DPP4 and colitis: These discrepancies between anti-inflammatory and pro-inflammatory effects of VIP on chemically induced colitis models may reflect the differences between endogenous and exogenous effects of VIP due to dose effects and peptide stability in the tissues and circulation because VIP is rapidly degraded by dipeptidyl peptidase 4 (DPP4), similar to the incretins106, and by other peptidases.