TY - JOUR
T1 - Glucocorticoids induce bone and muscle atrophy by tissue-specific mechanisms upstream of E3 ubiquitin ligases
AU - Sato, Amy Y.
AU - Richardson, Danielle
AU - Cregor, Meloney
AU - Davis, Hannah M.
AU - Au, Ernie D.
AU - McAndrews, Kevin
AU - Zimmers, Teresa A.
AU - Organ, Jason M.
AU - Peacock, Munro
AU - Plotkin, Lilian I.
AU - Bellido, Teresita
N1 - Publisher Copyright:
© 2017 by the Endocrine Society.
PY - 2017/3/1
Y1 - 2017/3/1
N2 - Glucocorticoid excess, either endogenous with diseases of the adrenal gland, stress, or aging or when administered for immunosuppression, induces bone and muscle loss, leading to osteopenia and sarcopenia. Muscle weakness increases the propensity for falling, which, combined with the lower bone mass, increases the fracture risk. The mechanisms underlying glucocorticoid-induced bone and muscle atrophy are not completely understood. We have demonstrated that the loss of bone and muscle mass, decreased bone formation, and reduced muscle strength, hallmarks of glucocorticoid excess, are accompanied by upregulation in both tissues in vivo of the atrophy-related genes atrogin1, MuRF1, and MUSA1. These are E3 ubiquitin ligases traditionally considered muscle-specific. Glucocorticoids also upregulated atrophy genes in cultured osteoblastic/osteocytic cells, in ex vivo bone organ cultures, and in muscle organ cultures and C2C12 myoblasts/myotubes. Furthermore, glucocorticoidsmarkedly increased the expression of components of the Notch signaling pathway inmuscle in vivo, ex vivo, and in vitro. In contrast, glucocorticoids did not increase Notch signaling in bone or bone cells. Moreover, the increased expression of atrophy-related genes in muscle, but not in bone, and the decreasedmyotube diameter induced by glucocorticoids were prevented by inhibiting Notch signaling. Thus, glucocorticoids activate different mechanisms in bone and muscle that upregulate atrophy-related genes. However, the role of these genes in the effects of glucocorticoids in bone is unknown. Nevertheless, these findings advance our knowledge of the mechanism of action of glucocorticoids in the musculoskeletal system and provide the basis for novel therapies to prevent glucocorticoid-induced atrophy of bone and muscle.
AB - Glucocorticoid excess, either endogenous with diseases of the adrenal gland, stress, or aging or when administered for immunosuppression, induces bone and muscle loss, leading to osteopenia and sarcopenia. Muscle weakness increases the propensity for falling, which, combined with the lower bone mass, increases the fracture risk. The mechanisms underlying glucocorticoid-induced bone and muscle atrophy are not completely understood. We have demonstrated that the loss of bone and muscle mass, decreased bone formation, and reduced muscle strength, hallmarks of glucocorticoid excess, are accompanied by upregulation in both tissues in vivo of the atrophy-related genes atrogin1, MuRF1, and MUSA1. These are E3 ubiquitin ligases traditionally considered muscle-specific. Glucocorticoids also upregulated atrophy genes in cultured osteoblastic/osteocytic cells, in ex vivo bone organ cultures, and in muscle organ cultures and C2C12 myoblasts/myotubes. Furthermore, glucocorticoidsmarkedly increased the expression of components of the Notch signaling pathway inmuscle in vivo, ex vivo, and in vitro. In contrast, glucocorticoids did not increase Notch signaling in bone or bone cells. Moreover, the increased expression of atrophy-related genes in muscle, but not in bone, and the decreasedmyotube diameter induced by glucocorticoids were prevented by inhibiting Notch signaling. Thus, glucocorticoids activate different mechanisms in bone and muscle that upregulate atrophy-related genes. However, the role of these genes in the effects of glucocorticoids in bone is unknown. Nevertheless, these findings advance our knowledge of the mechanism of action of glucocorticoids in the musculoskeletal system and provide the basis for novel therapies to prevent glucocorticoid-induced atrophy of bone and muscle.
UR - http://www.scopus.com/inward/record.url?scp=85014430317&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85014430317&partnerID=8YFLogxK
U2 - 10.1210/en.2016-1779
DO - 10.1210/en.2016-1779
M3 - Article
C2 - 28359087
AN - SCOPUS:85014430317
SN - 0013-7227
VL - 158
SP - 664
EP - 677
JO - Endocrinology
JF - Endocrinology
IS - 3
ER -