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)

Milk component 3 was an inhibitor of lipoprotein lipase activity responsible for spontaneous lipolysis occurring in milk stored at 4 degrees C. Experiments using a pH-stat apparatus and emulsified tributyrin showed that component 3 inhibited porcine pancreatic lipase. The lipolytic activity was fully restored by addition of sodium taurodeoxycholate and colipase to the emulsion containing component 3. Inhibition did not seem to be the result of a direct interaction between component 3 and the enzyme. Component 3 had a strong adsorption power superior to that of pancreatic lipase, as shown by tensiometric measurements at an n-tetradecane-water interface. Lipase inhibition by component 3 could be the consequence of a rapid diffusion and preferential adsorption of component 3 at the oil-water interface provoking an important decrease of interfacial tension and avoiding the adsorption of lipase.
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PMID:Study of mechanism of lipolysis inhibition by bovine milk proteose-peptone component 3. 840 64

In the present study, the stereoselectivity of Rhizomucor miehei lipase, lipoprotein lipase, Candida antarctica B lipase, and human gastric lipase towards racemic dicaprin spread as a monolayer at the air-water interface was investigated. For this purpose we have developed a method with which the enantiomeric excess of the residual substrate can be measured in monomolecular films. The stereoselectivity, which is one of the main aspects of enzymic catalysis, was found to depend on the surface pressure of the substrate. With all four lipases tested, low surface pressures enhanced the stereoselectivity while decreasing the enzymes' catalytic activity.
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PMID:Controlling lipase stereoselectivity via the surface pressure. 841 55

The hydrolysis of triacylglycerols of chylomicrons and very low density lipoproteins by lipoprotein lipase (LPL) requires the presence of apolipoprotein (apo) CII as a cofactor. To obtain further information on the interaction of apo CII and LPL, we generated two fusion proteins consisting of the complete LPL molecule and the mature form of apo CII. The cDNAs of both proteins were either connected directly or by a segment encoding a 16-amino-acid linker peptide. The fused cDNAs were stably expressed in human embryonic kidney (HEK) 293 cells and the enzymic properties of the recombinant proteins were examined. The fusion proteins hydrolysed both emulsified long-chain (lipase) triacyglycerol substrate and a water-soluble short-chain (esterase) fatty acid ester substrate (p-nitrophenylbutyrate), regardless of whether or not they contained the linker peptide. In the absence of exogenous apo CII, the fusion proteins had up to 3.5-times higher basal activity than wild-type LPL. Similar to wild-type LPL, the fusion proteins were inhibited by 1 M NaCl, however less than wild-type LPL. A polyclonal antibody specific for apo CII impaired their ability to hydrolyse triacylglycerol emulsions. A similar effect was seen when the tetrapeptide KGEE was used as inhibitor, which corresponds to the carboxy-terminal four amino acids of apo CII.
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PMID:Construction and functional characterization of recombinant fusion proteins of human lipoprotein lipase and apolipoprotein CII. 864 97

The levels of mRNA coding for the uncoupling protein (UCP) and for lipoprotein lipase (LPL) were monitored in the brown adipose tissue of newborn rat pups. At 5 h after birth, the mRNA levels of UCP and LPL were high in pups exposed singly to 28 degrees C and low in pups kept singly at thermoneutrality (36 degrees C); in pups staying with the dam, the UCP mRNA levels were intermediate. However, the LPL mRNA levels were lower in pups staying with the dam than in pups at 36 degrees C, implying that factors additional to environmental temperature influenced LPL gene expression. Injection of noradrenaline into pups at thermoneutrality (36 degrees C) led to increases in UCP and LPL gene expression, but noradrenaline injections had no further effect in cold-exposed pups. The adrenergic effects were mediated via beta-adrenergic receptors. The cold-induced increases in both UCP and LPL gene expression were abolished by the beta-adrenergic antagonist propranolol. Thus differences in adrenergic responsiveness could not explain the differential expression of the UCP and LPL genes observed in pups staying with the dam. The presence of a physiological suppressor was examined by feeding single pups at 28 degrees C with different foods: nothing, water, Intralipid, cow's milk, rat milk and rat colostrum. None of these agents led to suppression of UCP gene expression, but colostrum led to a selective suppression of LPL gene expression. It was concluded that the genes for UCP and LPL were responsive to adrenergic stimuli immediately after birth, and it is suggested that a component of rat colostrum can selectively suppress LPL gene expression.
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PMID:Postnatal selective suppression of lipoprotein lipase gene expression in brown adipose tissue (relative to the expression of the gene for the uncoupling protein) is not due to adrenergic insensitivity: a possible specific inhibitory effect of colostrum. 866 Feb 92

