The role of tyrosine 177 in human 11beta-hydroxysteroid dehydrogenase type 1 in substrate and inhibitor binding: an unlikely hydrogen bond donor for the substrate

Equisetin is an anti-obesity candidate through targeting 11β-HSD1

Obesity is increasingly prevalent globally, searching for therapeutic agents acting on adipose tissue is of great importance. Equisetin (EQST), a meroterpenoid isolated from a marine sponge-derived fungus, has been reported to display antibacterial and antiviral activities. Here, we revealed that EQST displayed anti-obesity effects acting on adipose tissue through inhibiting adipogenesis in vitro and attenuating HFD-induced obesity in mice, doing so without affecting food intake, blood pressure or heart rate. We demonstrated that EQST inhibited the enzyme activity of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), a therapeutic target of obesity in adipose tissue. Anti-obesity properties of EQST were all offset by applying excessive 11β-HSD1's substrates and 11β-HSD1 inhibition through knockdown in vitro or 11β-HSD1 knockout in vivo. In the 11β-HSD1 bypass model constructed by adding excess 11β-HSD1 products, EQST's anti-obesity effects disappeared. Furthermore, EQST directly bond to 11β-HSD1 protein and presented remarkable better intensity on 11β-HSD1 inhibition and better efficacy on anti-obesity than known 11β-HSD1 inhibitor. Therefore, EQST can be developed into anti-obesity candidate compound, and this study may provide more clues for developing higher effective 11β-HSD1 inhibitors.

Computational and Pharmacological Evaluation of Ferrocene-Based Acyl Ureas and Homoleptic Cadmium Carboxylate Derivatives for Anti-diabetic Potential

We investigated possible anti-diabetic effect of ferrocene-based acyl ureas: 4-ferrocenyl aniline (PFA), 1-(4-chlorobenzoyl)-3-(4-ferrocenylphenyl) urea (DPC1), 1-(3-chlorobenzoyl)-3-(4-ferrocenylphenyl) urea (DMC1), 1-(2-chlorobenzoyl)-3-(4-ferrocenylphenyl) urea (DOC1) and homoleptic cadmium carboxylates: bis (diphenylacetato) cadmium (II) (DPAA), bis (4-chlorophenylacetato) cadmium (II) (CPAA), using in silico and in vivo techniques. PFA, DPC1, DMC1, DOC1, DPAA and CPAA exhibited high binding affinities (ACE ≥ −350 Kcal/mol) against targets: aldose reductase, peroxisome proliferator-activated receptor γ, 11β-hydroxysteroid dehydrogenase-1, C-alpha glucosidase and glucokinase, while showed moderate affinities (ACE ≥ −250 Kcal/mol) against N-alpha glucosidase, dipeptidyl peptidase-IV, phosphorylated-Akt, glycogen synthase kinase-3β, fructose-1,6-bisphosphatase and phosphoenolpyruvate carboxykinase, whereas revealed lower affinities (ACE < −250 Kcal/mol) vs. alpha amylase, protein tyrosine phosphatases 1B, glycogen phosphorylase and phosphatidylinositol 3 kinase. In alloxan (300 mg/Kg)-induced diabetic mice, DPAA and DPC1 (1–10 mg/Kg) at day 1, 5, 10, 15, and 20th decreased blood glucose levels, compared to diabetic control group and improved the treated animals body weight. DPAA (10 mg/Kg) and DPC1 (5 mg/Kg) in time-dependent manner (30–120 min.) enhanced tolerance of oral glucose overload in mice. DPAA and DPCI dose-dependently at 1, 5, and 10 mg/Kg decreased glycosylated hemoglobin levels in diabetic animals, as caused by metformin. These results indicate that aforementioned derivatives of ferrocene and cadmium possess anti-diabetic potential.

