Metabolism of apoprotein B of plasma very low density lipoproteins in the rat.

Section: Discussionsupporting

confidence: 81%

Plasma lipoproteins after triglyceride clearance in cholesterol-fed rats.

Quarfordt¹,

Oswald²,

Farouk³

et al. 1993

“…This possibility has been invoked by other workers (50,51) including a preliminary report using the same methodology as employed in this work (52). Second, the "remnant" of VLDL may be removed by pathways other than conversion to LDL, particularly in hyperlipidemic subjects, as suggested for man by the work of Sigurdssoni et al (49), Reardlon et al (15), and Bermlani et al (53), anid for rats by Faergeman et al (54).…”

Section: Discussionmentioning

confidence: 97%

Transport of Very Low Density Lipoprotein Triglycerides in Varying Degrees of Obesity and Hypertriglyceridemia

Grundy¹,

Mok²,

Zech³

et al. 1979

271

107

A B S T R A C T Measurements oftransport oftriglycerides (TG) in very low density lipoproteins (VLDL) were carried out in 59 patients by injection of radioactive glycerol, determinations of specific activities of VLDL-TG for 48 h thereafter, and treatment of the data by multicompartmental analysis. The patients were divided into three groups: normal weight (89-120% ideal weight), mildly obese (120-135% ideal weight), and markedly obese (135% ideal weight). They had varying levels of VLDL-TG ranging from normal to markedly elevated. In many subjects, there was a positive correlation between concentrations and transport of VLDL indicating that overproduction of VLDL-TG contributed to hypertriglyceridemia. In others, and particularly in several markedly obese subjects, transport rates were greatly increased without significant hypertriglyceridemia, suggesting that they had enhanced capacity to clear TG. In all groups, however, there were patients whose degree ofhypertriglyceridemia seemed out of proportion to their transport rates. This finding and the fact that many patients have increased secretion ofVLDL-TG without elevated plasma TG suggests that both overproduction of VLDL-TG and insufficient enhancement of clearance contributed to the development of hypertriglyceridemia.The data showed a poor correlation between transport rates determined by our multicompartment analysis and single-exponential analysis used previously by other investigators (r = 0.46); this comparison was not improved by segregating patients according to their degree of obesity. Although two conversion pathways (fast and slow synthetic paths) were required to fit the data, there was no correlation between transport ratesThis work was presented, in part, at the 49th and 50th

“…While (39,40), and it has also been shown that more than half of LDL particles are taken up by liver in rabbits (20); thus the transfer pathway would be expected to deliver HDL cholesterol esters mostly to the liver. In the case of selective uptake, the pathway occurs predominantly (-90%) in the liver in rats (10).…”

Section: Discussionmentioning

confidence: 99%

Evaluation of pathways for the cellular uptake of high density lipoprotein cholesterol esters in rabbits.

Goldberg¹,

Beltz²,

Pittman³

1991

101

Cholesterol esters (CE) formed in HDL by lecithin:cholesterol acyltransferase are thought to mediate the return of cholesterol from extrahepatic tissues to the liver for excretion or reutilization. Several pathways may be involved in that process. Tracer kinetics were used to estimate the contributions of the various pathways to cellular uptake of HDL CE in rabbits. Tracers of HDL CE, HDL apo A-I, LDL apo B, and VLDL CE were simultaneously injected intravenously. Plasma decays were followed for 24 h in 4 lipoprotein pools: HDL without apo E, HDL with apo E, LDL, and VLDL. Kinetic analysis of the resulting plasma decay curves revealed that the preponderance of plasma CE (> 90%) originated in the HDL fraction. About 70% of HDL CE were cleared from plasma after transfer to LDL and VLDL, 20% were cleared directly from the HDL pool without HDL particle uptake ("selective" uptake), and 10% were cleared in HDL particles (including particles containing apo E). Since rabbits have about four times the plasma cholesterol ester transfer activity of man, and since the transfer pathway must compete with the selective uptake pathway, these results make it likely that selective uptake plays a substantial role in humans in the clearance of HDL CE. (J. Clin. Invest. 1991. 87 331-346.) Key words: low density lipoproteins * very low density lipoproteins * selective uptake -cholesterol ester transfer protein * reverse cholesterol transport