Daidzein Promotes the Proliferation of Porcine Mammary Epithelial Cells Through the mTOR Signaling Pathway

The purpose of this study was to examine the effect of daidzein on the proliferation of porcine mammary epithelial cells (PMECs) and elucidate the underlying molecular mechanisms. PMECs were treated with varying daidzein or rapamycin levels, and then cell proliferation and mTOR pathway protein expression were detected. When the concentration of daidzein added was in the range of 0–80 μM, cell proliferation was significantly promoted (p < 0.05). These results were in agreement with those obtained using the 5-ethynyl-2′-deoxyuridine (EdU) assay. Daidzein administration at 20 and 40 μM concentrations triggered significant activation of the mTOR signaling cascade and enhanced expression of downstream cell-cycle-regulatory proteins (cyclin D1) (p < 0.05). Moreover, exposure to 40 μM daidzein attenuated apoptotic signaling, as evidenced by reduced levels of Bax protein and cleaved caspase-3 (p < 0.05). These effects were reversed when rapamycin was used to inhibit the mTOR pathway. In conclusion, our findings suggest that daidzein activates PMEC proliferation via the mTOR pathway. The present work not only characterizes new functional properties of daidzein but also establishes mechanistic evidence supporting its role in augmenting sow lactation efficiency.