CLDN4 and infectious otitis media: The results showed that mice treated with AOM/DSS alone demonstrated significantly higher levels of fecal trypsin and chymotrypsin but a lower level of fecal β-glucuronidase, as well as exhibiting reduced occludin and increased claudin-1 and claudin-4 in muscosa and elevated serum D-Lac (Figure 2), suggesting damage to the gut barrier and increased gut permeability.