PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “LIPOPROTEIN LIPASE”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 829 records · Page 46Linked to original sources
PubMed1984

Comparison of acyl-oxyester and acyl-thioester lipids as substrates for bovine milk lipoprotein lipase.

The dithioester analog of dihexanoylphosphatidylcholine, rac-1,2-S,S-dihexanoyl-3-phosphocholine-1,2-dimercapto-3-propanol was synthesized and compared to the corresponding acyl-oxyester lipid as a substrate for bovine milk lipoprotein lipase. The apparent maximal reaction velocity (Vmax) for dihexanoyldithiophosphatidylcholine was considerably lower than that for dihexanoylphosphatidylcholine (0.12 vs. 5.0 mumol product released/min per mg lipoprotein lipase, respectively). The apparent Km values were 1.9 and 4.0 mM, respectively. 3-Butyrylthio-1,2-dibutyryloxypropane was also compared to tributyrylglycerol as a substrate for lipoprotein lipase; hydrolysis of the acyl-thioester bond was insignificant when compared to the corresponding oxyester derivative. Apolipoprotein C-II, the activator protein of lipoprotein lipase for long-chain fatty acyl substrates, had no effect on the hydrolysis of either the thio- or oxyester short-chain substrates. The low lipoprotein lipase activity for the thioester substrates is discussed in relation to the structure of the lipid and the active site of the enzyme.

Animals↗
PubMed1989

Evidence for an interaction of lipoprotein lipase with artery wall proteoglycans.

1. Artery wall proteoglycans-lipoprotein lipase binding characteristics were studied using bovine milk 125I-labelled lipoprotein lipase (LPL) and chondroitin sulphate-dermatan sulphate proteoglycans (PGs) purified from pig aorta. 2. The binding process was studied either by a soluble assay (gel filtration) or by an immobilized proteoglycan assay (ELISA). 3. The binding process was reversible, saturable and occurred at a stoichiometry 1:1. 4. The binding process involved ionic interactions between the positively charged groups of LPL and the negatively charged groups of PG carbohydrate chains. 5. The complex PG-LPL may lead to the production of remnant lipoproteins and, thereby, contribute to cholesteryl ester accumulation in the arterial wall.

Animals↗
PubMed1980

Lipoprotein lipase. Mechanism of product inhibition.

The rate at which lipoprotein lipase hydrolyzes triglycerides in lipoproteins and in synthetic emulsions decreases sharply with the amount of products formed unless albumin is present. Three factors which contribute to this inhibition as follows. (a) The fatty acids and the monoglycerides formed on hydrolysis locate at the lipid-water interface of the emulsion and, since they are substrates for the enzyme, act as competitive inhibitors of triglyceride hydrolysis. (b) The enzyme forms complexes with fatty acids. Therefore, as fatty acids accumulate in the system some of the enzyme will be sequestered into enzyme-fatty acid complexes. Albumin can prevent formation of such complexes since it has a higher affinity for fatty acids than the enzyme has. (c) Activator proteins do not enhance triglyceride hydrolysis unless a fatty acid acceptor is present. The strong inhibition of the enzyme itself and the loss of lipolysis-stimulating effects of activator proteins provide a feed-back regulation of the action of the lipase on lipoproteins at the capillary endothelium, ensuring that products are not generated more rapidly than they are utilized by the tissue.

Albumins↗
PubMed2001

Tissue-specific alterations in lipoprotein lipase activity in copper-deficient rats.