Substrate binding process and mechanistic functioning of type 1 11β-hydroxysteroid dehydrogenase from enhanced sampling methods

In humans, type 1 11β-hydroxysteroid dehydrogenase (11β-HSD-1) plays a key role in the regulation of the glucocorticoids balance by converting the inactive hormone cortisone into cortisol. Numerous functional aspects of 11β-HSD-1 have been understood thanks to the availability at the Worldwide Protein Data Bank of a number of X-ray structures of the enzyme either alone or in complex with inhibitors, and to several experimental data. However at present, a complete description of the dynamic behaviour of 11β-HSD-1 upon substrate binding is missing. To this aim we firstly docked cortisone into the catalytic site of 11β-HSD-1 (both wild type and Y177A mutant), and then we used steered molecular dynamics and metadynamics to simulate its undocking. This methodology helped shedding light at molecular level on the complex relationship between the enzyme and its natural substrate. In particular, the work highlights a) the reason behind the functional dimerisation of 11β-HSD-1, b) the key role of Y177 in the cortisone binding event, c) the fine tuning of the active site degree of solvation, and d) the role of the S228-P237 loop in ligand recognition.

Inhibitors of 11β-hydroxysteroid dehydrogenase type 1 in antidiabetic therapy

Glucocorticoid action is mediated by glucocorticoid receptor (GR), which upon cortisol binding is activated and regulates the transcriptional expression of target genes and downstream physiological functions. 11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) catalyzes the conversion of inactive cortisone to active cortisol. Since cortisol is also produced through biosynthesis in the adrenal glands, the total cortisol level in a given tissue is determined by both the circulating cortisol concentration and the local 11β-HSD1 activity. 11β-HSD1 is expressed in liver, adipose, brain, and placenta. Since it contributes to the local cortisol levels in these tissues, 11β-HSD1 plays a critical role in glucocorticoid action. The metabolic symptoms caused by glucocorticoid excess in Cushing's syndrome overlap with the characteristics of the metabolic syndrome, suggesting that increased glucocorticoid activity may play a role in the etiology of the metabolic syndrome. Consistent with this notion, elevated adipose expression of 11β-HSD1 induced metabolic syndrome-like phenotypes in mice. Thus, 11β-HSD1 is a proposed therapeutic target to normalize glucocorticoid excess in a tissue-specific manner and mitigate obesity and insulin resistance. Selective inhibitors of 11β-HSD1 are under development for the treatment of type 2 diabetes and other components of the metabolic syndrome.

11beta-Hydroxysteroid dehydrogenase 1 inhibiting constituents from Eriobotrya japonica revealed by bioactivity-guided isolation and computational approaches

The inhibition of 11beta-hydroxysteroid dehydrogenase 1 (11beta-HSD1), which catalyzes the conversion of inactive 11-ketoglucocorticoids to active 11beta-hydroxyglucocorticoids, emerged as promising strategy to treat symptoms of the metabolic syndrome, including obesity and type 2 diabetes. In this study the leaves of the anti-diabetic medicinal plant loquat (Eriobotrya japonica) were phytochemically investigated following hints from a pharmacophore-based virtual screening and a bioactivity-guided approach. Determination of the 11beta-HSD1 and 11beta-HSD2 inhibitory activities in cell lysates revealed triterpenes from the ursane type as selective, low micro-molar inhibitors of 11beta-HSD1, that is, corosolic acid (1), 3-epicorosolic acid methyl ester (4), 2-alpha hydroxy-3-oxo urs-12-en-28-oic acid (6), tormentic acid methyl ester (8), and ursolic acid (9). Importantly, a mixture of loquat constituents with moderate activities displayed a pronounced additive effect. By means of molecular modeling studies and the identification of the 11beta-HSD1-inhibiting 11-keto-ursolic acid (17) and 3-acetyl-11-keto-ursolic acid (18) a structure-activity relationship was deduced for this group of pentacyclic triterpenes. The mechanism of action elucidated in the present work together with the previously determined pharmacological activities provides these natural products with an astonishing multi-targeted anti-diabetic profile.

Antidiabetic effects of 11beta-HSD1 inhibition in a mouse model of combined diabetes, dyslipidaemia and atherosclerosis

AIM

11 beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) is considered to contribute to the aetiology of the metabolic syndrome, and specific inhibitors have begun to emerge as treatments for insulin resistance and other facets of the syndrome, including atherosclerosis. Given the role of glucocorticoids and 11beta-HSD1 in the anti-inflammatory response and the involvement of inflammation in the development of atherosclerosis, 11beta-HSD1 inhibition may exacerbate atherosclerosis. Our aim was to investigate in vivo the effects of a specific 11beta-HSD1 inhibitor (2922) on atherosclerosis while assessing glucose homeostasis.

