonical effects on the adrenal gland itself and on extra-adrenal organs and tissues; however, this would not have been possible without the recent advances in the pertinent technologies.

Targeted RNA sequencing of adrenal zones using immunohistochemistry-guided capture of formalin-fixed paraffin-embedded tissue

Adequate access to fresh or frozen normal adrenal tissue has been a primary limitation to the enhanced characterization of the adrenal zones via RNA sequencing (RNAseq). Herein, we describe the application of targeted RNAseq to formalin-fixed paraffin-embedded (FFPE) normal adrenal gland specimens. Immunohistochemistry (IHC) was used to visualize and guide the capture of the adrenocortical zones and medulla. Following IHC-based tissue capture and isolation of RNA, high-throughput targeted RNAseq highlighted clear transcriptomic differences and identified differentially expressed genes among the adrenal zones. Our data demonstrate the ability to capture FFPE adrenal zone tissue for targeted transcriptomic analyses. Future comparison of normal adrenal zones will improve our understanding of transcriptomic patterns and help identify potential novel pathways controlling zone-specific steroid production.

Adrenal androgens, adrenarche, and zona reticularis: A human affair?

In humans, reticularis cells of the adrenal cortex fuel the production of androgen steroids, constituting the driver of numerous morphological changes during childhood. These steps are considered a precocious stage of sexual maturation and are grouped under the term "adrenarche". This review describes the molecular and enzymatic characteristics of the zona reticularis, along with the possible signals and mechanisms that control its emergence and the associated clinical features. We investigate the differences between species and discuss new studies such as genetic lineage tracing and transcriptomic analysis, highlighting the rodent inner cortex's cellular and molecular heterogeneity. The recent development and characterization of mouse models deficient for Prkar1a presenting with adrenocortical reticularis-like features prompt us to review our vision of the mouse adrenal gland maturation. We expect these new insights will help increase our understanding of the adrenarche process and the pathologies associated with its deregulation.

Adrenal cortex development and related disorders leading to adrenal insufficiency

The adult human adrenal cortex produces steroid hormones that are crucial for life, supporting immune response, glucose homeostasis, salt balance and sexual maturation. It consists of three histologically distinct and functionally specialized zones. The fetal adrenal forms from mesodermal material and produces predominantly adrenal C₁₉ steroids from its fetal zone, which involutes after birth. Transition to the adult cortex occurs immediately after birth for the formation of the zona glomerulosa and fasciculata for aldosterone and cortisol production and continues through infancy until the zona reticularis for adrenal androgen production is formed with adrenarche. The development of this indispensable organ is complex and not fully understood. This article gives an overview of recent knowledge gained of adrenal biology from two perspectives: one, from basic science studying adrenal development, zonation and homeostasis; and two, from adrenal disorders identified in persons manifesting with various isolated or syndromic forms of primary adrenal insufficiency.

The Age-Dependent Changes of the Human Adrenal Cortical Zones Are Not Congruent

BACKGROUND

While previous studies indicate that the zonae reticularis (ZR) and glomerulosa (ZG) diminish with aging, little is known about age-related transformations of the zona fasciculata (ZF).

OBJECTIVES

To investigate the morphological and functional changes of the adrenal cortex across adulthood, with emphasis on (i) the understudied ZF and (ii) sexual dimorphisms.

METHODS

We used immunohistochemistry to evaluate the expression of aldosterone synthase (CYP11B2), visinin-like protein 1 (VSNL1), 3β-hydroxysteroid dehydrogenase type II (HSD3B2), 11β-hydroxylase (CYP11B1), and cytochrome b5 type A (CYB5A) in adrenal glands from 60 adults (30 men), aged 18 to 86. Additionally, we employed mass spectrometry to quantify the morning serum concentrations of cortisol, 11-deoxycortisol (11dF), 17α-hydroxyprogesterone, 11-deoxycorticosterone, corticosterone, and androstenedione in 149 pairs of age- and body mass index-matched men and women, age 21 to 95 years.

RESULTS

The total cortical area was positively correlated with age (r = 0.34, P = 0.008). Both the total (VSNL1-positive) and functional ZG (CYP11B2-positive) areas declined with aging in men (r = -0.57 and -0.67, P < 0.01), but not in women. The CYB5A-positive area declined with age in both sexes (r = -0.76, P < 0.0001). In contrast, the estimated ZF area correlated positively with age in men (r = 0.59, P = 0.0006) and women (r = 0.49, P = 0.007), while CYP11B1-positive area remained unchanged across ages. Serum cortisol, corticosterone, and 11-deoxycorticosterone levels were stable across ages, while 11dF levels increased slightly with age (r = 0.16, P = 0.007).

CONCLUSION

Unlike the ZG and ZR, the ZF and the total adrenal cortex areas enlarge with aging. An abrupt decline of the ZG occurs with age in men only, possibly contributing to sexual dimorphism in cardiovascular risk.

Nonclassic Congenital Adrenal Hyperplasia: What Do Endocrinologists Need to Know?

