Apolipoprotein AI and apolipoprotein B containing particle analysis in normolipidemic hemodialyzed patients: evidence of free apolipoprotein E.

Whole plasma from 6 normolipidemic chronic renal failure (CRF) patients undergoing hemodialysis treatment was passed through the anti-apolipoprotein (Apo) AI immunosorbent column connected to the anti-Apo B immunoaffinity column. Apo AI and B containing particles were analyzed for lipid and Apo contents. The results were compared with findings obtained in age-matched normolipidemic healthy controls. Although plasma Apo AI and AII levels decreased in CRF patients, the concentrations of Apo CII, CIII, and E coeluted with Apo AI were similar to those of the controls. The slightly elevated plasma concentrations of Apo CII and CIII in the CRF patients studied were shown to be associated with Apo B containing particles. The nonretained fraction from both groups contains no Apo AI and no Apo B, but still contains lipids and other Apo such as Apo AII and Apo CII. The occurrence of approximately 29% of plasma Apo E in this fraction constitutes the main abnormality found in these patients (< 5% in controls). A two-phase electroimmunoassay shows that this Apo E did not correspond to the plasma E-AII complex. These findings show that the compositional alterations of Apo AI and Apo B containing particles in CRF patients were observed even in normolipidemic patients and suggest that the kidney may play a metabolic role in the removal of free forms of lipoprotein particles such as free Apo E.