Objective: Albumin is one of the plasma antioxidants. The higher incidence of cardiovascular disease in dialysis patients with hypoalbuminemia may be related to decreased antioxidant capacity resulting from low serum albumin. We evaluated malondialdehyde (MDA), a marker of oxidative stress, and total antioxidant capacity (TAC) in relation to serum albumin in continuous ambulatory peritoneal dialysis (CAPD) patients.
Patients and methods: In this cross-sectional study, we measured MDA, TAC, albumin, uric acid (another important plasma antioxidant), prealbumin, and C-reactive protein (CRP) in the blood of 66 CAPD patients and 30 normal controls.Twenty-two CAPD patients with albumin less than or equal to 3.5 g/dL were divided into two groups: In the experimental group (n = 11), MDA,TAC, and CRP were measured before and after repeated infusion of 20% albumin 100 mL daily for 7 days. In the control group (n = 11), the same parameters were measured without albumin infusion.
Results: CAPD patients had lower albumin and higher MDA,TAC, and uric acid than normal controls. There were positive correlations between albumin and TAC or uric acid in CAPD patients. Contrary to our expectation, there was also positive correlation between albumin and MDA in CAPD patients (r = 0.37, p = 0.004). MDA showed a positive correlation with TAC. Uric acid was correlated with TAC. It did not, however, show correlation with MDA. Log CRP was negatively correlated with albumin, but did not show correlation with MDA or TAC. Prealbumin was correlated with MDA, TAC, albumin, and uric acid. Serum albumin in the experimental group increased from 2.5+/-0.3 g/dL to 3.6+/-0.2 g/dL (p < 0.001) at the end of repeated infusions. No changes were seen in MDA, TAC, and CRP in either group.
Conclusions: The present study suggests that lipid peroxidation is increased in CAPD patients and that this is not due to weakening of antioxidant defenses of plasma. Increased TAC was mainly caused by a higher level of uric acid. Reduced, rather than increased, MDA in hypoalbuminemic patients and lack of effects of albumin infusion on levels of MDA suggest that the frequent occurrence of cardiovascular disease in dialysis patients with hypoalbuminemia is not due to the decrease in antioxidant capacity resulting from low serum albumin.