Congenital adrenal hyperplasia encompasses a group of autosomal recessive defects in cortisol biosynthesis, and 21-hydroxylase deficiency accounts for 95% of such cases. Non-classic 21-hydroxylase deficiency is due to partial enzymatic defects, which present with normal cortisol synthesis, but excessive production of adrenal androgens, including 11-oxygenated androgens. Non-classic 21-hydroxylase deficiency is relatively common, and its phenotype resembles closely that of polycystic ovary syndrome. This review focuses primarily on non-classic 21-hydroxylase deficiency, its clinical features, diagnosis, and management.

11-Oxygenated androgens in health and disease

The adrenal gland is a source of sex steroid precursors, and its activity is particularly relevant during fetal development and adrenarche. Following puberty, the synthesis of androgens by the adrenal gland has been considered of little physiologic importance. Dehydroepiandrosterone (DHEA) and its sulfate, DHEAS, are the major adrenal androgen precursors, but they are biologically inactive. The second most abundant unconjugated androgen produced by the human adrenals is 11β-hydroxyandrostenedione (11OHA4). 11-Ketotestosterone, a downstream metabolite of 11OHA4 (which is mostly produced in peripheral tissues), and its 5α-reduced product, 11-ketodihydrotestosterone, are bioactive androgens, with potencies equivalent to those of testosterone and dihydrotestosterone. These adrenal-derived androgens all share an oxygen atom on carbon 11, so we have collectively termed them 11-oxyandrogens. Over the past decade, these androgens have emerged as major components of several disorders of androgen excess, such as congenital adrenal hyperplasia, premature adrenarche and polycystic ovary syndrome, as well as in androgen-dependent tumours, such as castration-resistant prostate cancer. Moreover, in contrast to the more extensively studied, traditional androgens, circulating concentrations of 11-oxyandrogens do not demonstrate an age-dependent decline. This Review focuses on the rapidly expanding knowledge regarding the implications of 11-oxyandrogens in human physiology and disease.

Cortisol levels after cold exposure are independent of adrenocorticotropic hormone stimulation

We previously showed that postmortem serum levels of adrenocorticotropic hormone (ACTH) were significantly higher in cases of hypothermia (cold exposure) than other causes of death. This study examined how the human hypothalamic-pituitary-adrenal axis, and specifically cortisol, responds to hypothermia. Human samples: Autopsies on 205 subjects (147 men and 58 women; age 15-98 years, median 60 years) were performed within 3 days of death. Cause of death was classified as either hypothermia (cold exposure, n = 14) or non-cold exposure (controls; n = 191). Cortisol levels were determined in blood samples obtained from the left and right cardiac chambers and common iliac veins using a chemiluminescent enzyme immunoassay. Adrenal gland tissues samples were stained for cortisol using a rabbit anti-human polyclonal antibody. Cell culture: AtT20, a mouse ACTH secretory cell line, and Y-1, a corticosterone secretory cell line derived from a mouse adrenal tumor, were analyzed in mono-and co-culture, and times courses of ACTH (in AtT20) and corticosterone (in Y-1) secretion were assessed after low temperature exposure mimicking hypothermia and compared with data for samples collected postmortem for other cases of death. However, no correlation between ACTH concentration and cortisol levels was observed in hypothermia cases. Immunohistologic analyses of samples from hypothermia cases showed that cortisol staining was localized primarily to the nucleus rather than the cytoplasm of cells in the zona fasciculata of the adrenal gland. During both mono-culture and co-culture, AtT20 cells secreted high levels of ACTH after 10-15 minutes of cold exposure, whereas corticosterone secretion by Y-1 cells increased slowly during the first 15-20 minutes of cold exposure. Similar to autopsy results, no correlation was detected between ACTH levels and corticosterone secretion, either in mono-culture or co-culture experiments. These results suggested that ACTH-independent cortisol secretion may function as a stress response during cold exposure.

Circulating 11-oxygenated androgens across species

The androgen precursors, dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEAS) are produced in high amounts by the adrenal cortex primarily in humans and a few other primates. The human adrenal also secretes 11-oxygenated androgens (11-oxyandrogens), including 11β-hydroxyandrostenedione (11OHA4), 11-ketoandrostenedione (11KA4), 11β-hydroxytestosterone (11OHT) and 11-ketotestosterone (11KT), of which 11OHT and 11KT are bioactive androgens. The 11-oxyandrogens, particularly 11KT, have been recognized as biologically important testicular androgens in teleost fishes for decades, but their physiological contribution in humans has only recently been established. Beyond fish and humans, however, the presence of 11-oxyandrogens in other species has not been investigated. This study provides a comprehensive analysis of a set of C₁₉ steroids, including the traditional androgens and 11-oxyandrogens, across 18 animal species. As previously shown, serum DHEA and DHEAS were much higher in primates than all other species. Circulating 11-oxyandrogens, especially 11KT, were observed in notable amounts in male, but not in female trout, consistent with gonadal origin in fish. The circulating concentrations of 11-oxyandrogens ranged from 0.1 to 10 nM in pigs, guinea pigs and in all the primates studied (rhesus macaque, baboon, chimpanzee and human) but not in rats or mice, and 11OHA4 was consistently the most abundant. In contrast to fish, serum 11KT concentrations were similar in male and female primates for each species, despite significantly higher circulating testosterone in males, suggesting that 11KT production in these species is not testis-dependent and primarily originates from adrenal-derived 11-oxyandrogen precursors.

