Association analysis of gut microbiota-metabolites-neuroendocrine changes in male rats acute exposure to simulated altitude of 5500 m

Hyperactivation of hypothalamic-pituitary-adrenal (HPA) axis and hypothalamic-pituitary-thyroid (HPT) axis were found in acute high altitude challenge, but the role of gut microbiota and metabolites is unknown. We utilized adult male Sprague-Dawley rats at a simulated altitude of 5500 m for 3 days in a hypobaric-hypoxic chamber. ELISA and metabolomic analyses of serum and 16S rRNA and metabolomic analyses of fecal samples were then performed. Compared with the normoxic group, serum corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH), corticosterone (CORT), and thyroxine (tT₄) were increased in the hypoxia group, whereas thyrotropin-releasing hormone (TRH) was decreased. Bacteroides, Lactobacillus, Parabacteroides, Butyricimonas, SMB53, Akkermansia, Phascolarctobacterium, and Aerococcus were enriched in hypoxia group, whereas [Prevotella], Prevotella, Kaistobacter, Salinibacterium, and Vogesella were enriched in normoxic group. Metabolomic analysis indicated that acute hypoxia significantly affected fecal and serum lipid metabolism. In addition, we found five fecal metabolites may mediate the cross-talk between TRH, tT₄, and CORT with [Prevotella], Kaistobacter, Parabacteroides, and Aerococcus, and 6 serum metabolites may mediate the effect of TRH and tT₄ on [Prevotella] and Kaistobacter by causal mediation analysis. In conclusion, this study provides new evidence that key metabolites mediate the cross-talk between gut microbiota with HPA and HPT axis under acute hypobaric hypoxia challenge.

Antifungal therapy with azoles and the syndrome of acquired mineralocorticoid excess

The syndromes of mineralocorticoid excess describe a heterogeneous group of clinical manifestations leading to endocrine hypertension, typically either through direct activation of mineralocorticoid receptors or indirectly by impaired pre-receptor enzymatic regulation or through disturbed renal sodium homeostasis. The phenotypes of these disorders can be caused by inherited gene variants and somatic mutations or may be acquired upon exposures to exogenous substances. Regarding the latter, the symptoms of an acquired mineralocorticoid excess have been reported during treatment with azole antifungal drugs. The current review describes the occurrence of mineralocorticoid excess particularly during the therapy with posaconazole and itraconazole, addresses the underlying mechanisms as well as inter- and intra-individual differences, and proposes a therapeutic drug monitoring strategy for these two azole antifungals. Moreover, other therapeutically used azole antifungals and ongoing efforts to avoid adverse mineralocorticoid effects of azole compounds are shortly discussed.

Medicinal Use of Testosterone and Related Steroids Revisited

Testosterone derivatives and related compounds (such as anabolic-androgenic steroids—AAS) are frequently misused by athletes (both professional and amateur) wishing to promote muscle development and strength or to cover AAS misuse. Even though these agents are vastly regarded as abusive material, they have important pharmacological activities that cannot be easily replaced by other drugs and have therapeutic potential in a range of conditions (e.g., wasting syndromes, severe burns, muscle and bone injuries, anemia, hereditary angioedema). Testosterone and related steroids have been in some countries treated as controlled substances, which may affect the availability of these agents for patients who need them for therapeutic reasons in a given country. Although these agents are currently regarded as rather older generation drugs and their use may lead to serious side-effects, they still have medicinal value as androgenic, anabolic, and even anti-androgenic agents. This review summarizes and revisits the medicinal use of compounds based on the structure and biological activity of testosterone, with examples of specific compounds. Additionally, some of the newer androgenic-anabolic compounds are discussed such as selective androgen receptor modulators, the efficacy/adverse-effect profiles of which have not been sufficiently established and which may pose a greater risk than conventional androgenic-anabolic agents.

Species-specific differences in the inhibition of 11β-hydroxysteroid dehydrogenase 2 by itraconazole and posaconazole

11β-hydroxysteroid dehydrogenase 2 (11β-HSD2) converts active 11β-hydroxyglucocorticoids to their inactive 11-keto forms, thereby preventing inappropriate mineralocorticoid receptor activation by glucocorticoids. Disruption of 11β-HSD2 activity by genetic defects or inhibitors causes the syndrome of apparent mineralocorticoid excess (AME), characterized by hypokalemia, hypernatremia and hypertension. Recently, the azole antifungals itraconazole and posaconazole were identified to potently inhibit human 11β-HSD2, and several case studies described patients with acquired AME. To begin to understand why this adverse drug effect was missed during preclinical investigations, the inhibitory potential of itraconazole, its main metabolite hydroxyitraconazole (OHI) and posaconazole against 11β-HSD2 from human and three commonly used experimental animals was assessed. Whilst human 11β-HSD2 was potently inhibited by all three compounds (IC₅₀ values in the nanomolar range), the rat enzyme was moderately inhibited (1.5- to 6-fold higher IC₅₀ values compared to human), and mouse and zebrafish 11β-HSD2 were very weakly inhibited (IC₅₀ values above 7 μM). Sequence alignment and application of newly generated homology models for human and mouse 11β-HSD2 revealed significant differences in the C-terminal region and the substrate binding pocket. Exchange of the C-terminus and substitution of residues Leu170,Ile172 in mouse 11β-HSD2 by the corresponding residues His170,Glu172 of the human enzyme resulted in a gain of sensitivity to itraconazole and posaconazole, resembling human 11β-HSD2. The results provide an explanation for the observed species-specific 11β-HSD2 inhibition by the studied azole antifungals. The obtained structure-activity relationship information should facilitate future assessments of 11β-HSD2 inhibitors and aid choosing adequate animal models for efficacy and safety studies.

