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PubMed1983

Established cell lines from rat adipose tissue that secrete lipoprotein lipase.

A number of cell lines derived from the stromal-vascular fraction of rat adipose tissue have been established that represent a variety of morphologic types. Despite their differing morphology, all of these cell lines secrete lipoprotein lipase in response to heparin. Because lipoprotein lipase secretion has been attributed to the presence of preadipocytes in the stromal-vascular fraction, we examined these cell lines for adipocyte conversion. None of the cell lines converted to adipocyte morphology when held at confluency or when exposed to media supplemented with high concentrations of fatty acid or very low density lipoproteins. These cell lines therefore do not seem to be preadipocytes, despite the presence of lipoprotein lipase. Among these cell lines are several that display the "cobblestone" morphology of endothelial cells, although they lack angiotensin-converting enzyme activity, reactivity with Factor VIII antibodies, and Weibel-Palade bodies. A number of authentic endothelial cells were found to be negative for lipoprotein lipase secretion. These data suggest that the "endothelial-like" cell lines established from adipose tissue are not endothelial cells.

Adipose Tissue↗

PubMed1990

In vitro remodelling of plasma lipoproteins in whole plasma by lipoprotein lipase in primary and secondary hypertriglyceridaemia.

In patients with familial lipoprotein lipase deficiency (FLPL-d) and glycogen storage disease type I (GSD-I), hypertriglyceridaemia (1445 +/- 247 and 1082 +/- 312 mg dl-1, n = 5 per group) was associated primarily with reduced extrahepatic lipoprotein lipase (LPL) activity (0.33 +/- 0.33 and 1.69 +/- 0.38 mumol FFA ml-1 h-1) when compared with controls (4.83 +/- 0.90). Hypercholesterolaemia was characterized by elevated LDL cholesterol (191 +/- 30 and 344 +/- 34 vs. 115 +/- 5 mg dl-1 in controls P less than 0.01) and low HDL cholesterol (12 +/- 2 and 22 +/- 2 vs. 56 +/- 3 in controls, P less than 0.001). In order to ascertain the role of LPL in the interconversion and remodelling of lipoproteins in these disorders, we analysed lipid and lipoprotein profiles before and following in vitro incubation of patient plasma with purified milk LPL (EC 3.1.1.34) for 6 h at 37 degrees C. The efficiency of exogenous LPL in vitro was demonstrated by the extent of hydrolysis of chylomicrons and of VLDL-TG in both groups. Concomitant with the disappearance of TG-rich lipoprotein particles, a consistent per cent increment of IDL (99.2 +/- 30.8 and 43.9 +/- 70.5), LDL (152.8 +/- 36.2 and 137.0 +/- 36.1) and of HDL2 (144.8 +/- 29.4 and 99.8 +/- 18.7) was observed in both groups of patients. The enhancement of the latter fractions contrasted with the decline of HDL3 mass concentration (25.4 +/- 7.7 and 51.4 +/- 5.8%), suggesting that a major shift of HDL3----HDL2 occurs following in vitro lipolysis by LDL. Simultaneous compositional and morphological changes of individual lipoprotein particles were noted, confirming the dynamic movement and exchange of neutral lipids and proteins. Specificity of LPL results was demonstrated by experiments in which incubation of the whole plasma at 37 degrees C without exogenous lipolytic enzyme did not cause any substantial changes. The present study, therefore, demonstrates a correction of the major lipoprotein abnormalities associated with FLPL-d and GSD-I by exogenous LPL. No substantial difference was noted between primary (FLPL-d) and secondary (GSD-I) hyperlipidaemias. These studies allow us to conclude that a simple in vitro system, utilizing an exogenous source of LPL and plasma from patients, may serve as a suitable model for the study of the metabolic relationships of lipoproteins. However, in view of the fact that the extent of lipolysis achieved in vitro did not differ between FLPL-d and GSD-I, it may not be able to separate primary from secondary hyperlipaemias.

Adolescent↗

PubMed1976

Lipoprotein lipase and uptake of chylomicron triglyceride by skeletal muscle of rats.

Uptake of chylomicron triglyceride and lipoprotein lipase was studied in red and white skeletal muscles, heart, and adipose tissue of rats. Retention of triglyceride fatty acids 10 min after injection was 1.6%/g in heart and adipose tissue, 0.2-0.4%/g in red (soleus and diaphragm) muscles, and 0.1%/g in white (psoas minor) muscles of fed rats. Fasting (24 h) increased retention two- to fourfold in red skeletal muscles and heart, had no effect in white muscles, and decreased retention greater than 75% in adipose tissue. Lipoprotein lipase activity in fed rats was lowest in white muscles and in certain red (posterior belly of digastric and medial head of triceps brachii) musclws, intermediate in soleus and diaphragm muscles and adipose tissue, and highest in heart. Fasting doubled lipoprotein lipase activity in all red skeletal muscles and heart, had no effect in white muscles, and decreased activity 60% in adipose tissue. The findings indicate that triglyceride uptake is related to lipoprotein lipase activity in skeletal muscle and the changes in enzyme activity during fasting divert blood triglyceride to red skeletal muscles.

