The role of the microbiota in neutralizing trypsin activity in a mouse model of Type 1 diabetes

The gastrointestinal tract contains high levels of proteases, one of the most abundant of which is trypsin, which is synthesized and secreted by pancreatic acinar cells. In addition to its primary function in digestion, proteolytic activity is also believed to play a role in mucus consistency and mucosal antigen processing. Accumulated evidence indicates that dysregulated proteolysis plays a pivotal role in the pathophysiology of several disorders centered on the colon. In our recent studies to investigate the effects of early-life gut microbiota on T1D onset in the non obese diabetic (NOD) mouse model, we observed that the perturbed early life gut microbiota may dysregulate mucosal physiology through mucin genes muc2 and muc4. Therefore, in this study, we aimed to evaluate intestinal trypsin activities in cecal contents in germ-free and conventional C57BL/6 mice, as well as in the single pulsed antibiotic (1PAT)-exposed NOD mice. Using an enzymatic approach, as expected, we found significantly higher trypsin activity in the cecum of germ-free compared with conventional mice. We also found that mice with antibiotic-perturbed microbiota had increased fecal trypsin levels at the end of the antibiotic treatment; however, the differences became reduced over time. By tracking the occurrence and development of T1D, we observed that the fecal trypsin levels in mice that developed T1D were higher than the mice that did not develop T1D. These results suggest that gut microbiota perturbation may dysregulate trypsin activity in the gut, which may have downstream effects on intestinal proteins, affecting T1D pathogenesis.