Copper deficiency results in alterations in lipid metabolism that include elevations in serum cholesterol and triglycerides and a decrease in whole-body respiratory quotient. Copper-deficient animals are also leaner even though electron micrographs of the myocardium present increased lipid droplet accumulation. To address whether a compromised copper status impacts triglyceride deposition in a tissue-specific manner, the activity of lipoprotein lipase was measured in adipose tissue and cardiac and skeletal muscle. Weanling rats fed a copper-restricted diet (<1 ppm) for 6 wk demonstrated a greater than twofold increase in cardiac lipoprotein lipase activity concomitant with a significant reduction in adipose tissue lipoprotein lipase activity. Skeletal muscle lipoprotein lipase activity was not altered by the copper-deficient state. The results of this study suggest that copper deficiency may induce a tissue-specific alteration in lipoprotein lipase activity in rats, which may contribute to the notable deposition of lipid substance in myocardium and the concomitant general body leanness.

Adipose Tissue↗
PubMedDate not supplied

[Use of potentiometric titration at constant pH for determination of the activity of lipoprotein lipase].

A method is developed for determination of the lipoprotein lipase activity. The method is based on the steady state potentiometric titration at constant pH value of higher fatty acids, liberated during the hydrolysis. An oil emulsion intralipid, activated by human blood serum, was used as a substrate. The sensitivity of the method was equal to 0.004-0.010 micronM of fatty acids per min. The reproducibility of the results was 2-5%. This simple and rapid method enabled to study kinetic of reactions, catalyzed by lipoprotein lipases.

Animals↗
PubMed1988

Regulation of lipoprotein lipase activity in the sand rat: effect of nutritional state and cAMP modulation.

The sand rat (Psammomys obesus) is a desert rodent in which obesity and diabetes mellitus appeared only subsequent to feeding laboratory animal chow. To study the role of lipoprotein lipase in the development and maintenance of obesity in the sand rat, enzyme activity in various organs and in plasma of sand rats or albino rats was determined following a 20-hour fast, or 16 hours after injection of cholera toxin. Despite comparable change in body weight, an altered pattern of enzyme distribution and regulation was observed in the sand rat. Neither fasting nor cholera toxin had an effect on heart and daiphragm muscle lipoprotein lipase activity of the sand rat, but caused a 1.5- to 2-fold increase in the treated albino rats. By using an isolated perfused heart system, we were able to measure enzyme activity present in the heparin-releasable fraction that represents the functional pool of the enzyme. In both species, the heparin-releasable fraction of the heart increased twofold following fasting, though initial values were lower in sand rat. In both species, fasting and cholera toxin administration resulted in an increase in plasma and liver lipoprotein lipase activity. Adipose tissue lipoprotein lipase activity of sand rat, unlike the albino rats, was similar in the various fat regions and was not lowered by food deprivation or cholera toxin administration. After both treatments, sand rat plasma insulin levels exceeded fivefold those of albino rats. Adipose tissue lipoprotein lipase activity of fed and fasted normal and diabetic sand rats correlated negatively with plasma insulin and glucose levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1980

Lipoprotein lipase activity of adult rat cardiocytes.

Cardiocytes were prepared by enzymatic dissociation of adult rat ventricular tissue, and comparative studies on lipoprotein lipase activity were conducted on fresh homogenates and acetone powders of these cells. Lipolytic activity in fresh homogenates was largely dependent on addition of serum activator to the assay, and the activity was sensitive to 1 M NaCl. Lipoprotein lipase activity was maximized in acetone powder preparations of cardiocytes. Approx. 10% of the total lipolytic activity was extractable from acetone powders of cells homogenized in the absence of serum, while approx. 50% was soluble from powders of cells homogenized with 10% serum. The non-extractable lipolytic activity was inhibited 80% with 1 M NaCl and about 47% with antibodies (IgG) to heart lipoprotein lipase. The buffer-extracted enzyme was completely sensitive to NaCl and was inhibited 80% by low concentrations of anti-lipoprotein lipase antibodies.

Animals↗
PubMed1981

Hormonal mediation of rat heart lipoprotein lipase activity after fat feeding.

