Studies on the protein composition of human serum very low density lipoproteins with particular reference to the presence or absence of late pre-β lipoprotein (Lpβ)

Abstract

The amount of tetramethylurea and isopropanol soluble protein, total protein, triglycerides and cholesterol was determined in very low density lipoprotein (VLDL) showing either pre-β mobility, or combined pre-β and late pre-β (Lpβ) or β-mobility from twenty-two different sera. The ratios cholesterol to triglyceride of the VLDL preparations varied between 0.30 and 1.75. A very strong positive linear correlation between soluble protein and triglycerides over the whole range of VLDL preparations was obtained. There was no difference between sera with and without Lpβ for this relationship. When apolipoprotein B, was plotted against triglycerides, a weak correlation was obtained, and VLDL preparations without Lpβ separated into a group below the regression line, indicating that Lpβ is triglyceride poor in relation to apolipoprotein B. The corresponding plot against cholesterol gave a better correlation but with an even distribution of values of VLDL with and without Lpβ. Total and soluble protein put against cholesterol showed a pronounced tendency of VLDL with pure pre-β mobility and those with Lpβ mobility to separate into groups, demonstrating that Lpβ is cholesterol rich relative to protein. The findings indicate that Lpβ-containing VLDL may represent the presence of a partly degraded VLDL.

Key Words:

• apolipoproteins
• electrophoresis
• hyperlipoproteinaemia
• lipids
• normolipoproteinaemia
• VLDL