FIS1 and diabetes mellitus: We found the expression of Fis1 was up-regulated in the diabetes model group (p < 0.01, vs. NC), indicating mitochondrial damage; following treatment with TFA or metformin, the expression of Fis1 was significantly down-regulated; we further found a significant down-regulation of NRF1 and HSP60 in the diabetes model group, indicating continuous activation of UPRmt in GECs.