Mineralocorticoid receptor function in bone metabolism and its role in glucocorticoid-induced osteopenia

Area of Science:

• Bone biology
• Endocrinology
• Pharmacology

Background:

• The mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) are present in bone cells, but MR's role in bone pathophysiology is unclear.
• Understanding MR's function is crucial for bone health, especially concerning glucocorticoid side effects.

Purpose of the Study:

• To investigate the pathophysiological role of the mineralocorticoid receptor (MR) in bone.
• To determine MR's involvement in glucocorticoid-induced bone loss.

Main Methods:

• Pharmacologic inhibition of MR using eplerenone in vivo.
• Genetic deletion of MR specifically in osteoblast lineage cells and osteocytes.
• Assessment of bone mass, bone formation, and bone resorption.
• Evaluation of effects on cortical bone thinning induced by prednisolone.

Main Results:

• Eplerenone treatment increased bone mass by stimulating bone formation and suppressing resorption.
• Genetic deletion of MR in osteoblast lineage cells did not affect bone mass.
• Both eplerenone treatment and osteocyte-specific MR deletion ameliorated prednisolone-induced cortical bone thinning.
• These findings suggest MR's involvement in the detrimental effects of excess glucocorticoids on cortical bone.

Conclusions:

• MR plays a significant role in regulating bone mass and protecting against glucocorticoid-induced bone loss, particularly in osteocytes.
• Targeting MR may offer a therapeutic strategy to mitigate bone damage caused by glucocorticoid excess.