Correlation between proteinuria and cardiac biomarker levels in kidney transplant recipients

Kidney transplantation is the preferred treatment for end-stage kidney disease, with improved short-term outcomes; however, long-term graft and patient survival remain suboptimal. Proteinuria is a strong predictor of adverse graft and cardiovascular outcomes. We investigated the relationship between proteinuria and selected cardiac and inflammatory biomarkers, including the interleukin-33 (IL-33)/soluble ST2 (sST2) axis, malondialdehyde, neprilysin, growth differentiation factor-15 (GDF-15), and angiotensin-converting enzyme 2 (ACE2), in kidney transplant recipients, with a focus on patients with heart failure. Methods: Sixty-five transplant recipients were included: 15 kidney transplant recipients with heart failure and 49 controls consisting of kidney or heart transplant recipients without heart failure. Patients were followed between November 2023 and June 2024 at the Division of Nephrology at the University of Debrecen. Proteinuria was assessed using the urinary protein-to-creatinine ratio. Laboratory analyses included routine biochemical parameters, inflammatory markers, NT-proBNP, soluble IL-33 receptor (sST2), neprilysin, GDF-15, and ACE2 activity. Discrete data were described as percentages and analyzed with Fisher’s exact test. Group comparisons were performed using the Kruskal–Wallis test, and correlations were assessed using non-parametric methods. Across all study groups, urinary protein excretion correlated weakly positively with sST2 levels (r = 0.27, p = 0.0448). Patients with heart failure had more pronounced anemia (p = 0.0470) and lower serum iron levels (p = 0.0041). Proteinuria was weakly positively associated with circulating sST2 concentrations. Further studies are needed to clarify the prognostic significance of this pathway in kidney transplant outcomes.