Insulin modulates rat liver glucocorticoid receptor

Area of Science:

• Endocrinology
• Molecular Biology
• Biochemistry

Background:

• The glucocorticoid receptor (GR) plays a crucial role in cellular responses to stress and metabolism.
• Insulin (INS) is a key metabolic hormone with known interactions with other signaling pathways.
• Understanding the interplay between insulin and the glucocorticoid system is vital for metabolic research.

Purpose of the Study:

• To investigate the effects of insulin (INS) on the functional properties of the glucocorticoid receptor (GR) in rat liver cytosol.
• To elucidate how insulin influences GR-ligand complex stability, dissociation, and nuclear translocation.
• To confirm the physiological relevance by examining insulin's impact on tryptophan oxygenase (TO) activity.

Main Methods:

• Utilized cytosol fraction from male Wistar rat livers post-insulin injection.
• Assessed insulin's effects on glucocorticoid receptor (GR) complex dissociation and protein stability.
• Measured the activation and nuclear accumulation of cytosol [3H] TA-R complexes.
• Evaluated tryptophan oxygenase (TO) activity in response to insulin and cortisol (CORT) in intact and adrenalectomized rats.

Main Results:

• Insulin significantly increased INS-stimulated dissociation of GR complexes by 133%.
• INS treatment markedly enhanced GR protein stability by 138%.
• Insulin stimulated the activation of cytosol [3H] TA-R complexes by 143% and their nuclear accumulation.
• Insulin stimulated TO activity, with a diminished effect in adrenalectomized rats, indicating CORT enhances this pathway.

Conclusions:

• Insulin treatment induces modifications in GR protein and nuclear components.
• Insulin activates the rat liver cortisol (CORT) signaling pathway.
• This activated pathway partially mediates insulin's effect on tryptophan oxygenase (TO) activity.