Biomedical subjects

Lyubomir G Nashev

Publications and source records attributed to Lyubomir G Nashev.

6 recordsLinked to original sources

PubMed2006

Coffee inhibits the reactivation of glucocorticoids by 11beta-hydroxysteroid dehydrogenase type 1: a glucocorticoid connection in the anti-diabetic action of coffee?

Recent epidemiological studies demonstrated a beneficial effect of coffee consumption for the prevention of type 2 diabetes, however, the underlying mechanisms remained unknown. We demonstrate that coffee extract, corresponding to an Italian Espresso, inhibits recombinant and endogenous 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) activity. The inhibitory component is heat-stable with considerable polarity. Coffee extract blocked 11beta-HSD1-dependent cortisol formation, prevented the subsequent nuclear translocation of the glucocorticoid receptor and abolished glucocorticoid-induced expression of the key gluconeogenic enzyme phosphoenolpyruvate carboxykinase. We suggest that at least part of the anti-diabetic effects of coffee consumption is due to inhibition of 11beta-HSD1-dependent glucocorticoid reactivation.

11-beta-Hydroxysteroid Dehydrogenase Type 1↗

PubMed2006

The discovery of new 11beta-hydroxysteroid dehydrogenase type 1 inhibitors by common feature pharmacophore modeling and virtual screening.

11beta-Hydroxysteroid dehydrogenase (11beta-HSD) enzymes catalyze the conversion of biologically inactive 11-ketosteroids into their active 11beta-hydroxy derivatives and vice versa. Inhibition of 11beta-HSD1 has considerable therapeutic potential for glucocorticoid-associated diseases including obesity, diabetes, wound healing, and muscle atrophy. Because inhibition of related enzymes such as 11beta-HSD2 and 17beta-HSDs causes sodium retention and hypertension or interferes with sex steroid hormone metabolism, respectively, highly selective 11beta-HSD1 inhibitors are required for successful therapy. Here, we employed the software package Catalyst to develop ligand-based multifeature pharmacophore models for 11beta-HSD1 inhibitors. Virtual screening experiments and subsequent in vitro evaluation of promising hits revealed several selective inhibitors. Efficient inhibition of recombinant human 11beta-HSD1 in intact transfected cells as well as endogenous enzyme in mouse 3T3-L1 adipocytes and C2C12 myotubes was demonstrated for compound 27, which was able to block subsequent cortisol-dependent activation of glucocorticoid receptors with only minor direct effects on the receptor itself. Our results suggest that inhibitor-based pharmacophore models for 11beta-HSD1 in combination with suitable cell-based activity assays, including such for related enzymes, can be used for the identification of selective and potent inhibitors.

11-beta-Hydroxysteroid Dehydrogenase Type 1↗

PubMed2006

Why is 11beta-hydroxysteroid dehydrogenase type 1 facing the endoplasmic reticulum lumen? Physiological relevance of the membrane topology of 11beta-HSD1.

11Beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) is essential for the local activation of glucocorticoid receptors (GR). Unlike unliganded cytoplasmic GR, 11beta-HSD1 is an endoplasmic reticulum (ER)-membrane protein with lumenal orientation. Cortisone might gain direct access to 11beta-HSD1 by free diffusion across membranes, indirectly via intracellular binding proteins or, alternatively, by insertion into membranes. Membranous cortisol, formed by 11beta-HSD1 at the ER-lumenal side, might then activate cytoplasmic GR or bind to ER-lumenal secretory proteins. Compartmentalization of 11beta-HSD1 is important for its regulation by hexose-6-phosphate dehydrogenase (H6PDH), which regenerates cofactor NADPH in the ER lumen and stimulates oxoreductase activity. ER-lumenal orientation of 11beta-HSD1 is also essential for the metabolism of the alternative substrate 7-ketocholesterol (7KC), a major cholesterol oxidation product found in atherosclerotic plaques and taken up from processed cholesterol-rich food. An 11beta-HSD1 mutant adopting cytoplasmic orientation efficiently catalyzed the oxoreduction of cortisone but not 7KC, indicating access to cortisone from both sides of the ER-membrane but to 7KC only from the lumenal side. These aspects may be relevant for understanding the physiological role of 11beta-HSD1 and for developing therapeutic interventions to control glucocorticoid reactivation.

