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)

Three levels of iron (5, 29, 307 ppm iron) were fed to rats from conception through the 18th day of lactation. Dams in the 5 ppm iron group and pups in the 5 and 29 ppm iron groups developed anemia characterized by lower hemoglobin and hematocrit values than control animals. Liver and spleen levels of iron in dams and pups in the 5 and 29 ppm iron groups were lower than in the 307 ppm iron groups. Milk iron was lower in the 5 ppm iron group than in the 29 and 307 ppm iron groups. Pups in the 5 ppm iron group had hyperlipidemia characterized by elevated serum triglycerides, cholesterol, and phospholipids. Milk lipids and post-heparin plasma lipoprotein lipase levels in pups did not differ among experimental groups. Triglyceride and CO2 production from [U-14C]glucose were significantly greater in the iron-deficient pups than in control pups. Hyperlipidemia in 18-day-old iron-deficient rat pups appears to be related to increased endogenous production of triglycerides.
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PMID:Iron deficiency hyperlipidemia in 18-day-old rat pups: effects of milk lipids, lipoprotein lipase, and triglyceride synthesis. 61 36

1. Lipoprotein lipase activity was measured in heart homogenates and in heparin-releasable and non-releasable fractions of isolated perfused rat hearts, after the intravenous injection of Triton WR-1339. 2. In homogenates of hearts from starved, rats, lipoprotein lipase activity was significantly inhibited (P less than 0.001) 2h after the injection of Triton. This inhibition was restricted exclusively to the heparin-releasable fraction. Maximum inhibition occurred 30 min after the injection and corresponded to about 60% of the lipoprotein lipase activity that could be released from the heart during 30 s perfusion with heparin. 3. Hearts of Triton-treated starved rats were unable to take up and utilize 14C-labelled chylomicron triacylglycerol fatty acids, even though about 40% of heparin-releasable activity remained in the hearts. 4. It is concluded that Triton selectively inhibits the functional lipoprotein lipase, i.e. the enzyme directly involved in the hydrolysis of circulating plasma triacylglycerols. 5. Lipoprotein lipase activities measured in homogenates of soleus muscle of starved rats and adipose tissue of fed rats were decreased by 25 and 39% respectively after Triton injection. It is concluded that, by analogy with the heart, these Triton-inhibitable activities correspond to the functional lipoprotein lipase.
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PMID:The inhibition in vivo of lipoprotein lipase (clearing-factor lipase) activity by triton WR-1339. 94 35

Hearts from rats that have been starved for 10 or 24 hr oxidize (14)C-labeled chylomicron triglyceride fatty acids perfused through them at a higher rate than do hearts from rats in the fed state. Starvation for such periods increases the total clearing factor lipase activity of the heart. It is suggested that most of this increase may be accounted for by a rise in that portion of the total enzyme activity of the tissue that is released on perfusion with heparin. In rats starved for 48 hr, removal of this portion by heparin preperfusion reduces the capacity of the heart to oxidize (14)C-labeled chylomicron triglyceride fatty acids perfused subsequently by more than 80%. It is concluded that correlations between triglyceride fatty acid utilization and clearing factor lipase activity in the heart should be sought only with that portion of the total enzyme activity which is released from the intact organ by heparin.
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PMID:The effect of fasting on the utilization of chylomicron triglyceride fatty acids in relation to clearing factor lipase (lipoprotein lipase) releasable by heparin in the perfused rat heart. 541 73

Heparin-independent release of lipoprotein lipase activity from isolated perfused rat hearts was measured and related to the rapid turnover of the enzyme. Hearts consistently released lipoprotein lipase activity (2.1 +/- 0.2 U/g released per min) during 60 min of nonrecirculating perfusion without heparin. This rate of release did not significantly differ from that measured in heparin-perfused hearts after the first 10 min of perfusion (2.2 +/- 0.2 U/g released per min). The fractional release rate of lipoprotein lipase activity during nonheparin perfusion was 1.3% per min, which was higher than that calculated for alkaline phosphatase (0.002%) and creatine kinase (0.03%) activities. The lipase activity released was activated 4-fold by serum and inhibited 94 and 88% by 0.5 M NaCl and 3 mg/ml protamine sulfate, respectively. Lipoprotein lipase activity in the 1-min heparin-releasable (extracellular) and residual (intracellular) compartment remained stable during the last 40 min of nonheparin perfusion. During this period total heart, intracellular and extracellular enzyme t1/2 were calculated to be 52, 42 and 10 min, respectively. The results are consistent with the postulate that continuous release of lipoprotein lipase into the vascular compartment may be an important determinant of its rapid turnover in the heart, and possibly other tissues.
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PMID:Heparin-independent release of lipoprotein lipase activity from perfused rat hearts. 688 86

