Liraglutide, a GLP-1 Receptor Agonist, Mitigates LPS-Induced Osteoclastogenesis and Bone Loss by Downregulating Macrophage TNF-α Expression

Liraglutide, a glucagon-like peptide-1 (GLP-1) receptor agonist, restores hyperglycemic conditions in patients with type 2 diabetes and has recently shown promising anti-inflammatory properties. In this study, we explored its potential to suppress osteoclast formation and bone loss triggered by lipopolysaccharide (LPS), an inflammatory agent. In animal models, the co-administration of liraglutide with LPS on the calvaria regions in mice markedly reduced osteoclast numbers and bone resorption areas relative to treatment with LPS alone. Furthermore, the expression levels of receptor activators of the NF-κB ligand (RANKL) and tumor necrosis factor (TNF)-α mRNA were notably lower in the group receiving liraglutide and LPS compared to treatment with LPS alone. Moreover, in vitro tests revealed that liraglutide has no direct inhibitory effect on RANKL-induced osteoclastogenesis and TNF-α-induced osteoclastogenesis. In addition, liraglutide had no direct inhibitory effect on LPS-stimulated RANKL expression in osteoblasts. Moreover, liraglutide effectively suppressed TNF-α mRNA expression in macrophages stimulated by LPS. These findings suggest that liraglutide prevents inflammatory bone destruction not by targeting osteoclast formation directly but by inhibiting the production of TNF-α within macrophages.