Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

To establish a simplified, nonradioactive approach for identifying mRNAs on Northern blots, antisense oligonucleotides have been used as probes in combination with chemiluminescence-based detection. Oligonucleotides (approximately 32-mer) were end-labeled with digoxigenin (DIG) and used in conjunction with adamantyl 1,2-dioxetane aryl phosphate substrates (Lumigen PPD and CSPD). Oligonucleotides were designed as probes for several mRNAs in tissues of rats and mice, including the mitochondrial uncoupling protein, lipoprotein lipase, GLUT1, GLUT4, and beta-actin. Uncoupling protein mRNA was detected in total RNA from brown adipose tissue with a 32-mer DIG-labeled oligonucleotide, within 2 min of exposure to film. This mRNA could also be detected when as little as 250 ng of total RNA was applied to the gel, following 4 h exposure to film, and was present only in brown fat. The mRNA for lipoprotein lipase was detectable with a 30-mer DIG-labeled oligonucleotide in 1 micrograms of total RNA from mouse heart, within 2 h of exposure. The mRNA for the GLUT1 glucose transporter was detected in total RNA from rat midbrain using a 32-mer DIG-labeled oligonucleotide, while beta-actin mRNA was detected with a 30-mer oligonucleotide. The mRNA for the insulin-sensitive glucose transporter GLUT4 was detected with a 32-mer DIG-labeled oligonucleotide and found only in those tissues in which glucose uptake is stimulated by insulin. The speed of detection was greater with CSPD and was augmented by exposure of membranes to film at 37 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Chemiluminescent detection of mRNAs on northern blots with digoxigenin end-labeled oligonucleotides. 785 53

A lipase from the latex of Euphorbia characias was purified using a method involving extraction with apolar solvent and adsorption chromatography on silica gel. The lipase (specific activity, 1500 international units/mg of protein) was eluted from silica gel complexes with a lipid. The main protein fraction, which had a molecular mass of 38 kDa, was inactive when dissociated from the lipid fraction. When the lipid and protein fractions were reassociated, 72% of the lipolytic activity was recovered. This lipolytic activity was inhibited by diethyl p-nitrophenyl phosphate, which was shown to bind the lipase with a molar ratio of 0.75. High specific activities (1000 international units/mg) were measured for the lipase of E. characias on lipid extracts rich in galactosyl diacylglycerols. The apolipase was sequenced up to residue 23. The B chain of ricin has a strong homology (43.5%) with that sequence and cross-reacted with antibodies raised against the purified lipase from E. characias. The activity of the B chain of ricin was comparable (54 international units/mg) to that of the apolipase of E. characias (100 international units/mg) mixed with the same lipid cofactor complex. The primary structure (residues 68-72) of the B chain of ricin contains the lipase consensus sequence Gly-Xaa-Ser-Xaa-Gly. Its reactivity with diethyl p-nitrophenyl phosphate indicates the presence of an activated serine that, in addition to its well-documented lectin activity for galactosides, suggests that the B chain of ricin may be a galactosyl diacylglycerol lipase, closely analogous to the lipase from E. characias.
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PMID:Lipases of the euphorbiaceae family: purification of a lipase from Euphorbia characias latex and structure-function relationships with the B chain of ricin. 797 58

As CT and MR-imaging revealed an enlargement of retrobulbar fat tissue in patients with Graves' ophthalmopathy, the role of the retrobulbar adipocytes in the pathogenesis of this disorder remains to be elucidated. To evaluate the in vitro influence of humoral immunity on retrobulbar adipose tissue, the effects of IgG and sera from 56 euthyroid ophthalmopathy patients and 53 controls on both porcine and human (patients' and controls') retrobulbar adipocytes were measured by means of several assays: An enzyme-linked immunosorbent assay was employed to reveal specific binding of antibodies to the adipocytes. Metabolic activity was determined by means of a colorimetric dimethyl thiazolium-diphenyl-tetrazolium bromide test which quantifies the activity of mitochondrial dehydrogenases; cell proliferation was measured by incorporation of [3H]-thymidine in 24 h, and activities of adipocyte specific enzymes, such as membrane-bound lipoprotein lipase and 1-glycerol-3-phosphate-dehydrogenase were determined. By means of these specific enzyme tests no distinctions could be made between patients and controls. Furthermore, a significant difference between patients' (untreated and treated) and controls' IgG to bind to, to activate or to stimulate the proliferation of porcine or human (patients' and controls') retrobulbar adipocytes could not be detected under the employed experimental conditions. The effects of patients' heat-inactivated and non-inactivated sera were indistinguishable from those of the controls. Incubation with autologous sera, however, led to an activation of the retrobulbar adipocytes which was higher than the median caused by the patients' group and that engendered by incubation with autologous IgG.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Retrobulbar adipocytes and humoral immunity in Graves' ophthalmopathy. 811 65

