Colonic inflammation induces changes in glucose levels through modulation of incretin system.

The role of the incretin hormone, glucagon-like peptide (GLP-1), in Crohn's disease (CD), is still poorly understood. The aim of this study was to investigate whether colitis is associated with changes in blood glucose levels and the possible involvement of the incretin system as an underlaying factor. We used a murine model of colitis induced by 2,4,6-trinitrobenzenesulfonic acid (TNBS). Macroscopic and microscopic score and expression of inflammatory cytokines were measured. The effect of colitis on glucose level was studied by measurement of fasting glucose and GLP-1, dipeptidyl peptidase IV (DPP IV) levels, prohormone convertase 1/3 (PC 1/3) and GLP-1 receptor (GLP-1R) expression in mice. We also measured the level of GLP-1, DPP IV and expression of glucagon (GCG) and PC 1/3 mRNA in serum and colon samples from healthy controls and CD patients. Fasting glucose levels were increased in animals with colitis compared to controls. GLP-1 was decreased in both serum and colon of mice with colitis in comparison to the control group. DPP IV levels were significantly increased in serum, but not in the colon of mice with colitis as compared to healthy animals. Furthermore, PC 1/3 and GLP-1R expression levels were increased in mice with colitis as compared to controls. In humans, no differences were observed in fasting glucose level between healthy subjects and CD patients. GLP-1 levels were significantly decreased in the serum. Interestingly, GLP-1 level was significantly increased in colon samples of CD patients compared to healthy subjects. No significant differences in DPP IV levels in serum and colon samples were observed between groups. Changes in the incretin system during colitis seem to contribute to the impaired glucose levels. Differences in incretin levels seem to be modulated by degrading enzyme DPP-IV and PC 1/3. Obtained results suggest that the incretin system may become a novel therapeutic approach in the treatment of CD.