Hexose-6-phosphate dehydrogenase determines the reaction direction of 11beta-hydroxysteroid dehydrogenase type 1 as an oxoreductase

A BioID-based approach uncovers the interactome of hexose-6-phosphate dehydrogenase in breast cancer cells and identifies anterior gradient protein 2 as an interacting partner

BACKGROUND

Hexose-6-phosphate dehydrogenase (H6PD) catalyzes the first two steps of the pentose-phosphate-pathway (PPP) within the endoplasmic reticulum, generating NADPH. H6PD modulates essential physiological processes, including energy and redox metabolism. Its sole reported interacting partner is 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1), utilizing NADPH to reactivate glucocorticoids, linking energy status with hormonal response. Previous studies showed that loss of H6PD affects breast cancer cell properties, independent of 11β-HSD1. It remains unknown whether this is due to impaired concentrations of NADPH or PPP products downstream of H6PD. To gain insight into novel roles and pathways influenced by this enzyme, we aimed to assess the H6PD interactome.

RESULTS

We adapted the proximity-dependent Biotin Identification (BioID) method to identify novel H6PD interacting partners. First, we validated the method and confirmed the known interaction between H6PD and 11β-HSD1. Next, we constructed a triple-negative breast cancer MDA-MB-231 cell clone stably expressing a H6PD-biotin ligase fusion protein. Enriched biotinylated proteins were analyzed by mass-spectrometry and potential candidates assessed further by co-immunoprecipitation and functional assays. The resulting interactome revealed proteins of the calreticulin/calnexin cycle, unfolded-protein response (UPR) and chaperone activation pathways. Due to its known association with breast cancer, we examined the PDI Anterior gradient protein 2 (AGR2) as H6PD interacting partner. Gene set enrichment analysis revealed multiple overlapping pathways enriched in breast cancer tissues with relatively high H6PD and AGR2 expression. These included glycolysis, fatty acid metabolism, hypoxia, angiogenesis and epithelial to mesenchymal transition. Co-immunoprecipitation (Co-IP) from MCF7 cells confirmed a physical interaction between H6PD and AGR2. ARG2 knockdown in these cells increased H6PD protein levels but decreased activity. Coexpression with AGR2 in HEK-293 cells did not affect expression but enhanced H6PD activity.

CONCLUSION

BioID was successfully applied in the endoplasmic reticulum to identify AGR2 as H6PD interactor. This was confirmed using Co-IP from MCF7 cells endogenously expressing both proteins. The results indicate that AGR2 controls H6PD protein expression and enhances its activity. Whether higher H6PD activity due to increased AGR2 expression promotes a more aggressive cancer cell phenotype, for example by altering energy metabolism, Ca2+-related processes or UPR and chaperone activation pathways, warrants further investigations.

UV-filter benzophenones suppress human, pig, rat, and mouse 11β-hydroxysteroid dehydrogenase 1: Structure-activity relationship and in silico docking analysis

Benzophenone chemicals (BPs) have been developed to prevent the adverse effects of UV radiation and they are widely contaminated. 11β-Hydroxysteroid dehydrogenase 1 (11β-HSD1) catalyze the conversion of inactive glucocorticoid to active glucocorticoid, playing critical role in many physiological function. However, the direct effect of BPs on human, pig, rat, and mouse 11β-HSD1 remains unclear. In this study, we screened the inhibitory strength of 12 BPs on 4 species, and performed the structure-activity relationship (SAR) and in silico docking analysis. The inhibitory potency of BPs was: for human 11β-HSD1, BP6 (IC50 = 18.76 μM) > BP8 (40.84 μM) > BP (88.89 μM) > other BPs; for pig 11β-HSD1, BP8 (45.57 μM) > BP6 (59.44 μM) > BP2 (65.12 μM) > BP (135.56 μM) > other BPs; for rat 11β-HSD1, BP7 (67.17 μM) > BP (68.83 μM) > BP8 (133.04 μM) > other BPs; and for mouse 11β-HSD1, BP8 (41.41 μM) > BP (50.61 μM) > other BPs. These BP chemicals were mixed/competitive inhibitors of these 11β-HSD1 enzymes. The 2,2'-dihydroxy substitutions in two benzene rings play a key role in enhancing the effectiveness of inhibiting 11β-HSD1, possibly via increasing hydrogen bond interactions. Docking analysis shows that these BPs bind to NADPH/glucocorticoid binding sites and forms hydrogen bonds with catalytic residues Ser and/or Tyr. In conclusion, this study demonstrates that BP chemicals can inhibit 11β-HSD1 from 4 species, and there are subtle species-dependent difference in the inhibitory strength and structural variations of BPs.

C11-hydroxy and C11-oxo C19 and C21 Steroids: Pre-Receptor Regulation and Interaction with Androgen and Progesterone Steroid Receptors

C11-oxy C19 and C11-oxy C21 steroids have been identified as novel steroids but their function remains unclear. This study aimed to investigate the pre-receptor regulation of C11-oxy steroids by 11β-hydroxysteroid dehydrogenase (11βHSD) interconversion and potential agonist and antagonist activity associated with the androgen (AR) and progesterone receptors (PRA and PRB). Steroid conversions were investigated in transiently transfected HEK293 cells expressing 11βHSD1 and 11βHSD2, while CV1 cells were utilised for agonist and antagonist assays. The conversion of C11-hydroxy steroids to C11-oxo steroids by 11βHSD2 occurred more readily than the reverse reaction catalysed by 11βHSD1, while the interconversion of C11-oxy C19 steroids was more efficient than C11-oxy C21 steroids. Furthermore, 11-ketodihydrotestosterone (11KDHT), 11-ketotestosterone (11KT) and 11β-hydroxydihydrotestosterone (11OHDHT) were AR agonists, while only progestogens, 11β-hydroxyprogesterone (11βOHP4), 11β-hydroxydihydroprogesterone (11βOHDHP4), 11α-hydroxyprogesterone (11αOHP4), 11α-hydroxydihydroprogesterone (11αOHDHP4), 11-ketoprogesterone (11KP4), 5α-pregnan-17α-diol-3,11,20-trione (11KPdione) and 21-deoxycortisone (21dE) exhibited antagonist activity. C11-hydroxy C21 steroids, 11βOHP4, 11βOHDHP4 and 11αOHP4 exhibited PRA and PRB agonistic activity, while only C11-oxo steroids, 11KP4 and 11-ketoandrostanediol (11K3αdiol) demonstrated PRB agonism. While no steroids antagonised the PRA, 11OHA4, 11β-hydroxytestosterone (11OHT), 11KT and 11KDHT exhibited PRB antagonism. The regulatory role of 11βHSD isozymes impacting receptor activation is clear-C11-oxo androgens exhibit AR agonist activity; only C11-hydroxy progestogens exhibit PRA and PRB agonist activity. Regulation by the downstream metabolites of active C11-oxy steroids at the receptor level is apparent-C11-hydroxy and C11-oxo metabolites antagonize the AR and PRB, progestogens the former, androgens the latter. The findings highlight the intricate interplay between receptors and active as well as "inactive" C11-oxy steroids, suggesting novel regulatory tiers.

In vitro methods to assess 11β-hydroxysteroid dehydrogenase type 1 activity

11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) converts inactive 11-keto-glucocorticoids to their active 11β-hydroxylated forms. It also catalyzes the oxoreduction of other endogenous and exogenous substrates. The ubiquitously expressed 11β-HSD1 shows high levels in liver and other metabolically active tissues such as brain and adipose tissue. Pharmacological inhibition of 11β-HSD1 was found to ameliorate adverse metabolic effects of elevated glucocorticoids in rodents and humans, improve wound healing and delay skin aging, and enhance memory and cognition in rodent Alzheimer's disease models. Thus, there is an interest to develop 11β-HSD1 inhibitors for therapeutic purposes. This chapter describes in vitro methods to assess 11β-HSD1 enzyme activity for different purposes, be it in disease models, for the assessment of the kinetics of novel substrates or for the screening and characterization of inhibitors. 11β-HSD1 protein expression and preparations of the different biological samples are discussed first, followed by a description of a well-established and easily adaptable 11β-HSD1 enzyme activity assay. Finally, different readout methods are shortly described. This chapter should provide the reader with a toolbox of methods to assess 11β-HSD1 activity with instructions in the form of a decision tree for the choice and implementation of an appropriate enzyme activity assay.

Cardiac Hypertrophy and Related Dysfunctions in Cushing Syndrome Patients-Literature Review

The survival rate of adrenal Cushing syndrome patients has been greatly increased because of the availability of appropriate surgical and pharmacological treatments. Nevertheless, increased possibility of a heart attack induced by a cardiovascular event remains a major risk factor for the survival of affected patients. In experimental studies, hypercortisolemia has been found to cause cardiomyocyte hypertrophy via glucocorticoid receptor activation, including the possibility of cross talk among several hypertrophy signals related to cardiomyocytes and tissue-dependent regulation of 11β-hydroxysteroid dehydrogenase type 1. However, the factors are more complex in clinical cases, as both geometric and functional impairments leading to heart failure have been revealed, and their associations with a wide range of factors such as hypertension are crucial. In addition, knowledge regarding such alterations in autonomous cortisol secretion, which has a high risk of leading to heart attack as well as overt Cushing syndrome, is quite limited. When considering the effects of treatment, partial improvement of structural alterations is expected, while functional disorders are controversial. Therefore, whether the normalization of excess cortisol attenuates the risk related to cardiac hypertrophy has yet to be fully elucidated.

Potential Mechanisms by which Glucocorticoids Induce Breast Carcinogenesis through Nrf2 Inhibition

Breast cancer is the most common malignancy among women worldwide. Several studies indicate that, in addition to established risk factors for breast cancer, other factors such as cortisol release related to psychological stress and drug treatment with high levels of glucocorticoids may also contribute significantly to the initiation of breast cancer. There are several possible mechanisms by which glucocorticoids might promote neoplastic transformation of breast tissue. Among these, the least known and studied is the inhibition of the nuclear erythroid factor 2-related (Nrf2)-antioxidant/electrophile response element (ARE/EpRE) pathway by high levels of glucocorticoids. Specifically, Nrf2 is a potent transcriptional activator that plays a central role in the basal and inducible expression of many cytoprotective genes that effectively protect mammalian cells from various forms of stress and reduce the propensity of tissues and organisms to develop disease or malignancy including breast cancer. Consequently, a loss of Nrf2 in response to high levels of gluco-corticoids may lead to a decrease in cellular defense against oxidative stress, which plays an important role in the initiation of human mammary carcinogenesis. In the present review, we provide a comprehensive overview of the current state of knowledge of the cellular mechanisms by which both glucocorticoid pharmacotherapy and endogenous GCs (cortisol in humans and corticosterone in rodents) may contribute to breast cancer development through inhibition of the Nrf2-ARE/EpRE pathway and the protective role of melatonin against glucocorticoid-induced apoptosis in the immune system.

