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)

5 French Alpine Goats were studied after normal or premature parturition. Mammary tissue acetyl-C oA carboxylase, glucose-6-phosphate dehydrogenase, malic enzyme and lipoprotein lipase (LPL) activities varied in parallel with milk fat secretion from the 3rd to the 9th week of lactation. Variations of mammary LPL activity and of long chain fatty acid secretion were positively highly correlated during that period. In goats with normal parturition, lipogenic activities seemed to reach a maximum level shortly after parturition. There was a positive correlation between mammary Ll activities and plasma non esterified fatty acid contents, possibly reflecting a relationship between adipose tissue mobilisation and mammary metabolism.
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PMID:[Changes in mammary tissue lipid metabolism in the goats during the first 2 months of lactation]. 3 69

Insulin and tumor necrosis factor alpha (TNF alpha) produce potent and opposing physiological signals in adipocytes. However, genes that are co-regulated by the hormone and cytokine during and after adipocyte differentiation have not been characterized. Using 3T3-L1 cells, we have studied the regulation of the expression of genes encoding acyl-CoA synthetase (ACS), and stearoyl CoA desaturase-1 (SCD-1), two enzymes that play key roles in the metabolism of long chain fatty acids. Insulin is required for triggering the transcriptional activation of the ACS and SCD-1 genes at an early stage in adipocyte differentiation. In mature adipocytes insulin elicits a 4-fold increase in the rates of transcription of the two genes. However, when 3T3-L1 adipocytes are treated with TNF alpha the cytokine causes a 75-90% decrease in the levels of ACS and SCD-1 mRNAs. The decline in mRNA content is associated with similar decrements in the rates of transcription of the ACS and SCD-1 genes. Thus, the ACS and SCD-1 genes are subject to stimulation and counter-regulation (at the transcriptional level) by insulin and TNF alpha, respectively. The opposing effects of insulin and TNF alpha are observed in developing and terminally differentiated adipocytes. Unlike the ACS and SCD-1 genes, the genes that encode the lipogenic enzymes lipoprotein lipase and malic enzyme are not subject to counter-regulation by insulin and TNF alpha at the transcriptional level in 3T3-L1 adipocytes. These observations on the control of ACS and SCD-1 expression suggest possible mechanisms by which adipocytes can markedly adjust their capacity for long chain fatty acid metabolism in response to external stimuli.
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PMID:Regulation of gene expression by insulin and tumor necrosis factor alpha in 3T3-L1 cells. Modulation of the transcription of genes encoding acyl-CoA synthetase and stearoyl-CoA desaturase-1. 168 80

Pancreatic lipase (triacylglycerol acylhydrolase, EC 3.1.1.3) hydrolyzes dietary long chain triacylglycerol to free fatty acids and monoacylglycerols in the intestinal lumen. In the presence of bile acids, the activity of lipase is stimulated by colipase. As a prelude to studying the relationship of the protein structures to the functional properties of lipase and colipase, a cDNA encoding human pancreatic lipase was isolated from a lambda gt11 cDNA library screened with a rabbit polyclonal anti-human pancreatic lipase antibody. The full length cDNA clone of 1477 base pairs contained an open reading frame encoding a 465-amino acid protein, including a 16-amino acid signal peptide. The nucleotide sequence was 69% identical to the dog pancreatic lipase cDNA. The predicted NH2-terminal protein sequence agreed with the published NH2-terminal sequence of human pancreatic lipase and the predicted protein sequence was 85 and 70% identical to the protein sequences of pig and dog pancreatic lipase, respectively. A region of homology around Ser-153 is conserved in a number of lipid-binding proteins. Human hepatic lipase and lipoprotein lipase share extensive homology with pancreatic lipase, suggesting that the three proteins are members of a small gene family. In vitro translation of mRNA transcribed from the cDNA resulted in a protein of the expected molecular size that could be processed by microsomal membranes to yield a glycolated protein with proper signal peptide cleavage. RNA blot analysis demonstrated tissue specificity for pancreatic lipase. Thus, for the first time, a full length human pancreatic lipase cDNA has been isolated and characterized. The demonstrated regions of homology with other lipases will aid definition of interactions with substrate and colipase through site-specific mutagenesis.
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PMID:Cloning and characterization of human pancreatic lipase cDNA. 247 44

The aim of the present work is to learn if intravenous administration of L-carnitine accelerates the clearance of a lipid emulsion. Intravenous fat tolerance tests have been done on rats (0.4 g triacylglycerols.kg-1 B.W.). Measurement of the light scattering index of the plasma permitted determination of the exogenous lipid concentration and thus allowed to represent the clearance curve of the infused emulsion. It was found that prior administration of L-carnitine (110, 160 or 560 mg.kg-1 B.W.) does not modify the clearance rate either of a long chain triglyceride emulsion or of a medium chain triglyceride based emulsion. The observed clearance in L-carnitine deficient animals, resulting either from intraperitoneal injections of D-carnitine (3 g.kg-1 B.W. for four days) or from a 6-months long diet of suboptimal amounts of precursor amino acids and vitamins for carnitine biosynthesis, was not reduced relative to the clearance in corresponding control animals. Also, the in vitro activities of the two enzymes involved in the clearance of the infused lipids, lipoprotein lipase (diaphragm and adipose tissue) and hepatic endothelial lipase, were unmodified by the L-carnitine.
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PMID:Carnitine supplementation and fat emulsion clearance and utilization. 318 97

