Elevated autoantibodies against dipeptidyl peptidase-4 are associated with poor prognosis in patients with type 2...

Dipeptidyl peptidase-4 (DPP4) is involved in immune regulation and metabolic homeostasis. Although DPP4 inhibitors are widely used in type 2 diabetes, the clinical relevance of autoantibodies against DPP4 (DPP4-Ab) remains unclear. In this study, we aimed to investigate the association between circulating DPP4-Ab levels and mortality in 274 patients with type 2 diabetes (mean age, 63 years). Serum DPP4-Ab levels were measured using amplified luminescent proximity homogeneous assay-linked immunosorbent assay (AlphaLISA), and survival was assessed using Kaplan-Meier analysis and Cox proportional hazards regression analysis. During a mean follow-up of approximately 5 years, 32 deaths had occurred. Patients with elevated DPP4-Ab titers (>1,676.8 alpha counts) had a higher mortality rate than those with low titers (22.2% vs. 9.3%, p = 0.0177). In Cox proportional hazards regression analysis, DPP4-Ab titers showed a trend toward association with all-cause mortality when analyzed as a continuous variable per 100 alpha counts (a.c.) increase (hazard ratio [HR], 1.042; 95% confidence interval [CI], 0.996-1.090; p = 0.071). When patients were stratified using the predefined cutoff value of 1,676.8 a.c., the high DPP4-Ab group showed significantly higher mortality risk than the low DPP4-Ab group (HR, 2.30; 95% CI, 1.09-4.84; p = 0.028). Addition of DPP4-Ab to an age-based model only slightly improved predictive discrimination. These findings suggest that elevated DPP4-Ab titers may be associated with mortality risk; however, this association should be interpreted cautiously and warrants further investigation as a potential adjunctive immunometabolic biomarker in type 2 diabetes.