Semaglutide protects against glucocorticoid-induced osteoporosis by modulating BMSC fate via HIF-2α-AKT signaling

Metabolic bone diseases, such as osteoporosis, are characterized by an imbalance in bone remodeling, often exacerbated by factors like glucocorticoid use, leading to glucocorticoid-induced osteoporosis (GIO). A critical contributor to this imbalance is the altered lineage commitment of bone marrow mesenchymal stem cells (BMSCs), which can aberrantly differentiate into adipocytes at the expense of osteoblasts. Current therapies often target osteoclast activity or bone formation, but directly modulating BMSC fate remains a significant therapeutic gap. While glucagon-like peptide-1 (GLP-1) receptor agonists are known for their metabolic benefits, their direct role in regulating BMSC osteo-adipogenic differentiation and its implications for bone health, particularly in GIO, has been unclear, despite some evidence suggesting GLP-1 receptor expression in bone-related tissues.

Researchers investigated GLP-1's effects on BMSC fate using RNA sequencing to identify key pathways. They performed in vitro gain- and loss-of-function experiments on BMSCs to assess osteogenesis and adipogenesis. For in vivo validation, they utilized BMSC-specific Hif-2α knockout mice with glucocorticoid-induced osteoporosis, treating them with semaglutide (dose not specified in abstract). The primary endpoints included trabecular bone mass and the differentiation markers of BMSCs. Control groups included wild-type osteoporotic mice and Hif-2α-knockout osteoporotic mice, both untreated, to isolate the specific effects of semaglutide and the role of HIF-2α.

GLP-1 significantly suppressed adipogenesis and promoted osteogenesis of BMSCs in a dose-dependent manner. Transcriptomic analysis revealed that PI3K-AKT and hypoxia signaling were the major pathways regulated by GLP-1 in BMSCs. Mechanistically, GLP-1 inhibited AKT activation during adipogenesis and dynamically reshaped AKT signaling during osteogenesis. Crucially, the loss of HIF-2α largely abolished GLP-1-mediated regulation of AKT activity, indicating a direct mechanistic link. In vivo, semaglutide improved trabecular bone mass in osteoporotic mice. This bone-protective effect was markedly diminished in Hif-2α-knockout mice, underscoring the critical role of HIF-2α in mediating semaglutide's skeletal benefits. These findings establish a novel pathway: GLP-1 modulates BMSC lineage commitment by inhibiting adipogenesis and enhancing osteogenesis through HIF-2α-associated regulation of AKT signaling. This provides a mechanistic explanation for GLP-1's observed bone-protective effects.

Semaglutide significantly improved trabecular bone mass in osteoporotic mice, an effect that was markedly diminished in Hif-2α-knockout mice, highlighting the critical role of HIF-2α in GLP-1's bone-protective mechanism.