Abnormal lipid composition of chylomicrons in broad-β disease (type III hyperlipoproteinemia)

Abstract

A B S T R A C T Chylomicron (primary particles) were detected by polyvinylpyrollidone (PVP) flocculation in plasma collected after an overnight fast from eight hyperlipemic subjects with broad-P disease (type III hyperlipoproteinemia). The composition of these chylomicrons was abnormal: relatively poor in triglyceride and rich in cholesterol, giving rise to a triglyceride/ cholesterol ratio of < 3.0 in all cases, uniformly below the ratio in chylomicrons from eight fasting subjects with mixed lipemia. By contrast, at the peak of alimentary lipemia following an oral fat load (2 g/kg), chylomicrons from broad-P subjects had normal, triglyceride-rich composition (triglyceride/cholesterol= 14.0) and resembled chylomicrons from subjects with mixed lipemia, endogenous lipemia, and familial hypercholesterolemia after similar fat loads. As the alimentary lipemia cleared, chylomicrons remaining in broad-P subjects 14-24 hr after the fat load were again rich in cholesterol. However, a similar degree of cholesterol enrichment was observed in chylomicrons from the subjects with familial hypercholesterolemia, while only a minor increase in cholesterol was recorded in chylomicrons from subjects with mixed or endogenous lipemia. Parallel studies of changes in chylomicron composition during in vitro incubation of whole plasma and of St > 400 with Sf < 400 lipoproteins from subjects with the different forms of hyperlipoproteinemia revealed equal cholesterol enrichment of chylomicrons from a subject with mixed lipemia and from a subject with broad-p disease in media of equivalent cholesterol content. These experiments suggested neither excessive avidity of chylomicrons for cholesterol uptake nor excessive influence of St < 400 lipoproteins upon chylomicron composition in broad-P disease.Thus, results in this study suggest that the cholesterolrich chylomicrons observed in subjects with broad-, disease after an overnight fast may originate in the in-

Remnants of lipoproteins of intestinal and hepatic origin in familial dysbetalipoproteinemia.

“…We found that the content of cholesteryl esters, both in the fraction rich in chylomicron-derived remnants and in the smaller, hepatogenous "beta VLDL," is much higher than in normal prebeta VLDL, extending the earlier observations of Hazzard et al 4 and others.…”

“…A protein with an apparent molecular weight identical to that of intestinal B-48 is secreted by rat liver. 4 *^ « It is found in VLDL, IDL and in lower density fractions of LDL. It is not yet known whether it is structurally identical to the intestinal protein.…”

“…12 Clinically, it is associated with arteriosclerosis of both the coronary and peripheral circulations. 3 These remnant-like lipoprotein particles are enriched with choiesteryi esters 1 2 ' 4 and have beta mobility upon electrophoresis in agarose gel, in contrast with normal very low density lipoproteins (VLDL), which have prebeta mobility. The electrophoretic mobility of remnant particles is accounted for principally by deficiency of the C-apoproteins, which are normally the preponderant species in VLDL, with retention of appreciable quantities of less anionic apolipoprotein E (apo E).…”

A Colorimetric Microdetermination of Plasma Chylomicron-triglyceride after Membrane Filter Filtration

“…The level corresponds to 50-70% of the fasting total plasma triglyceride and these figures are consistent with those obtained by PVP flocculation method in patients with mixed lipemia (Hazzard et al 1970). According to our method, a considerable amount of chylomicron was detected in plasma from subjects without marked hyperlipemia as shown in Table 3.…”

Hyperlipidemia in Coronary Heart Disease III. EVALUATION OF LIPOPROTEIN PHENOTYPES OF 156 GENETICALLY DEFINED SURVIVORS OF MYOCARDIAL INFARCTION

“…§ Glucose and uric acid levels were measured on fasting plasma samples as described in the accompanying paper (11 [18]) was compared on paper and agarose gel, p-VLDL migrated slightly faster in agarose to a "slow" pre-fl-position. However, in the present study such mobility has been designated as 'P" to permit comparison ide = 0.474) (18); a low level of LDL-cholesterol; and cholesterol-rich fasting chylomicrons isolated by PVP flocculation (cholesterol/triglyceride = 0.41) (19). In addition, polyacrylamide gel electrophoresis of his whole plasma revealed the characteristic trail of lipoproteins migrating in a zone intermediate between normal VLDL and normal LDL, both of which were barely detectable in this subject (Fig.…”