11-beta-Hydroxysteroid Dehydrogenase Type 1↗

PubMed2005

Organotins disrupt the 11beta-hydroxysteroid dehydrogenase type 2-dependent local inactivation of glucocorticoids.

Organotins, important environmental pollutants widely used in agricultural and industrial applications, accumulate in the food chain and induce imposex in several marine species as well as neurotoxic and immunotoxic effects in higher animals. Reduced birth weight and thymus involution, observed upon exposure to organotins, can also be caused by excessive glucocorticoid levels. We now demonstrate that organotins efficiently inhibit 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2), converting active 11beta-hydroxyglucocorticoids into inactive 11-ketoglucocorticoids, but not 11beta-HSD1, which catalyzes the reverse reaction. Di- and tributyltin as well as di- and triphenyltin inhibited recombinant and endogenous 11beta-HSD2 in lysates and intact cells with IC50 values between 500 nM and 3 microM. Dithiothreitol protected 11beta-HSD2 from organotin-dependent inhibition, indicating that organotins act by binding to one or more cysteines. Mutational analysis and 3-D structural modeling revealed several important interactions of cysteines in 11beta-HSD2. Cys90, Cys228, and Cys264 were essential for enzymatic stability and catalytic activity, suggesting that disruption of such interactions by organotins leads to inhibition of 11beta-HSD2. Enhanced glucocorticoid concentrations due to disruption of 11beta-HSD2 function may contribute to the observed organotin-dependent toxicity in some glucocorticoid-sensitive tissues such as thymus and placenta.

11-beta-Hydroxysteroid Dehydrogenase Type 1↗

PubMed2004

PhenomicDB: a multi-species genotype/phenotype database for comparative phenomics.

UNLABELLED: We have created PhenomicDB, a multi-species genotype/phenotype database by merging public genotype/phenotype data from a wide range of model organisms and Homo sapiens. Until now these data were available in distinct organism-specific databases (e.g. WormBase, OMIM, FlyBase and MGI). We compiled this wealth of data into a single integrated resource by coarse-grained semantic mapping of the phenotypic data fields, by including common gene indices (NCBI Gene), and by the use of associated orthology relationships. With its use-case-oriented user interface, PhenomicDB allows scientists to compare and browse known phenotypes for a given gene or a set of genes from different organisms simultaneously. AVAILABILITY: PhenomicDB has been implemented at Schering AG as described below. A PhenomicDB implementation differing in some technical details has been set up for the public at Metalife AG http://www.phenomicDB.de SUPPLEMENTARY INFORMATION: database model, semantic mapping table.

Animals↗

PubMed2004

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

The impact of hexose-6-phosphate dehydrogenase (H6PDH) on 11beta-hydroxysteroid dehydrogenase (11beta-HSD) type 1 activity was investigated upon coexpression in HEK-293 cells. Confocal microscopy analysis indicated colocalisation of both enzymes at the lumenal side of the endoplasmic reticulum (ER) membrane. Functional analysis in intact cells revealed fivefold stimulation of 11beta-HSD1 oxoreductase activity and sixfold decrease of dehydrogenase activity upon coexpression with H6PDH, without changing kinetic parameters in cell lysates. Thus, H6PDH directly determines the reaction direction of 11beta-HSD1 in intact cells as an oxoreductase without changing intrinsic catalytic properties of 11beta-HSD1 by regenerating NADPH in the ER-lumen.

11-beta-Hydroxysteroid Dehydrogenases↗