BACKGROUND:Irisin,a myokine isolated from the transmembrane protein FNDC5 by muscle cells during exercise,has the function of inducing the browning of white adipose tissue,but its effect on lipotoxicity-induced osteogenic differentiation and the mechanism is unclear. OBJECTIVE:To investigate the effect of irisin on the osteogenic ability of palmitic acid-induced bone marrow mesenchymal stem cells and the mechanism of action. METHODS:CCK-8 assay was used to detect the effect of different concentrations of palmitic acid on the proliferation of mouse bone marrow mesenchymal stem cells and the effect of irisin on the proliferation of mouse bone marrow mesenchymal stem cells in the presence of palmitic acid.After pretreatment with irisin and palmitic acid for 24 hours,osteogenic differentiation of mouse bone marrow mesenchymal stem cells was induced by alkaline phosphatase staining as well as qRT-PCR was performed to detect the expression of osteogenesis-related genes on day 7 of osteogenic induction culture.The expression of proteins related to the AMPK/BMP2/SMAD signaling pathway was detected by western blot assay.Alizarin red staining was conducted on day 21 to detect osteogenic differences. RESULTS AND CONCLUSION:(1)The CCK-8 assay results suggested that the amplification of bone marrow mesenchymal stem cells was inversely proportional to the concentration of palmitic acid,but at 0.02 mmol/L concentration,palmitic acid had no significant effect on the amplification of bone marrow mesenchymal stem cells,and irisin did not affect the proliferation of bone marrow mesenchymal stem cells when its mass concentration was in the range of 0.1-20 μg/L.(2)Alkaline phosphatase staining and alizarin red staining showed that palmitic acid inhibited the osteogenic differentiation ability of bone marrow mesenchymal stem cells.Irisin improved palmitic acid-induced osteogenic inhibition of bone marrow mesenchymal stem cells.qRT-PCR results showed that palmitic acid could cause the downregulation of osteogenic-related genes,and irisin could inhibit this trend.(3)Western blot assay results showed that compared with the palmitic acid intervention group,irisin treatment enhanced AMPK/BMP2/SMAD signal transduction in bone marrow mesenchymal stem cells.It is found that irisin can improve the osteogenic differentiation ability of bone marrow mesenchymal stem cells pretreated with palmitic acid,and proposed that the specific mechanism might be mediated by AMPK/BMP/SMAD signaling pathway.