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Regulation of glucocorticoid receptor alpha and beta isoforms and type I 11beta-hydroxysteroid dehydrogenase expression in human skeletal muscle cells: a key role in the pathogenesis of insulin resistance?

Regulation of glucocorticoid receptor alpha and beta isoforms and type I 11beta-hydroxysteroid dehydrogenase expression in human skeletal muscle cells: a key role in the pathogenesis of insulin resistance?
Regulation of glucocorticoid receptor alpha and beta isoforms and type I 11beta-hydroxysteroid dehydrogenase expression in human skeletal muscle cells: a key role in the pathogenesis of insulin resistance?

Glucocorticoid excess frequently results in obesity, insulin resistance, glucose intolerance, and hypertension and may be the product of altered glucocorticoid hormone action. Tissue sensitivity to glucocorticoid is regulated by the expression of glucocorticoid receptor isoforms (GRalpha and GRbeta) and 11beta-hydroxysteroid dehydrogenase type I (11betaHSD1)-mediated intracellular synthesis of active cortisol from inactive cortisone. We have analyzed the expression of GRalpha, GRbeta, and 11betaHSD1 and their hormonal regulation in skeletal myoblasts from men (n = 14) with contrasting levels of adiposity and insulin resistance. Immunohistochemical, Northern blot, and Western blot analysis indicated abundant expression of GRalpha and 11betaHSD1 under basal conditions. The apparent K(m) and maximum velocity for the conversion of cortisone to cortisol were 440 +/- 14 nmol/L and 75 +/- 7 pmol/mg protein.h and 437 +/- 16 nmol/L and 33 +/- 6 pmol/mg protein.h (mean +/- SEM; n = 4) in the presence and absence of 20% serum. Incubation of myoblasts with increasing concentrations of glucocorticoid (50-1000 nmol/L) resulted in a dose-dependent decline in GRalpha expression and a dose-dependent increase in GRbeta expression. 11betaHSD1 activity was sensitively up-regulated by increasing concentrations of glucocorticoid (50-1000 nmol/L: P < 0.05). Abolition of these effects by the GR antagonist, RU38486, indicates that regulation of GRalpha, GRbeta, and 11betaHSD1 expression is mediated exclusively by the GRalpha ligand-binding variant. In contrast, 11betaHSD1 was down-regulated by insulin (20-100 mU/mL: P < 0.01) in the presence of 20% serum, whereas incubation with insulin under serum-free conditions resulted in a dose-dependent increase in 11betaHSD1 activity (P < 0.05). Incubation with insulin-like growth factor I resulted in a similar pattern of 11betaHSD1 activity. Although neither testosterone nor androstenedione (5-200 nmol/L) affected 11betaHSD1 activity, incubation of myoblasts with dehydroepiandrosterone (500 nmol/L) resulted in a decline in 11betaHSD1 activity (P < 0.05). These data suggest that glucocorticoid hormone action in skeletal muscle is determined principally by autoregulation of GRalpha, GRbeta, and 11betaHSD1 expression by the ligand-binding GRalpha isoform. Additionally, insulin and insulin-like growth factor I regulation of 11betaHSD1 may represent a novel mechanism that maintains insulin sensitivity in skeletal muscle tissue by diminishing glucocorticoid antagonism of insulin action.

11-beta-Hydroxysteroid Dehydrogenase Type 2, Adult, Aged, Cells, Cultured, Gene Expression Regulation/drug effects, Glucose/pharmacology, Humans, Hydrocortisone/pharmacology, Hydroxysteroid Dehydrogenases/genetics, Immunohistochemistry, Insulin/pharmacology, Insulin Resistance, Male, Middle Aged, Muscle, Skeletal/cytology, RNA, Messenger/analysis, Receptors, Glucocorticoid/genetics
0021-972X
2296-308
Whorwood, C B
25713369-da12-4c30-8d2d-b121a349f03e
Donovan, S J
cfb98bc3-2b7b-4d38-b894-93d1bc487a7e
Wood, P J
25dfb6db-7f77-4fdb-acc1-6343c6db9432
Phillips, D I
8f0a3c06-5a71-4344-8df0-d8f864e42524
Whorwood, C B
25713369-da12-4c30-8d2d-b121a349f03e
Donovan, S J
cfb98bc3-2b7b-4d38-b894-93d1bc487a7e
Wood, P J
25dfb6db-7f77-4fdb-acc1-6343c6db9432
Phillips, D I
8f0a3c06-5a71-4344-8df0-d8f864e42524

Whorwood, C B, Donovan, S J, Wood, P J and Phillips, D I (2001) Regulation of glucocorticoid receptor alpha and beta isoforms and type I 11beta-hydroxysteroid dehydrogenase expression in human skeletal muscle cells: a key role in the pathogenesis of insulin resistance? Journal of Clinical Endocrinology & Metabolism, 86 (5), 2296-308. (doi:10.1210/jcem.86.5.7503).