Steroid biomarkers in human adrenal disease

Adrenal steroidogenesis is a robust process, involving a series of enzymatic reactions that facilitate conversion of cholesterol into biologically active steroid hormones under the stimulation of angiotensin II, adrenocorticotropic hormone and other regulators. The biosynthesis of mineralocorticoids, glucocorticoids, and adrenal-derived androgens occur in separate adrenocortical zones as a result of the segregated expression of steroidogenic enzymes and cofactors. This mini review provides the principles of adrenal steroidogenesis, including the classic and under-appreciated 11-oxygenated androgen pathways. Several adrenal diseases result from dysregulated adrenal steroid synthesis. Herein, we review growing evidence that adrenal diseases exhibit characteristic modifications from normal adrenal steroid pathways that provide opportunities for the discovery of biomarker steroids that would improve diagnosis and monitoring of adrenal disorders.

A tale of two steroids: The importance of the androgens DHEA and DHEAS for early neurodevelopment

DHEA and DHEAS are neuroactive neurosteroids that interact with several major receptor systems in the brain, including sigma (σ), glutamate, and GABA-A receptors. It has been recognized as early as 1952, that the loss of DHEA/DHEAS in adult life is associated with neuropsychiatric disorders (eg schizophrenia, depression). However, the mechanistic role for DHEA/DHEAS in any of these domains remains speculative, not the least because the presence of these androgens in the adrenal gland and brain is largely confined to humans and only some non-human primates. DHEA and DHEAS are dynamically regulated from before birth and before the onset of puberty, and therefore an understanding of the synthesis, regulation, and functions of this important androgen pathway warrants attention. Here, we draw attention to the possible modulating influence of DHEA/DHEAS in early brain development from fetal life to the remarkable increase of these steroids in early childhood - the adrenarche. We propose that the pre-pubertal DHEA/DHEAS surge plays a key role in modulating early brain development, perhaps by prolonging brain plasticity during childhood to allow the pre-adolescent brain to adapt and re-wire in response to new, and ever-changing social challenges. Nonetheless, the aetiology of neurodevelopmental phenomena in relation to DHEA/DHEAS synthesis and action cannot be easily studied in humans due to the obvious ethical restrictions on mechanistic studies, the uncertainty of predicting the future mental characteristics of individuals, and the difficulty of conducting retrospective investigations based on pre-birth and/or neonatal complications. We discuss new opportunities for animal studies to resolve these important questions.

PKA signaling drives reticularis differentiation and sexually dimorphic adrenal cortex renewal

The adrenal cortex undergoes remodeling during fetal and postnatal life. How zona reticularis emerges in the postnatal gland to support adrenarche, a process whereby higher primates increase prepubertal androgen secretion, is unknown. Using cell-fate mapping and gene deletion studies in mice, we show that activation of PKA has no effect on the fetal cortex, while it accelerates regeneration of the adult cortex, triggers zona fasciculata differentiation that is subsequently converted into a functional reticularis-like zone, and drives hypersecretion syndromes. Remarkably, PKA effects are influenced by sex. Indeed, testicular androgens increase WNT signaling that antagonizes PKA, leading to slower adrenocortical cell turnover and delayed phenotype whereas gonadectomy sensitizes males to hypercorticism and reticularis-like formation. Thus, reticularis results from ultimate centripetal conversion of adult cortex under the combined effects of PKA and cell turnover that dictate organ size. We show that PKA-induced progenitor recruitment is sexually dimorphic and may provide a paradigm for overrepresentation of women in adrenal diseases.

NNT is a key regulator of adrenal redox homeostasis and steroidogenesis in male mice

Nicotinamide nucleotide transhydrogenase, NNT, is a ubiquitous protein of the inner mitochondrial membrane with a key role in mitochondrial redox balance. NNT produces high concentrations of NADPH for detoxification of reactive oxygen species by glutathione and thioredoxin pathways. In humans, NNT dysfunction leads to an adrenal-specific disorder, glucocorticoid deficiency. Certain substrains of C57BL/6 mice contain a spontaneously occurring inactivating Nnt mutation and display glucocorticoid deficiency along with glucose intolerance and reduced insulin secretion. To understand the underlying mechanism(s) behind the glucocorticoid deficiency, we performed comprehensive RNA-seq on adrenals from wild-type (C57BL/6N), mutant (C57BL/6J) and BAC transgenic mice overexpressing Nnt (C57BL/6J^BAC). The following results were obtained. Our data suggest that Nnt deletion (or overexpression) reduces adrenal steroidogenic output by decreasing the expression of crucial, mitochondrial antioxidant (Prdx3 and Txnrd2) and steroidogenic (Cyp11a1) enzymes. Pathway analysis also revealed upregulation of heat shock protein machinery and haemoglobins possibly in response to the oxidative stress initiated by NNT ablation. In conclusion, using transcriptomic profiling in adrenals from three mouse models, we showed that disturbances in adrenal redox homeostasis are mediated not only by under expression of NNT but also by its overexpression. Further, we demonstrated that both under expression or overexpression of NNT reduced corticosterone output implying a central role for it in the control of steroidogenesis. This is likely due to a reduction in the expression of a key steroidogenic enzyme, Cyp11a1, which mirrored the reduction in corticosterone output.

