title: Dipeptidyl peptidase IV inhibition with MK0431 improves islet graft survival in diabetic NOD mice partially via T-cell modulation.
abstract: OBJECTIVE
  The endopeptidase dipeptidyl peptidase-IV (DPP-IV) has been shown to NH2-terminally truncate incretin hormones, glucose-dependent insulinotropic polypeptide, and glucagon-like peptide-1, thus ablating their ability to potentiate glucose-stimulated insulin secretion. Increasing the circulating levels of incretins through administration of DPP-IV inhibitors has therefore been introduced as a therapeutic approach for the treatment of type 2 diabetes. DPP-IV inhibitor treatment has also been shown to preserve islet mass in rodent models of type 1 diabetes. The current study was initiated to define the effects of the DPP-IV inhibitor sitagliptin (MK0431) on transplanted islet survival in nonobese diabetic (NOD) mice, an autoimmune type 1 diabetes model.
  
  
  METHODS
  Effects of MK0431 on islet graft survival in diabetic NOD mice were determined with metabolic studies and micropositron emission tomography imaging, and its underlying molecular mechanisms were assessed.
  
  
  RESULTS
  Treatment of NOD mice with MK0431 before and after islet transplantation resulted in prolongation of islet graft survival, whereas treatment after transplantation alone resulted in small beneficial effects compared with nontreated controls. Subsequent studies demonstrated that MK0431 pretreatment resulted in decreased insulitis in diabetic NOD mice and reduced in vitro migration of isolated splenic CD4+ T-cells. Furthermore, in vitro treatment of splenic CD4+ T-cells with DPP-IV resulted in increased migration and activation of protein kinase A (PKA) and Rac1.
  
  
  CONCLUSIONS
  Treatment with MK0431 therefore reduced the effect of autoimmunity on graft survival partially by decreasing the homing of CD4+ T-cells into pancreatic beta-cells through a pathway involving cAMP/PKA/Rac1 activation.
authors.affiliation: Department of Cellular and Physiological Sciences and the Diabetes Research Group, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Su-Jin
authors.initials: SJ
authors.lastname: Kim
authors.forename: Cuilan
authors.initials: C
authors.lastname: Nian
authors.forename: Doris J
authors.initials: DJ
authors.lastname: Doudet
authors.forename: Christopher H S
authors.initials: CH
authors.lastname: McIntosh
mesh_terms: D000818:Animals; D003922:Diabetes Mellitus, Type 1 / Q000601:surgery*; D018819:Dipeptidyl Peptidase 4 / Q000378:metabolism*; D054873:Dipeptidyl-Peptidase IV Inhibitors / Q000494:pharmacology*; D006084:Graft Rejection / Q000517:prevention & control; D006085:Graft Survival / Q000187:drug effects* / Q000276:immunology*; D016381:Islets of Langerhans Transplantation / Q000276:immunology*; D008297:Male; D051379:Mice; D016688:Mice, Inbred NOD; D011719:Pyrazines / Q000494:pharmacology*; D000068900:Sitagliptin Phosphate; D013601:T-Lymphocytes / Q000276:immunology*; D014185:Transplantation, Isogeneic / Q000502:physiology; D014230:Triazoles / Q000494:pharmacology*
chemical_list: D054873:Dipeptidyl-Peptidase IV Inhibitors; D011719:Pyrazines; D014230:Triazoles; D018819:Dipeptidyl Peptidase 4; D000068900:Sitagliptin Phosphate