Despite the established link between visceral obesity and major chronic diseases, little is known about physiologic factors that directly and specifically lead to the accumulation of visceral fat. I hypothesize that reduced intra-abdominal temperature might be a physical factor underlying the partitioning of adipose tissue to the intra-abdominal region rather than the periphery. The hypothesis is supported by biochemical reports that rat and bovine lipoprotein lipase have increased activity when incubated at lower temperatures. Persons exercising in cool water have been found to preserve subcutaneous fat whereas comparable exercise without local cooling results in subcutaneous fat loss. Pima Indians, a group that commonly acquires extreme levels of visceral fat, have been found to have lower intra-abdominal temperatures during sleep than weight-matched European-Americans. In a study of four young men and four young women, I have noted that mean intra-abdominal basal temperatures were higher for women than men (36.51 +/- 0.18 degrees C vs. 35.91 +/- 0.11 degrees C; p = .0014). Since the men are more likely to acquire visceral obesity at later age, this also provides support for my hypothesis. Investigators might wish to examine further the temperature dependence of adipose-tissue lipoprotein lipase, the temperature variation between sites of adipose tissue, and the effects of foods, physical activities, smoking and drugs on localized body temperature.
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PMID:The accumulation of visceral adipose tissue may be influenced by intra-abdominal temperature. 873 66

Female rats receiving alcohol (20%) in drinking water during lactation (AL) were compared to pair-fed animals (PF) and normal controls (C) fed ad lib. All animals were killed on the 12th day of lactation. When compared to C rats, food intake decreased in both AL and PF groups, and this effect was followed by a lower body weight and mammary gland (MG), liver, and parametrial adipose tissue weights. Mammary glands triacylglyceride concentration (TG) was much lower in PF than in AL, although in the latter, values did not reach those of C, and had higher liver TG concentration than any of the other groups. Both PF and AL rats had lower plasma TG, glycerol, and free fatty acid concentrations and higher beta-hydroxybutyrate concentration than C rats. When compared to C rats, the rate of lipogenesis in MG was higher in both PF and AL rats, whereas in liver it was higher in PF and lower in AL rats, and in adipose tissue it was higher in PF and unchanged in AL rats. The appearance of 14C lipids 4 h after oral [14]triolein in both MG and liver was lower in AL and PF rats and only lower in adipose tissue of AL rats as compared to the c rats. Lipoprotein lipase and hormone-sensitive lipase activities were lower in MG in both PF and AL rats than in C, whereas in adipose tissue the activity of lipoprotein lipase did not differ between AL and C rats and the activity of HSL was lower in the former. These findings therefore show that in spite of reduced uptake of orally administered triglycerides due to decreased LPL activity, maternal alcohol feeding during lactation in the rat preserves the mammary gland triglyceride content thanks to enhanced lipogenetic activity. On the other hand, it causes liver triglycerides accumulation, probably as a result of the decreased rate of triglycerides released into circulation, and these changes are not caused by the reduced food intake of the animals.
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PMID:Effects of ethanol intake on lipid metabolism in the lactating rat. 888 39