Pathways Linking Nicotinamide Adenine Dinucleotide Phosphate Production to Endoplasmic Reticulum Protein Oxidation and Stress

The endoplasmic reticulum (ER) lumen is highly oxidizing compared to other subcellular compartments, and maintaining the appropriate levels of oxidizing and reducing equivalents is essential to ER function. Both protein oxidation itself and other essential ER processes, such as the degradation of misfolded proteins and the sequestration of cellular calcium, are tuned to the ER redox state. Simultaneously, nutrients are oxidized in the cytosol and mitochondria to power ATP generation, reductive biosynthesis, and defense against reactive oxygen species. These parallel needs for protein oxidation in the ER and nutrient oxidation in the cytosol and mitochondria raise the possibility that the two processes compete for electron acceptors, even though they occur in separate cellular compartments. A key molecule central to both processes is NADPH, which is produced by reduction of NADP+ during nutrient catabolism and which in turn drives the reduction of components such as glutathione and thioredoxin that influence the redox potential in the ER lumen. For this reason, NADPH might serve as a mediator linking metabolic activity to ER homeostasis and stress, and represent a novel form of mitochondria-to-ER communication. In this review, we discuss oxidative protein folding in the ER, NADPH generation by the major pathways that mediate it, and ER-localized systems that can link the two processes to connect ER function to metabolic activity.

Structural homology between 11 beta-hydroxysteroid dehydrogenase and Mycobacterium tuberculosis Inh-A enzyme: Dehydroepiandrosterone as a potential co-adjuvant treatment in diabetes-tuberculosis comorbidity

Metabolic syndrome is considered the precursor of type 2 diabetes mellitus. Tuberculosis is a leading infection that constitutes a global threat remaining a major cause of morbi-mortality in developing countries. People with type 2 diabetes mellitus are more likely to suffer from infection with Mycobacterium tuberculosis. For both type 2 diabetes mellitus and tuberculosis, there is pulmonary production of anti-inflammatory glucocorticoids mediated by the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). The adrenal hormone dehydroepiandrosterone (DHEA) counteracts the glucocorticoid effects of cytokine production due to the inhibition of 11β-HSD1. Late advanced tuberculosis has been associated with the suppression of the Th1 response, evidenced by a high ratio of cortisol/DHEA. In a murine model of metabolic syndrome, we determined whether DHEA treatment modifies the pro-inflammatory cytokines due to the inhibition of the 11β-HSD1 expression. Since macrophages express 11β-HSD1, our second goal was incubating them with DHEA and Mycobacterium tuberculosis to show that the microbicide effect was increased by DHEA. Enoyl-acyl carrier protein reductase (InhA) is an essential enzyme of Mycobacterium tuberculosis involved in the mycolic acid synthesis. Because 11β-HSD1 and InhA are members of a short-chain dehydrogenase/reductase family of enzymes, we hypothesize that DHEA could be an antagonist of InhA. Our results demonstrate that DHEA has a direct microbicide effect against Mycobacterium tuberculosis; this effect was supported by in silico docking analysis and the molecular dynamic simulation studies between DHEA and InhA. Thus, DHEA increases the production of pro-inflammatory cytokines in the lung, inactivates GC by 11β-HSD1, and inhibits mycobacterial InhA. The multiple functions of DHEA suggest that this hormone or its synthetic analogs could be an efficient co-adjuvant for tuberculosis treatment.

Attenuation of 7-ketocholesterol- and 7β-hydroxycholesterol-induced oxiapoptophagy by nutrients, synthetic molecules and oils: Potential for the prevention of age-related diseases

Age-related diseases for which there are no effective treatments include cardiovascular diseases; neurodegenerative diseases such as Alzheimer's disease; eye disorders such as cataract and age-related macular degeneration; and, more recently, Severe Acute Respiratory Syndrome (SARS-CoV-2). These diseases are associated with plasma and/or tissue increases in cholesterol derivatives mainly formed by auto-oxidation: 7-ketocholesterol, also known as 7-oxo-cholesterol, and 7β-hydroxycholesterol. The formation of these oxysterols can be considered as a consequence of mitochondrial and peroxisomal dysfunction, leading to increased in oxidative stress, which is accentuated with age. 7-ketocholesterol and 7β-hydroxycholesterol cause a specific form of cytotoxic activity defined as oxiapoptophagy, including oxidative stress and induction of death by apoptosis associated with autophagic criteria. Oxiaptophagy is associated with organelle dysfunction and in particular with mitochondrial and peroxisomal alterations involved in the induction of cell death and in the rupture of redox balance. As the criteria characterizing 7-ketocholesterol- and 7β-hydroxycholesterol-induced cytotoxicity are often simultaneously observed in major age-related diseases (cardiovascular diseases, age-related macular degeneration, Alzheimer's disease) the involvement of these oxysterols in the pathophysiology of the latter seems increasingly likely. It is therefore important to better understand the signalling pathways associated with the toxicity of 7-ketocholesterol and 7β-hydroxycholesterol in order to identify pharmacological targets, nutrients and synthetic molecules attenuating or inhibiting the cytotoxic activities of these oxysterols. Numerous natural cytoprotective compounds have been identified: vitamins, fatty acids, polyphenols, terpenes, vegetal pigments, antioxidants, mixtures of compounds (oils, plant extracts) and bacterial enzymes. However, few synthetic molecules are able to prevent 7-ketocholesterol- and/or 7β-hydroxycholesterol-induced cytotoxicity: dimethyl fumarate, monomethyl fumarate, the tyrosine kinase inhibitor AG126, memantine, simvastatine, Trolox, dimethylsufoxide, mangafodipir and mitochondrial permeability transition pore (MPTP) inhibitors. The effectiveness of these compounds, several of which are already in use in humans, makes it possible to consider using them for the treatment of certain age-related diseases associated with increased plasma and/or tissue levels of 7-ketocholesterol and/or 7β-hydroxycholesterol.

11β-hydroxysteroid dehydrogenases: A growing multi-tasking family

This review briefly addresses the history of the discovery and elucidation of the three cloned 11β-hydroxysteroid dehydrogenase (11βHSD) enzymes in the human, 11βHSD1, 11βHSD2 and 11βHSD3, an NADP⁺-dependent dehydrogenase also called the 11βHSD1-like dehydrogenase (11βHSD1L), as well as evidence for yet identified 11βHSDs. Attention is devoted to more recently described aspects of this multi-functional family. The importance of 11βHSD substrates other than glucocorticoids including bile acids, 7-keto sterols, neurosteroids, and xenobiotics is discussed, along with examples of pathology when functions of these multi-tasking enzymes are disrupted. 11βHSDs modulate the intracellular concentration of glucocorticoids, thereby regulating the activation of the glucocorticoid and mineralocorticoid receptors, and 7β-27-hydroxycholesterol, an agonist of the retinoid-related orphan receptor gamma (RORγ). Key functions of this nuclear transcription factor include regulation of immune cell differentiation, cytokine production and inflammation at the cell level. 11βHSD1 expression and/or glucocorticoid reductase activity are inappropriately increased with age and in obesity and metabolic syndrome (MetS). Potential causes for disappointing results of the clinical trials of selective inhibitors of 11βHSD1 in the treatment of these disorders are discussed, as well as the potential for more targeted use of inhibitors of 11βHSD1 and 11βHSD2.

The ratio of ursodeoxycholyltaurine to 7-oxolithocholyltaurine serves as a biomarker of decreased 11β-hydroxysteroid dehydrogenase 1 activity in mouse

Background and Purpose

11β‐Hydroxysteroid dehydrogenase 1 (11β‐HSD1) regulates tissue‐specific glucocorticoid metabolism and its impaired expression and activity are associated with major diseases. Pharmacological inhibition of 11β‐HSD1 is considered a promising therapeutic strategy. This study investigated whether alternative 7‐oxo bile acid substrates of 11β‐HSD1 or the ratios to their 7‐hydroxy products can serve as biomarkers for decreased enzymatic activity.

Experimental Approach

Bile acid profiles were measured by ultra‐HPLC tandem‐MS in plasma and liver tissue samples of four different mouse models with decreased 11β‐HSD1 activity: global (11KO) and liver‐specific 11β‐HSD1 knockout mice (11LKO), mice lacking hexose‐6‐phosphate dehydrogenase (H6pdKO) that provides cofactor NADPH for 11β‐HSD1 and mice treated with the pharmacological inhibitor carbenoxolone. Additionally, 11β‐HSD1 expression and activity were assessed in H6pdKO‐ and carbenoxolone‐treated mice.

Key Results

The enzyme product to substrate ratios were more reliable markers of 11β‐HSD1 activity than absolute levels due to large inter‐individual variations in bile acid concentrations. The ratio of the 7β‐hydroxylated ursodeoxycholyltaurine (UDC‐Tau) to 7‐oxolithocholyltaurine (7oxoLC‐Tau) was diminished in plasma and liver tissue of all four mouse models and decreased in H6pdKO‐ and carbenoxolone‐treated mice with moderately reduced 11β‐HSD1 activity. The persistence of 11β‐HSD1 oxoreduction activity in the face of H6PD loss indicates the existence of an alternative NADPH source in the endoplasmic reticulum.

Conclusions and Implications

The plasma UDC‐Tau/7oxo‐LC‐Tau ratio detects decreased 11β‐HSD1 oxoreduction activity in different mouse models. This ratio may be a useful biomarker of decreased 11β‐HSD1 activity in pathophysiological situations or upon pharmacological inhibition.