The Rise, Fall, and Resurrection of 11-Oxygenated Androgens in Human Physiology and Disease

The 11-oxyandrogens, particularly 11-ketotestosterone, have been recognized as a biologically important gonadal androgen in teleost (bony) fishes for decades, and their presence in human beings has been known but poorly understood. Today, we recognize that 11-oxyandrogens derive from the human adrenal glands and are major bioactive androgens, particularly in women and children. This article will review their biosynthesis and metabolism, abundance in normal and pathologic states, and potential as biomarkers of adrenal developmental changes and disease. Specifically, 11-oxyandrogens are the dominant active androgens in many patients with 21-hydroxylase deficiency.

Adrenocorticotropin Acutely Regulates Pregnenolone Sulfate Production by the Human Adrenal In Vivo and In Vitro

Background

Dehydroepiandrosterone sulfate (DHEAS) is the most abundant steroid in human circulation, and adrenocorticotropic hormone (ACTH) is considered the major regulator of its synthesis. Pregnenolone sulfate (PregS) and 5-androstenediol-3-sulfate (AdiolS) have recently emerged as biomarkers of adrenal disorders.

Objective

To define the relative human adrenal production of Δ5-steroid sulfates under basal and cosyntropin-stimulated conditions.

Methods

Liquid chromatography-tandem mass spectrometry was used to quantify three unconjugated and four sulfated Δ5-steroids in (1) paired adrenal vein (AV) and mixed venous serum samples (21 patients) and (2) cultured human adrenal cells both before and after cosyntropin stimulation, (3) microdissected zona fasciculata (ZF) and zona reticularis (ZR) from five human adrenal glands, and (4) a reconstituted in vitro human 17α-hydroxylase/17,20-lyase/(P450 17A1) system.

Results

Of the steroid sulfates, PregS had the greatest increase after cosyntropin stimulation in the AV (32-fold), whereas DHEAS responded modestly (1.8-fold). PregS attained concentrations comparable to those of DHEAS in the AV after cosyntropin stimulation (AV DHEAS/PregS, 24 and 1.3 before and after cosyntropin, respectively). In cultured adrenal cells, PregS demonstrated the sharpest response to cosyntropin, whereas DHEAS responded only modestly (21-fold vs 1.8-fold higher compared with unstimulated cells at 3 hours, respectively). Steroid analyses in isolated ZF and ZR showed similar amounts of PregS and 17α-hydroxypregnenolone in both zones, whereas DHEAS and AdiolS were higher in ZR (P < 0.05).

Conclusion

Our studies demonstrated that unlike DHEAS, PregS displayed a prominent acute response to cosyntropin. PregS could be used to interrogate the acute adrenal response to ACTH stimulation and as a biomarker in various adrenal disorders.

Adrenal C11-oxy C21 steroids contribute to the C11-oxy C19 steroid pool via the backdoor pathway in the biosynthesis and metabolism of 21-deoxycortisol and 21-deoxycortisone

21-Hydroxylase deficiency presents with increased levels of cytochrome P450 21-hydroxylase substrates, progesterone and 17α-hydroxyprogesterone, which have been implicated in the production of androgens via the backdoor pathway. This study shows the biosynthesis of C11-oxy C₂₁ steroids, 21-deoxycortisol and 21-deoxycortisone, and their metabolism by steroidogenic enzymes in the backdoor pathway yielding novel steroid metabolites: 5α-pregnan-11β,17α-diol-3,20-dione; 5α-pregnan-17α-ol-3,11,20-trione; 5α-pregnan-3α,11β,17α-triol-20-one and 5α-pregnan-3α,17α-diol-11,20-dione. The metabolism of 21-deoxycortisol was validated in LNCaP cells expressing the relevant steroidogenic enzymes showing for the first time that the steroid, produced at high levels in 21OHD, is metabolised via the C11-oxy derivatives of 5α-pregnan-17α-ol-3,20-dione and 5α-pregnan-3α,17α-diol-20-one to substrates for the lyase activity of CYP17A1, leading to the production of C11-oxy C₁₉ steroids. 21-Deoxycortisol thus contributes to the pool of potent androgens in 21OHD, with novel steroid metabolites also presenting possible biomarkers in disease identification.

11-Oxygenated Androgens Are Biomarkers of Adrenal Volume and Testicular Adrenal Rest Tumors in 21-Hydroxylase Deficiency

CONTEXT

Patients with 21-hydroxylase deficiency (21OHD) have long-term complications, resulting from poor disease control and/or glucocorticoid overtreatment. Lack of optimal biomarkers has made it challenging to tailor therapy and predict long-term outcomes.

OBJECTIVE

To identify biomarkers of disease control and long-term complications in 21OHD.