METHODS

We conducted a 12-week study administering 2922 (at three doses, 3, 10 and 100 mg/kg body weight) in Ldlr 3KO (Ldlr(-/-)Apob(100/100)Lep(ob/ob)) mice, a genetic model of obesity, insulin resistance, dyslipidaemia and atherosclerosis. Rosiglitazone and simvastatin were used to test the responsiveness of our model in both types of therapy.

RESULTS

2922 was effective in reducing 11beta-HSD1 activity in inguinal adipose tissue (>90% for 100 mg/kg) and was efficacious in improving glucose homeostasis at doses > or =10 mg/kg. Plasma insulin, blood glucose, glucose tolerance and homeostatic model assessment indices were all improved in mice treated with 2922 (100 mg/kg) compared with control animals. Despite an improvement in these parameters, no differences were observed in body weight, adipose or lean tissue masses in the 2922-treated mice. Interestingly, circulating lipids, proinflammatory cytokines and atherosclerosis were unaltered in response to 2922, although a small reduction in LDL cholesterol was detected.

CONCLUSIONS

Importantly, 11beta-HSD1 inhibition leads to improved glucose metabolism and does not result in a worsening of atherosclerotic lesion area, yet retained antidiabetic potential in the face of multiple severe metabolic aberrations. This study reinforces the potential use of 11beta-HSD1 inhibitors in patients with the metabolic syndrome without negatively impacting atherosclerosis.

Therapeutic manipulation of glucocorticoid metabolism in cardiovascular disease

The therapeutic potential for manipulation of glucocorticoid metabolism in cardiovascular disease was revolutionized by the recognition that access of glucocorticoids to their receptors is regulated in a tissue-specific manner by the isozymes of 11beta-hydroxysteroid dehydrogenase. Selective inhibitors of 11beta-hydroxysteroid dehydrogenase type 1 have been shown recently to ameliorate cardiovascular risk factors and inhibit the development of atherosclerosis. This article addresses the possibility that inhibition of 11beta-hydroxsteroid dehydrogenase type 1 activity in cells of the cardiovascular system contributes to this beneficial action. The link between glucocorticoids and cardiovascular disease is complex as glucocorticoid excess is linked with increased cardiovascular events but glucocorticoid administration can reduce atherogenesis and restenosis in animal models. There is considerable evidence that glucocorticoids can interact directly with cells of the cardiovascular system to alter their function and structure and the inflammatory response to injury. These actions may be regulated by glucocorticoid and/or mineralocorticoid receptors but are also dependent on the 11beta-hydroxysteroid dehydrogenases which may be expressed in cardiac, vascular (endothelial, smooth muscle) and inflammatory (macrophages, neutrophils) cells. The activity of 11beta-hydroxysteroid dehydrogenases in these cells is dependent upon differentiation state, the action of pro-inflammaotory cytokines and the influence of endogenous inhibitors (oxysterols, bile acids). Further investigations are required to clarify the link between glucocorticoid excess and cardiovascular events and to determine the mechanism through which glucocorticoid treatment inhibits atherosclerosis/restenosis. This will provide greater insights into the potential benefit of selective 11beta-hydroxysteroid dehydrogenase inhibitors in treatment of cardiovascular disease.