Drug-induced endocrine blood pressure elevation

Patients with uncontrolled hypertension are at risk for cardiovascular complications. The majority of them suffers from unidentified forms of hypertension and a fraction has so-called secondary hypertension with an identifiable cause. The patient's medications, its use of certain herbal supplements and over-the-counter agents represent potential causal factors for secondary hypertension that are often overlooked. The current review focuses on drugs that are likely to elevate blood pressure by affecting the human endocrine system at the level of steroid synthesis or metabolism, mineralocorticoid receptor activity, or by affecting the catecholaminergic system. Drugs with known adverse effects but where benefits outweigh their risks, drug candidates and market withdrawals are reviewed. Finally, potential therapeutic strategies are discussed.

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.

Adverse health effects of androgen use

Anabolic androgenic steroids (AAS) are performance enhancing drugs commonly used by athletes and bodybuilders to improve appearance and athletic capability. Unfortunately, these testosterone derivatives can be associated with serious and potentially irreversible side effects, and can impact multiple organ systems. It is important that physicians be familiar with these adverse consequences so that they can appropriately counsel patients whom they suspect of AAS-abuse. In this chapter, we will review the negative effects of these compounds on various organ systems in men using AAS.

Recent advances in the study of 11β-Hydroxysteroid dehydrogenase type 2 (11β-HSD2)Inhibitors

11β-Hydroxysteroid dehydrogenase (11β-HSD), which interconverts hormonally active cortisol and inactive cortisone in multiple human tissues, has two distinct isoforms named 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) and 11β-hydroxysteroid dehydrogenase 2 (11β-HSD2). 11β-HSD2 is an NAD⁺-dependent oxidase which lowers cortisol by converting it to cortisone while 11β-HSD1 mainly catalyzes the reduction which converts cortisone into cortisol. Selective inhibition of 11β-HSD2 is generally detrimental to health because the accumulation of cortisol can cause metabolic symptoms such as apparent mineralocorticoid excess (AME), fetal developmental defects and lower testosterone levels in males. There has been some advances on the study of 11β-HSD2 inhibitors and we think it necessary to make a summary of the characteristics and inhibiting properties of latest 11β-HSD2 inhibitors. As another review on 11β-HSD2 inhibitors has been issued on 2011 (see review (Ma et al., 2011)), this mini-review concerns advances during the last 5 years.

Inhibition of 11β-hydroxysteroid dehydrogenase 2 by the fungicides itraconazole and posaconazole

Impaired 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2)-dependent cortisol inactivation can lead to electrolyte dysbalance, hypertension and cardiometabolic disease. Furthermore, placental 11β-HSD2 essentially protects the fetus from high maternal glucocorticoid levels, and its impaired function has been associated with altered fetal growth and a higher risk for cardio-metabolic diseases in later life. Despite its important role, 11β-HSD2 is not included in current off-target screening approaches. To identify potential 11β-HSD inhibitors among approved drugs, a pharmacophore model was used for virtual screening, followed by biological assessment of selected hits. This led to the identification of several azole fungicides as 11β-HSD inhibitors, showing a significant structure-activity relationship between azole scaffold size, 11β-HSD enzyme selectivity and inhibitory potency. A hydrophobic linker connecting the azole ring to the other, more polar end of the molecule was observed to be favorable for 11β-HSD2 inhibition and selectivity over 11β-HSD1. The most potent 11β-HSD2 inhibition, using cell lysates expressing recombinant human 11β-HSD2, was obtained for itraconazole (IC₅₀ 139±14nM), its active metabolite hydroxyitraconazole (IC₅₀ 223±31nM) and posaconazole (IC₅₀ 460±98nM). Interestingly, experiments with mouse and rat kidney homogenates showed considerably lower inhibitory activity of these compounds towards 11β-HSD2, indicating important species-specific differences. Thus, 11β-HSD2 inhibition by these compounds is likely to be overlooked in preclinical rodent studies. Inhibition of placental 11β-HSD2 by these compounds, in addition to the known inhibition of cytochrome P450 enzymes and P-glycoprotein efflux transport, might contribute to elevated local cortisol levels, thereby affecting fetal programming.

Synthetic androgens as designer supplements

Anabolic androgenic steroids (AAS) are some of the most common performance enhancing drugs (PED) among society. Despite the broad spectrum of adverse effects and legal consequences, AAS are illicitly marketed and distributed in many countries. To circumvent existing laws, the chemical structure of AAS is modified and these designer steroids are sold as nutritional supplements mainly over the Internet. Several side effects are linked with AAS abuse. Only little is known about the pharmacological effects and metabolism of unapproved steroids due to the absence of clinical studies. The large number of designer steroid findings in dietary supplements and the detection of new compounds combined with legal loopholes for their distribution in many countries show that stricter regulations and better information policy are needed.