The effect of acute fat feeding on the response of two fractions of lipoprotein lipase in heart was explored. In rats, previously fasted, lipoprotein lipase activity released into the perfusate by heparin increased approximately 50% 4 h after fat feeding. The lipase activity remaining in the heart tissue after heparin perfusion showed no significant difference. When rats maintained ad libitum were intubated with glucose 2 h before the fat dose, a relatively larger increase (5-10-fold) in the heparin-releasable lipase activity was observed. The capacity of these hearts to hydrolyze 14C-labeled chylomicrons was also increased 4-5-fold over the controls. Fat ingestion has been reported to elevated plasma corticosteroid levels in rats. When adrenalectomized rats were fed fat, no significant changes in the heparin-releasable lipase activity were observed Hydrocortisone and corticotropin treatment increased the heparin-releasable lipase activity to the same degree as observed with fat feeding. These data suggest that the increase in heart lipoprotein lipase activity following fat feeding is mediated via corticosteroids.

Adrenocorticotropic Hormone↗
PubMed1978

Lipoprotein lipase activity in adipose tissue and skeletal muscle of runners: relation to serum lipoproteins.

Physically well-trained people generally have lower VLDL-triglyceride and higher HDL-cholesterol levels than sedentary subjects. To examine the underlying mechanisms of this lipoprotein pattern, we measured the lipoprotein lipase (LPL) activity in needle biopsy specimens of adipose tissue and skeletal muscle of competitive runners and of body weight-matched, physically less-active controls. The active sportsmen were either sprinters, whose training program consisted mainly of athletics of short duration or long distance runners undergoing a strenuous endurance exercise program. In sprinters (all males) the serum lipid and lipoprotein concentrations did not differ significantly from those of controls and the mean LPL activities in muscle and adipose tissue were also similar in these two groups. The long distance runners (both sexes), on the other hand, had higher means levels of HDL-cholesterol than the respective controls. The LPL-activity of both adipose tissue (p less than 0.05) and skeletal muscle (p less than 0.01) was significantly higher in male long distance runners than in control males. Female runners had higher muscle LPL activity than controls (p less than 0.01) but in adipose tissue the difference in LPL activity was not significant. Rough estimates calculated for LPL activity present in whole body adipose tissue and skeletal muscle indicated that total LPL activity was 2.3 times higher in male long distance runners and 1.5 times higher in female long distance runners than in the respective controls. In combined groups of male runners and controls, there was a highly significant positive correlation between the serum HDL-cholesterol level and the LPL activity of adipose tissue expressed per tissue weight (r = +0.72, p less than 0.001) or per whole body fat (r = +0.62, p less than 0.001). The group means of HDL-cholesterol and adipose tissue LPL activity in the five cohorts studied (male sprinters, distance runners and controls and female distance runners and controls) were also positively correlated (r = +0.94). It is concluded that endurance training is associated with an adaptive increase of LPL activity not only in skeletal muscle but also in adipose tissue. These changes are not observed in sprinters who are trained by exercises of shorter duration. The high HDL-cholesterol levels of physically well-trained people are probably accounted for, at least partly, by the increased LPL activity and the concomitant rapid turnover or triglyceride-rich lipoproteins.

Adipose Tissue↗
PubMed1999

A novel frameshift mutation in exon 6 (the site of Asn 291) of the lipoprotein lipase gene in type I hyperlipidemia.

