scholarly journals The effect in vitro of high-density lipoprotein on hydrolysis of triacylglycerol by lipoprotein lipase

1981 ◽  
Vol 200 (2) ◽  
pp. 453-456 ◽  
Author(s):  
M P Rogers ◽  
I Hutchinson
Keyword(s):  
Adipose Tissue ◽  
High Density Lipoprotein ◽  
Lipoprotein Lipase ◽  
Bovine Milk ◽  
Density Lipoprotein ◽  
High Density ◽  
Rat Adipose Tissue ◽  
Adipose Tissue Lipoprotein Lipase ◽  
Hydrolysis Of

In an incubation system in vitro with fully activated Intralipid as substrate, rat high-density lipoprotein inhibits the hydrolysis of triacylglycerol by lipoprotein lipase from rat adipose tissue, but does not inhibit hydrolysis by the enzyme from bovine milk. The pattern of inhibition suggests that substrate and high-density lipoprotein may compete for association with rat adipose-tissue lipoprotein lipase.

scholarly journals Clearance from plasma of lymph chylomicrons and chylomicron remnants labelled with 125I-tyramine-cellobiose

1992 ◽  
Vol 286 (3) ◽  
pp. 937-943 ◽  
Author(s):  
H L Ly ◽  
B C Mortimer ◽  
E Baker ◽  
T G Redgrave
Keyword(s):  
High Density Lipoprotein ◽  
Lipoprotein Lipase ◽  
Bovine Milk ◽  
Density Lipoprotein ◽  
High Density ◽  
Low Density ◽  
Apolipoprotein B48 ◽  
Chylomicron Remnants

The aims of the present study were to evaluate the metabolism of chylomicrons (CM) and of CM remnants after labelling with radioactive iodine and converting the iodinated CM into remnants in vitro. Lymph CM were radiolabelled with 125I or sham-labelled with 127I by either the ICl procedure or the tyramine-cellobiose (TC) procedure, then injected into rats. The clearance from plasma of the iodinated CM was compared with control non-iodinated lipid-labelled CM. After iodination with ICl, the plasma removal of endogenously labelled CM was significantly different from non-iodinated CM, with increased uptake of CM triacylglycerols by the liver. In contrast, the clearances from plasma and the uptake by organs of radiolabelled lipids of CM iodinated by the TC method (TC-CM) were similar to control CM. About 40% of the label from 125I-TC-CM was insoluble in 50% propan-2-ol, indicating association with CM apolipoprotein B48. Only about 8% of label was lipid soluble, mostly in phosphatidylethanolamine. Radioactivity from 125I-TC-CM injected intravenously in rats was cleared rapidly and by 30 min only 20% remained in plasma, whereas 48% was recovered in the liver. After fractionation of the plasma by density-gradient ultracentrifugation, most label remained associated with d (relative density) less than 1.006 lipoproteins. In intact rats label was also found associated with the low-density and high-density lipoprotein fractions of plasma. When the liver was excluded from circulation, the recovery of label in low-density- and high-density-lipoprotein fractions was greatly decreased. CM remnants were prepared in vivo by injecting 125I-TC-CM into functionally hepatectomized donors and compared with remnants prepared in vitro by incubation with purified bovine milk lipoprotein lipase. Although remnants prepared in vitro cleared from plasma slower than remnants prepared in vivo, the size, lipid composition and apolipoprotein profile on gradient PAGE of the remnants were similar. We conclude that labelling of CM by the TC method avoided the ‘artefactual’ changes in metabolism seen after labelling by the ICl procedure. CM remnants when prepared in vitro using lipoprotein lipase were found to be similar to those prepared in vivo after injection into functionally hepatectomized rats.

scholarly journals Free cholesterol transfer to high-density lipoprotein (HDL) upon triglyceride lipolysis underlies the U-shape relationship between HDL-cholesterol and cardiovascular disease

