Carbohydrate content of human VLDL, IDL, LDL and HDL plasma apoproteins from fasting normal and hyperlipemic patients

VLDL and IDL contain a significant amount of hexose. The carbohydrate content of LDL apolipoprotein is compatible with the value reported by Ehnholm. The HDL hexose value is slightly higher than that given by Scanu. The hexose content of IDL and HDL is increased by a factor of two in type V untreated hyperlipemic patients while it decreases in type III hyperlipoproteinemia. An improvement of the hyperlipemic state (reduction in the serum lipid levels) causes a normalization of the hexose content both in type V and type III patients. Hexosamines only increase in HDL apolipoprotein of type V (27.2 μg/mg of protein) and remain practically constant for the other apolipoproteins. Sialic acid contents in HDL and LDL confirm the reported values. In a normal or 'normalized' fasting subject, IDL are, among lipoproteins, those which contain the highest percentage of hexose. As both VLDL and LDL (derived essentially from VLDL through LDL) contain less hexose, the high hexose content of IDL may only be explained by three hypotheses: an addition of carbohydrate when the IDL particle is formed; a false evaluation of the amount of hexose per mg of protein due to the fact that apoproteins B and C, which are the normal constituents of both VLDL and IDL, contain radically different amounts of hexose (preliminary results show that this is not the case); less likely, a qualitative change in the hexose linked to IDL (e.g. an increase in glucose or fucose, to which the anthrone reaction is more sensitive at the expense of galactose and mannose, used as standard in our procedure). The increase in hexose content of IDL apolipoprotein from type V patients, compared to normal, could possibly result from the presence of two distinct lipoproteins in the class of density 1.006-1.019, one of which may be increased in this pathologic state.SCOPUS: ar.j