A new heterozygous lipoprotein lipase gene defect has been identified in a type I hyperlipidemic patient at the position of notable amino acid Asn 291. The patient is a 33-year-old male. His body mass index (BMI) was 18.5 kg/m2. The total cholesterol (TC), triglycerides (TG) and high density lipoprotein-cholesterol (HDL-C) concentration from his fasting plasma were 4.8, 11.9 and 0.4 mmol/l, respectively. The lipoprotein lipase (LPL) activity and mass in the postheparin plasma (PHP) from the patient were 0.58 mmol/ml/h (normal range: 7.7+/-2.6) and 244 ng/ml (normal range: 192+/-30), respectively. The hepatic lipase activity of the PHP from the patient was 10.6 mmol/ml/h (normal range: 9.9+/-3.6). DNA analysis of the LPL gene revealed that this patient had a heterozygous one nucleotide deletion of A coding Asn 291, resulting in a premature termination of the LPL protein at amino acid residue 303. The other abnormality in the LPL gene of the proband was an amino acid residue 194 defect (Ile194-->Thr), which is known to cause a defective enzyme. A medium-chain triglyceride (MCT) loading test was conducted to find how this triglyceride affects plasma lipoprotein metabolism in this patient in a short term (Fig. 3). The plasma total cholesterol (TC) or high density lipoprotein (HDL)-C levels did not change significantly after oral administration of a fatty meal containing long chain triglycerides (LCT) or MCT. The plasma TG level, on the other hand, increased from 11.9 to 19.2 mmol/l (+61%) at 6 h after loading a fatty meal containing LCT, whereas the plasma TG levels tended to even decrease at 6 h after oral administration of an MCT, tricaprin (from 11.6 to 10.5 mmol/l (-9.4%)). These results suggest that MCT, as opposed to LCT, is useful for treatment of type I hyperlipidemia with a novel mutation at the notable amino acid Asn 291 of the LPL gene.

Adult↗
PubMed1999

Lipoprotein lipase, a key role in atherosclerosis?

Lipoprotein lipase (LPL) plays a central role in lipid metabolism and transport by catalysing the hydrolysis of triacylglycerol-rich lipoproteins. The importance of LPL expressed by the adipose tissue and muscles in the provision of non-esterified fatty acids and 2-monoacylglycerol for tissue utilisation is well established. However, recent studies on LPL expressed by cells of the vascular wall, particularly macrophages, have identified additional actions of the enzyme that contribute to the promotion of foam cell formation and atherosclerosis. This review deals with the role of LPL in atherosclerosis, and its regulation by mediators that are known to be present in the lesion.

Arteriosclerosis↗
PubMed1983

Immunochemical properties of lipoprotein lipase. Development of an immunoassay applicable to several mammalian species.

The reaction of bovine lipoprotein lipase with its antibodies was found to be conformation-dependent. One aspect of this was that most antisera were more reactive with denatured than with native 125I-labeled lipoprotein lipase. Another aspect was that denatured lipase did not compete effectively with native lipase for those antibodies which caused inhibition of the enzyme's activity. This latter observation leads to the conclusion that the inhibiting antibodies recognize conformation-dependent determinants on the native enzyme. Fab fragments prepared from an inhibiting antiserum blocked the binding of the lipase to triacylglycerol/phospholipid droplets. This suggests that the inhibition results from reaction of the antibodies with the enzyme as it exists in solution, either covering the lipid-binding site on the enzyme or making it impossible for the enzyme to go through the conformational transitions necessary for binding to lipid. Most rabbit antisera did not react with rat or mouse lipoprotein lipase, but some sera showed a weak cross-reaction. Antisera raised in hens showed a much stronger cross-reaction, enough to be useful for heterologous immunoassays. An immunoassay for the bovine lipase was developed. For reproducible results it was necessary to have tracer, standard and samples in denatured form. This was accomplished by heating them in SDS, and running the immunoreaction in a Triton X-100-containing medium.

Animals↗
PubMed1982

Studies on the substrate specificity of purified human milk lipoprotein lipase.

The fatty acid specificity of purified human milk lipoprotein lipase was studied using the C18 to C54 (total acyl carbon number) saturated and the C54 mono-, di- and triunsaturated monoacid triacylglycerols. Kinetic determinations indicated that the medium-chain triacylglycerols were better substrates than long- or very short-chain saturated triacylglycerols. The unsaturated triacylglycerols were hydrolyzed at rates comparable to that of tricaprylin with triolein having the highest rate of hydrolysis of the unsaturated species tested. The enzyme attacked the primary ester bond much more readily than the secondary ester bond. The purified human milk lipoprotein lipase showed a preferential stereospecific lipolysis of the sn-1-position of the triacylglycerol molecule.