LINKED ARTICLES

This article is part of a themed issue on Oxysterols, Lifelong Health and Therapeutics. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.16/issuetoc

Lack of adipose-specific hexose-6-phosphate dehydrogenase causes inactivation of adipose glucocorticoids and improves metabolic phenotype in mice

Excessive glucocorticoid (GC) production in adipose tissue promotes the development of visceral obesity and metabolic syndrome (MS). 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) is critical for controlling intracellular GC production, and this process is tightly regulated by hexose-6-phosphate dehydrogenase (H6PDH). To better understand the integrated molecular physiological effects of adipose H6PDH, we created a tissue-specific knockout of the H6PDH gene mouse model in adipocytes (adipocyte-specific conditional knockout of H6PDH (H6PDHAcKO) mice). H6PDHAcKO mice exhibited almost complete absence of H6PDH expression and decreased intra-adipose corticosterone production with a reduction in 11β-HSD1 activity in adipose tissue. These mice also had decreased abdominal fat mass, which was paralleled by decreased adipose lipogenic acetyl-CoA carboxylase (ACC) and ATP-citrate lyase (ACL) gene expression and reduction in their transcription factor C/EBPα mRNA levels. Moreover, H6PDHAcKO mice also had reduced fasting blood glucose levels, increased glucose tolerance, and increased insulin sensitivity. In addition, plasma free fatty acid (FFA) levels were decreased with a concomitant decrease in the expression of lipase adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) in adipose tissue. These results indicate that inactivation of adipocyte H6PDH expression is sufficient to cause intra-adipose GC inactivation that leads to a favorable pattern of metabolic phenotypes. These data suggest that H6PDHAcKO mice may provide a good model for studying the potential contributions of fat-specific H6PDH inhibition to improve the metabolic phenotype in vivo. Our study suggests that suppression or inactivation of H6PDH expression in adipocytes could be an effective intervention for treating obesity and diabetes.

Induction of the nicotinamide riboside kinase NAD+ salvage pathway in a model of sarcoplasmic reticulum dysfunction

Background

Hexose-6-Phosphate Dehydrogenase (H6PD) is a generator of NADPH in the Endoplasmic/Sarcoplasmic Reticulum (ER/SR). Interaction of H6PD with 11β-hydroxysteroid dehydrogenase type 1 provides NADPH to support oxo-reduction of inactive to active glucocorticoids, but the wider understanding of H6PD in ER/SR NAD(P)(H) homeostasis is incomplete. Lack of H6PD results in a deteriorating skeletal myopathy, altered glucose homeostasis, ER stress and activation of the unfolded protein response. Here we further assess muscle responses to H6PD deficiency to delineate pathways that may underpin myopathy and link SR redox status to muscle wide metabolic adaptation.

Methods

We analysed skeletal muscle from H6PD knockout (H6PDKO), H6PD and NRK2 double knockout (DKO) and wild-type (WT) mice. H6PDKO mice were supplemented with the NAD⁺ precursor nicotinamide riboside. Skeletal muscle samples were subjected to biochemical analysis including NAD(H) measurement, LC-MS based metabolomics, Western blotting, and high resolution mitochondrial respirometry. Genetic and supplement models were assessed for degree of myopathy compared to H6PDKO.

Results

H6PDKO skeletal muscle showed adaptations in the routes regulating nicotinamide and NAD⁺ biosynthesis, with significant activation of the Nicotinamide Riboside Kinase 2 (NRK2) pathway. Associated with changes in NAD⁺ biosynthesis, H6PDKO muscle had impaired mitochondrial respiratory capacity with altered mitochondrial acylcarnitine and acetyl-CoA metabolism. Boosting NAD⁺ levels through the NRK2 pathway using the precursor nicotinamide riboside elevated NAD⁺/NADH but had no effect to mitigate ER stress and dysfunctional mitochondrial respiratory capacity or acetyl-CoA metabolism. Similarly, H6PDKO/NRK2 double KO mice did not display an exaggerated timing or severity of myopathy or overt change in mitochondrial metabolism despite depression of NAD⁺ availability.

Conclusions

These findings suggest a complex metabolic response to changes in muscle SR NADP(H) redox status that result in impaired mitochondrial energy metabolism and activation of cellular NAD⁺ salvage pathways. It is possible that SR can sense and signal perturbation in NAD(P)(H) that cannot be rectified in the absence of H6PD. Whether NRK2 pathway activation is a direct response to changes in SR NAD(P)(H) availability or adaptation to deficits in metabolic energy availability remains to be resolved.

Hormonal Regulation of Glucocorticoid Inactivation and Reactivation in αT3-1 and LβT2 Gonadotroph Cells

The regulation of reproductive function by glucocorticoids occurs at all levels of the hypothalamo-pituitary-gonadal axis. Within the pituitary, glucocorticoids have been shown to directly alter gene expression in gonadotrophs, indicating that these cell types are sensitive to regulation by the glucocorticoid receptor. Whilst the major glucocorticoid metabolising enzymes, 11β-hydroxysteroid dehydrogenase (11βHSD; HSD11B1 and HSD11B2), have been described in human pituitary adenomas, the activity of these enzymes within different pituitary cell types has not been reported. Radiometric conversion assays were performed in αT3-1, LβT2 (gonadotrophs), AtT-20 (corticotrophs) and GH3 (somatolactotrophs) anterior pituitary cell lines, using tritiated cortisol, corticosterone, cortisone or 11-dehydrocorticosterone as substrates. The net oxidation of cortisol/corticosterone and net reduction of cortisone/11-dehydrocorticosterone were significantly higher in the two gonadotroph cells lines compared with the AtT-20 and GH3 cells after 4 h. Whilst these enzyme activities remained the same in αT3-1 and LβT2 cells over a 24 h period, there was a significant increase in glucocorticoid metabolism in both AtT-20 and GH3 cells over this same period, suggesting cell-type specific activity of the 11βHSD enzyme(s). Stimulation of both gonadotroph cell lines with either 100 nM GnRH or PACAP (known physiological regulators of gonadotrophs) resulted in significantly increased 11β-dehydrogenase (11βDH) and 11-ketosteroid reductase (11KSR) activities, over both 4 and 24 h. These data reveal that gonadotroph 11βHSD enzyme activity can act to regulate local glucocorticoid availability to mediate the influence of the HPA axis on gonadotroph function.

11β-Hydroxysteroid dehydrogenases control access of 7β,27-dihydroxycholesterol to retinoid-related orphan receptor γ

Oxysterols previously were considered intermediates of bile acid and steroid hormone biosynthetic pathways. However, recent research has emphasized the roles of oxysterols in essential physiologic processes and in various diseases. Despite these discoveries, the metabolic pathways leading to the different oxysterols are still largely unknown and the biosynthetic origin of several oxysterols remains unidentified. Earlier studies demonstrated that the glucocorticoid metabolizing enzymes, 11β-hydroxysteroid dehydrogenase (11β-HSD) types 1 and 2, interconvert 7-ketocholesterol (7kC) and 7β-hydroxycholesterol (7βOHC). We examined the role of 11β-HSDs in the enzymatic control of the intracellular availability of 7β,27-dihydroxycholesterol (7β27OHC), a retinoid-related orphan receptor γ (RORγ) ligand. We used microsomal preparations of cells expressing recombinant 11β-HSD1 and 11β-HSD2 to assess whether 7β27OHC and 7-keto,27-hydroxycholesterol (7k27OHC) are substrates of these enzymes. Binding of 7β27OHC and 7k27OHC to 11β-HSDs was studied by molecular modeling. To our knowledge, the stereospecific oxoreduction of 7k27OHC to 7β27OHC by human 11β-HSD1 and the reverse oxidation reaction of 7β27OHC to 7k27OHC by human 11β-HSD2 were demonstrated for the first time. Apparent enzyme affinities of 11β-HSDs for these novel substrates were equal to or higher than those of the glucocorticoids. This is supported by the fact that 7k27OHC and 7β27OHC are potent inhibitors of the 11β-HSD1-dependent oxoreduction of cortisone and the 11β-HSD2-dependent oxidation of cortisol, respectively. Furthermore, molecular docking calculations explained stereospecific enzyme activities. Finally, using an inducible RORγ reporter system, we showed that 11β-HSD1 and 11β-HSD2 controlled RORγ activity. These findings revealed a novel glucocorticoid-independent prereceptor regulation mechanism by 11β-HSDs that warrants further investigation.

11α-Hydroxyprogesterone, a potent 11β-hydroxysteroid dehydrogenase inhibitor, is metabolised by steroid-5α-reductase and cytochrome P450 17α-hydroxylase/17,20-lyase to produce C11α-derivatives of 21-deoxycortisol and 11-hydroxyandrostenedione in vitro

11α-Hydroxyprogesterone (11αOHP4) and 11β-hydroxyprogesterone (11βOHP4) have been reported to be inhibitors of 11β-hydroxysteroid dehydrogenase (11βHSD) type 2, together with 11β-hydroxytestosterone and 11β-hydroxyandrostenedione, and their C11-keto derivatives being inhibitors of 11βHSD1. Our in vitro assays in transiently transfected HEK293 cells, however, show that 11αOHP4 is a potent inhibitor of 11βHSD2 and while this steroid does not serve as a substrate for the enzyme, the aforementioned C11-oxy steroids are indeed substrates for both 11βHSD isozymes. 11βOHP4 is metabolised by 11βHSD2 yielding 11-ketoprogesterone with 11βHSD1 catalysing the reverse reaction, similar to the reduction of the other C11-oxy steroids. In the same model system, novel 11αOHP4 metabolites were detected in its conversion by steroid-5α-reductase (SRD5A) types 1 and 2 yielding 11α-hydroxydihydroprogesterone and its conversion by cytochrome P450 17A1 (CYP17A1) yielding the hydroxylase product, 11α,17α-dihydroxyprogesterone, and the 17,20 lyase product, 11α-hydroxyandrostenedione. We also detected both 11αOHP4 and 11βOHP4 in prostate cancer tissue- ∼23 and ∼32 ng/g respectively with 11KP4 levels >300 ng/g. In vitro assays in PC3 and LNCaP prostate cancer cell models, showed that the metabolism of 11αOHP4 and 11βOHP4 was comparable. In LNCaP cells expressing CYP17A1, 11αOHP4 and 11βOHP4 were metabolised with negligible substrate, 4%, remaining after 48 h, while the steroid substrate 11β,17α-dihydroxyprogesterone (21dF) was metabolised to C11-keto C₁₉ steroids yielding 11-ketotestosterone. Despite the fact that 11αOHP4 is not metabolised by 11βHSD2, it is a substrate for SRD5A and CYP17A1, yielding C11α-hydroxy C₁₉ steroids as well as the C11α-hydroxy derivative of 21dF-the latter associated with clinical conditions characterised by androgen excess. With our data showing that 11αOHP4 is present at high levels in prostate cancer tissue, the steroid may serve as a precursor to unique C11α-hydroxy C₁₉ steroids. The potential impact of 11αOHP4 and its metabolites on human pathophysiology can however only be fully assessed once C11α-hydroxyl metabolite levels are comprehensively analysed.