The apoprotein and lipid composition of HDL-like products arising from lipolysis of human VLDL was studied. The VLDL was perfused through beating rat hearts in the absence of serum to avoid possible alteration of the primary products of lipolysis due to apoprotein exchange with serum lipoproteins. The lipolytic products were separated by gel filtration to obviate possible losses of apoproteins from the lipoproteins during ultracentrifugation. Apoprotein B, E, C-II, and C-III were quantitated by electroimmunoassay and lipids were determined by chemical methods. During perfusion, a 50% hydrolysis of the VLDL triacylglycerols was associated with the appearance of 11% of the apoC-II, 30% of the apoC-III, and 20% of apoE of the VLDL in HDL-like particles as isolated by agarose gel filtration. The shift of the apoproteins to these particles was associated with a similar redistribution of cholesterol, phospholipid, and cholesteryl ester. The lipid composition of the HDL-like particles was cholesterol (15.1 +/- 4.0%), phospholipid (37.8 +/- 3.2%), cholesteryl ester (34.2 +/- 2.6%), and triglyceride (12.9 +/- 3.2%). The particles possessed a hydrated density of 1.063-1.21 g/ml and were spherical, with particle diameters (mean 124 +/- 36 A, range 50-160 A) that were comparable to the diameter (140 A) estimated from calculations of the surface to volume ratio, assuming a spherical particle consisting of a neutral lipid core surrounded by cholesterol, phospholipid, and protein. No discoidal forms or rouleau structures were observed in the HDL-sized fraction isolated by gel filtration. The HDL-like fraction could be resolved further by heparin-Sepharose chromatography into an unretained fraction containing predominantly apoC-III with apoE and apoC-II, and a retained fraction containing apoC-III and apoE. Small amounts of apoE were also recovered in extremely small particles that are normally observed in the d > 1.21 g/ml fraction after ultracentrifugation. No apoC-II or C-III was observed in this fraction. Incubation of VLDL with lipoprotein lipase, mobilized from hearts by heparin perfusion, yielded results that were similar to those with the perfused heart. Hearts perfused with VLDL removed apoB but not apoC-II, C-III, E, or phospholipids from the perfusate. It is concluded that the initial products of VLDL catabolism include spherical particles, similar in size to HDL, that contain apoC-II, C-III, E, cholesterol, cholesteryl esters, and phospholipids. ApoE is also released as a small extensively delipidated particle.-Tam, S. P., L. Dory, and D. Rubinstein. Fate of apolipoproteins C-II, C-III, and E during lipolysis of human very low density lipoproteins in vitro.
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PMID:Fate of apolipoproteins C-1, C-iii, and E during lipolysis of human very low density lipoproteins in vitro. 727 37

Metabolism of nonesterified fatty acid (palmitate, 1.1 mM) and triacylglycerol (TAG; triolein, 0.4 mM in the form of both rat chylomicrons and very low density lipoproteins) was studied in isolated perfused working hearts from fed nulliparous, lactating, and weaned rats. Hearts from virgin rats oxidized palmitate readily, but optimal cardiac mechanical performance occurred during perfusion with chylomicrons. In hearts from lactating dams, there was a significant increase in palmitate oxidation and a marked decrease in TAG oxidation from both chylomicrons and very low density lipoproteins compared with hearts from nulliparous animals. There was a concomitant decrease in lipoprotein lipase activity in hearts from lactating animals, and TAG in the absence of palmitate could not support optimal cardiac mechanical function. After litter removal, the changes in fatty acid and TAG metabolism observed in lactation returned to nulliparous values within 96 h. These results suggest that, during lactation, both exogenous and endogenous TAGs are directed away from heart and toward the lactating mammary gland; the heart, therefore, has to rely to a greater extent on nonesterified fatty acid for energy provision under these conditions.
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PMID:Alterations in myocardial lipid metabolism during lactation in the rat. 968 28

We examined whether administration of very low-density lipoproteins (VLDL) to pregnant rats increases surfactant phosphatidylcholine (PtdCho) content in fetal pre-type II alveolar epithelial cells. VLDL-triglycerides are hydrolyzed to fatty acids by lipoprotein lipase (LPL), an enzyme activated by heparin. Fatty acids released by LPL can incorporate into the PtdCho molecule or activate the key biosynthetic enzyme cytidylyltransferase (CCT). Dams were given BSA, heparin, VLDL, or VLDL with heparin intravenously. Radiolabeled VLDL given to the pregnant rat crossed the placenta and was distributed systemically in the fetus and incorporated into disaturated PtdCho (DSPtdCho) in pre-type II cells. Maternal administration of VLDL with heparin increased DSPtdCho content in cells by 45% compared with control (P < 0.05). VLDL produced a dose-dependent, saturable, and selective increase in CCT activity. VLDL did not significantly alter immunoreactive CCT content but increased palmitic, stearic, and oleic acids in pre-type II cells. Furthermore, hypertriglyceridemic apolipoprotein E knockout mice contained significantly greater levels of DSPtdCho content in alveolar lavage and CCT activity compared with either LDL receptor knockout mice or wild-type controls that have normal serum triglycerides. Thus the nutritional or genetic modulation of serum VLDL-triglycerides provides specific fatty acids that stimulate PtdCho synthesis and CCT activity thereby increasing surfactant content.
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PMID:Maternal loading with very low-density lipoproteins stimulates fetal surfactant synthesis. 1211 92

