On the lipoprotein abnormality in type III hyperlipoproteinemia

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Abstract
Two lipoprotein species were isolated by starch block electrophoresis from the very low density lipoproteins (VLDL) (Sf 20-400) of patients with type III hyperlipoproteinemia. One of these, α2-VLDL, had a content of lipid and protein and physical characteristics similar to VLDL from normal subjects or patients with other forms of hyperglyceridemia. The other species, β-VLDL, contained more cholesterol and less triglyceride in relation to the protein, than normal VLDL. Only the apoprotein of low density lipoprotein was immunochemically detectable in the β-VLDL; the proteins in the α2-VLDL reacted with antisera specific for low density lipoprotein and high density lipoprotein. The electrophoretic mobility of β-VLDL was similar to that of low density lipoprotein and significantly less than that of α2-VLDL. Isolated β-VLDL had a lesser mean flotation rate than α2-VLDL, but both α2- and β-VLDL were found throughout the Sf 20-400 flotation range. The relative quantities of α2- and β-VLDL could be varied by changing the diet or by heparin administration. Most of the VLDL from type III patients on a high carbohydrate diet was in the α2-VLDL form. During fasting, α2-VLDL fell and β-VLDL increased becoming the predominant species of VLDL. Heparin-induced acceleration of triglyceride clearance also increased β-VLDL and decreased α2-VLDL. These findings suggest a precursor-product relationship between the α2- and β-forms of VLDL.