Enzymatic interconversion of the oxysterols 7β,25-dihydroxycholesterol and 7-keto,25-hydroxycholesterol by 11β-hydroxysteroid dehydrogenase type 1 and 2

Oxysterols are cholesterol metabolites derived through either autoxidation or enzymatic processes. They consist of a large family of bioactive lipids that have been associated with the progression of multiple pathologies. In order to unravel (patho-)physiological mechanisms involving oxysterols, it is crucial to elucidate the underlying formation and degradation of oxysterols. A role of 11β-hydroxysteroid dehydrogenases (11β-HSDs) in oxysterol metabolism by catalyzing the interconversion of 7-ketocholesterol (7kC) and 7β-hydroxycholesterol (7βOHC) has already been reported. The present study addresses a function of 11β-HSD1 in the enzymatic generation of 7β,25-dihydroxycholesterol (7β25OHC) from 7-keto,25-hydroxycholesterol (7k25OHC) and tested whether 11β-HSD2 is able to catalyze the reverse reaction. For the first time, using recombinant enzymes, the formation of 7k25OHC from 7kC by cholesterol 25-hydroxylase (CH25H) and further stereospecific oxoreduction to 7β25OHC by human and mouse 11β-HSD1 could be demonstrated. Additionally, experiments using human 11β-HSD2 showed the oxidation of 7β25OHC to 7k25OHC. Molecular modeling provided an explanation for the stereospecific interconversion of 7β25OHC and 7k25OHC. Production of the Epstein-Barr virus-induced gene 2 (EBI2) ligand 7β25OHC from 7k25OHC in challenged tissue by 11β-HSD1 may be important in inflammation. In conclusion, these results demonstrate a novel glucocorticoid-independent pre-receptor regulation mediated by 11β-HSDs.

The 11β-hydroxysteroid dehydrogenase isoforms: pivotal catalytic activities yield potent C11-oxy C19 steroids with 11βHSD2 favouring 11-ketotestosterone, 11-ketoandrostenedione and 11-ketoprogesterone biosynthesis

The 11β-hydroxysteroid dehydrogenase (11βHSD) types 1 and 2 are primarily associated with glucocorticoid inactivation and reactivation. Several adrenal C11-oxy C₁₉ and C11-oxy C₂₁ steroids, which have been identified in prostate cancer, 21-hydroxylase deficiency and polycystic ovary syndrome, are substrates for these isozymes. This study describes the kinetic parameters of 11βHSD1 and 11βHSD2 towards the C11-keto and C11-hydroxy derivatives of the C₁₉ and C₂₁ steroids. The apparent K_m and V_max values indicate the more prominent 11βHSD2 activity towards 11β-hydroxy androstenedione, 11β-hydroxytestosterone and 11β-hydroxyprogesterone in contrast to the 11βHSD1 reduction of the C11-keto steroids, as was demonstrated in the LNCaP cell model in the production of 11-ketotestosterone and 11-ketodihydrotestosterone. Data highlighted the role of 11βHSD2 and cytochrome P450 17A1 in the contribution of C11-oxy C₂₁ steroids to the C11-oxy C₁₉ steroid pool in the C11-oxy backdoor pathway. In addition, 11βHSD2 activity, catalysing 11-ketotestosterone biosynthesis, was shown to be key in the production of prostate specific antigen and in the progression of prostate cancer to castration resistant prostate cancer. The study at hand thus provides evidence that 11βHSD isozymes play key roles in pathophysiological states, more so than was previously put forward.

Expression and activity of the cortisol-activating enzyme 11β-hydroxysteroid dehydrogenase type 1 is tissue and species-specific

The microsomal enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) interconverts glucocorticoid receptor-inert cortisone (11-dehydrocorticosterone in rodents) to its receptor-active form cortisol (corticosterone in rodents). Thus, 11β-HSD1 amplifies glucocorticoid action at the tissue level. According to the current literature, dysregulation of glucocorticoid signaling may contribute to the pathogenesis of the metabolic syndrome in which regeneration of cortisol by 11β-HSD1 may be an important factor. This is why the enzyme has been very intensely investigated as a potential therapeutic target to treat metabolic complications such as obesity and diabetes type 2. However, due to controversial results from the various animal and human studies as well as from different findings with regard to tissue-specific expression and activity, the varied results unfortunately do not yield a consistent picture. Therefore, the precise role of 11β-HSD1 in the development of complications associated with the metabolic syndrome has still not been deciphered yet. Overall, the prominent role of this enzyme in the pathogenesis of the metabolic syndrome becomes more and more dubious and therefore further studies are necessary to clarify its role finally. This short review gives an overview on the main contradicting findings on the role of 11β-HSD1 in the development of visceral obesity and diabetes type 2.

Dehydroepiandrosterone and Its CYP7B1 Metabolite 7α-Hydroxydehydroepiandrosterone Regulates 11β-Hydroxysteroid Dehydrogenase 1 Directions in Rat Leydig Cells

Background: The purpose of this study was to investigate cytochrome P450-7B1 (CYP7B1) in the human and rat testes to regulate 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) activity. We hypothesized that dehydroepiandrosterone (DHEA) and its product 7α-hydroxydehydroepiandrosterone (7αOHD) after catalysis of CYP7B1 played a critical role in driving the direction of 11β-HSD1, because 7αOHD is an alternative substrate for 11β-HSD1. Methods: We examined the influence of DHEA and 7αOHD on 11β-HSD1 activities in both intact Leydig cells and microsomes using radioactive substrates and identified the location of CYP7B1 in Leydig cells using immunohistochemical staining, Western blot, and qPCR. Results: We found that DHEA stimulated 11β-HSD1 oxidase activity in intact cells (EC₅₀ = 0.97 ± 0.11 μM) and inhibited its reductase activity (IC₅₀ = 1.04 ± 0.06 μM). In microsomes, DHEA was a competitive inhibitor of the reductase activity. The 11β-HSD1 oxidase activity in intact cells was inhibited by 7αOHD (IC₅₀ = 1.18 ± 0.12 μM), and the reductase activity was enhanced (EC₅₀ = 0.7 ± 0.04 μM). 7αOHD was a competitive inhibitor of 11β-HSD1 oxidase. CYP7B1 was present in rat Leydig cells, as shown by immunohistochemistry, Western blotting, and qPCR analysis. Conclusion: Our results are consistent with a conclusion that DHEA in the circulation driving 11β-HSD1 toward an oxidase in Leydig cells mainly through inhibiting the reductase of the enzyme, while 7αOHD (CYP7B1 catalytic product of DHEA) drives the enzyme toward the opposite direction.

Alterations of Cortisol Metabolism in Human Disorders

The interconversion of active and inactive corticosteroids - cortisol and cortisone, respectively, in humans - is modulated by isozymes of 11β-hydroxysteroid dehydrogenase (11-HSD). Studies of this process have provided crucial insights into glucocorticoid effects in a wide variety of tissues. The 11-HSD1 isozyme functions mainly as an oxoreductase (cortisone to cortisol) and is expressed at high levels in the liver and other glucocorticoid target tissues. Because it is required for full physiological effects of cortisol, it has emerged as a drug target for metabolic syndrome and type 2 diabetes. Mutations in the corresponding HSD11B1 gene, or in the H6PD gene encoding hexose-6-phosphate dehydrogenase (which supplies the NADPH required for the oxoreductase activity of 11-HSD1), cause apparent cortisone reductase deficiency, a rare syndrome of adrenocortical hyperactivity and hyperandrogenism. In contrast, the 11-HSD2 isozyme functions as a dehydrogenase (cortisol to cortisone) and is expressed mainly in mineralocorticoid target tissues, where it bars access of cortisol to the mineralocorticoid receptor. Mutations in the HSD11B2 gene encoding 11-HSD2 cause the syndrome of apparent mineralocorticoid excess, a severe form of familial hypertension. The role of this enzyme in the pathogenesis of common forms of low-renin hypertension remains uncertain.

Design, synthesis, and biological evaluation of novel selective peptide inhibitors of 11β-hydroxysteroid dehydrogenase 1

The enzyme 11β-HSD1 plays a crucial role in the tissue-specific regulation of cortisol levels and it has been associated with various diseases. Inhibition of 11β-HSD1 is an attractive intervention strategy and the discovery of novel selective 11β-HSD1 inhibitors is of high relevance. In this study, we identified and evaluated a new series of selective peptide 11β-HSD1 inhibitors with potential for skin care applications. This novel scaffold was designed with the aid of molecular modeling and two previously reported inhibitors. SAR optimization yielded highly active peptides (IC₅₀ below 400 nM) that were inactive at 1 µM concentration against structurally related enzymes (11β-HSD2, 17β-HSD1 and 17β-HSD2). The best performing peptides inhibited the conversion of cortisone into cortisol in primary human keratinocytes and the most active compound, 5d, was further shown to reverse cortisone-induced collagen damage in human ex-vivo tissue.

Absence of hexose-6-phosphate dehydrogenase results in reduced overall glucose consumption but does not prevent 11β-hydroxysteroid dehydrogenase-1-dependent glucocorticoid activation

Hexose-6-phosphate dehydrogenase (H6PD) is thought to be the major source of NADPH within the endoplasmic reticulum (ER), determining 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) reaction direction to convert inert 11-oxo- to potent 11β-hydroxyglucocorticoids. Here, we tested the hypothesis whether H6pd knock-out (KO) in primary murine bone marrow-derived macrophages results in a switch from 11β-HSD1 oxoreduction to dehydrogenation, thereby inactivating glucocorticoids (GC) and affecting macrophage phenotypic activation as well as causing a more aggressive M1 macrophage phenotype. H6pdKO did not lead to major disturbances of macrophage activation state, although a slightly more pronounced M1 phenotype was observed with enhanced proinflammatory cytokine release, an effect explained by the decreased 11β-HSD1-dependent GC activation. Unexpectedly, ablation of H6pd did not switch 11β-HSD1 reaction direction. A moderately decreased 11β-HSD1 oxoreduction activity by 40-50% was observed in H6pdKO M1 macrophages but dehydrogenation activity was undetectable, providing strong evidence for the existence of an alternative source of NADPH in the ER. H6pdKO M1 activated macrophages showed decreased phagocytic activity, most likely a result of the reduced 11β-HSD1-dependent GC activation. Other general macrophage functions reported to be influenced by GC, such as nitrite production and cholesterol efflux, were altered negligibly or not at all. Importantly, assessment of energy metabolism using an extracellular flux analyzer and lactate measurements revealed reduced overall glucose consumption in H6pdKO M1 activated macrophages, an effect that was GC independent. The GC-independent influence of H6PD on energy metabolism and the characterization of the alternative source of NADPH in the ER warrant further investigations. ENZYMES: 11β-HSD1, EC 1.1.1.146; H6PD, EC 1.1.1.47.