Record type: Article

Abstract

Glucocorticoid excess frequently results in obesity, insulin resistance, glucose intolerance, and hypertension and may be the product of altered glucocorticoid hormone action. Tissue sensitivity to glucocorticoid is regulated by the expression of glucocorticoid receptor isoforms (GRalpha and GRbeta) and 11beta-hydroxysteroid dehydrogenase type I (11betaHSD1)-mediated intracellular synthesis of active cortisol from inactive cortisone. We have analyzed the expression of GRalpha, GRbeta, and 11betaHSD1 and their hormonal regulation in skeletal myoblasts from men (n = 14) with contrasting levels of adiposity and insulin resistance. Immunohistochemical, Northern blot, and Western blot analysis indicated abundant expression of GRalpha and 11betaHSD1 under basal conditions. The apparent K(m) and maximum velocity for the conversion of cortisone to cortisol were 440 +/- 14 nmol/L and 75 +/- 7 pmol/mg protein.h and 437 +/- 16 nmol/L and 33 +/- 6 pmol/mg protein.h (mean +/- SEM; n = 4) in the presence and absence of 20% serum. Incubation of myoblasts with increasing concentrations of glucocorticoid (50-1000 nmol/L) resulted in a dose-dependent decline in GRalpha expression and a dose-dependent increase in GRbeta expression. 11betaHSD1 activity was sensitively up-regulated by increasing concentrations of glucocorticoid (50-1000 nmol/L: P < 0.05). Abolition of these effects by the GR antagonist, RU38486, indicates that regulation of GRalpha, GRbeta, and 11betaHSD1 expression is mediated exclusively by the GRalpha ligand-binding variant. In contrast, 11betaHSD1 was down-regulated by insulin (20-100 mU/mL: P < 0.01) in the presence of 20% serum, whereas incubation with insulin under serum-free conditions resulted in a dose-dependent increase in 11betaHSD1 activity (P < 0.05). Incubation with insulin-like growth factor I resulted in a similar pattern of 11betaHSD1 activity. Although neither testosterone nor androstenedione (5-200 nmol/L) affected 11betaHSD1 activity, incubation of myoblasts with dehydroepiandrosterone (500 nmol/L) resulted in a decline in 11betaHSD1 activity (P < 0.05). These data suggest that glucocorticoid hormone action in skeletal muscle is determined principally by autoregulation of GRalpha, GRbeta, and 11betaHSD1 expression by the ligand-binding GRalpha isoform. Additionally, insulin and insulin-like growth factor I regulation of 11betaHSD1 may represent a novel mechanism that maintains insulin sensitivity in skeletal muscle tissue by diminishing glucocorticoid antagonism of insulin action.

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More information

Published date: 1 May 2001
Keywords: 11-beta-Hydroxysteroid Dehydrogenase Type 2, Adult, Aged, Cells, Cultured, Gene Expression Regulation/drug effects, Glucose/pharmacology, Humans, Hydrocortisone/pharmacology, Hydroxysteroid Dehydrogenases/genetics, Immunohistochemistry, Insulin/pharmacology, Insulin Resistance, Male, Middle Aged, Muscle, Skeletal/cytology, RNA, Messenger/analysis, Receptors, Glucocorticoid/genetics

Identifiers

Local EPrints ID: 476375
URI: http://eprints.soton.ac.uk/id/eprint/476375
ISSN: 0021-972X
PURE UUID: 462426a8-27ba-4a99-902d-bb015cef1175

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Date deposited: 19 Apr 2023 16:47
Last modified: 17 Mar 2024 00:43

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Contributors

Author: C B Whorwood
Author: S J Donovan
Author: P J Wood
Author: D I Phillips

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