SETTING AND PARTICIPANTS

Cross-sectional study of 114 patients (70 males), ages 2 to 67 years (median, 15 years), seen in a tertiary referral center.

METHODS

We correlated a mass-spectrometry panel of 23 steroids, obtained before first morning medication, with bone age advancement (children), adrenal volume (adults), testicular adrenal rest tumors (TART), hirsutism, menstrual disorders, and pituitary hormones.

RESULTS

Total adrenal volume correlated positively with 18 steroids, most prominently 21-deoxycortisol and four 11-oxygenated-C19 (11oxC19) steroids: 11β-hydroxyandrostenedione (11OHA4), 11-ketoandrostenedione (11ketoA4), 11β-hydroxytestosterone (11OHT), and 11-ketotestosterone (11ketoT) (r ≈ 0.7, P < 0.0001). Nine steroids were significantly higher (P ≤ 0.01) in males with TART compared with those without TART, including 11OHA4 (6.8-fold), 11OHT (4.9-fold), 11ketoT (3.6-fold), 11ketoA4 (3.3-fold), and pregnenolone sulfate (PregS; 4.8-fold). PregS (28.5-fold) and 17-hydroxypregnenolone sulfate (19-fold) levels were higher (P < 0.01) in postpubertal females with menstrual disorders. In males, testosterone levels correlated positively with all 11oxC19 steroids in Tanner stages 1 and 2 (r ≈ 0.7; P < 0.001) but negatively in Tanner stage 5 (r = -0.3 and P < 0.05 for 11ketoA4 and 11ketoT). In females, testosterone level correlated positively with all four 11oxC19 steroids across all Tanner stages (r ≈ 0.8; P < 0.0001).

CONCLUSION

11oxC19 steroids and PregS might serve as clinically useful biomarkers of disease control and long-term complications in 21OHD.

Clinical significance of 11-oxygenated androgens

PURPOSE OF REVIEW

The adrenal gland is considered a source of weak androgens, such as dehydroepiandrosterone, dehydroepiandrosterone sulfate, and androstenedione. Emerging evidence proposes a set of 11-oxygenated 19-carbon (11oxC19) adrenal-derived steroids as clinically important androgens. Such steroids include 11β-hydroxyandrostenedione, 11-ketoandrostenedione, 11β-hydroxytestosterone, and 11-ketotestosterone. The present review will discuss the synthesis, androgenic activity, and clinical implications of the 11oxC19 steroids.

RECENT FINDINGS

The clinical relevance of the 11oxC19 steroids resides in two key characteristics: the synthesis of all 11oxC19 originates predominantly in the adrenal cortex, and 11-ketotestosterone and its 5α-reduced metabolite, 11-ketodihydrotestosterone are potent agonists of the human androgen receptor, similar to the classic androgens testosterone and dihydrotestosterone, respectively. Recent studies have demonstrated higher than normal circulating levels of 11oxC19 steroids in patients with 21-hydroxylase deficiency and in polycystic ovary syndrome. The 11oxC19 steroids are also thought to contribute to castration-resistant prostate cancer progression. In addition, the 11oxC19 steroids might have clinical implications in adrenarche and postmenopausal women.

SUMMARY

Future prospective studies are needed to establish the clinical utility of the 11oxC19 steroids for individualized patient care. Preliminary data suggest that these biomarkers hold promise to improve the evaluation and management of androgen excess disorders.

Structural insights into the function of steroidogenic cytochrome P450 17A1

Cytochrome P450 17A1 (CYP17A1) operates at the core of human steroidogenesis, directing precursors into mineralocorticoids, glucocorticoids, or sex steroids. Although the 17α-hydroxylase and 17,20-lyase activities of this dual function enzyme have been investigated extensively, until recently no CYP17A1 structures were available to inform our understanding. Structures of CYP17A1 with a range of steroidal inhibitors and substrates are now available. This review relates functional knowledge of this enzyme to structural features defining the selective differentiation between its various substrates. While both hydroxylase and lyase substrates have similar orientations with respect to the heme, subtle differences in hydrogen bonding between CYP17A1 and the C3 substituent at the opposite end of ligands appear to correlate with differential substrate utilization and product formation. Complementary structural information from solution NMR supports cytochrome b₅ allosteric modulation of the lyase reaction, implicating regions involved in ligand access to the otherwise buried active site.

The Human Adrenal Gland Proteome Defined by Transcriptomics and Antibody-Based Profiling

The adrenal gland is a composite endocrine organ with vital functions that include the synthesis and release of glucocorticoids and catecholamines. To define the molecular landscape that underlies the specific functions of the adrenal gland, we combined a genome-wide transcriptomics approach using messenger RNA sequencing of human tissues with immunohistochemistry-based protein profiling on tissue microarrays. Approximately two-thirds of all putative protein coding genes were expressed in the adrenal gland, and the analysis identified 253 genes with an elevated pattern of expression in the adrenal gland, with only 37 genes showing a markedly greater expression level (more than fivefold) in the adrenal gland compared with 31 other normal human tissue types analyzed. The analyses allowed for an assessment of the relative expression levels for well-known proteins involved in adrenal gland function but also identified previously poorly characterized proteins in the adrenal cortex, such as the FERM (4.1 protein, ezrin, radixin, moesin) domain containing 5 and the nephroblastoma overexpressed (NOV) protein homolog. We have provided a global analysis of the adrenal gland transcriptome and proteome, with a comprehensive list of genes with elevated expression in the adrenal gland and spatial information with examples of protein expression patterns for corresponding proteins. These genes and proteins constitute important starting points for an improved understanding of the normal function and pathophysiology of the adrenal glands.