Dehydroepiandrosterone Antagonizes Pain Stress-Induced Suppression of Testosterone Production in Male Rats

Background: Leydig cells secrete the steroid hormone, testosterone, which is essential for male fertility and reproductive health. Stress increases the secretion of glucocorticoid [corticosterone, (CORT) in rats] that decreases circulating testosterone levels in part through a direct action on its receptors in Leydig cells. Intratesticular CORT level is dependent on oxidative inactivation of CORT by 11β-hydroxysteroid dehydrogenase 1 (HSD11B1) in rat Leydig cells. Pain may cause the stress, thus affecting testosterone production in Leydig cells.

Methods: Adult male Sprague–Dawley rats orally received vehicle control or 5 or 10 mg/kg dehydroepiandrosterone (DHEA) 0.5 h before being subjected to pain stimulation for 1, 3, and 6 h. In the present study, we investigated the time-course changes of steroidogenic gene expression levels after acute pain-induced stress in rats and the possible mechanism of DHEA that prevented it. Plasma CORT, luteinizing hormone (LH), and testosterone (T) levels were measured, and Leydig cell gene expression levels were determined. The direct regulation of HSD11B1 catalytic direction by DHEA was detected in purified rat Leydig, liver, and rat Hsd11b1-transfected COS1 cells.

Results: Plasma CORT levels were significantly increased at hour 1, 3, and 6 during the pain stimulation, while plasma T levels were significantly decreased starting at hour 3 and 6. Pain-induced stress also decreased Star, Hsd3b1, and Cyp17a1 expression levels at hour 3. When 5 and 10 mg/kg DHEA were orally administered to rats 0.5 h before starting pain stimulation, DHEA prevented pain-mediated decrease in plasma T levels and the expression of Star, Hsd3b1, and Cyp17a1 without affecting plasma CORT levels. DHEA was found to modulate HSD11B1 activities by increasing its oxidative activity and decreasing its reductive activity, thus decreasing the intracellular CORT levels in Leydig cells.

Conclusion: Stress induced by acute pain can inhibit Leydig cell T production by upregulation of corticosterone. DHEA can prevent the negative effects of excessive corticosterone by modulating HSD11B1 activity.

Comparison of flavonoids and isoflavonoids to inhibit rat and human 11β-hydroxysteroid dehydrogenase 1 and 2

Many flavonoids and isoflavonoids have anti-diabetic effects in animal models. However, the mechanisms that are involved are generally unclear. Since 11β-hydroxysteroid dehydrogenases (HSD11Bs) play important roles in diabetes, we hypothesize that flavonoids and isoflavonoids may affect diabetes by targeting two isoforms of HSD11B differently. The inhibitory effects of flavonoids (apigenin and quercetin) and isoflavonoids [genistein and (±) equol] on rat and human HSD11B1 and HSD11B2 were analyzed. The potencies of inhibition on human HSD11B1 reductase was in the order of apigenin > quercetin > genistein > (±) equol, with IC₅₀ values of 2.19, 5.36, 11.00, and over 100 μM, respectively. Genistein also inhibited rat HSD11B1 reductase with IC₅₀ value of 24.58 μM, while other three chemicals showed no effects on the enzyme activity with IC₅₀ values over 100 μM. However, apigenin and (±) equol did not inhibit human HSD11B2 at concentrations as high as 100 μM, while genistein and quercetin inhibited human HSD11B2 by 60% and 50% at 100 μM, respectively. The effective flavonoids and isoflavonoids are noncompetitive inhibitors of HSD11B1 when steroid substrates were used. Docking analysis showed that they bound to the steroid-binding site of the human HSD11B1. These data indicate that apigenin is a selective inhibitor of human HSD11B1 of two HSD11B isoforms, which may be useful in managing symptoms of the metabolic syndrome.

Intrauterine growth restriction combined with a maternal high-fat diet increased adiposity and serum corticosterone levels in adult rat offspring

Intrauterine growth restriction (IUGR) and fetal exposure to a maternal high-fat diet (HFD) independently increase the risk of developing obesity in adulthood. Excess glucocorticoids increase obesity. We hypothesized that surgically induced IUGR combined with an HFD would increase adiposity and glucocorticoids more than in non-IUGR offspring combined with the same HFD, findings that would persist despite weaning to a regular diet. Non-IUGR (N) and IUGR (I) rat offspring from dams fed either regular rat chow (R) or an HFD (H) were weaned to either a regular rat chow or an HFD. For non-IUGR and IUGR rats, this study design resulted in three diet groups: offspring from dams fed a regular diet and weaned to a regular diet (NRR and IRR), offspring rats from dams fed an HFD and weaned to a regular diet (NHR and IHR) and offspring from dams fed an HFD and weaned to an HFD (NHH and IHH). Magnetic resonance imaging or fasting visceral and subcutaneous adipose tissue collection occurred at postnatal day 60. IHH male rats had greater adiposity than NHH males, findings that were only partly normalized by weaning to a regular chow. IHH male rats had a 10-fold increase in serum corticosterone levels. IHH female rats had increased adiposity and serum triglycerides. We conclude that IUGR combined with an HFD throughout life increased adiposity, glucocorticoids and triglycerides in a sex-specific manner. Our data suggest that one mechanism through which the perinatal environment programs increased adiposity in IHH male rats may be via increased systemic glucocorticoids.

Hexose-6-phosphate dehydrogenase controls cancer cell proliferation and migration through pleiotropic effects on the unfolded-protein response, calcium homeostasis, and redox balance

Hexose-6-phosphate dehydrogenase (H6PD) produces reduced NADPH in the endoplasmic reticulum (ER) lumen. NADPH constitutes a cofactor for many reducing enzymes, and its inability to traverse biologic membranes makes in situ synthesis of NADPH in the ER lumen indispensable. The H6PD gene is amplified in several types of malignancies, and earlier work pointed toward a potential involvement of the enzyme in cancer cell growth. In the present study, we demonstrated a pivotal role of H6PD in proliferation and migratory potential of 3 human breast cancer cell lines. Knockdown of H6PD decreased proliferation and migration in SUM159, MCF7, and MDA-MB-453 cells. To understand the mechanism through which H6PD exerts its effects, we investigated the cellular changes after H6PD silencing in SUM159 cells. Knockdown of H6PD resulted in an increase in ER lumen oxidation, and down-regulation of many components of the unfolded protein response, including the transcription factors activating transcription factor-4, activating transcription factor-6, split X-box binding protein-1, and CCAAT/enhancer binding protein homologous protein. This effect was accompanied by an increase in sarco/endoplasmic reticulum Ca²⁺-ATPase-2 pump expression and an decrease in inositol trisphosphate receptor-III, which led to augmented levels of calcium in the ER. Further characterization of the molecular pathways involving H6PD could greatly broaden our understanding of how the ER microenvironment sustains malignant cell growth.-Tsachaki, M., Mladenovic, N., Štambergová, H., Birk, J., Odermatt, A. Hexose-6-phosphate dehydrogenase controls cancer cell proliferation and migration through pleiotropic effects on the unfolded protein response, calcium homeostasis, and redox balance.

Identification of a tumor-promoter cholesterol metabolite in human breast cancers acting through the glucocorticoid receptor

Breast cancer (BC) remains the primary cause of death from cancer among women worldwide. Cholesterol-5,6-epoxide (5,6-EC) metabolism is deregulated in BC but the molecular origin of this is unknown. Here, we have identified an oncometabolism downstream of 5,6-EC that promotes BC progression independently of estrogen receptor α expression. We show that cholesterol epoxide hydrolase (ChEH) metabolizes 5,6-EC into cholestane-3β,5α,6β-triol, which is transformed into the oncometabolite 6-oxo-cholestan-3β,5α-diol (OCDO) by 11β-hydroxysteroid-dehydrogenase-type-2 (11βHSD2). 11βHSD2 is known to regulate glucocorticoid metabolism by converting active cortisol into inactive cortisone. ChEH inhibition and 11βHSD2 silencing inhibited OCDO production and tumor growth. Patient BC samples showed significant increased OCDO levels and greater ChEH and 11βHSD2 protein expression compared with normal tissues. The analysis of several human BC mRNA databases indicated that 11βHSD2 and ChEH overexpression correlated with a higher risk of patient death, highlighting that the biosynthetic pathway producing OCDO is of major importance to BC pathology. OCDO stimulates BC cell growth by binding to the glucocorticoid receptor (GR), the nuclear receptor of endogenous cortisol. Interestingly, high GR expression or activation correlates with poor therapeutic response or prognosis in many solid tumors, including BC. Targeting the enzymes involved in cholesterol epoxide and glucocorticoid metabolism or GR may be novel strategies to prevent and treat BC.

Interplay between H6PDH and 11β-HSD1 implicated in the pathogenesis of type 2 diabetes mellitus

Extensive studies have been performed on the role of 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) in metabolic diseases. Our previous study reported glucose could directly regulate hexose-6-phosphate dehydrogenase (H6PDH) and 11β-HSD1. Recently, we further investigated the interplay of H6PDH and 11β-HSD1 and their roles in hepatic gluconeogenesis and insulin resistance to elucidate the importance of H6PDH and 11β-HSD1 in pathogenesis of type 2 diabetes mellitus (T2DM). T2DM rats model and H6PDH or 11β-HSD1 siRNA transfected in CBRH-7919 cells were used to explore the effect of H6PDH and 11β-HSD1 in T2DM. The results showed that the expression and activity of H6PDH and 11β-HSD1 in livers of diabetic rats were increased, with the expressions of PEPCK and G6Pase or liver corticosterone increased apparently. It also showed that H6PDH siRNA and 11β-HSD1 siRNA could inhibit the protein expression and enzyme activity by each other. With H6PDH siRNA, the enhancement of gluconeogenesis was blocked and insulin resistance stimulated by corticosterone was reduced. H6PDH and 11β-HSD1 might be the effective and prospective targets for T2DM and metabolic syndromes, based on the interplay between these two enzymes.

