Effects of vitamin C supplementation on oxidative stress and serum paraoxonase/arylesterase activities in patients on long-term hemodialysis

Abstract

Background: Oxidative stress increases oxidizability of apolipoprotein-B containing lipoproteins and decreases paraoxonase (PON) activity in hemodialysis (HD) patients and plays an important part in the development of atherosclerotic cardiovascular diseases. In HD patients, plasma ascorbic acid (AA) levels are decreased either due to the loss by hemodialysis membranes or due to malnutrition and contribute to the imbalance of antioxidant defense mechanisms. We hypothesized that long-term ascorbic acid (AA) supplementation recovers oxidizability of lipoproteins in HD patients by reinforcing PON activity. Methods: Twenty-nine adult patients were treated with 100 mg and 500 mg AA at the end of each HD session thrice a week for two consecutive 16 weeks-periods, respectively. Blood samples were obtained before the first HD session and prior to the first HD sessions following the 100 mg AA-supplemented and the 500 mg AA-supplemented periods. Results: PON activities were significantly increased after 100 mg (p < 0.05) and 500 mg AA (p < 0.001) supplementation periods compared to the basal level. Apo-B lipoprotein oxidizability (Δ-MDA) was significantly decreased after 500 mg AA supplementation compared to both basal (p < 0.05) and 100 mg AA supplementation periods (p < 0.05). Plasma AA concentrations were negatively correlated with Δ-MDA levels (R = −0.327; p < 0.01). Conclusion: Our results suggest that long-term parenteral 500 mg AA supplementation improves PON activity alleviating apo B-containing lipoproteins oxidizability in HD patients.