Renoprotective Effect of a Dipeptidyl Peptidase-4 Inhibitor on Aging Mice

Dipeptidyl peptidase 4 (DPP-4) inhibitors exert pleiotropic effects beyond glycemic control. We investigated the renoprotective effects of DPP-4 inhibitors on aging mice mediated by the renin-angiotensin system (RAS). C57BL/6 mice were divided into three groups: the two-month-old mice (YM group), the eighteen-month-old mice (AM group) and the eighteen-month-old, linagliptin-treated mice (AM + LIN group). Renal function was improved, based on serum creatinine and cystatin-C levels (p < 0.05 compared with the AM group for both parameters). Fibrotic areas and the levels of proteins related to fibrosis improved in the AM + LIN group (p < 0.001 compared with the AM group for all parameters). In the AM + LIN group, the DPP-4-positive area and activity and expressions of DPP-4 were decreased (p < 0.05 compared with the AM group for all parameters). The levels of proteins related to the RAS, including prorenin receptor, angiotensin-converting enzyme, angiotensin II and angiotensin 1 receptor, were decreased in the AM + LIN group (p < 0.05, p < 0.01, p < 0.05, and p < 0.01 compared with the AM group, respectively). NADPH oxidase 2 and NADPH oxidase 4 levels decreased in the AM + LIN group (p < 0.001 compared with the AM group for both proteins), whereas the levels of endothelial nitric oxide synthase (eNOS) phosphorylated at serine(1177) and superoxide dismutase 1 were increased (p < 0.01 compared with the AM group for both proteins). DPP-4 inhibitors may exert renoprotective effects via prorenin receptor/angiotensin-converting enzyme/angiotensin II/angiotensin 1 receptor axis.