Hence, in addition to DSS, we also used IFN-γ or LPS to mimic the environment of colitis in Caco2 cells respectively (Araki et al., 2006; Cao et al., 2013; Satyam et al., 2017), and we found that metformin could up-regulate the decreased expression of tight junction proteins upon these three stimulations (Figure 6). Here, IFNG is linked to colitis.