Buffalo rat liver cells were stably transfected with an expression vector containing rat GH (rGH) receptor cDNA. Transfected cells expressed rGH receptor mRNA and specifically bound GH with high affinity. When transfected cells were stimulated with GH, levels of lipoprotein lipase (LPL) mRNA were increased in a time- and dose-dependent fashion, while glyceraldehyde-3-phosphate-dehydrogenase mRNA levels were unaffected. No GH binding or LPL mRNA could be detected in untransfected cells. Treatment of transfected cells with actinomycin D inhibited the GH-stimulated increase in LPL mRNA, indicating that GH acts at a transcriptional level. When protein synthesis was inhibited using cycloheximide, basal levels of LPL mRNA were increased, and there was no GH stimulation. This suggests that LPL gene expression is constantly repressed by a labile protein. Chloramphenicol acetyltransferase constructs containing the human LPL promoter could be regulated by GH. In conclusion, stimulation of the rGH receptor in stably transfected Buffalo rat liver cells results in specific induction of LPL gene expression. This provides a novel model to study the mechanism of GH action, particularly in relation to gene regulation.
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PMID:A novel in vitro model for studying signal transduction and gene regulation via the growth hormone receptor. 823 17

2-Furoic acid was shown to be effective in lowering both serum cholesterol and serum triglyceride levels significantly in rats with an elevation of HDL cholesterol level at 20 mg/kg/day orally. LDL receptor activity was reduced in hepatocytes, aorta foam cells, small intestinal epithelium cells and fibroblasts. HDL receptor activity was elevated in the rat hepatocytes and small intestinal cells. These activities were correlated with inhibition of acyl CoA cholesterol acyl transferase activity. Neutral cholesterol ester hydrolase activity was elevated in rat hepatocytes and human fibroblasts. Thus, 2-furoic acid appears to interfere directly with activity of intracellular enzymes rather than affecting high affinity-mediated lipoprotein membrane receptors. In vivo treatment with 2-furoic acid led to reduction in the liver and small intestine ATP dependent citrate lyase, acetyl CoA synthetase, acyl CoA cholesterol acyl transferase, sn-glycerol 3-phosphate acyl transferase, phosphatidylate phosphohydrolase and heparin induced lipoprotein lipase activities. 2-Furoic acid reduced biliary cholesterol levels but the agent increased bile salts which are lithogenic. Acute toxicity studies in mice suggest that the agent has some hepatic toxicity effects. The LD50 was relatively low at 250 mg/kg IP in mice.
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PMID:The hypolipidemic effects of 2-furoic acid in Sprague-Dawley rats. 844 21

The cyclic imides, o-(N-phthalimido)acetophenone, 2,3-dihydrophthazine-1,4-dione and N(4-methyl phenyl)diphenimide, were evaluated for their effects on bile lipids, bile acids, small intestinal absorption of cholesterol and cholic acid and liver and small intestinal enzyme activities involved in lipid metabolism. The agent at 20 mg/kg/day orally elevated rat bile excretion of lipids, e.g. cholesterol and phospholipids, and increased the bile flow rate. These agents altered the composition of the bile acids, but there was no significant increase in lithocholic acid which is most lithogenic in rats. The three agents did decrease cholesterol and cholic acid absorption from isolated in situ intestinal duodenum loops in the presence of drug. Hepatic and small intestinal mucosa enzyme activities, e.g. ATP-dependent citrate lyase, acyl CoA cholesterol acyl transferase, cholesterol-7-alpha hydroxylase, sn-glycerol-3-phosphate acyl transferase, phosphatidylate phosphohydrolase, and lipoprotein lipase were reduced. However, the cyclic imides did not accelerate HMG-CoA reductase activity, the regulatory enzyme for cholesterol synthesis, in a manner which would accelerate biliary cholesterol excretion. There was no evidence of hepatic cell damage afforded by the drugs based on clinical chemistry values which would induce alterations in bile acid concentrations after treatment of the rat.
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PMID:The effects of cyclic imides on lipid absorption from the intestine and on bile lipids and bile acids of Sprague Dawley rats. 847 58

