Lipoprotein Combine Index Is Associated with Multi-Compartment Oxidative Stress in Clinically Stable Peritoneal...

Background/Objectives: Background: Dyslipidaemia and oxidative stress (OS) are frequent in peritoneal dialysis (PD). The Lipoprotein Combine Index (LCI) integrates lipid parameters, but its relationship with peritoneal transport and OS is unclear. Methods: This cross-sectional study included 100 clinically stable adults on continuous ambulatory PD with preserved ultrafiltration and adequate dialysis. LCI was calculated as (total cholesterol × triglycerides × LDL-C)/HDL-C and analyzed by tertiles. Lipid peroxidation and antioxidant markers were measured in serum, erythrocytes, urine, and spent dialysate. Multivariable regression models examined associations between LCI, peritoneal solute transport, and dialysate OS markers. Results: Higher LCI was independently associated with lower peritoneal solute transport. LCI correlated inversely with the 4 h dialysate-to-plasma creatinine ratio (ρ = -0.32, p = 0.001) and remained significant after adjustment (adjusted R² = 0.224, p < 0.001). Increasing LCI was associated with higher malondialdehyde levels in serum, urine, and dialysate (all p ≤ 0.008) and impaired antioxidant defenses, including lower total peroxidase activity in erythrocytes and dialysate (both p = 0.001), reduced serum sulfhydryl groups (p = 0.011), decreased oxidative resistance of erythrocytes, and increased peroxide-induced hemolysis (both p = 0.001). In adjusted models, logLCI was independently associated with higher dialysate malondialdehyde (p < 0.001) and lower dialysate peroxidase activity (p = 0.005). Conclusions: In clinically stable PD patients, higher lipid burden assessed by LCI is independently associated with lower peritoneal solute transport and a marked increase in systemic and local OS. Our findings suggest that dyslipidaemia may contribute to early metabolic and oxidative changes even before overt peritoneal membrane dysfunction develops.