INS and type 1 diabetes mellitus: To assess islet morphology, we stained pancreatic islets from each treatment group (green indicates insulin; red indicates glucagon; blue indicates DAPI), and the representative images are shown in Figure 2A. We observed that treatment with 4-MU in STZ-induced T1D mice induced a significantly increased number of β cells (Figure 2B) and a significantly decreased number of α cells (Figure 2C), thereby producing an increased proportion of β cells to α cells (Figure 2D).