Abstract: Objective  To explore the influence of insulin receptor substrate 1(IRS-1)/transcriptional coactivator with PDZ-binding motif(TAZ) signaling on the adipogenic differentiation of bone marrow derived mesenchymal stem cells(BMSCs). 
Methods  In vivo, the adipocyte count of rat femurs in control group, sham group and ovariectomy(OVX) group was analyzed by hematoxylin and eosin(HE) staining and immunofluorescence assay, and the IRS-1 concentration in rat femurs was tested by enzyme-linked immunosorbent assay(ELISA). In vitro, the plasmid transfection was used to change the IRS-1 and TAZ expression in BMSCs, the oil red O staining and western blot was used to analyze the lipid droplets and the expression of the adipogenic differentiation related proteins. 
Results  The adipocyte count and the IRS-1 concentration in rat femurs in OVX group was significantly reduced. High expression of IRS-1 in BMSCs increased the expression of TAZ protein, and decreased the expression of CCAAT/enhancer binding protein β(C/EBPβ) and peroxisome proliferator activated receptor γ(PPARγ) proteins, which inhibited the adipogenic differentiation of BMSCs. Knockout of IRS-1 or TAZ promoted the adipogenic differentiation of BMSCs. 
Conclusion  IRS-1 increased the TAZ expression, which inhibited the adipogenic differentiation of BMSCs. IRS-1/TAZ signaling in stem cells might be a new target to control the bone marrow lipogenesis of osteoporosis patients.

Key words: osteoporosis, bone marrow derived mesenchymal stem cell, insulin receptor substrate 1