Lipoprotein lipase is the principal enzyme that hydrolyzes circulating triglycerides and liberates free fatty acids that can be used as energy by cardiac muscle. Although lipoprotein lipase is expressed by and is found on the surface of cardiomyocytes, its transfer to the luminal surface of endothelial cells is thought to be required for lipoprotein lipase actions. To study whether nontransferable lipoprotein lipase has physiological actions, we placed an alpha-myosin heavy-chain promoter upstream of a human lipoprotein lipase minigene construct with a glycosylphosphatidylinositol anchoring sequence on the carboxyl terminal region. Hearts of transgenic mice expressed the altered lipoprotein lipase, and the protein localized to the surface of cardiomyocytes. Hearts, but not postheparin plasma, of these mice contained human lipoprotein lipase activity. More lipid accumulated in hearts expressing the transgene; the myocytes were enlarged and exhibited abnormal architecture. Hearts of transgenic mice were dilated, and left ventricular systolic function was impaired. Thus, lipoprotein lipase expressed on the surface of cardiomyocytes can increase lipid uptake and produce cardiomyopathy.
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PMID:Lipoprotein lipase (LpL) on the surface of cardiomyocytes increases lipid uptake and produces a cardiomyopathy. 1256 68

Lipid accumulation is associated with cardiac dysfunction in diabetes and obesity. Transgenic mice expressing non-transferable lipoprotein lipase (LpL) with a glycosylated phosphatidyl-inositol (GPI) anchor in cardiomyocytes have dilated cardiomyopathy. However, the mechanisms responsible for lipid accumulation and cardiomyopathy are not clear. Hearts from 3-month-old mice expressing GPI-anchored human LpL (hLpLGPI) mice had increased fatty acid oxidation and heart failure genes and decreased glucose transporter genes. 6-month-old mice had increased mRNA expression and activation of the apoptosis marker caspase-3. Moreover, hLpLGPI hearts had significant cytochrome c release from mitochondria to cytosol. Low density lipoprotein uptake was greater in hLpLGPI hearts, and this was associated with more intracellular apolipoprotein B (apoB). To test whether lipid accumulation in the hLpLGPI heart is reduced by cardiac expression of apoB, hLpLGPI mice were bred with transgenic human apoB (HuB)-expressing mice. Hearts of HuB/hLpLGPI mice had less triglyceride (38%) and free fatty acids (19%), secreted more apoB, and expressed less atrial natriuretic factor (ANF) and brain natriuretic peptide (BNP) and more glucose transporter 4 (GLUT4). The increased mortality of the mice was abrogated by the transgenic expression of apoB. Therefore, we hypothesize that cardiac apoB expression improves cardiomyopathy by increasing lipid resecretion from the heart.
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PMID:Apolipoprotein B production reduces lipotoxic cardiomyopathy: studies in heart-specific lipoprotein lipase transgenic mouse. 1463 11

The "fuel gauge" AMP-activated protein kinase (AMPK) facilitates ATP production to meet energy demands during metabolic stress. Given the importance of lipoprotein lipase (LPL) in providing hearts with fatty acids (FA), the preferred substrate consumed by the heart, the objective of the present study was to investigate whether activation of AMPK influences LPL at its functionally relevant location, the coronary lumen. Hearts from overnight-fasted rats were first perfused with heparin to release LPL, and homogenates from these hearts were then used to measure total and phospho-AMPK-alpha by Western blotting. Manipulation of AMPK activity [with drugs like adenine 9-beta-D-arabinofuranoside (Ara-A) and insulin (that inhibit) or perhexiline and oligomycin (that stimulate)] and its influence on LPL was also determined. Fasting augmented the activity of both AMPK and luminal LPL on immediate removal of hearts, effects that still remained even after in vitro perfusion of hearts for 1 h. Inhibition of AMPK in fasted hearts using an inhibitor like Ara-A or through provision of insulin markedly lowered the enhanced luminal LPL activity. In contrast, AMPK activators, like perhexiline and oligomycin, produced a significant elevation in heparin-releasable LPL activity. Thus, with fasting or drugs that influence AMPK, a strong correlation between this metabolic switch and cardiac LPL activity was established. Our data suggest that, in addition to its direct role in promoting FA oxidation, AMPK-mediated recruitment of LPL to the coronary lumen could represent an immediate compensatory response by the heart to guarantee FA supply.
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PMID:The metabolic "switch" AMPK regulates cardiac heparin-releasable lipoprotein lipase. 1532 75


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