Background: Peroxidation of low-density lipoprotein (LDL) plays an important role in the development of dyslipidemias associated with the progression of chronic renal disorders. We recently reported [J Lipid Res 2001; 42: 697, 2002; 43: 1486, 2003; 44: 716] that oxidized LDL (oxLDL) interacts with an endogenous plasma protein, beta(2)-glycoprotein I (beta(2)GPI), via specific ligands. In the present study, the prevalence and clinical significance of oxLDL/beta(2)GPI complexes were evaluated in patients with chronic renal disorders. Methods: Serum levels of oxLDL/beta(2)GPI complexes were measured by ELISA in patients with chronic renal disease and their association with clinical manifestations was assessed. Results: The serum levels of oxLDL/beta(2)GPI complexes were significantly higher in patients with chronic renal failure (CRF), chronic nephritis (CN) and diabetes mellitus than those in healthy individuals. The presence of complexes in patients with CN was significantly associated with high dietary protein and sodium chloride intake, but not with lipid metabolic parameters. Malondialdehyde-modified LDL was significantly associated with total cholesterol and LDL cholesterol in all patient groups, but did not correlate with renal function parameters. Conclusions: Serum oxLDL/beta(2)GPI complexes, generated by oxidative stress and associated with high dietary protein and salt intake, might be a novel risk factor and a diagnostic marker for the development of chronic renal diseases, especially IgA nephropathy. Copyright (C) 2004 S. Karger AG, Basel.