Previous studies had pointed to an important function of a putative exposed loop in the C-terminal domain of lipoprotein lipase for activity against emulsified lipid substrates. This loop contains 3 tryptophan residues (Trp390, Trp393, and Trp394). We have expressed and characterized lipase mutants with tryptophan to alanine substitutions at positions 55, 114, 382, 390, 393, and 394 and a double mutant at residues 393 and 394. The substitutions in the N-terminal domain (W55A and W114A) led to poor expression of completely inactive lipase variants. Heparin-Sepharose chromatography showed that mutant W114A eluted at the same salt concentration as inactive wild-type monomers, indicating that this substitution prevented subunit interaction or led to an unstable dimer. In contrast, all mutants in the C-terminal domain were expressed as mixtures of monomers and dimers similarly to the wild-type. The dimers displayed at least some catalytic activity and had the same apparent heparin affinity as the active wild-type dimers. The mutants W390A, W393A, W394A, and W393A/W394A had decreased reactivity with the monoclonal antibody 5D2, indicating that the 5D2 epitope is longer than was reported earlier, or that conformational changes affecting the epitope had occurred. The mutants W390A, W393A, W394A, and W393A/W394A had decreased catalytic activity against a synthetic lipid emulsion of long-chain triacylglycerols (IntralipidR) and in particular against rat lymph chylomicrons. The most pronounced decrease of activity was found for the double mutant W393A/W394A which retained only 6% of the activity of the wild-type lipase, while 70% of the activity against water-soluble tributyrylglycerol was retained. In the case of chylomicrons also the affinity for the substrate particles was lowered, as indicated by severalfold higher apparent Km values. This effect was less prominent with the synthetic lipid emulsion. We conclude that the tryptophan cluster Trp390-Trp393-Trp394 contributes to binding of lipoprotein lipase to lipid/water interfaces. Utilizing different lipid substrates in different physical states, we have demonstrated that the tryptophan residues in the C-terminal domain may have a role also in the productive orientation of the enzyme at the lipid/water interface.
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PMID:Mutation of tryptophan residues in lipoprotein lipase. Effects on stability, immunoreactivity, and catalytic properties. 899 62

Mechanisms responsible for the accumulation of low-density lipoprotein (LDL) were investigated in a new model, the perfused hamster aorta. To do this, we developed a method to study LDL flux in real time in individually perfused arteries; each artery served as its own control. Using quantitative fluorescence microscopy, the rates of LDL accumulation and efflux were separately determined. Perfusion of arteries with buffer plus lipoprotein lipase (LpL) increased LDL accumulation 5-fold (0.1 +/- 0.03 mV/min [control] versus 0.5 +/- 0.05 mV/min [LpL]) by increasing LDL retention in the artery wall. This effect was blocked by heparin and monoclonal antibodies directed against the amino-terminal region of apolipoprotein B (apo B). This suggests that specific regions of apo B are involved in LDL accumulation within arteries. Also, the effect of hydrolysis of triglyceride-rich lipoproteins on endothelial barrier function was studied. We compared endothelial layer permeability using a water-soluble reference molecule, fluorescently labeled dextran. When LpL was added to hypertriglyceridemic plasma, dextran accumulation within the artery wall increased > 4-fold (0.024 +/- 0.01 mV/min [control] versus 0.098 +/- 0.05 mV/min [LpL]). Under the same conditions, LpL increased LDL accumulation approximately 3-fold (0.016 +/- 0.003 mV/min [control] versus 0.047 +/- 0.013 mV/min [LpL]). Rapid efflux of LDL from the artery wall indicated that increased endothelial layer permeability was the primary mechanism during periods of increased lipolysis. Our data demonstrate two LpL-mediated effects that may increase the amount of LDL in the artery wall. These findings may pertain to the observed relationship between increased postprandial lipemia and atherosclerosis.
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PMID:Lipoprotein lipase increases lipoprotein binding to the artery wall and increases endothelial layer permeability by formation of lipolysis products. 916 84