Age-dependent Increases in Adrenal Cytochrome b5 and Serum 5-Androstenediol-3-sulfate

CONTEXT

Adrenal production of dehydroepiandrosterone sulfate (DHEA-S) increases throughout childhood owing to expansion of the zona reticularis (ZR). ZR features cells with a steroidogenic phenotype distinct from that of the adjacent zona fasciculata, with higher expression of cytochrome b₅ type A (CYB5A) and steroid sulfotransferase type 2A1 but decreased 3β-hydroxysteroid dehydrogenase type 2 (HSD3B2). In addition to DHEA-S, three adrenal Δ5-steroid sulfates could provide additional tools to define adrenal maturation.

OBJECTIVE

This study sought to simultaneously measure serum levels of four adrenal Δ5-steroid sulfates, pregnenolone sulfate (Preg-S), 17α-hydroxypregnenolone sulfate (17OHPreg-S), DHEA-S, and 5-androstenediol-3-sulfate (Adiol-S) as a function of age and relate their production to the age-dependent adrenal localization of CYB5A.

PARTICIPANTS AND METHODS

Δ5-steroid sulfates were quantified by liquid chromatography-tandem mass spectrometry in sera from 247 normal children (129 males,118 females) age 1.5-18 y and 42 adults (20 males, 22 females). Immunofluorescence localized HSD3B2 and CYB5A in normal adrenal glands from subjects age 2-35 y. Finally, HAC15 adrenocortical cells were transduced with lentiviral short hairpin RNA to suppress CYB5A expression.

RESULTS

Of the Δ5-steroid sulfates quantified, DHEA-S was most abundant. Adiol-S increased in parallel with DHEA-S. Steroid ratios (17OHPreg-S/DHEA-S) suggested increases in 17,20-lyase activity during childhood. Immunofluorescence analysis showed age-related increases in ZR CYB5A immunoreactivity. Furthermore, silencing CYB5A in HAC15 adrenocortical cells significantly reduced DHEA-S and Adiol-S production.

CONCLUSION

Adiol-S shows a similar age-related increase to that of DHEA-S. This likely results from the childhood expansion of CYB5A-expressing ZR, which enhances 17,20-lyase activity and the production of DHEA-S and Adiol-S.

Functional Zonation of the Adult Mammalian Adrenal Cortex

The standard model of adrenocortical zonation holds that the three main zones, glomerulosa, fasciculata, and reticularis each have a distinct function, producing mineralocorticoids (in fact just aldosterone), glucocorticoids, and androgens respectively. Moreover, each zone has its specific mechanism of regulation, though ACTH has actions throughout. Finally, the cells of the cortex originate from a stem cell population in the outer cortex or capsule, and migrate centripetally, changing their phenotype as they progress through the zones. Recent progress in understanding the development of the gland and the distribution of steroidogenic enzymes, trophic hormone receptors, and other factors suggests that this model needs refinement. Firstly, proliferation can take place throughout the gland, and although the stem cells are certainly located in the periphery, zonal replenishment can take place within zones. Perhaps more importantly, neither the distribution of enzymes nor receptors suggest that the individual zones are necessarily autonomous in their production of steroid. This is particularly true of the glomerulosa, which does not seem to have the full suite of enzymes required for aldosterone biosynthesis. Nor, in the rat anyway, does it express MC2R to account for the response of aldosterone to ACTH. It is known that in development, recruitment of stem cells is stimulated by signals from within the glomerulosa. Furthermore, throughout the cortex local regulatory factors, including cytokines, catecholamines and the tissue renin-angiotensin system, modify and refine the effects of the systemic trophic factors. In these and other ways it more and more appears that the functions of the gland should be viewed as an integrated whole, greater than the sum of its component parts.

60 YEARS OF POMC: Adrenal and extra-adrenal functions of ACTH

The pituitary adrenocorticotropic hormone (ACTH) plays a pivotal role in homeostasis and stress response and is thus the major component of the hypothalamo-pituitary-adrenal axis. After a brief summary of ACTH production from proopiomelanocortin (POMC) and on ACTH receptor properties, the first part of the review covers the role of ACTH in steroidogenesis and steroid secretion. We highlight the mechanisms explaining the differential acute vs chronic effects of ACTH on aldosterone and glucocorticoid secretion. The second part summarizes the effects of ACTH on adrenal growth, addressing its role as either a mitogenic or a differentiating factor. We then review the mechanisms involved in steroid secretion, from the classical Cyclic adenosine monophosphate second messenger system to various signaling cascades. We also consider how the interaction between the extracellular matrix and the cytoskeleton may trigger activation of signaling platforms potentially stimulating or repressing the steroidogenic potency of ACTH. Finally, we consider the extra-adrenal actions of ACTH, in particular its role in differentiation in a variety of cell types, in addition to its known lipolytic effects on adipocytes. In each section, we endeavor to correlate basic mechanisms of ACTH function with the pathological consequences of ACTH signaling deficiency and of overproduction of ACTH.

