Irisin deficiency disturbs bone metabolism

Area of Science:

• Bone Biology and Metabolism
• Endocrinology
• Skeletal Physiology

Background:

• Maintaining bone homeostasis requires a balance between bone formation and resorption.
• Novel factors regulating bone metabolism are crucial for preventing bone diseases.
• Irisin, a myokine, has been implicated in conditions affecting bone mineral density.

Purpose of the Study:

• To investigate the specific role of FNDC5/irisin, deleted in osteoblasts, in bone metabolism.
• To elucidate the mechanisms by which bone-derived irisin influences bone development and systemic metabolic crosstalk.
• To evaluate irisin's potential as a therapeutic target for bone metabolic disorders.

Main Methods:

• Generation of Osx-Cre:FNDC5/irisin knockout (KO) mice for targeted gene deletion in osteoblasts.
• Analysis of bone density, development, mineralization, and gene expression in KO mice.
• In vitro studies using mesenchymal stem cells (MSCs) and primary cells to assess osteogenesis and osteoclastogenesis.
• Evaluation of exercise effects and rescue by recombinant irisin administration.

Main Results:

• KO mice exhibited significantly decreased bone density, delayed bone development, and impaired mineralization.
• Osteoblastogenesis was inhibited, and osteoclastogenesis was increased in FNDC5/irisin deficient bone tissues and cultured MSCs.
• Bone-derived irisin deletion reduced adipose tissue browning, and exercise benefits on bone strength were diminished.
• Recombinant irisin administration rescued the negative effects of irisin deficiency.

Conclusions:

• Irisin plays a critical role in regulating bone metabolism, promoting osteogenesis, and inhibiting osteoclastogenesis.
• Bone-derived irisin mediates crosstalk between bone and adipose tissue, influencing systemic metabolism.
• Irisin is a promising therapeutic target for treating bone metabolic diseases like osteopenia and osteoporosis.