Chromatography, Gas↗
PubMed1967

Relationship of lipoprotein lipase activity to triglyceride uptake in adipose tissue.

Fasted rats injected with actinomycin or fed glucose show increased lipoprotein lipase activity of epididymal adipose tissue. Data from the actinomycin-treated animals showed a direct correlation between the lipoprotein lipase activity and the uptake of lipoprotein triglyceride by the epididymal fat pad in vitro and in vivo. Data from the animals fed glucose confirmed these findings in vitro. These data strongly suggest that lipoprotein lipase plays a major role in triglyceride deposition in adipose tissue.

Adipose Tissue↗
PubMed1976

A stable, radioactive substrate emulsion for assay of lipoprotein lipase.

A method is described for the assay of lipoprotein lipase, using a stable, radioactive substrate emulsion. Fatty acid-labeled trioleoylglycerol was emulsified by homogenization in glycerol with lecithin as detergent. This anhydrous emulsion was stable for at least six weeks. Substrate solutions for enzyme assay were prepared by diluting the emulsion with buffer containing serum and albumin. The fatty acid produced on hydrolysis was isolated in a one-step liquid-liquid partition system. Incubations with extracts of acetone powders from adipose tissue displayed characteristics of lipoprotein lipase activity, i.e., serum dependence and inhibition by NaCl and protamine. The method is rapid (less than 1 hour), sensitive and reproducible, and suitable for routine use.

Animals↗
PubMed1984

Lipoprotein lipase- and phospholipase A2-catalyzed hydrolysis of phospholipid vesicles with an encapsulated fluorescent dye. Effects of apolipoproteins.

The self-quenching dye, 6-carboxyfluorescein, has been encapsulated into sonicated vesicles of egg phosphatidylcholine. Porcine pancreatic phospholipase A2 and bovine milk lipoprotein lipase catalyze the hydrolysis of the phosphatidylcholine resulting in the release of the encapsulated dye and a large increase in 6-carboxyfluorescein fluorescence. The fluorescence increase occurs in parallel with the formation of lysophosphatidylcholine and is strongly dependent on Ca2+ for phospholipase A2 catalysis and on apolipoprotein C-II for hydrolysis by lipoprotein lipase. Other apolipoproteins, including apolipoproteins C-III, C-I, and A-I, do not enhance lipoprotein lipase activity towards this substrate. We conclude that the enhancement of lipoprotein lipase activity by apolipoprotein C-II is a specific property of the activator protein due to its interaction with lipoprotein lipase or an enzyme/lipid interface and not a characteristic of lipid-binding proteins in general.

Animals↗
PubMed1987

Cell-free translation of avian adipose tissue lipoprotein lipase messenger RNA.

Poly(A)+ mRNA isolated from chicken adipose tissue directed cell-free translation in a rabbit reticulocyte lysate system. Immunoadsorption with polyclonal antibodies against lipoprotein lipase detected a protein of 56 +/- 2 kDa. Immunodetection of this protein was prevented by inclusion of purified lipoprotein lipase in the assay mixture. Identification of the 56 kDa protein as lipoprotein lipase was confirmed by immunoadsorption to the monoclonal antibody CAL 1-11. Inclusion of dog pancreatic microsomal membranes in the translation system resulted in isolation of an additional protein of 62 kDa. Treatment of the 62 kDa protein with endo-beta-N-acetylglycosaminidase H or endo-beta-N-acetylglucosaminidase F decreased the observed molecular mass to that of the primary translation product, indicating that the increase in molecular mass resulted from the addition of N-linked oligosaccharides. Starving and refeeding chickens prior to poly(A)+ mRNA isolation resulted in a 3-fold increase in the amount of immunodetectable lipoprotein lipase synthesized.

Adipose Tissue↗