Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.1.34 (lipoprotein lipase)
 7,025 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Adipocyte precursors derived from the epididymal fat pads of young adult lean (FaFa) and obese (fafa) Zucker rats were established in primary culture. The two types of culture were used to assess intrinsic cellular differences in proliferative capacity, lipoprotein lipase (LPL) activity and triglyceride (TG) accumulation related to genotype. Proliferative capacity was similar over seven days in vitro in lean- and obese-derived cultures. Heparin-releasable LPL activity was significantly greater in lean- than in obese-derived cultures grown in media supplemented with penicillin and streptomycin (pen-strep). However, when grown in media supplemented with cephalothin, heparin-releasable and total LPL activity increased significantly in obese-derived cultures and equalled LPL activity in lean-derived cultures. Substantial LPL activity was measurable in both types of culture at confluence, before exposure to media that promoted lipid-filling. TG accumulation was significantly greater in lean-than in obese-derived cultures in the presence of pen-strep but was similar in both culture types grown in cephalothin. These data support our hypothesis that the fa gene may affect mechanisms of protein turnover regulation, since pen-strep, but not cephalothin, has inhibitory effects on mammalian protein synthesis and degradation. The substantial LPL activity present in confluent, but unconverted cultures, suggests that some percentage of cells in the confluent monolayers are adipoblasts.
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PMID:Primary culture of adipoblasts from obese and lean Zucker rat adipose tissue. 707 34

We have studied the mechanism of hydrolysis of labeled long-chain triacylglycerols in the isolated, ventilated, perfused rat lung. Hydrolysis of emulsified tri[3H]oleate or doubly labeled [3H]glyceryl, tri[14C]oleate was measured by quantitation of [3H]oleate or of [14C]oleate and [3H]glycerol released into the perfusate. Hydrolysis was directly proportional to the initial triacylglycerol concentration of the perfusate in the range of 0.30 to 2.2 mM. The release of free fatty acids was linear after an initial lag period, the length of which was inversely proportional to the triacylglycerol concentration. Studies with doubly labeled [3H]glyceryl, tri[14C]oleate showed that, during triacylglycerol hydrolysis, the molar ratio of free fatty acid to glycerol released is close to 1, suggesting that about one-third of the fatty acids hydrolyzed is released into the pulmonary circulation. The earlier appearance of free fatty acid than glycerol in the venous effluent indicates that the first step in triacylglycerol hydrolysis occurs at the endothelial surface. In order to investigate the role of lipoprotein lipase in this process, we administered heparin, which leads to immediate release of lipoprotein lipase from the endothelium to the circulation in vivo, 10 min and 4 h before isolation and perfusion of the lungs. Heparin administration 10 min prior to perfusion led to marked release of lipoprotein lipase from the lungs and completely abolished the subsequent hydrolysis of circulating triacylglycerols. Perfusions carried out 4 h after heparin administration show that in the lung, endothelial lipoprotein lipase levels did not return to normal within 4 h after heparin administration. The data show that circulating triacylglycerols are hydrolyzed by endothelial lipoprotein lipase during passage through the lung.
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PMID:Triacylglycerol hyrolysis in the isolated, perfused rat lung. 715 Jun 11

Rat hearts were perfused retrogradely using a modified technique that allows the separate collection of coronary (Qrv) and interstitial (Qi) effluents. Evidence is presented that Qrv contains products from the coronary vasculature and that Qi contains products arising from cardiac myocytes. Heparin perfusion of rat hearts led to a release of lipolytic activity in Qrv and Qi which was characterized as lipoprotein lipase (LPL). The relative amounts of LPL released in Qrv and Qi were dependent on the feeding condition of the rat. A high LPL activity was recovered from Qrv of fasted rats, and Qi was high in LPL during feeding. On perfusion of hearts with [3H]cholesterol-labeled chylomicrons, the tissue uptake of cholesterol was highest in the fasted state, whereas release of radioactivity in Qi was predominant in the fed state. This radioactivity in Qi appeared to be associated with chylomicron degradation products (remnants and surface fragments). Our experiments indicate that cholesterol uptake during chylomicron breakdown is inhibited in the fed state, and the relationship between myocyte LPL activity and interstitial formation of chylomicron degradation products suggests a role for the myocyte LPL in lipoprotein metabolism.
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PMID:Dual localization of lipoprotein lipase in rat heart. Its relationship to chylomicron degradation. 717 Apr 39