Endothelin-1 (ET-1) is a potent vasoconstrictor peptide that also stimulates production of prostacyclin (PGI2) from arachidonic acid. The purpose of this study was to determine the contribution of phospholipases (PLs) A2, C, and/or D in ET-1-induced PGI2 formation in the rat aorta, measured as immunoreactive 6-ketoprostaglandin (PG) F1 alpha. ET-1 increased 6-keto-PGF1 alpha formation, which was not affected by a PLA2 inhibitor, 7,7-dimethyl eicosadienoic acid (DEDA). Furthermore, ET-1 failed to stimulate PLA2 activity measured in the cytosol (cPLA2), using phosphatidylcholine, L-a-1-palmitoyl-2-arachidonyl[14C] as a substrate. However, the adrenergic agonist norepinephrine increased 6-keto-PGF1 alpha formation, which was attenuated by DEDA, and enhanced PLA2 activity. ET-1 enhanced PLC activity, as indicated by increased inositol phosphate production, which was prevented by a PLC inhibitor, U-73122. However, ET-1-induced 6-keto-PGF1 alpha production was not altered by U-73122. An inhibitor of PLD activation, C2-ceramide, attenuated ET-1-induced PLD activity, as indicated by the production of phosphatidylethanol. Furthermore, ET-1-induced 6-keto-PGF1 alpha formation was inhibited by C2-ceramide as well as by ethanol treatment. Moreover, inhibitors of phosphatidate phosphohydrolase (propranolol) and diacylglycerol lipase (RHC-80267), attenuated ET-1-induced 6-keto-PGF1 alpha formation. Finally, ET-1-induced activation of PLD was not attenuated by a selective PKC inhibitor, bisindolylmaleimide I. These data suggest a novel pathway for ET-1-induced PGI2 formation in the rat aorta involving activation of PLD but not cPLA2 and independent of PLC or PKC activation.
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PMID:Prostacyclin formation elicited by endothelin-1 in rat aorta is mediated via phospholipase D activation and not phospholipase C or A2. 875 4

The association of prostaglandin D2 (PGD2) production as well as arachidonic acid release with the phospholipase D (PLD)-linked mechanism was studied in rat peritoneal mast cells. Stimulation of mast cells with cross-linking of the high-affinity Fc receptor for IgE caused increases in the release of arachidonic acid and PGD2, which are suppressed almost completely by ethanol or RHC 80267, a diacylglycerol lipase inhibitor. Ethanol did not influence inositol phosphate release in response to an antigen. An increase in diacylglycerol, that is inhibited by propranolol, was observed, with a peak within 1 min. Antigen stimulation induced little production of lysophosphatidylcholine, while ionomycin as a control markedly induced the production. However, the phospholipase A2 (PLA2) activity in the cytosol of antigen-stimulated cells increased to the level in ionomycin-stimulated cells. The addition of the ADP-ribosylation factor-containing fraction prepared from bovine brain, that is known to specifically activate PLD, to permeabilized mast cells in the presence of GTP gamma S, apparently increased arachidonic acid and PGD2 release, but not in the presence of ethanol. Furthermore, arachidonic acid release by an antigen was enhanced by melittin, that activates PLA2, but PGD2 production was not. These results suggest that antigen-stimulated PGD2 production as well as arachidonic acid release are strongly associated with the sequential PLD-linked pathway.
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PMID:Importance of the phospholipase D-initiated sequential pathway for arachidonic acid release and prostaglandin D2 generation by rat peritoneal mast cells. 890 28