The synthesis of cholesterol and its uptake from plasma LDL are regulated by two membrane-bound transcription factors, designated sterol regulatory element binding protein-1 and -2 (SREBP-1 and SREBP-2). Here, we used the technique of homologous recombination to generate mice with disruptions in the gene encoding the two isoforms of SREBP-1, termed SREBP-1a and SREBP-1c. Heterozygous gene-disrupted mice were phenotypically normal, but 50- 85% of the homozygous (-/-) mice died in utero at embryonic day 11. The surviving -/- mice appeared normal at birth and throughout life. Their livers expressed no functional SREBP-1. There was a 1.5-fold upregulation of SREBP-2 at the level of mRNA and a two- to threefold increase in the amount of mature SREBP-2 in liver nuclei. Previous studies showed that SREBP-2 is much more potent than SREBP-1c, the predominant hepatic isoform of SREBP-1, in activating transcription of genes encoding enzymes of cholesterol synthesis. Consistent with this observation, the SREBP-1 -/- animals manifested elevated levels of mRNAs for 3-hydroxy-3-methylglutaryl coenzyme A synthase and reductase, farnesyl diphosphate synthase, and squalene synthase. Cholesterol synthesis, as measured by the incorporation of [3H]water, was elevated threefold in livers of the -/- mice, and hepatic cholesterol content was increased by 50%. Fatty acid synthesis was decreased in livers of the -/- mice. The amount of white adipose tissue was not significantly decreased, and the levels of mRNAs for lipogenic enzymes, adipocyte lipid binding protein, lipoprotein lipase, and leptin were normal in the -/- mice. We conclude from these studies that SREBP-2 can replace SREBP-1 in regulating cholesterol synthesis in livers of mice and that the higher potency of SREBP-2 relative to SREBP-1c leads to excessive hepatic cholesterol synthesis in these animals.
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PMID:Elevated levels of SREBP-2 and cholesterol synthesis in livers of mice homozygous for a targeted disruption of the SREBP-1 gene. 937 3

The present study was addressed to determining the comparative responsiveness of lipoprotein lipase (LPL) activity, in white adipose tissue and mammary gland, to a prolonged hyperinsulinemic stimulus, in pregnant and virgin rats. Pregnant rats at the 17th day of gestation and virgin animals were subjected, under conscious and unrestrained conditions, to a continuous infusion with either 50% glucose or double-distilled water (controls) (35 ml/day) for 72 h through a catheter in the jugular vein. The basal plasma-glucose levels were lower in pregnant than in virgin rats. After the glucose infusion plasma-glucose levels remained unchanged but plasma-insulin levels were much higher, and this effect was greater in pregnant than in virgin rats. Whereas LPL activity in white adipose tissue in the controls was lower in pregnant than in virgin rats, in rats receiving the glucose infusion it increased more in pregnant than in virgin rats. However, LPL activity in the mammary gland was already higher in control pregnant rats than in virgin controls and the glucose infusion caused a similar increase in both groups. Although there was a linear correlation when individual values, from all the studied rats, for LPL activity in both tissues were plotted against plasma insulin levels, the correlation coefficient was much higher for mammary-gland LPL activity than for adipose-tissue LPL activity. Plasma-triglyceride levels were higher in pregnant than in virgin rats. The glucose infusion did not modify this parameter, probably because of the changes in LPL activity in other tissues which are known to occur in the opposite direction to those observed in this study for adipose tissue and mammary gland. The present results support the notion that the insulin resistant condition which normally occurs during late gestation is responsible for the decreased LPL activity in adipose tissue, but that the mammary gland remains sensitive to insulin and so maternal hyperinsulinemia would contribute to the induction of LPL activity in this organ prior to parturition.
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PMID:Comparative responsiveness to prolonged hyperinsulinemia between adipose-tissue and mammary-gland lipoprotein lipase activities in pregnant rats. 936


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