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'.

Evidence for glucocorticoid-mediated hypertension after uninephrectomy

Recently, evidence was presented that uninephrectomy induces salt-sensitive hypertension in rats. The increase in blood pressure was abrogated by a mineralocorticoid receptor antagonist but not by an aldosterone synthase inhibitor. Here, we hypothesize that mineralocorticoid receptor activation occurred by an 11beta-hydroxy-glucocorticosteroid, as a consequence of dysregulated 11beta-hydroxysteroid dehydrogenase enzymes. Therefore, 3-week-old Sprague-Dawley rats were either uninephrectomized or sham operated and given a normal (0.4%) or high (8%)-salt diet. At week 8, a telemetric device was implanted, and during week 13 blood pressure continuously measured and urine was collected. The animals were sacrificed thereafter and liver and kidney were harvested. Steroid metabolites were analyzed by GC-MS and mRNA assessed by PCR. Uninephrectomy caused a distinct salt-sensitive hypertension. The increase in blood pressure correlated significantly with a decline in the apparent activity of 11beta-hydroxysteroid dehydrogenase 2 and an increase of 11beta-hydroxysteroid dehydrogenase 1, when urinary corticosterone metabolites were considered. These results were mirrored by the corresponding metabolite ratios assessed in renal and liver tissue. Changes in enzyme activities were in part explained by changes in the mRNA content. In conclusion, mineralocorticoid receptor-dependent salt sensitivity after UNX in rats appears to be mediated by glucocorticoids.

Pharmacophore Model Refinement for 11β-Hydroxysteroid Dehydrogenase Inhibitors: Search for Modulators of Intracellular Glucocorticoid Concentrations

11β-Hydroxysteroid dehydrogenases (11β-HSD) control the intracellular concentrations of glucocorticoids: 11β-HSD1 converts the inactive cortisone to the active cortisol, and 11β-HSD2 is responsible for the opposite reaction. Inhibition of 11β-HSD1 is beneficial in the treatment of metabolic syndrome, whereas 11β-HSD2 inhibition leads to hypertension. Therefore, 11β-HSD1 inhibitors should be selective over 11β-HSD2. To support drug discovery and toxicological studies, we have previously reported pharmacophore models for 11β-HSD1 and 2 inhibition. These models represent the common chemical features of 11β-HSD inhibitors, which were used as virtual screening filter. Since new inhibitors are constantly discovered, the quality of the pharmacophore models has to be evaluated in order to maintain a good predictive power. In this study, we report a systematic evaluation and refinement of our pharmacophore model collection. We employed our models for virtual screening, especially focusing on the 11β-HSD2 inhibition. In total, 42 compounds were biologically evaluated and among these we discovered 17 11β-HSD inhibitors that decreased the residual enzyme activity to 50% or less at the concentration of 20 µM. The experimental 11β-HSD1 and 2 readouts from these compounds were used for further model refinement. Evaluation metrics were applied for a quantitative comparison of the old and newly generated models which resulted in a set of improved pharmacophore models offering reliable in silico tools for the identification of novel and selective 11β-HSD inhibitors.

Species-specific differences in the inhibition of human and zebrafish 11β-hydroxysteroid dehydrogenase 2 by thiram and organotins

Dithiocarbamates and organotins can inhibit enzymes by interacting with functionally essential sulfhydryl groups. Both classes of chemicals were shown to inhibit human 11β-hydroxysteroid dehydrogenase 2 (11β-HSD2), which converts active cortisol into inactive cortisone and has a role in renal and intestinal electrolyte regulation and in the feto-placental barrier to maternal glucocorticoids. In fish, 11β-HSD2 has a dual role by inactivating glucocorticoids and generating the major androgen 11-ketotestosterone. Inhibition of this enzyme may enhance glucocorticoid and diminish androgen effects in fish. Here, we characterized 11β-HSD2 activity of the model species zebrafish. A comparison with human and mouse 11β-HSD2 revealed species-specific substrate preference. Unexpectedly, assessment of the effects of thiram and several organotins on the activity of zebrafish 11β-HSD2 showed weak inhibition by thiram and no inhibition by any of the organotins tested. Sequence comparison revealed the presence of an alanine at position 253 on zebrafish 11β-HSD2, corresponding to cysteine-264 in the substrate-binding pocket of the human enzyme. Substitution of alanine-253 by cysteine resulted in a more than 10-fold increased sensitivity of zebrafish 11β-HSD2 to thiram. Mutating cysteine-264 on human 11β-HSD2 to serine resulted in 100-fold lower inhibitory activity. Our results demonstrate significant species differences in the sensitivity of human and zebrafish 11β-HSD2 to inhibition by thiram and organotins. Site-directed mutagenesis revealed a key role of cysteine-264 in the substrate-binding pocket of human 11β-HSD2 for sensitivity to sulfhydryl modifying agents.