Hypoalbuminemia increases lysophosphatidylcholine in low-density lipoprotein of normocholesterolemic subjects

Hypoalbuminemia increases lysophosphatidylcholine in low-density lipoprotein of normocholesterolemic subjects.BackgroundA phospholipid, lysophosphatidylcholine (LPC), is the major determinant of the atherosclerotic properties of oxidized low-density lipoprotein (LDL). Under normal circumstances most LPC is bound to albumin. We hypothesized that lipoprotein LPC concentrations are increased in hypoalbuminemic patients with the nephrotic syndrome, irrespective of their lipid levels. To test this hypothesis, we selected nephrotic and control subjects with matched LDL cholesterol levels.MethodsLipoproteins and the albumin-rich lipoprotein-deficient fractions were separated by ultracentrifugation and their phospholipid composition was analyzed by thin-layer chromatography.ResultsNephrotic subjects (albumin 23 ± 2 g/liter and LDL cholesterol 3.1 ± 0.2 mmol/liter) had a LDL LPC concentration that was increased (P < 0.05) to 66 ± 7 vs. 35 ± 6 μmol/liter in matched controls (albumin 42 ± 5 g/liter and LDL cholesterol 3.1 ± 0.2 mmol/liter). LPC in very low-density lipoprotein plus intermediate-density lipoprotein (VLDL + IDL) in these subjects was also increased to 33 ± 7 vs. 9 ± 2 μmol/liter in controls (P < 0.05). Conversely, LPC was decreased to 19 ± 4 μmol/liter in the albumin-containing fraction of these hypoalbuminemic patients, as compared to 46 ± 10 μmol/liter in the controls (P < 0.05). LPC was also low (14 ± 4 μmol/liter) in the albumin-containing fraction of hypoalbuminemic, hypocholesterolemic patients with nonrenal diseases. In hyperlipidemic nephrotic subjects (albumin 21 ± 2 g/liter and LDL cholesterol 5.7 ± 0.5 mmol/liter) the LPC levels in LDL and VLDL + IDL were further increased, to 95 ± 20 and 56 ± 23 μmol/liter, respectively (P < 0.05).ConclusionThese findings suggest that in the presence of hypoalbuminemia in combination with proteinuria, LPC shifts from albumin to VLDL, IDL and LDL. This effect is independent of hyperlipidemia. Increased LPC in lipoproteins may be an important factor in the disproportionate increase in cardiovascular disease in nephrotic patients with hypoalbuminemia