Cellular and genetic models of H6PDH and 11β-HSD1 function in skeletal muscle

Glucocorticoids are important for skeletal muscle energy metabolism, regulating glucose utilization, insulin sensitivity, and muscle mass. Nicotinamide adenine dinucleotide phosphate‐dependent 11β‐hydroxysteroid dehydrogenase type 1 (11β‐HSD1)‐mediated glucocorticoid activation in the sarcoplasmic reticulum (SR) is integral to mediating the detrimental effects of glucocorticoid excess in muscle. 11β‐Hydroxysteroid dehydrogenase type 1 activity requires glucose‐6‐phosphate transporter (G6PT)‐mediated G6P transport into the SR for its metabolism by hexose‐6‐phosphate dehydrogenase (H6PDH) for NADPH generation. Here, we examine the G6PT/H6PDH/11β‐HSD1 triad in differentiating myotubes and explore the consequences of muscle‐specific knockout of 11β‐HSD1 and H6PDH. 11β‐Hydroxysteroid dehydrogenase type 1 expression and activity increase with myotube differentiation and in response to glucocorticoids. Hexose‐6‐phosphate dehydrogenase shows some elevation in expression with differentiation and in response to glucocorticoid, while G6PT appears largely unresponsive to these particular conditions. When examining 11β‐HSD1 muscle‐knockout mice, we were unable to detect significant decrements in activity, despite using a well‐validated muscle‐specific Cre transgene and confirming high‐level recombination of the floxed HSD11B1 allele. We propose that the level of recombination at the HSD11B1 locus may be insufficient to negate basal 11β‐HSD1 activity for a protein with a long half‐life. Hexose‐6‐phosphate dehydrogenase was undetectable in H6PDH muscle‐knockout mice, which display the myopathic phenotype seen in global KO mice, validating the importance of SR NADPH generation. We envisage these data and models finding utility when investigating the muscle‐specific functions of the 11β‐HSD1/G6PT/H6PDH triad.

DHRS7 (SDR34C1) - A new player in the regulation of androgen receptor function by inactivation of 5α-dihydrotestosterone?

DHRS7 (SDR34C1) has been associated with potential tumor suppressor effects in prostate cancer; however, its function remains largely unknown. Recent experiments using purified recombinant human DHRS7 suggested several potential substrates, including the steroids cortisone and Δ4-androstene-3,17-dione (androstenedione). However, the substrate and cofactor concentrations used in these experiments were very high and the physiological relevance of these observations needed to be further investigated. In the present study, recombinant human DHRS7 was expressed in intact HEK-293 cells in order to investigate whether glucocorticoids and androgens serve as substrates at sub-micromolar concentrations and at physiological cofactor concentrations. Furthermore, the membrane topology of DHRS7 was revisited using redox-sensitive green-fluorescent protein fusions in living cells. The results revealed that (1) cortisone is a substrate of DHRS7; however, it is not reduced to cortisol but to 20β-dihydrocortisone, (2) androstenedione is not a relevant substrate of DHRS7, (3) DHRS7 catalyzes the oxoreduction of 5α-dihydrotestosterone (5αDHT) to 3α-androstanediol (3αAdiol), with a suppressive effect on androgen receptor (AR) transcriptional activity, and (4) DHRS7 is anchored in the endoplasmic reticulum membrane with a cytoplasmic orientation. Together, the results show that DHRS7 is a cytoplasmic oriented enzyme exhibiting 3α/20β-hydroxysteroid dehydrogenase activity, with a possible role in the modulation of AR function. Further research needs to address the physiological relevance of DHRS7 in the inactivation of 5αDHT and AR regulation.

Fructose, Glucocorticoids and Adipose Tissue: Implications for the Metabolic Syndrome

The modern Western society lifestyle is characterized by a hyperenergetic, high sugar containing food intake. Sugar intake increased dramatically during the last few decades, due to the excessive consumption of high-sugar drinks and high-fructose corn syrup. Current evidence suggests that high fructose intake when combined with overeating and adiposity promotes adverse metabolic health effects including dyslipidemia, insulin resistance, type II diabetes, and inflammation. Similarly, elevated glucocorticoid levels, especially the enhanced generation of active glucocorticoids in the adipose tissue due to increased 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) activity, have been associated with metabolic diseases. Moreover, recent evidence suggests that fructose stimulates the 11β-HSD1-mediated glucocorticoid activation by enhancing the availability of its cofactor NADPH. In adipocytes, fructose was found to stimulate 11β-HSD1 expression and activity, thereby promoting the adipogenic effects of glucocorticoids. This article aims to highlight the interconnections between overwhelmed fructose metabolism, intracellular glucocorticoid activation in adipose tissue, and their metabolic effects on the progression of the metabolic syndrome.

Fructose increases corticosterone production in association with NADPH metabolism alterations in rat epididymal white adipose tissue

Metabolic syndrome is an array of closely metabolic disorders that includes glucose intolerance/insulin resistance, central obesity, dyslipidemia, and hypertension. Fructose, a highly lipogenic sugar, has profound metabolic effects in adipose tissue, and has been associated with the etiopathology of many components of the metabolic syndrome. In adipocytes, the enzyme 11 β-HSD1 amplifies local glucocorticoid production, being a key player in the pathogenesis of central obesity and metabolic syndrome. 11 β-HSD1 reductase activity is dependent on NADPH, a cofactor generated by H6PD inside the endoplasmic reticulum. Our focus was to explore the effect of fructose overload on epididymal white adipose tissue (EWAT) machinery involved in glucocorticoid production and NADPH and oxidants metabolism. Male Sprague-Dawley rats fed with a fructose solution (10% (w/v) in tap water) during 9 weeks developed some characteristic features of metabolic syndrome, such as hypertriglyceridemia, and hypertension. In addition, high levels of plasma and EWAT corticosterone were detected. Activities and expressions of H6PD and 11 β-HSD1, NAPDH content, superoxide anion production, expression of NADPH oxidase 2 subunits, and indicators of oxidative metabolism were measured. Fructose overloaded rats showed an increased potential in oxidant production respect to control rats. In parallel, in EWAT from fructose overloaded rats we found higher expression/activity of H6PD and 11 β-HSD1, and NADPH/NADP⁺ ratio. Our in vivo results support that fructose overload installs in EWAT conditions favoring glucocorticoid production through higher H6PD expression/activity supplying NADPH for enhanced 11 β-HSD1 expression/activity, becoming this tissue a potential extra-adrenal source of corticosterone under these experimental conditions.

Getting to the heart of intracellular glucocorticoid regeneration: 11β-HSD1 in the myocardium

Corticosteroids influence the development and function of the heart and its response to injury and pressure overload via actions on glucocorticoid (GR) and mineralocorticoid (MR) receptors. Systemic corticosteroid concentration depends largely on the activity of the hypothalamic-pituitary-adrenal (HPA) axis, but glucocorticoid can also be regenerated from intrinsically inert metabolites by the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), selectively increasing glucocorticoid levels within cells and tissues. Extensive studies have revealed the roles for glucocorticoid regeneration by 11β-HSD1 in liver, adipose, brain and other tissues, but until recently, there has been little focus on the heart. This article reviews the evidence for glucocorticoid metabolism by 11β-HSD1 in the heart and for a role of 11β-HSD1 activity in determining the myocardial growth and physiological function. We also consider the potential of 11β-HSD1 as a therapeutic target to enhance repair after myocardial infarction and to prevent the development of cardiac remodelling and heart failure.

Genome-wide analysis reveals adaptation to high altitudes in Tibetan sheep

Tibetan sheep have lived on the Tibetan Plateau for thousands of years; however, the process and consequences of adaptation to this extreme environment have not been elucidated for important livestock such as sheep. Here, seven sheep breeds, representing both highland and lowland breeds from different areas of China, were genotyped for a genome-wide collection of single-nucleotide polymorphisms (SNPs). The FST and XP-EHH approaches were used to identify regions harbouring local positive selection between these highland and lowland breeds, and 236 genes were identified. We detected selection events spanning genes involved in angiogenesis, energy production and erythropoiesis. In particular, several candidate genes were associated with high-altitude hypoxia, including EPAS1, CRYAA, LONP1, NF1, DPP4, SOD1, PPARG and SOCS2. EPAS1 plays a crucial role in hypoxia adaption; therefore, we investigated the exon sequences of EPAS1 and identified 12 mutations. Analysis of the relationship between blood-related phenotypes and EPAS1 genotypes in additional highland sheep revealed that a homozygous mutation at a relatively conserved site in the EPAS1 3' untranslated region was associated with increased mean corpuscular haemoglobin concentration and mean corpuscular volume. Taken together, our results provide evidence of the genetic diversity of highland sheep and indicate potential high-altitude hypoxia adaptation mechanisms, including the role of EPAS1 in adaptation.

Amphetamine withdrawal differentially affects hippocampal and peripheral corticosterone levels in response to stress

Amphetamine withdrawal is associated with heightened anxiety-like behavior, which is directly driven by blunted stress-induced glucocorticoid receptor-dependent serotonin release in the ventral hippocampus. This suggests that glucocorticoid availability in the ventral hippocampus during stress may be reduced during amphetamine withdrawal. Therefore, we tested whether amphetamine withdrawal alters either peripheral or hippocampal corticosterone stress responses. Adult male rats received amphetamine (2.5mg/kg, ip) or saline for 14 days followed by 2 weeks of withdrawal. Contrary to our prediction, microdialysis samples from freely-moving rats revealed that restraint stress-induced corticosterone levels in the ventral hippocampus are enhanced by amphetamine withdrawal relative to controls. In separate groups of rats, plasma corticosterone levels increased immediately after 20min of restraint and decreased to below stress-naïve levels after 1h, indicating negative feedback regulation of corticosterone following stress. However, plasma corticosterone responses were similar in amphetamine-withdrawn and control rats. Neither amphetamine nor stress exposure significantly altered protein expression or enzyme activity of the steroidogenic enzymes 11β-hydroxysteroid dehydrogenase (11β-HSD1) or hexose-6-phosphate dehydrogenase (H6PD) in the ventral hippocampus. Our findings demonstrate for the first time that amphetamine withdrawal potentiates stress-induced corticosterone in the ventral hippocampus, which may contribute to increased behavioral stress sensitivity previously observed during amphetamine withdrawal. However, this is not mediated by either changes in plasma corticosterone or hippocampal steroidogenic enzymes. Establishing enhanced ventral hippocampal corticosterone as a direct cause of greater stress sensitivity may identify the glucocorticoid system as a novel target for treating behavioral symptoms of amphetamine withdrawal.