Equilibrium-binding data of highly purified avian lipoprotein lipase to cultured bovine endothelial cells demonstrate the presence of a class of high affinity sites. Analysis of the binding function by weighted least squares technique yielded an association constant of K = 0.7 X 10(7) M-1 and a maximum binding capacity of 1.6 micrograms/1.9 X 10(6) cells. Lipoprotein lipase was monitored both by its catalytic activity and a sensitive radioimmunoassay which permitted the accurate measurement of nanogram quantities of enzyme protein. Specific activity of the bound enzyme was similar to that of the initial purified enzyme. Lipoprotein lipase binding to endothelial cells was inhibited 80% by preincubating cells in 0.1% trypsin for 3 min at 37 degrees C, 92% by 0.01% pronase, and 91% by 0.008% proteinase K. Heparin was most efficient in releasing lipoprotein lipase from endothelial cells. Fifty per cent of the enzyme appeared in the medium at a concentration of 3 micrograms/ml of heparin. At the same concentration of heparan sulfate, 20% of the enzyme was released. Hyaluronic acid and chondroitin sulfate were not effective in stimulating enzyme release. Preincubating endothelial cells with purified human platelet endoglucuronidase for 1 h at 37 degrees C led to a 90% reduction in lipoprotein lipase binding. Endoglucuronidase was purified 20,000-fold as compared to the initial platelet lysate by a 5-step purification method. The extent of inhibition of binding was shown to be dependent on concentration of endoglucuronidase in the preincubation medium. The specificity of platelet endoglucuronidase and the demonstration that the preparation utilized contained no detectable protease activity is further evidence that lipoprotein lipase is bound to endothelial cell heparan sulfate or heparan sulfate-like molecules.
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PMID:Binding of lipoprotein lipase to endothelial cells in culture. 730 39

The mechanism of action of bovine milk lipoprotein lipase was studied by using a monomolecular film of 1,2-didecanoylglycerol. The apparent rate of hydrolysis of diglyceride increased with increasing surface pressures above 12 mN/m; the enzyme was inactive at pressures less than 12 mN/m. We have measured the effects of four plasma apolipoproteins (apoC-II, apoC-III, apo-I, and apoE), bovine serum albumin, porcine pancreatic colipase, heparin, and NaCl on the kinetics of lipid hydrolysis. At a surface pressure of 15 mN/m, all of the proteins, with the exception of colipase, gave increased enzyme activity compared to lipase alone; apoC-II gave maximal activation. At 25 mN/m, apoC-II at concentrations of less than 0.25 microgram/mL showed a specific activation, whereas the other proteins had no effect. Heparin activated at both high and low surface pressures; NaCl had little or no effect in this system. At a higher concentration of apoC-II (0.50 microgram/mL), the apoprotein inhibited the enzyme. The addition of apoC-III, apoA-I, or apoE (final concentration 0.25 microgram/mL), but not albumin or colipase, to apoC-II (0.25 microgram/mL) caused an increase in surface pressure of 5-6 mN/m and an apparent rate which was less than half that found for lipase alone, suggesting that all of the apoproteins inhibit the apoC-II specific activation.
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PMID:Mechanism of action of milk lipoprotein lipase at substrate interfaces: effects of apolipoproteins. 735 91

Hypertriglyceridemia has been noted in patients with acute pancreatitis and respiratory failure. Utilizing an isolated, perfused, canine pulmonary lobe, the effect of triglyceride infusion on pulmonary function was evaluated. When heparin was used to anticoagulate the perfusion circuit, the addition of triglyceride to the autologous blood perfusate resulted in massive weight gain (226 gm), intrapulmonary shunting (36%), and a marked drop in pulmonary compliance (congruent to 50%). Heparin activates lipoprotein lipase, and therefore some triglyceride in the perfusate was lipolyzed with a resultant increase in serum free fatty acids (FFAs) to 253 mumole/dl. When anticoagulation of the perfusion circuit was accomplished by defibrinogenation with Arvin, the addition of triglyceride to the autologous blood perfusate caused minimal weight gain (28 gm), no intrapulmonary shunting, and only a slight decrease in pulmonary compliance (22%). Arvin has no effect on lipoprotein lipase, and the FFA level in the perfusate remained normal (less than 70 mumole/dl). Thus it appears that FFA release secondary to the action of pulmonary lipoprotein lipase on blood triglyceride is the important pathogenic step in the induction of respiratory failure in this model.
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PMID:Respiratory failure in acute pancreatitis: the role of free fatty acids. 736 1

Sera from heparinized patients commonly display anodal slurring of both the alpha and beta lipoproteins when they are examined by high-resolution electrophoresis (HRE). In this study, the authors examined the effect of heparin and lipoprotein lipase on the electrophoretic migration of alpha and beta lipoproteins in sera. The addition of 10 to 1,000 units of heparin/mL to normal sera resulted in a concentration-dependent anodal slurring of the beta lipoproteins. At 40 units/mL, the beta lipoprotein band was not visible when the Paragon blue protein stain was used. The beta lipoprotein could be seen as a wide, faintly staining band with lipoprotein stain. The alpha lipoprotein band on the same gel was unaffected by the added heparin. High-resolution electrophoresis of other sera from patients who were therapeutically heparinized demonstrated anodal slurring of both alpha and beta lipoproteins independent of heparin concentration. Immunofixation electrophoresis (IFE) studies confirmed that apolipoproteins A and B were slurred within their respective bands. Heparin activates lipoprotein lipase with release of free fatty acids (FFA) from very low density lipoproteins and chylomicrons. To test this effect on migration, sera were incubated with lipoprotein lipase in vitro. The anodal slurring of both the alpha and beta lipoprotein was associated with the amount of FFA production. Individuals interpreting electrophoretic patterns should be aware that both the alpha and beta lipoproteins can migrate and slur anodally in heparinized patients. In addition, when the beta lipoprotein band interferes with the identification of monoclonal gammopathies, its migration can be selectively altered by the addition of 40 units/mL heparin to the sample.
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PMID:The effects of heparin on lipoproteins in high-resolution electrophoresis of serum. 757

