FO041URINARY PROTEOMICS MAY UNMASK THE RENAL POTENTIAL OF THE DPP-4 INHIBITOR LINAGLIPTIN IN PATIENTS WITH DIABETIC KIDNEY DISEASE

Abstract

Introduction and Aims: Diabetic kidney disease (DKD) is a serious complication of hyperglycemia and novel treatments to preserve renal function are needed. Dipeptidyl peptidase-4 (DPP-4) inhibitors are commonly used glucose-lowering drugs in patients with type 2 diabetes (T2D). Among these, linagliptin (LINA) has previously been suggested to have renal potential independent of its effects on hyperglycemia. The aim of this study was to characterize the urinary proteomic profile (UPP) before and after treatment with LINA in T2D patients at early stages of DKD. Methods: Samples were derived from the previously reported MARLINA-T2D trial (NCT01792518). In brief, T2D patients (n=360) with prevalent albuminuria (>30 mg/g) despite stable background RAS blockade, were randomized 1:1 to receive double-blind, oral treatment with LINA 5 mg or placebo for 24 weeks. Urine samples were collected at baseline and after treatment. Capillary electrophoresis coupled with mass-spectrometry (CE-MS) platform was performed to assess UPP and a previously developed CKD273 score. Results: Urine samples were available for 88.8% of the total study population (n=320). At baseline, the CKD273 score showed a strong correlation with urinary albumin creatinine ratio (UACR, rho=0.54), and eGFR (rho=-0.41), respectively (both p<0.0001). In addition, baseline CKD273 (p=0.027) and baseline eGFR (p=0.015), but not baseline UACR, were associated with eGFR decline per year in the placebo group. Treatment with LINA was not associated with a significant overall difference in eGFR as compared to placebo at study end. However, after stratification of the study population according to low and high risk for renal disease progression (based on CKD273 score) we identified numerically less renal function loss in high risk patients with LINA (median GFR: 90.0 ml/min/1.73m2 at study end) ascompared to placebo (median GFR: 65.0 ml/min/1.73m2 at study end; p=0.06). No differences in eGFR at study end between the LINA and placebo groups were observed in the low risk group. We further compared the UPP before and after treatment with LINA (n=164). We identified 993 peptides potentially affected by LINA and sequenced 314 of those. The majority of sequenced peptides were increased after LINA. This finding was overall expected based on the protease feature of the DPP-4. Consequently, out of the 95 most altered peptides, 53 had the amino-acid proline in penultimate position. This sequence is compatible with the DPP-IV active site, known to cleave X-proline dipeptides from the N-terminus. Therefore, the UPP after LINA was enriched for peptides containing the N-terminal X-proline, and consequently peptides lacking the DPP-4 signature dipeptide were decreased. We were able to identify such pairs of peptides. Finally, we found a significant (p<0.05), negative correlation between the urinary concentration increase with reduced plasma DPP-4 activity for 20 peptides. Conclusions: This sub-study of the MARLINA-T2D trial confirms previous evidence of the CKD273 score to be associated with markers of DKD. A novel finding was that CKD273 could not only identify patients at high risk for DKD progression but may also be indicative for the potential of LINA to slow renal function loss. Furthermore, our comprehensive assessment of the UPP revealed a significant impact of LINA on urinary peptides with a pattern reflective of the specific protease fingerprint of the DPP-4 enzyme.