Plasma remnant-like particle lipid and apolipoprotein levels in normolipidemic and hyperlipidemic subjects

Abstract

Remnant-like particle (RLP) lipid and apolipoprotein (apo) levels were determined in the plasma of normolipidemic and hyperlipidemic subjects, in order to investigate the relationship between RLP levels and the concentration of other plasma lipoprotein parameters. Plasma RLP fractions were isolated with the use of an immunoaffinity gel (RLP-Cholesterol Jimro II, Japan Immunoresearch Lab.), containing specific anti-apoB-100 and anti-apoA-I antibodies. Four groups of human subjects were selected, who had either matching or significantly different levels of plasma triglyceride (TG) and low-density lipoprotein cholesterol (LDL-C): (1) normolipidemic control (NC) subjects (n = 10), (2) patients with elevated levels of LDL-C (type IIa, LDL-C (mean +/- S.E.), 4.65 +/- 0.09 mmol/l, n = 10), (3) hypertriglyceridemic (HTG) patients with elevated LDL-C (type IIb, TG: 3.86 +/- 0.36; LDL-C: 4.67 +/- 0.21 mmol/l, n = 10), and (4) HTG patients with normal LDL-C (type IV, TG: 3.71 +/- 0.39 mmol/l, n = 10). NC subjects (RLP-C: 0.22 +/- 0.01; RLP-TG: 0.24 +/- 0.03 mmol/l) had RLP apoB, apoC-III and apoE levels of 3.2 +/- 0.3, 1.8 +/- 0.3, and 1.4 +/- 0.1 mg/dl, representing 3.2 +/- 0.4, 14.5 +/- 1.4 and 32.1 +/- 2.1% of total plasma levels, respectively. RLP lipid and apolipoprotein concentrations were significantly higher in HTG groups (type IIb and IV) compared to NTG groups (NC and type IIa) (e.g. RLP-C: 0.50 +/- 0.07 and 0.58 +/- 0.11 vs. 0.22 +/- 0.01 and 0.21 +/- 0.01 mmol/l, respectively (P < 0.01); RLP apoB: 8.4 +/- 1.6 and 8.2 +/- 0.9 vs. 3.2 +/- 0.3 and 3.4 +/- 0.2 mg/dl, respectively (P < 0.01)). No significant difference in RLP levels was observed between groups having different LDL levels, and thus no correlation existed between RLP-C and LDL-C levels (r = 0.24, n.s.). RLP-C and RLP apoB levels were, however, correlated with VLDL-C and VLDL apoB (r = 0.86, P < 0.001 and r = 0.70, P < 0.001, respectively). These results demonstrate that elevated levels of both RLP lipids and apolipoproteins are characteristic of patients with increased levels of plasma triglyceride, and not patients with increased levels of LDL.