Fats provide 40-50% of the total calories in human milk or infant formula. The milk secreted by mothers of preterm infants differs in fat composition from that of mothers of full-term infants in having higher levels of medium chain fatty acids (C12, C14) throughout the first 3 months of lactation, and higher levels of long chain polyenoic fatty acids during the first 3 months of lactation. These differences in composition benefit the preterm infant by providing higher levels of rapidly absorbed medium chain fatty acids and long chain polyenoic fatty acids needed for brain development. Fat digestion: The low levels of pancreatic lipase and bile salts in the preterm infant are compensated for by lipolysis in the stomach by lingual and gastric lipase and by the intestinal hydrolysis of fat through the action of human milk bile salt-stimulated lipase. Fat digestion is efficient in the preterm infant who absorbs about 80-90% of ingested fat. Lipid clearing from the circulation depends upon the activity of the enzymes lipoprotein lipase, hepatic lipase, and lecithin-cholesterol acyltransferase. The activity of these enzymes is lower or equal to that of term infants, depending upon the degree of prematurity and the nutritional regimen, especially in parenterally fed infants.
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PMID:Lipid metabolism in premature infants. 332 34

A systematic study was undertaken to observe the effects of dietary (dioleoyl) triacyl-sn-glycerol structure on chylomicron composition and metabolism. First studied was a series of 1,2-dioleoyl-3-(saturated)acyl-sn-glycerols, where the fatty acid esterified at the 3-position was varied from 14 to 24 carbons. Next a series of 1,3-dioleoyl-2-acyl glycerols was studied, with various fatty acids esterified at the glycerol 2-position. These stereospecific triacyl-sn-glycerols were fed to donor rats and lymph chylomicrons were isolated, analyzed, and reinjected into recipient rats to study their disappearance from plasma and delivery to tissues. As shown by their compositions, chylomicrons obtained after feeding triacylglycerols containing all sn-3 fatty acid of chain length greater than 20 carbons were under-represented, possibly due to poorer digestion by lipases, or poorer absorption by the intestine. The 18-carbon saturated chain fatty acid (stearic acid) was equally well represented in chylomicrons whether in the 2- or 3-position of the fed triacylglycerol. The presence of increased amounts of long-chain saturated fatty acids in donor chylomicron triacylglycerols affected the metabolism of chylomicrons injected into the bloodstream of recipient rats. In particular the rate of removal of labeled cholesteryl esters, tracing removal of the partially degraded chylomicron remnants was slowed by the saturated chains, with palmitic acid and the 20-carbon fatty acid, arachidic acid, showing the most severe effects. There were clear differences in the removal from plasma of injected lymph chylomicrons derived from fed triacylglycerols containing stearic acid in either the 2- or 3-position, with evidence for remnants from the symmetrical triacylglycerols being less rapidly removed from the circulating blood. This effect was investigated further by injected model emulsions of chylomicrons, where the 2-position was substituted with saturated or transunsaturated acyl chains. Quantitation of removal from the blood stream of these model lipoproteins confirmed that a saturated or transunsaturated long chain fatty acid at the 2-position of the emulsion triacylglycerols slowed remnant removal from the blood. In some cases, with both lymph chylomicron and with emulsions, the lipolytic step mediated by lipoprotein lipase was also slowed.
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PMID:The effect of triacyl-sn-glycerol structure on the metabolism of chylomicrons and triacylglycerol-rich emulsions in the rat. 335 83

This report describes studies on the plasma and milk lipid composition of a patient with primary Type I hyperlipoproteinemia who had been followed through her second pregnancy. Post-partum she lactated, supplying milk for assay. It was abnormal in the low content of its total lipid and in the bizarre composition of its fatty acids. The proportion of long chain fatty acids was unusually low, and that of medium chain fatty acids unusually high. Furthermore, the fatty acids of the patient's milk differed greatly from those of her plasma triglycerides. This was in marked contrast to normal nursing mothers' milk, in which the fatty acid composition is comparable to that of plasma triglycerides. The patient's milk fatty acids were shorter in chain length and deficient in essential fatty acids. During the time of lactation, the patient remained hyperlipidemic and her post-heparin plasma had no lipolytic activity. These data and the differences between the plasma and milk fatty acids suggested that in the patient the circulating triglyceride fatty acids did not enter the mammary gland. Without preformed fatty acids entering it from plasma or adipose tissue, the lactating breast apparently synthesized fatty acids de novo. These newly synthesized fatty acids were of medium, rather than long chain length. This accounted for the abundance of medium chain length triglycerides in the patient's milk. The studies suggested that the deficit of lipoprotein lipase in Type I hyperlipoproteinemia extended to the mammary gland.
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PMID:Milk and plasma lipid composition in a lactating patient with type I hyperlipoproteinemia. 396 15

