Add-On Therapy with DPP-4 Inhibitors May Improve Renal Function Decline in α-Glucosidase Inhibitor and Metformin Users: A Retrospective Observational Study

PURPOSE: We retrospectively evaluated the long-term effect of dipeptidyl peptidase (DPP)-4 inhibitors on estimated glomerular filtration rate (eGFR) slopes, and then evaluated the beneficial interaction between DPP-4 inhibitor initiation and baseline use of α-glucosidase inhibitor and/or metformin in patients with diabetic kidney disease. PATIENTS AND METHODS: Altogether, 1512 patients with type 2 diabetes were receiving DPP-4 inhibitor therapy over 1 year and were followed up for a maximum of 2 years before and after 7 years of treatment. The decline in renal function was estimated as the slope of the individual linear regression line of eGFR over 2-year follow-up. Prescription data on medications before and after DPP-4 inhibitor treatment were examined. RESULTS: The mean length of DPP-4 inhibitor treatment was 5.3 ± 2.6 years. The baseline mean eGFR slope (mL/min/1.73m(2)/year) was −2.24 ± 6.05. After DPP-4 inhibitor treatment, mean eGFR slope was significantly improved (−1.53 ± 6.36, P < 0.01) in patients with type 2 diabetes. This effect appeared more pronounced for baseline use of α-glucosidase inhibitor and/or metformin in patients with diabetic kidney disease. These non-users showed a trend towards attenuation or no effects. CONCLUSION: In the present study, patients treated with DPP-4 inhibitors had a significantly slower annual loss of kidney function. The benefit appears pronounced in α-glucosidase inhibitor and metformin users with advanced renal dysfunction. These results suggest that the beneficial effects of DPP-4 inhibitors on kidney function may have occurred in the presence of an α-glucosidase inhibitor and/or metformin.