Xanthine oxidoreductase (XDH + XO, EC 1.2.3.2) is released into the circulation from organs rich in XO activity. Herein we report the specific high affinity binding of XO to glycosaminoglycans (GAGs) and the preferential association of XO with heparin, compared with heparan sulfate, chondroitin sulfate, and dematan sulfate. The binding of XO to Sepharose 6B-conjugated heparin (HS6B) occurs at physiological ionic strength and increased with pH, with Scatchard analysis revealing a nonlinear binding pattern at pH 7.4. The dissociation constant (Kd) for XO binding was 0.4 to 1.8 x 10(-7) M, similar to the heparin-reversible binding of lipoprotein lipase to vascular endothelium. The binding energy of 9-13 kcal/mol was concordant with noncovalent electrostatic interactions. Xanthine oxidase immobilization to HS6B rendered a catalytically active enzyme from that had kinetic characteristics distinct from XO in free solution. While the Km and Ki for xanthine in phosphate buffer at pH 7.4 were 3 microM and 1.6 mM, respectively, for free XO, they were 15 microM and 2.8 mM for immobilized XO. Inhibition constants for guanine and uric acid were also increased upon XO binding to HS6B. Changes in kinetic parameters were related to a real and not apparent decrease in binding affinity for substrate and inhibitors and were not due to diffusion-controlled processes within the gel matrix. Changes in Km and Ki for xanthine also had a significant influence on the relative quantities of O2.- and H2O2 generated by a given substrate concentration. Superoxide formed by HS6B-bound XO was partially consumed within the gel microenvironment which electrostatically excluded CuZn SOD. Immobilization of XO increased the half-life of enzyme activity in buffer and in the absence of substrate from 67 to 120 h at 4 degrees C. These data indicate that binding to cell surfaces will strongly influence the catalytic properties, oxidant producing capacity, and stability of XO.
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PMID:Xanthine oxidase binding to glycosaminoglycans: kinetics and superoxide dismutase interactions of immobilized xanthine oxidase-heparin complexes. 905 42

During periods of intense activity such as phagocytosis, macrophages are thought to derive most of their energy from glucose metabolism under both aerobic and anaerobic conditions. To determine whether fatty acids released from lipoproteins by macrophage lipoprotein lipase (LPL) could substitute for glucose as a source of energy for phagocytosis, we cultured peritoneal macrophages from normal and LPL knockout (LPL-KO) mice that had been rescued from neonatal demise by expression of human LPL via the muscle creatine kinase promoter. Normal and LPL-KO macrophages were cultured in medium containing normal (5 mM) or low (1 mM) glucose, and were tested for their capacity to phagocytose IgG-opsonized sheep erythrocytes. LPL-KO macrophages maintained in 1 and 5 mM glucose phagocytosed 67 and 79% fewer IgG-opsonized erythrocytes, respectively, than macrophages from normal mice. Addition of VLDL to LPL-expressing macrophages maintained in 1 mM glucose enhanced the macrophages' phagocytosis of IgG-opsonized erythrocytes, but did not stimulate phagocytosis by LPL-KO macrophages. Inhibition of secreted LPL with a monoclonal anti-LPL antibody or with tetrahydrolipstatin blocked the ability of VLDL to enhance phagocytosis by LPL-expressing macrophages maintained in 1 mM glucose. Addition of oleic acid significantly enhanced phagocytosis by both LPL-expressing and LPL-KO macrophages maintained in 1 mM glucose. Moreover, oleic acid stimulated phagocytosis in cells cultured in non-glucose-containing medium, and increased the intracellular stores of creatine phosphate. Inhibition of oxidative phosphorylation, but not of glycolysis, blocked the capacity of oleic acid to stimulate phagocytosis. Receptor-mediated endocytosis of acetyl LDL by macrophages from LPL-expressing and LPL-KO mice was similar whether the cells were maintained in 5 or 1 mM glucose, and was not augmented by VLDL. We postulate that fatty acids derived from macrophage LPL-catalyzed hydrolysis of triglycerides and phospholipids provide energy for macrophages in areas that have limited amounts of ambient glucose, and during periods of intense metabolic activity.
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PMID:Lipoprotein lipase regulates Fc receptor-mediated phagocytosis by macrophages maintained in glucose-deficient medium. 923 12


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