In this study, with in vitro and in vivo models of DN, we determined whether NAD anabolism disturbance exists, whether normalizing NAD anabolism or replenishing NAD pool can alleviate MSC injury, and how NMN, as an intermediate of NAD salvage synthesis, affects Sirt1/NF-κB P65/FN in the MSC. This evidence concerns the gene FN1 and liver dysplastic nodule.