Structural basis for catalysis by onconase

Onconase (ONC) is a homolog of bovine pancreatic ribonuclease (RNase A) from the frog Rana pipiens. ONC displays antitumoral activity and is in advanced clinical trials for the treatment of cancer. Here, we report the first atomic structures of ONC-nucleic acid complexes: a T89N/E91A ONC-5'-AMP complex at 1.65 A resolution and a wild-type ONC-d(AUGA) complex at 1.90 A resolution. The latter structure and site-directed mutagenesis were used to reveal the atomic basis for substrate recognition and turnover by ONC. The residues in ONC that are proximal to the scissile phosphodiester bond (His10, Lys31, and His97) and uracil nucleobase (Thr35, Asp67, and Phe98) are conserved from RNase A and serve to generate a similar bell-shaped pH versus k(cat)/K(M) profile for RNA cleavage. Glu91 of ONC forms two hydrogen bonds with the guanine nucleobase in d(AUGA), and Thr89 is in close proximity to that nucleobase. Installing a neutral or cationic residue at position 91 or an asparagine residue at position 89 virtually eliminated the 10(2)-fold guanine:adenine preference of ONC. A variant that combined such substitutions, T89N/E91A ONC, actually preferred adenine over guanine. In contrast, installing an arginine residue at position 91 increased the guanine preference and afforded an ONC variant with the highest known k(cat)/K(M) value. These data indicate that ONC discriminates between guanine and adenine by using Coulombic interactions and a network of hydrogen bonds. The structure of the ONC-d(AUGA) complex was also used to probe other aspects of catalysis. For example, the T5R substitution, designed to create a favorable Coulombic interaction between ONC and a phosphoryl group in RNA, increased ribonucleolytic activity by twofold. No variant, however, was more toxic to human cancer cells than wild-type ONC. Together, these findings provide a cynosure for understanding catalysis of RNA cleavage in a system of high medicinal relevance.

Cofactor-specific modulation of 11beta-hydroxysteroid dehydrogenase 1 inhibitor potency

11beta-hydroxysteroid dehydrogenase 1 regulates the tissue availability of cortisol by interconverting cortisone and cortisol. It is capable of functioning as both a reductase and a dehydrogenase depending upon the surrounding milieu. In this work, we have studied the reaction mechanism of a soluble form of human 11beta-hydroxysteroid dehydrogenase 1 and its mode of inhibition by potent and selective inhibitors belonging to three different structural classes. We found that catalysis follows an ordered addition with NADP(H) binding preceding the binding of the steroid. While all three inhibitors tested bound to the steroid binding pocket, they differed in their interactions with the cofactor NADP(H). Compound A, a pyridyl amide bound more efficiently to the NADPH-bound form of 11beta-hydroxysteroid dehydrogenase 1. Compound B, an adamantyl triazole, was unaffected by NADP(H) binding and the sulfonamide, Compound C, showed preferential binding to the NADP+ -bound form of 11beta-hydroxysteroid dehydrogenase 1. These differences were found to augment significant selectivity towards inhibition of the reductase reaction versus the dehydrogenase reaction. This selectivity may translate to differences in the in vivo effects of 11beta-hydroxysteroid dehydrogenase 1 inhibitors.

High capacity homogeneous non-radioactive cortisol detection assays for human 11beta-hydroxysteroid dehydrogenase type 1

11beta-Hydroxysteroid dehydrogenase type 1 (11beta-HSD1) catalyzes the interconversion of inert glucocorticoid (cortisone) to the active glucocorticoid (cortisol) and is enriched in liver and fat tissues. Increasing evidence suggests that selective inhibition of 11beta-HSD1 may reduce the excess glucocorticoid levels that underlie the etiology of many common disorders that constitute the metabolic syndrome. Measurement of 11beta-HSD1 activity has historically involved the detection of cortisol by methods unfavorable for large-scale screening, such as high performance liquid chromatography or thin layer chromatography. Here we describe the development and validation of novel homogeneous time-resolved fluorescence resonance energy transfer (TR-FRET) and electrochemiluminescence assays for the measurement of cortisol. These non-radioactive assays were easy to perform and produced robust results with reference compound values comparable to those obtained by conventional methods. The TR-FRET assay was easily automated and was successfully employed for the high-throughput screening of a large compound library for inhibitors of purified human recombinant 11beta-HSD1.

The selectivity of tyrosine 280 of human 11β-hydroxysteroid dehydrogenase type 1 in inhibitor binding

11beta-Hydroxysteroid dehydrogenase type 1 is a homodimer where the carboxyl terminus of one subunit covers the active site of the dimer partner. Based on the crystal structure with CHAPS, the carboxyl terminal tyrosine 280 (Y280) has been postulated to interact with the substrate/inhibitor at the binding pocket of the dimer partner. However, the co-crystal structure with carbenoxolone argues against this role. To clarify and reconcile these findings, here we report our mutagenesis data and demonstrate that Y280 is not involved in substrate binding but rather plays a selective role in inhibitor binding. The involvement of Y280 in inhibitor binding depends on the inhibitor chemical structure. While Y280 is not involved in the binding of carbenoxolone, it is critical for the binding of glycyrrhetinic acid.