SLC15A1 and colitis: From the above results, the underlying mechanism of Ala-Gln in alleviating colitis of mice can be concluded as follows: (1) the transport of Ala-Gln via PepT1 into intestinal epithelial cells, (2) the decrease in IL-1β, IL-6, TNF-α, and MPO and the increase in IgA, IgG, IgM, and SOD, and (3) the normalization of microbiota and microbial metabolism (Figure 8).