Heparin-derived deca- and octa-saccharides were subjected to affinity chromatography on lipoprotein lipase-Sepharose and the fractions eluted at high salt concentration were analysed by strong-anion-exchange chromatography. Two high-affinity decasaccharides were isolated and the structure determined by one- and two-dimensional 1H-n.m.r. spectroscopy. The affinities of 3H-labelled low-molecular-mass heparin and size-fractionated deca-, octa-, and hexa-saccharides for lipoprotein lipase immobilized on microtitre plates were determined from saturation curves. From competition experiments the affinities of unlabelled heparins and pure deca- and hexa-saccharide fragments were determined. The binding was size- and charge-dependent, but structural dependency was also indicated. Thus substitution of a 2-O-sulphated L-iduronic acid with D-glucuronic acid was less important than the sulphation pattern of the D-glucosamine residue for affinity for lipoprotein lipase. Heparin inhibits binding of lipoprotein lipase to alpha 2-macroglobulin-receptor/low-density-lipoprotein receptor-related protein. The effects of size, charge and structure for this inhibition were studied. The ability of the heparin fragments to inhibit binding correlated with their affinity for lipoprotein lipase. This indicates that the inhibition of the binding of lipoprotein lipase to alpha 2-macroglobulin-receptor/low-density-lipoprotein receptor-related protein by heparin is exclusively mediated by binding of heparin to lipoprotein lipase.
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PMID:Structure of heparin fragments with high affinity for lipoprotein lipase and inhibition of lipoprotein lipase binding to alpha 2-macroglobulin-receptor/low-density-lipoprotein-receptor-related protein by heparin fragments. 771 77

Short-term detraining has been characterized by increased body mass and rapid body fat accretion. However, detraining has also been associated with increased food intake, especially in rats genetically predisposed to obesity. Thus, it has been difficult to separate refeeding effects from alterations resulting from the cessation of exercise training. In the present study, the in vitro activity of adipose tissue lipoprotein lipase (ATLPL) was measured in freely running wheel-trained rats and rats that had stopped training for 1, 2, or 3 days or 1 or 2 wk, respectively. Heparin-releasable ATLPL activity was measured at rest and after acute exhaustive exercise. Feeding efficiency (change in body mass/kJ ingested energy), fat pad mass, and adipocyte size were also measured. The rate of weight gain in 1- and 2-wk detrained rats was significantly higher than that of sedentary control or trained rats (P < 0.05). Feeding efficiency was also higher in 1-wk detrained rats than in all other groups (P < 0.005). However, food energy intake was not different between trained rats, 1- and 2-wk detrained rats, or sedentary control rats. ATLPL activity in all groups was highest after acute exhaustive exercise. ATLPL activity in 1-wk detrained rats was nearly threefold higher compared with that in trained rats (P < 0.005) and was not different from that of sedentary control rats. These results suggest that the cessation of exercise training causes an enhanced capacity for lipogenesis independent of changes in food energy intake or the acute effects of the last bout of exercise.
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PMID:Enhanced adipose tissue lipoprotein lipase activity in detrained rats: independent of changes in food intake. 789 92

We examined the effects of reproductive stage and fasting on lipoprotein lipase (LPL) activity and mRNA in the mouse mammary gland. Heparin-releasable and cell-associated LPL activity rose immediately after birth, followed 1-2 days later by an increase in LPL mRNA. Fasting decreased LPL activity in the mammary gland at all reproductive stages. During lactation, both milk and heparin-releasable LPL were substantially decreased by an overnight fast, whereas cell-associated LPL was less affected and LPL mRNA did not change. These studies indicate that the extracellular, heparin-releasable, fraction of mammary LPL activity responds most rapidly to alterations in physiological state, usually accompanied by smaller changes in cellular enzyme activity. Changes in the level of LPL mRNA were seen only during the transition from pregnancy to lactation, and these tended to follow, rather than precede, changes in enzyme activity. We conclude that in the mammary gland as in adipose tissue, LPL is regulated primarily at the translational and post-translational level.
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PMID:Regulation of lipoprotein lipase activity and mRNA in the mammary gland of the lactating mouse. 813 37


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