DPP-4 Inhibition Ameliorates Pancreatic β-Cell Failure and Improves Glucose Tolerance in the Mouse Model of Wolfram Syndrome

Wolfram syndrome, an autosomal recessive disorder associated with diabetes and optic atrophy, is caused by mutations in the WFS1 gene encoding wolframin, an endoplasmic reticulum membrane protein. Recent development of incretin-based drugs demonstrates promising outcomes for treatment of diabetes mellitus. The aim of this study is to evaluate whether dipeptidyl peptidase-4 inhibition is effective for treating endoplasmic reticulum stress-mediated β-dell failure and impaired glucose tolerance in WFS1-deficient mice (Wfs1－/－). Wfs1－/－ mice were orally administrated with vildagliptin (50 mg/kg), a dipeptidyl peptidase-4 inhibitor, twice a day for 4 weeks. The pancreases of these mice were subjected to morphological and biochemical analyses and their glucose tolerance was studied. Electron microscopic studies revealed that vildagliptin reduced number of β-cell containing swollen endoplasmic reticulum in Wfs1－/－ mice. Vildagliptin treatment increased pancreatic insulin content by 30% in Wfs1－/－ mice. Oral and intraperitoneal glucose tolerance tests showed improved glucose tolerance in vildagliptin-treated Wfs1－/－ mice with increased glucose responsiveness of insulin secretion as compared with vehicle-treated mutant mice. These effects by dipeptidyl peptidase-4 inhibition were partly prevented by glucagon-like peptide-1 receptor blockade. These findings provide evidence that activation of the incretin system by dipeptidyl peptidase-4 inhibition plays a protective role against β-cell failure in wolframin-deficiency. Our data suggest that diabetes in patients affected with Wolfram syndrome could be treated by incretin-based drugs. Furthermore, since WFS1 dysfunction could be involved in common forms of type 2 diabetes mellitus, our results strengthen the mechanistic rational of using this drug for the disease.