Abstract: Treatment of diabetes type 2 using chronic pharmacological inhibition of dipeptidyl peptidase 4 (DP4) still requires an in-depth analysis of models for chronic DP4 deficiency, because adverse reactions induced by some DP4 inhibitors have been described.: In the present study, a novel congenic rat model of DP4 deficiency on a “DP4-high” DA rat genetic background was generated (DA.F344-: Similar to chronic pharmacological inhibition of DP4, DP4 deficient rats exhibited a phenotype involving reduced diet-induced body weight gain and improved glucose tolerance associated with increased levels of glucagon-like peptide-1 (GLP-1) and bound leptin as well as decreased aminotransferases and triglycerides. Additionally, DA.F344-: While this animal model confirms a critical role of DP4 in GLP-1-dependent glucose regulation, genetically induced chronic DP4 deficiency apparently also affects stress-regulatory and immune-regulatory systems, indicating that the use of chronic DP4 inhibitors might have the potential to interfere with central nervous system and immune functions in vivo.Clin Chem Lab Med 2009;47:275–87.