Cortisol promotes endoplasmic glucose production via pyridine nucleotide redox

Both increased adrenal and peripheral cortisol production, the latter governed by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), contribute to the maintenance of fasting blood glucose. In the endoplasmic reticulum (ER), the pyridine nucleotide redox state (NADP/NADPH) is dictated by the concentration of glucose-6-phosphate (G6P) and the coordinated activities of two enzymes, hexose-6-phosphate dehydrogenase (H6PDH) and 11β-HSD1. However, luminal G6P may similarly serve as a substrate for hepatic glucose-6-phophatase (G6Pase). A tacit belief is that the G6P pool in the ER is equally accessible to both H6PDH and G6Pase. Based on our inhibition studies and kinetic analysis in isolated rat liver microsomes, these two aforesaid luminal enzymes do share the G6P pool in the ER, but not equally. Based on the kinetic modeling of G6P flux, the ER transporter for G6P (T1) preferentially delivers this substrate to G6Pase; hence, the luminal enzymes do not share G6P equally. Moreover, cortisol, acting through 11β-HSD1, begets a more reduced pyridine redox ratio. By altering this luminal redox ratio, G6P flux through H6PDH is restrained, allowing more G6P for the competing enzyme G6Pase. And, at low G6P concentrations in the ER lumen, which occur during fasting, this acute cortisol-induced redox adjustment promotes glucose production. This reproducible cortisol-driven mechanism has been heretofore unrecognized.

Endocrine disruptors and other inhibitors of 11β-hydroxysteroid dehydrogenase 1 and 2: Tissue-specific consequences of enzyme inhibition

Numerous chemicals in the environment have the ability to interact with the endocrine system. These compounds are called endocrine disruptors (EDs). Exposure to EDs represents one of the hypotheses for decreasing fertility, the increased risk of numerous cancers and obesity, metabolic syndrome and type 2 diabetes. There are various mechanisms of ED action, one of which is their interference in the action of 11β-hydroxysteroid dehydrogenase (11βHSD) that maintains a balance between active and inactive glucocorticoids on the intracellular level. This enzyme has two isoforms and is expressed in various tissues. Inhibition of 11βHSD in various tissues can have different consequences. In the case of EDs, the results of exposure are mainly adverse; on the other hand pharmaceutically developed inhibitors of 11βHSD type 1 are evaluated as an option for treating metabolic syndrome, as well as related diseases and depressive disorders. This review focuses on the effects of 11βHSD inhibitors in the testis, colon, adipose tissue, kidney, brain and placenta.

Metabolic Coupling Determines the Activity: Comparison of 11β-Hydroxysteroid Dehydrogenase 1 and Its Coupling between Liver Parenchymal Cells and Testicular Leydig Cells

Background

11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) interconverts active 11β-hydroxyl glucocorticoids and inactive 11keto forms. However, its directionality is determined by availability of NADP+/NADPH. In liver cells, 11β-HSD1 behaves as a primary reductase, while in Leydig cells it acts as a primary oxidase. However, the exact mechanism is not clear. The direction of 11β-HSD1 has been proposed to be regulated by hexose-6-phosphate dehydrogenase (H6PDH), which catalyzes glucose-6-phosphate (G6P) to generate NADPH that drives 11β-HSD1 towards reduction.

Methodology

To examine the coupling between 11β-HSD1 and H6PDH, we added G6P to rat and human liver and testis or Leydig cell microsomes, and 11β-HSD1 activity was measured by radiometry.

Results and Conclusions

G6P stimulated 11β-HSD1 reductase activity in rat (3 fold) or human liver (1.5 fold), but not at all in testis. S3483, a G6P transporter inhibitor, reversed the G6P-mediated increases of 11β-HSD1 reductase activity. We compared the extent to which 11β-HSD1 in rat Leydig and liver cells might be coupled to H6PDH. In order to clarify the location of H6PDH within the testis, we used the Leydig cell toxicant ethane dimethanesulfonate (EDS) to selectively deplete Leydig cells. The depletion of Leydig cells eliminated Hsd11b1 (encoding 11β-HSD1) expression but did not affect the expression of H6pd (encoding H6PDH) and Slc37a4 (encoding G6P transporter). H6pd mRNA level and H6PDH activity were barely detectable in purified rat Leydig cells. In conclusion, the availability of H6PDH determines the different direction of 11β-HSD1 in liver and Leydig cells.

Localisation of 11β-Hydroxysteroid Dehydrogenase Type 2 in Mineralocorticoid Receptor Expressing Magnocellular Neurosecretory Neurones of the Rat Supraoptic and Paraventricular Nuclei

An accumulating body of evidence suggests that the activity of the mineralocorticoid, aldosterone, in the brain via the mineralocorticoid receptor (MR) plays an important role in the regulation of blood pressure. MR was recently found in vasopressin and oxytocin synthesising magnocellular neurosecretory cells (MNCs) in both the paraventricular (PVN) and supraoptic (SON) nuclei in the hypothalamus. Considering the physiological effects of these hormones, MR in these neurones may be an important site mediating the action of aldosterone in blood pressure regulation within the brain. However, aldosterone activation of MR in the hypothalamus remains controversial as a result of the high binding affinity of glucocorticoids to MR at substantially higher concentrations compared to aldosterone. In aldosterone-sensitive epithelia, the enzyme 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) prevents glucocorticoids from binding to MR by converting glucocorticoids into inactive metabolites. The present study aimed to determine whether 11β-HSD2, which increases aldosterone selectivity, is expressed in MNCs. Specific 11β-HSD2 immunoreactivity was found in the cytoplasm of the MNCs in both the SON and PVN. In addition, double-fluorescence confocal microscopy demonstrated that MR-immunoreactivity and 11β-HSD2-in situ hybridised products are colocalised in MNCs. Lastly, single-cell reverse transcriptase-polymerase chain reaction detected MR and 11β-HSD2 mRNAs from cDNA libraries derived from single identified MNCs. These findings strongly suggest that MNCs in the SON and PVN are aldosterone-sensitive neurones.

11β-Hydroxysteroid dehydrogenase 1: Regeneration of active glucocorticoids is only part of the story

11β-Hydroxysteroid dehydrogenase 1 (11β-HSD1) is an endoplasmic reticulum membrane enzyme with its catalytic site facing the luminal space. It functions primarily as a reductase, driven by the supply of its cosubstrate NADPH by hexose-6-phosphate dehydrogenase (H6PDH). Extensive research has been performed on the role of 11β-HSD1 in the regeneration of active glucocorticoids and its role in inflammation and metabolic disease. Besides its important role in the fine-tuning of glucocorticoid action, 11β-HSD1 is a multi-functional carbonyl reductase converting several 11- and 7-oxosterols into the respective 7-hydroxylated forms. Moreover, 11β-HSD1 has a role in phase I biotransformation reactions and catalyzes the carbonyl reduction of several non-steroidal xenobiotics. Recent observations from experiments using selective inhibitors and studies with transgenic mice indicated a role for 11β-HSD1 in oxysterol metabolism and in bile acid homeostasis, with evidence for glucocorticoid-independent effects on gene expression. This review focuses on the promiscuity of 11β-HSD1 to accept structurally distinct substrates and discusses recent progress mainly on non-glucocorticoid substrates. This article is part of a Special Issue entitled 'Enzyme Promiscuity and Diversity'.

C21-steroids inactivation and glucocorticoid synthesis in the developing lung

Glucocorticoids (GCs) are important regulators of lung development. The genes normally involved in GC synthesis in adrenals are co-expressed with 20α-hydroxysteroid dehydrogenase (20α-HSD) in the developing lung. In this study, C21-steroid metabolism was investigated in fetal and postnatal mouse lungs. Incubation of [(3)H]-progesterone with lung explant cultures of different perinatal developmental time points revealed two different (antenatal vs. postnatal) complex metabolization patterns. Progesterone inactivation was predominant. 20αOH-derivatives were more abundant after birth and some metabolites were 5α-reduced. Using [(3)H]-progesterone as substrate, corticosterone synthesis was only observed in a fraction of lung explants from gestation day (GD) 15.5. Neither aldosterone synthase nor P450c17 activity was observed. With epithelial-enriched primary cell cultures, deoxycorticosterone synthesis from [(3)H]-progesterone was observed. With lung explants incubated with [(3)H]-corticosterone as substrate, [(3)H]-4-pregnen-21-ol-3,11,20-trione (11-dehydrocorticosterone), the product of 11β-HSD2, accumulated in higher proportion on GD 15.5 than at later developmental time points. The temporal correlation observed between levels of progesterone inactivation by 20α-HSD (higher after birth) and the sensitivity of lung development to GCs suggests a role for 20α-HSD in the modulation of GR occupancy through the control of 21-hydroxylase substrate and product levels. In conclusion, the developing lung is characterized by effective inactivation of c21-steroids by 20α-HSD. The formation of active GCs from the "adrenal"-like pathway was observed with some lung explants and primary epithelial cell cultures. Coexistence of this GC synthesis pathway with 20α-HSD activity strongly suggests local regulation of GC action and is compatible with intracrine/paracrine actions of GC.

Genistein inhibits glucocorticoid amplification in adipose tissue by suppression of 11β-hydroxysteroid dehydrogenase type 1

Excess glucocorticoids promote visceral obesity, hyperlipidemia, and insulin resistance. The main regulator of intracellular glucocorticoid levels is 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), which converts inactive glucocorticoids into bioactive forms such as cortisol in humans and corticosterone in rodents. Hexose-6-phosphate dehydrogenase (H6PD), which is colocalized with 11β-HSD1 in the intralumen of the endoplasmic reticulum, supplies a crucial coenzyme, NADPH, for full reductase activity of 11β-HSD1. Therefore, it is possible that inhibition of 11β-HSD1 will become a considerable medical treatment for metabolic diseases including obesity and diabetes. Genistein, a soy isoflavone, has received attention for its therapeutic potential for obesity, diabetes, and cardiovascular disease, and has been proposed as a promising compound for the treatment of metabolic disorders. However, the mechanisms underlying the pleiotropic anti-obesity effects of genistein have not been fully clarified. Here, we demonstrate that genistein was able to inhibit 11β-HSD1 and H6PD activities within 10 or 20min, in dose- and time-dependent manners. Inhibition of 11β-HSD2 activity was not observed in rat kidney microsomes. The inhibition was not reversed by two estrogen receptor antagonists, tamoxifen and ICI182,780. A kinetic study revealed that genistein acted as a non-competitive inhibitor of 11β-HSD1, and its apparent Km value for 11-dehydrocorticosterone was 0.5μM. Genistein also acted as a non-competitive inhibitor of H6PD, and its apparent Km values for G6P and NADP were 0.9 and 3.3μM, respectively. These results suggest that genistein may exert its inhibitory effect by interacting with these enzymes.

