Background: A convenient method for the measurement of sialic acid in plasma apoB-containing lipoproteins is described.
Methods: Dextran sulphate-Mg2+ precipitation and enzymatic sialic acid assay were combined and applied to analysis of plasma from 96 healthy controls and 136 hyperlipidaemic subjects of types IIa (n=46), IIb (n=43), and IV (n=47).
Results: The sialic acid concentrations (mean±SD) in plasma apoB-containing lipoproteins were 19.4±5.9, 24.3±4.7 (P<0.0001 versus normal), 23.0±4.7 (P<0.0001), 27.9±5.2 (P<0.0001), and 22.3±3.4 mg/L (P<0.002), for normal, all types of hyperlipidaemia, types IIa, IIb, and IV, respectively. The contents of sialic acid in apoB were 2.03±0.41%, 2.09±0.35% (no significance versus normal), 1.86±0.27% (P<0.0001), 1.97±0.26% (P<0.02), and 2.28±0.41% (P<0.002), for normal, all types of hyperlipidaemia, types IIa, IIb, and IV, respectively.
Conclusion: The content of sialic acid in apoB decreased significantly in type IIa but increased in type IV hyperlipidaemia, which may reflect the presence of sialic acid in very low-density lipoprotein apolipoproteins other than apoB. This simple precipitation method will be useful to evaluate the sialic acid content in low-density lipoprotein in hyperlipidaemic subjects, especially of type IIa.
