DAO and type 2 diabetes mellitus: As shown in Figure 1, the activity of DAO and the content of D-LAC in the Normal group were 8.67 ± 0.57 U/L and 0.66 ± 0.07 μmol/mL, which were significantly increased to 10.80 ± 1.48 U/L and 0.78 ± 0.07 μmol/mL in the Diseased group, respectively, suggesting that the gastrointestinal barrier of the T2DM mice was impaired.