Previous studies have suggested that reduction of dietary fat intake, with or without caloric restriction, may lead to improvement in certain of the characteristic abnormalities that accompany total lipodystrophy (TLD). We have studied the effects of eucaloric medium chain triglyceride (MCT) substitution for dietary long chain fatty acids in a patient with acquired total lipodystrophy and unusual somatic and visceral anomalies. The patient exhibited insulin resistance, carbohydrate intolerance, striking fasting- and glucose-stimulated hyperinsulinemia, hyperglucagonemia, type V hyperlipoproteinemia, and lipoprotein lipase deficiency on a normal diet. Improvement in chylomicronemia, hypertriglyceridemia, and xanthomatosis occurred during eucaloric MCT substitution. Carbohydrate intolerance decreased and fasting immunoreactive glucagon and insulin concentrations fell 37% and 83%, respectively. Plasma triglyceride polyunsaturated fatty acid concentrations decreased to very low levels. With long term MCT feeding supplemented by polyunsaturated fatty acids, hepatomegaly has gradually decreased, while body weight has remained stable. The patient has not yet required insulin therapy. These observations suggest that the abnormalities in carbohydrate metabolism are closely linked to, and perhaps dependent on, the abnormalities in lipoprotein transport in TLD. Long chain triglyceride restriction and MCT supplementation should be attempted in additional patients with the features of TLD to determine whether this is a generally effective therapeutic approach.
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PMID:Eucaloric substitution of medium chain triglycerides for dietary long chain fatty acids in acquired total lipodystrophy: effects on hyperlipoproteinemia and endogenous insulin resistance. 634 62

Enzyme activity in rat serum was examined utilizing the potent tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) and various glycerolipids as substrates. The serum activity was specific for hydrolysis of the long chain tetradecanoate moiety of TPA, hydrolyzed mono- and diacylglycerols, but was not effective against triacylglycerols, cholesterylesters, or phospholipids. Heating the enzyme preparation at 56 degrees C for 1 min was dually effective in reducing the hydrolysis of both TPA and dioleoylglycerol by 83-86% of control levels. The potent diacylglycerol lipase inhibitor, RHC 80267, inhibited the hydrolysis of TPA in the 0.2-1.0 microM range and was also a potent blocker of monoacyl- and diacylglycerol hydrolysis. In substrate competition studies, exogenous unlabeled TPA was added to the [14C]dioleoylglycerol-containing reaction mixture, however, this produced an approximate 3-fold stimulation of [14]dioleoylglycerol hydrolysis. Although we have not established whether the hydrolysis of TPA and diacylglycerol is the work of one enzyme, the effectiveness of the specific lipase inhibitor, RHC 80267, demonstrates that diacylglycerol lipase can utilize TPA as substrate, a finding never before documented. This point is of interest in light of the theory that phorbol esters act by mimicry of the natural lipid mediator, diacylglycerols.
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PMID:Tumor promoting phorbol diesters: substrates for diacylglycerol lipase. 659 20

In this study we used monoacid triacylglycerols of various acyl-chain lengths as substrates for probing the active-site structure and substrate specificity of lipoprotein lipase (LPL). An unexpected finding was that the albumin ligand binding site is accessible not only to long-chain fatty acids for its recognized functional role as a fatty acid acceptor, but also to short- and medium-chain monoacid triacylglycerol substrates. The observed striking inhibitory effect (99%) of albumin on the LPL-catalyzed hydrolysis of trihexanoylglycerol is probably the result of the high affinity interaction of albumin with this substrate. Spectrophotometric analyses indicated that there is one high affinity binding site per albumin molecule (apparent KD = 1.8 +/- 0.9 microM) for the interaction with trihexanoylglycerol. Despite LPL acyl-chain specificity being obscured by the substrate binding effect of albumin, a systematic study of the lipolysis reaction under various assay conditions demonstrated that tributyroylglycerol represents the best substrate for LPL, and the preferential order of LPL catalysis for both the basal and apoC-II-activated activities is: C4 > C6 > C8 > C10 > C12 > C18:1. In some assay conditions, the presence of albumin affects the above-mentioned order, which can be attributed to substrate binding by albumin, rather than an alteration in the specificity of LPL. The synergistic effect of apoC-II and albumin resulted in the preferential activation of LPL for the hydrolysis of long-chain triacylglycerols. Even with optimal assay conditions for the hydrolysis of long chain triacylglycerols, there is still a preferential reactivity of LPL with short- and medium-chain triacylglycerols.
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PMID:Effects of albumin and apolipoprotein C-II on the acyl-chain specificity of lipoprotein lipase catalysis. 830 Dec 29


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