Inverse association of highly chlorinated dioxin congeners in maternal breast milk with dehydroepiandrosterone levels in three-year-old Vietnamese children

This study aims to evaluate the endocrine-disrupting effect of dioxin congeners on adrenal steroid hormones in mother-child pairs. In our previous study, we found that cortisol and cortisone levels were higher in the blood and the saliva of mothers living in a dioxin hotspot area than in mothers from a non-exposed region in Vietnam. In this follow-up study, we determined the salivary steroid hormone levels in 49 and 55 three-year-old children of these mothers in the hotspot and non-exposed region, respectively. Steroid hormones were determined by liquid chromatography-tandem mass spectrometry, and dioxin in the maternal breast milk was determined by gas chromatography-mass spectrometry. Dioxin levels in the breast milk of mothers from the hotspot (median total toxic equivalents polychlorinated dibenzodioxins/polychlorinated dibenzofurans; (TEQ PCDD/Fs) of 11pg/g lipid) were three to four times higher than those of mothers in the non-exposed region (median TEQ PCDD/Fs of 3.07pg/g lipid). Salivary dehydroepiandrosterone (DHEA) levels in children were found to be significantly lower in the hotspot than in the non-exposed region, while cortisol and cortisone levels were not different between the two regions. Highly chlorinated dioxin congeners, such as octacholorodibenzodioxin (OCDD), 1,2,3,4,6,7,8-heptacholorodibenzodioxin (HpCDD) and 1,2,3,4 (or 6), 7,8-hexachlorodibenzodioxin Hx(CDD), showed stronger inverse associations with the children's salivary DHEA than other lowly chlorinated dioxin congeners. Glucocorticoid levels in the mothers exhibited a significantly positive correlation with OCDD and HpCDD/F (polychlorinated dibenzofurans). In conclusion, highly chlorinated dioxin congeners are more strongly correlated with endocrine-disrupting effects on adrenal hormones, resulting in high cortisol levels in the mothers and low DHEA levels in their three-year-old children.

Disruption of steroidogenesis: Cell models for mechanistic investigations and as screening tools

In the modern world, humans are exposed during their whole life to a large number of synthetic chemicals. Some of these chemicals have the potential to disrupt endocrine functions and contribute to the development and/or progression of major diseases. Every year approximately 1000 novel chemicals, used in industrial production, agriculture, consumer products or as pharmaceuticals, are reaching the market, often with limited safety assessment regarding potential endocrine activities. Steroids are essential endocrine hormones, and the importance of the steroidogenesis pathway as a target for endocrine disrupting chemicals (EDCs) has been recognized by leading scientists and authorities. Cell lines have a prominent role in the initial stages of toxicity assessment, i.e. for mechanistic investigations and for the medium to high throughput analysis of chemicals for potential steroidogenesis disrupting activities. Nevertheless, the users have to be aware of the limitations of the existing cell models in order to apply them properly, and there is a great demand for improved cell-based testing systems and protocols. This review intends to provide an overview of the available cell lines for studying effects of chemicals on gonadal and adrenal steroidogenesis, their use and limitations, as well as the need for future improvements of cell-based testing systems and protocols.

Preliminary evidence of altered steroidogenesis in women with Alzheimer's disease: Have the patients "OLDER" adrenal zona reticularis?

Alzheimer's disease (AD) represents more than half of total dementias. Various factors including altered steroid biosynthesis may participate in its pathophysiology. We investigated how the circulating steroids (measured by GC-MS and RIA) may be altered in the presence of AD. Sixteen women with AD and 22 age- and BMI-corresponding controls aged over 65 years were enrolled in the study. The steroid levels (47 steroids and steroid polar conjugates) and their ratios in AD female patients indicated increased CYP11A1 activity, weakened activity of the CYP17A1C17,20 lyase metabolic step and attenuated sulfotransferase SULT2A1 activity at higher activity of the CYP17A1 17-hydroxylase step. The patients showed diminished HSD3B2 activity for C21 steroids, abated conversion of 17-hydroxyprogesterone to cortisol, and significantly elevated cortisol. The women with AD had also attenuated steroid 7α-hydroxylation forming immunoprotective Δ(5)-C19 steroids, attenuated aromatase activity forming estradiol that induces autoimmunity and a shift from the 3β-hydroxy-5α/β-reduced C19 steroids to their neuroinhibitory and antiinflammatory GABAergic 3α-hydroxy- counterparts and showed higher levels of the 3α-hydroxy-5α/β-reduced C21 steroids and pregnenolone sulfate (improves cognitive abilities but may be both protective and excitotoxic). Our preliminary data indicated functioning of alternative "backdoor" pathway in women with AD showing higher levels of both 5α/β-reduced C21 steroids but reduced levels of both 5α/β-reduced C21 steroids, which implied that the alternative "backdoor" pathway might include both 5α- and 5β-reduced steroids. Our study suggested relationships between AD status in women based on the age of subjects and levels of 10 steroids measured by GC-MS.

