| Abstract
| - Background. The nephrotic syndrome (NS) is associated with an increased risk of coronary heart disease. Increased oxidant stress may contribute to this by means of hyperlipidaemia and/or hypoalbuminaemia. In this study we assessed the contributory role of oxidant stress, as measured by F2-isoprostanes and plasma oxygen radical absorbance capacity (ORAC), in subjects with NS. Methods. We studied 14 subjects with NS and 17 age- and sex-matched healthy non-proteinuric controls. Measurement of plasma and urinary F2-isoprostanes was carried out using a combination of silica and reverse-phase cartridges, high-performance liquid chromatography, and gas chromatography mass spectrometry using electron-capture negative ionization. The plasma ORAC assay measured the decrease in fluorescence of phycoerythrin added to plasma in the presence of a free-radical generator. The ORAC value (μM) was calculated as the ratio of the area under the fluorescence decay curve for plasma to the area under the fluorescence decay curve for a Trolox standard. Results. Plasma ORAC was significantly lower in NS patients compared with controls: mean (standard error) NS patients 3306 μM (286); controls 4882 μM (496), P=0.011. In univariate linear regression analysis, plasma albumin was significantly positively correlated with plasma ORAC (r=0.40, P=0.03). Plasma and urinary F2-isoprostanes did not differ significantly between NS and control groups. Conclusions. This study demonstrates that in the NS there is decreased free-radical trapping capacity of plasma that is inversely correlated with hypoalbuminaemia, but no increase in plasma and urinary F2-isoprostanes. Decreased total plasma antioxidant potential in combination with hyperlipidaemia may contribute to the increased risk of cardiovascular disease seen in NS.
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