Liraglutide regulates proliferation, differentiation, and apoptosis of preosteoblasts through a signaling network of Notch/Wnt/Hedgehog signaling pathways

OBJECTIVE: This study aims to investigate whether liraglutide can affect proliferation, osteogenic differentiation and serum deprivation-induced apoptosis of preosteoblast cell line MC3T3-E1 through the Notch, Wnt/beta-catenin, and Hedgehog (Hh) signaling pathways. MATERIALS AND METHODS: MC3T3-E1 cells were exposed to different treatments (via Notch inhibitor DAPT, an Hh inhibitor cyclopamine. or serum deprivation) or transfections of different siRNAs (targeting glucagon-like peptide-1 receptor (GLP-1R), beta-catenin, or Gli1) in the presence or absence of 100 nM liraglutide. Cell proliferation. mRNA levels of osteogenic differentiation-related genes. mRNA and protein levels of the Notch and Hh signaling pathway proteins, and apoptosis-related proteins were assessed. RESULTS: Liraglutide significantly increased proliferation of MC3T3-E1 cells, expression levels of the Notch and Hh signaling pathway proteins and beta-catenin, and mRNA levels of osteogenic differentiation-related genes and TC-F7L2. Moreover. liraglutide promoted a translocation of beta-catenin. increased a ratio of Bcl-2/Bax proteins, reduced serum deprivation-induced apoptosis of MC3T3-E1 cells, and a ratio of caspase-3/procaspase-3. However, a cotreatment with liraglutide and DAPT reversed the alterations. A cyclopamine treatment and knockdowns of GLP-1R. Gli1, and p-catenin significantly reduced the expression of Notch proteins. Furthermore, the knockdown of GLP-1R. beta-catenin, or Gli1 significantly increased apoptosis, which could be inhibited by liraglutide. CONCLUSIONS: In summary, liraglutide can promote proliferation and differentiation of MC3T3-E1 cells, and inhibit their serum deprivation-induced apoptosis by activating both the Notch and Hh signaling pathways involving beta-catenin and Gli1. These results provide a therapeutic foundation that patients with diabetes and osteoporosis may be cured with treatments of liraglutide.