Regulation of human (adrenal) androgen biosynthesis-New insights from novel throughput technology studies

Androgens are precursors for sex steroids and are predominantly produced in the human gonads and the adrenal cortex. They are important for intrauterine and postnatal sexual development and human reproduction. Although human androgen biosynthesis has been extensively studied in the past, exact mechanisms underlying the regulation of androgen production in health and disease remain vague. Here, the knowledge on human androgen biosynthesis and regulation is reviewed with a special focus on human adrenal androgen production and the hyperandrogenic disorder of polycystic ovary syndrome (PCOS). Since human androgen regulation is highly specific without a good animal model, most studies are performed on patients harboring inborn errors of androgen biosynthesis, on human biomaterials and human (tumor) cell models. In the past, most studies used a candidate gene approach while newer studies use high throughput technologies to identify novel regulators of androgen biosynthesis. Using genome wide association studies on cohorts of patients, novel PCOS candidate genes have been recently described. Variant 2 of the DENND1A gene was found overexpressed in PCOS theca cells and confirmed to enhance androgen production. Transcriptome profiling of dissected adrenal zones established a role for BMP4 in androgen synthesis. Similarly, transcriptome analysis of human adrenal NCI-H295 cells identified novel regulators of androgen production. Kinase p38α (MAPK14) was found to phosphorylate CYP17 for enhanced 17,20 lyase activity and RARB and ANGPTL1 were detected in novel networks regulating androgens. The discovery of novel players for androgen biosynthesis is of clinical significance as it provides targets for diagnostic and therapeutic use.

The Regulation of Steroid Action by Sulfation and Desulfation

Steroid sulfation and desulfation are fundamental pathways vital for a functional vertebrate endocrine system. After biosynthesis, hydrophobic steroids are sulfated to expedite circulatory transit. Target cells express transmembrane organic anion-transporting polypeptides that facilitate cellular uptake of sulfated steroids. Once intracellular, sulfatases hydrolyze these steroid sulfate esters to their unconjugated, and usually active, forms. Because most steroids can be sulfated, including cholesterol, pregnenolone, dehydroepiandrosterone, and estrone, understanding the function, tissue distribution, and regulation of sulfation and desulfation processes provides significant insights into normal endocrine function. Not surprisingly, dysregulation of these pathways is associated with numerous pathologies, including steroid-dependent cancers, polycystic ovary syndrome, and X-linked ichthyosis. Here we provide a comprehensive examination of our current knowledge of endocrine-related sulfation and desulfation pathways. We describe the interplay between sulfatases and sulfotransferases, showing how their expression and regulation influences steroid action. Furthermore, we address the role that organic anion-transporting polypeptides play in regulating intracellular steroid concentrations and how their expression patterns influence many pathologies, especially cancer. Finally, the recent advances in pharmacologically targeting steroidogenic pathways will be examined.

Regulation of human 3-beta-hydroxysteroid dehydrogenase type-2 (3βHSD2) by molecular chaperones and the mitochondrial environment affects steroidogenesis

Human 3-β-hydroxysteroid dehydrogenase/isomerase types 1 and 2 (3βHSD1 and 3βHSD2, respectively) are expressed in a tissue-specific pattern by different genes. Site-directed mutagenesis studies have confirmed the function of the catalytic amino acids (Tyr154, Lys 158, Ser124 in both isoenzymes), substrate/inhibitor isoform-specific residues (His156 and Arg195 in 3βHSD1) and cofactor binding residues (Asp36 provides NAD(+) specificity in both isoenzymes). However, detailed analysis of isoform-specific organelle localization and characterization is difficult due to the 93% amino acid identity between the two isoforms. With recent advances in the knowledge of mitochondrial architecture and localization of the various translocases, our laboratory has studied the mechanisms regulating mitochondrial 3βHSD2 localization. The mitochondrial N-terminal leader sequence of 3βHSD2 directs its entry into the mitochondria where it is localized to the intermembrane space (IMS). Unlike other mitochondrial proteins, the N-terminal signal sequence of 3βHSD2 is not cleaved upon mitochondrial import. 3βHSD2 interacts with the mitochondrial translocase, Tim50, to regulate progesterone and androstenedione formation. Our studies suggest that its activity at the IMS is facilitated in a partially unfolded "molten globule" conformation by the proton pump between the matrix and IMS. The unfolded protein is refolded by the mitochondrial chaperones. The protons at the IMS are absorbed by the lipid vesicles, to maintain the proton pump and recycle 3βHSD2. As a result, one molecule of 3βHSD2 may participate in multiple catalytic reactions. In summary, the steroidogenic cell recycles 3βHSD2 to catalyze the reactions needed to produce androstenedione, progesterone and 17α-hydroxyprogesterone on demand in coordination with the mitochondrial translocase, Tim50. This article is part of a Special Issue entitled 'Steroid/Sterol signaling'.