2019 ◽  
Vol 27 (15) ◽  
pp. 1606-1616 ◽  
Author(s):  
Ma Feng ◽  
Maryam Darabi ◽  
Emilie Tubeuf ◽  
Aurélie Canicio ◽  
Marie Lhomme ◽  
...  
Keyword(s):  
Cardiovascular Disease ◽  
Cardiovascular Risk ◽  
High Density Lipoprotein ◽  
Lipoprotein Lipase ◽  
Free Cholesterol ◽  
Density Lipoprotein ◽  
High Density ◽  
Knock Out ◽  
Low Hdl

Background Low concentrations of high-density lipoprotein cholesterol (HDL-C) represent a well-established cardiovascular risk factor. Paradoxically, extremely high HDL-C levels are equally associated with elevated cardiovascular risk, resulting in the U-shape relationship of HDL-C with cardiovascular disease. Mechanisms underlying this association are presently unknown. We hypothesised that the capacity of high-density lipoprotein (HDL) to acquire free cholesterol upon triglyceride-rich lipoprotein (TGRL) lipolysis by lipoprotein lipase underlies the non-linear relationship between HDL-C and cardiovascular risk. Methods To assess our hypothesis, we developed a novel assay to evaluate the capacity of HDL to acquire free cholesterol (as fluorescent TopFluor® cholesterol) from TGRL upon in vitro lipolysis by lipoprotein lipase. Results When the assay was applied to several populations markedly differing in plasma HDL-C levels, transfer of free cholesterol was significantly decreased in low HDL-C patients with acute myocardial infarction (−45%) and type 2 diabetes (–25%), and in subjects with extremely high HDL-C of >2.59 mmol/L (>100 mg/dL) (−20%) versus healthy normolipidaemic controls. When these data were combined and plotted against HDL-C concentrations, an inverse U-shape relationship was observed. Consistent with these findings, animal studies revealed that the capacity of HDL to acquire cholesterol upon lipolysis was reduced in low HDL-C apolipoprotein A-I knock-out mice and was negatively correlated with aortic accumulation of [3H]-cholesterol after oral gavage, attesting this functional characteristic as a negative metric of postprandial atherosclerosis. Conclusions Free cholesterol transfer to HDL upon TGRL lipolysis may underlie the U-shape relationship between HDL-C and cardiovascular disease, linking HDL-C to triglyceride metabolism and atherosclerosis.

scholarly journals Effects of insulin, glucocorticoids and adrenaline on the activity of rat adipose-tissue lipoprotein lipase

1980 ◽  
Vol 188 (1) ◽  
pp. 185-192 ◽  
Author(s):  
P Ashby ◽  
D S Robinson
Keyword(s):  
Protein Synthesis ◽  
Adipose Tissue ◽  
Lipoprotein Lipase ◽  
Lipase Activity ◽  
Lipoprotein Lipase Activity ◽  
Fat Bodies ◽  
Rat Adipose Tissue ◽  
Adipose Tissue Lipoprotein Lipase

The lipoprotein lipase activity of epididymal fat-bodies from starved rats was measured during incubations at 37 degrees C in vitro. Protein synthesis independent activation of the enzyme, previously observed during incubations at 25 decrease C, also occurs at 37 degrees C. Protein-synthesis-dependent increases in the activity of the enzyme occur in the presence of insulin and are markedly potentiated by glucocorticoids. The effects on the activity of the enzyme of insulin alone, or in the presence of glucocorticoids, are correlated with its effects on total protein synthesis in the tissue. Adrenaline antagonizes the increase in activity of the enzyme brought about by insulin and abolishes the potentiation of insulin action by glucocorticoids. These changes may be due, at least in part, to its stimulation of inactivation of the enzyme in the tissue. It is suggested that changes in adipose-tissue lipoprotein lipase activity that occur with changes in nutritional status in vivo result from the combined effects of changes in plasma insulin and glucocorticoid concentrations.

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