Studies on the Characterization of Human Serum Lipoproteins Separated by Ultracentrifugation in a Density Gradient

Abstract

Hyperlipemia is characterized by elevated chylomicron and S_f 10–400 and lowered S_f 3–9 and high density lipoprotein fractions. Chemical analyses suggest that the chylomicron fraction contains very low density lipoproteins of hepatic origin as well as chylomicrons of alimentary origin. The composition and distribution of lipoprotein molecules within S_f 10–400 subfractions (D < 1.005 and D > 1.005) suggests that S_f 10–400 lipoprotein subfractions are not elevated proportionally in all hyperlipemic subjects. Chemical analyses indicate that a constant triglyceride:phospholipid ratio is important in the formation and stability of S_f 10–400 lipoproteins. Atypical lipoproteins with low cholesterol: phospholipid and high fatty acid ester:cholesterol ratios are found in the S_f 3–9 lipoprotein fractions of hyperlipemic subjects. Hyperlipemia is corrected by the administration of insulin to a subject with diabetic acidosis and the administration of linoleate to two subjects with idiopathic hyperlipemia and associated diabetes mellitus. The sequences in serum lipoprotein metabolism in hyperlipemic states are discussed with reference to overproduction and underutilization. The chylomicron fraction is defined operationally and functionally and the relative contribution of alimentary chylomicrons and endogenous lipoproteins to hyperlipemia discussed.