Oxidant stress in nephrotic syndrome: comparison of F-2-isprostanes and plasma antioxidant potential

Background. The nephrotic syndrome (NS) is associated with an increased ris k of coronary heart disease. Increased oxidant stress may contribute to thi s by means of hyperlipidaemia and/or hypoalbuminaemia. In this study we ass essed the contributory role of oxidant stress, as measured by F-2-isoprosta nes 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 F-2-isoprostan es was carried out using a combination of silica and reverse-phase cartridg es, high-performance liquid chromatography, and gas chromatography mass spe ctrometry 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 (muM) was calculat ed as the ratio of the area under the fluorescence decay curve for plasma t o the area under the fluorescence decay curve for a Trolox standard. Results. Plasma ORAC was significantly lower in NS patients compared with c ontrols: mean (standard error) NS patients 3306 muM (286); controls 4882 mu M (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 F-2-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 hypo albuminaemia, but no increase in plasma and urinary F-2-isoprostanes. Decre ased total plasma antioxidant potential in combination with hyperlipidaemia may contribute to the increased risk of cardiovascular disease seen in NS.