Cortisol in tissue and systemic level as a contributing factor to the development of metabolic syndrome in severely obese patients

CONTEXT

Adrenal and extra-adrenal cortisol production may be involved in the development of metabolic syndrome (MetS).

OBJECTIVE

To investigate the activity of the hypothalamic-pituitary-adrenal (HPA) axis and the expression of HSD11B1, nuclear receptor subfamily 3, group C, member 1 (glucocorticoid receptors) α (NR3C1α) and β (NR3C1β) in the liver, subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) of severely obese patients with and without MetS.

METHODS

The study included 37 severely obese patients (BMI ≥ 40 kg/m(2)), 19 with MetS (MetS+ group) and 18 without (MetS- group), studied before and during bariatric surgery. Before the day of surgery, urinary free cortisol (UFC) and diurnal variation of serum and salivary cortisol were estimated. During surgery, biopsies of the liver, VAT and SAT were obtained. The expression of HSD11B1, NR3C1α and NR3C1β was evaluated by RT-PCR.

RESULTS

UFC and area under the curve for 24-h profiles of serum and salivary cortisol were lower in the MetS- group. In the MetS- group, mRNA levels of HSD11B1 in liver exhibited a negative correlation with liver NR3C1α (LNR3C1α) and VAT expression of HSD11B1 was lower than the MetS+ group.

CONCLUSIONS

We observed a downregulation of the NR3C1α expression and lower VAT mRNA levels of HSD11B1 in the MetS- group, indicating a lower selective tissue cortisol production and action that could protect these patients from the metabolic consequences of obesity. In the MetS- group, a lower activity of the HPA axis was also detected. Taken together, cortisol in tissue and systematic level might play a role in the development of MetS in severely obese patients.

Brain mineralocorticoid receptors in cognition and cardiovascular homeostasis

Mineralocorticoid receptors (MR) mediate diverse functions supporting osmotic and hemodynamic homeostasis, response to injury and inflammation, and neuronal changes required for learning and memory. Inappropriate MR activation in kidneys, heart, vessels, and brain hemodynamic control centers results in cardiovascular and renal pathology and hypertension. MR binds aldosterone, cortisol and corticosterone with similar affinity, while the glucocorticoid receptor (GR) has less affinity for cortisol and corticosterone. As glucocorticoids are more abundant than aldosterone, aldosterone activates MR in cells co-expressing enzymes with 11β-hydroxydehydrogenase activity to inactivate them. MR and GR co-expressed in the same cell interact at the molecular and functional level and these functions may be complementary or opposing depending on the cell type. Thus the balance between MR and GR expression and activation is crucial for normal function. Where 11β-hydroxydehydrogenase 2 (11β-HSD2) that inactivates cortisol and corticosterone in aldosterone target cells of the kidney and nucleus tractus solitarius (NTS) is not expressed, as in most neurons, MR are activated at basal glucocorticoid concentrations, GR at stress concentrations. An exception may be pre-autonomic neurons of the PVN which express MR and 11β-HSD1 in the absence of hexose-6-phosphate dehydrogenase required to generate the requisite cofactor for reductase activity, thus it acts as a dehydrogenase. MR antagonists, valuable adjuncts to the treatment of cardiovascular disease, also inhibit MR in the brain that are crucial for memory formation and exacerbate detrimental effects of excessive GR activation on cognition and mood. 11β-HSD1 inhibitors combat metabolic and cognitive diseases related to glucocorticoid excess, but may exacerbate MR action where 11β-HSD1 acts as a dehydrogenase, while non-selective 11β-HSD1&2 inhibitors cause injurious disruption of MR hemodynamic control. MR functions in the brain are multifaceted and optimal MR:GR activity is crucial. Therefore selectively targeting down-stream effectors of MR specific actions may be a better therapeutic goal.

The multifaceted mineralocorticoid receptor

The primary adrenal cortical steroid hormones, aldosterone, and the glucocorticoids cortisol and corticosterone, act through the structurally similar mineralocorticoid (MR) and glucocorticoid receptors (GRs). Aldosterone is crucial for fluid, electrolyte, and hemodynamic homeostasis and tissue repair; the significantly more abundant glucocorticoids are indispensable for energy homeostasis, appropriate responses to stress, and limiting inflammation. Steroid receptors initiate gene transcription for proteins that effect their actions as well as rapid non-genomic effects through classical cell signaling pathways. GR and MR are expressed in many tissues types, often in the same cells, where they interact at molecular and functional levels, at times in synergy, others in opposition. Thus the appropriate balance of MR and GR activation is crucial for homeostasis. MR has the same binding affinity for aldosterone, cortisol, and corticosterone. Glucocorticoids activate MR in most tissues at basal levels and GR at stress levels. Inactivation of cortisol and corticosterone by 11β-HSD2 allows aldosterone to activate MR within aldosterone target cells and limits activation of the GR. Under most conditions, 11β-HSD1 acts as a reductase and activates cortisol/corticosterone, amplifying circulating levels. 11β-HSD1 and MR antagonists mitigate inappropriate activation of MR under conditions of oxidative stress that contributes to the pathophysiology of the cardiometabolic syndrome; however, MR antagonists decrease normal MR/GR functional interactions, a particular concern for neurons mediating cognition, memory, and affect.

Glucocorticoid receptor gene expression in adipose tissue and associated metabolic risk in black and white South African women

BACKGROUND

Black women have lower visceral adipose tissue (VAT) but are less insulin sensitive than white women; the mechanisms responsible are unknown.

OBJECTIVE

The study aimed to test the hypothesis that variation in subcutaneous adipose tissue (SAT) sensitivity to glucocorticoids might underlie these differences.

METHODS

Body fatness (dual energy X-ray absorptiometry) and distribution (computerized tomography), insulin sensitivity (SI, intravenous and oral glucose tolerance tests), and expression of 11β-hydroxysteroid dehydrogenase-1 (11HSD1), hexose-6-phosphate dehydrogenase and glucocorticoid receptor-α (GRα), as well as genes involved in adipogenesis and inflammation were measured in abdominal deep SAT, superficial SAT and gluteal SAT (GLUT) depots of 56 normal-weight or obese black and white premenopausal South African (SA) women. We used a combination of univariate and multivariate statistics to evaluate ethnic-specific patterns in adipose gene expression and related body composition and insulin sensitivity measures.

RESULTS

Although 11HSD1 activity and mRNA did not differ by ethnicity, GRα mRNA levels were significantly lower in SAT of black compared with white women, particularly in the GLUT depot (0.52±0.21 vs 0.91±0.26 AU, respectively, P<0.01). In black women, lower SAT GRα mRNA levels were associated with increased inflammatory gene transcript levels and abdominal SAT area, and reduced adipogenic gene transcript levels, VAT/SAT ratio and SI. Abdominal SAT 11HSD1 activity associated with increased VAT area and decreased SI in white, but not in black women.

CONCLUSIONS

In black SA women, downregulation of GRα mRNA levels with obesity and reduced insulin sensitivity, possibly via increased SAT inflammation, is associated with reduced VAT accumulation.

Expression of mineralocorticoid and glucocorticoid receptors in preautonomic neurons of the rat paraventricular nucleus

Activation of mineralocorticoid receptors (MR) of the hypothalamic paraventricular nucleus (PVN) increases sympathetic excitation. To determine whether MR and glucocorticoid receptors (GR) are expressed in preautonomic neurons of the PVN and how they relate to endogenous aldosterone levels in healthy rats, retrograde tracer was injected into the intermediolateral cell column at T4 to identify preautonomic neurons in the PVN. Expression of MR, GR, 11-β hydroxysteroid dehydrogenase1 and 2 (11β-HSD1, 2), and hexose-6-phosphate dehydrogenase (H6PD) required for 11β-HSD1 reductase activity was assessed by immunohistochemistry. RT-PCR and Western blot analysis were used to determine MR gene and protein expression. Most preautonomic neurons were in the caudal mediocellular region of PVN, and most expressed MR; none expressed GR. 11β-HSD1, but not 11β-HSD2 nor H6PD immunoreactivity, was detected in the PVN. In rats with chronic low or high sodium intakes, the low-sodium diet was associated with significantly higher plasma aldosterone, MR mRNA and protein expression, and c-Fos immunoreactivity within labeled preautonomic neurons. Plasma corticosterone and sodium and expression of tonicity-responsive enhancer binding protein in the PVN did not differ between groups, suggesting osmotic adaptation to the altered sodium intake. These results suggest that MR within preautonomic neurons in the PVN directly participate in the regulation of sympathetic nervous system drive, and aldosterone may be a relevant ligand for MR in preautonomic neurons of the PVN under physiological conditions. Dehydrogenase activity of 11β-HSD1 occurs in the absence of H6PD, which regenerates NADP(+) from NADPH and may increase MR gene expression under physiological conditions.

Environmental pollutants and hydroxysteroid dehydrogenases

Hydroxysteroid dehydrogenases (HSD) are a group of steroidogenic enzymes that are involved in the steroid biosynthesis and metabolism. Four classes of HSDs, namely, 3β-, 11β-, 17β-, and 20α-HSDs, are discussed. 3β-HSDs catalyze the conversion of pregnenolone, 17α-hydroxypregnenolone, and dehydroepiandrosterone to progesterone, 17α-hydroxyprogesterone, and androstenedione, respectively. 11β-HSDs catalyze the interconversion between active cortisol and inactive cortisone. 17β-HSDs catalyze the interconversion between 17β-hydroxyl steroids and 17-ketoandrogens and estrogens. 20α-HSDs catalyze the conversion of progesterone into 20α-hydroxyprogesterone. Many environmental pollutants directly inhibit one or more enzymes of these HSDs, thus interfering with endogenous active steroid hormone levels. These chemicals include industrial materials (perfluoroalkyl compounds, phthalates, bisphenol A, and benzophenone), pesticides/biocides (methoxychlor, organotins, 1,2-dibromo-3-chloropropane, and prochloraz), and plant constituents (genistein, gossypol, and licorice). This chapter reviews these inhibitors targeting on HSDs.