Animals↗

PubMedDate not supplied

Inheritance of high density lipoprotein and lipoprotein lipase and hepatic lipase activity.

The role of genetic and environmental factors in the regulation of plasma high density lipoprotein (HDL) was estimated in 17 monozygotic (MZ) and 18 dizygotic (DZ) male twins randomly selected from the Finnish Twin Cohort Study. In addition to HDL cholesterol, we determined the HDL subfractions, HDL2 and HDL3, and the major HDL apoproteins (apo) A-I and A-II. The activities of lipoprotein lipase (LPL) and hepatic lipase (HL) were also assayed from postheparin plasma to get information on their possible contribution to the heritability of HDL. Evidence for the genetic component in the regulation of plasma HDL received support from the heritability estimate of 0.34. The different heritability estimates of HDL2 and HDL3 (h2 of 0.56 and less than 0, respectively) support the idea that the HDL subfraction distribution might be important in the genetic regulation of plasma HDL level. This also received support from the heritability of apo A-I (h2 = 0.66), mainly varying in HDL2, and the lack of it in apo A-II, found mainly in HDL3. These conclusions were strengthened by standardizing the data with relative ponderosity. Postheparin plasma HL activity had a high pairwise correlation coefficient in the MZ twins (r = 0.80, p less than 0.001), whereas LPL displayed no within-pair correlation. Neither of the lipolytic enzymes, LPL or HL, showed any correlation in the DZ twins. Therefore, it is suggested that part of the genetic regulation of the HDL and its subfraction distribution might be mediated through the activity of HL.

Apolipoprotein A-II↗

PubMed1992

Lipoproteins, lipases, and the metabolic cardiovascular syndrome.

High levels of plasma triglycerides and very-low-density lipoproteins and low levels of high-density lipoproteins are consistently found in the metabolic cardiovascular syndrome. These changes are exaggerated postprandially. In the liver, synthesis and secretion of triglyceride-rich particles are increased. In addition, the removal capacity of plasma triglycerides is decreased, due to downregulation of lipoprotein lipase in skeletal muscles by hyperinsulinemia. Resistance to insulin-stimulated glucose uptake is believed to be the main pathogenetic factor. However, increased flux of free fatty acids from abdominally localized adipose tissue must also be considered when discussing pathogenesis. Treatment is primarily nonpharmacological, with diet and increased physical activity.

Blood Glucose↗

PubMed1969

Effect of heparin on the inactivation of serum lipoprotein lipase by the liver in unanesthetized dogs.

The injection of heparin into the circulation produces a rapid increase in circulating serum lipoprotein lipase. The lipolysis system apparently circulates as a heparin-apoenzyme complex. Lipoprotein lipase activity disappears from the circulation in an exponential fashion. Available evidence suggests that a major site of removal of lipoprotein lipase activity is the liver. We have evaluated the efficiency of the inactivation system in catheterized unanesthetized dogs by studying the portal vein-hepatic vein difference in lipoprotein lipase activity. Our results demonstrate the high efficiency of the inactivation system in vivo. The results of this study also show that high levels of heparin can block the inactivation system and suggest a possible two-step mechanism. The first step in inactivation may involve the destruction of heparin by a liver heparinase. This step may induce dissociation of the active complex. After dissociation, the apoenzyme is apparently removed in a second step.

Animals↗

PubMed1986

Does vitellogenin inhibit lipoprotein lipase in the laying hen?

Vitellogenin isolated from laying-hen plasma strongly inhibited chicken adipose-tissue lipoprotein lipase in vitro, but inhibition was reduced or prevented by Ca2+ and Mg2+ ions and by partial dephosphorylation. Plasma from blood collected from laying hens using EDTA as anticoagulant was a potent inhibitor of lipoprotein lipase, but serum from laying hen blood caused inhibition only when dilute or after addition of EDTA. Heparin reduced or abolished the inhibition of lipoprotein lipase by plasma, serum and purified vitellogenin. The results suggest that inhibition of lipoprotein lipase by vitellogenin requires the presence of charged phosphate groups on vitellogenin and an unoccupied heparin-binding site on the enzyme. Neither condition is likely to occur in the laying hen in vivo.

Adipose Tissue↗

PubMedDate not supplied

Transient lipoprotein lipase deficiency with hyperchylomicronemia.

Type I hyperlipoproteinemia is a rare disorder characterized by the presence of chylomicrons in fasting plasma and dysfunction of the lipoprotein lipase system. The disease may result from primary genetic defects leading to the lack of the enzyme lipoprotein lipase or to a deficiency in the CII apoprotein activator of that enzyme. It may also appear secondary to underlying systemic diseases. We now describe a case of hyperchylomicronemia and pancreatitis with a lack of lipoprotein lipase activity as assessed by three different methods. The patient had no evidence of a plasma inactivator of lipoprotein lipase, and his plasma was able to activate the enzyme in control postheparin plasma. The postheparin plasma hepatic triglyceride lipase was normal. Tests for associated systemic diseases were negative. Six weeks after presentation, that patient's lipoprotein levels and postheparin plasma lipase activities were normal. This was a unique case of hyperchylomicronemia which for a limited time was indistinguishable from primary lipoprotein lipase deficiency by current biochemical techniques.

Child↗

PubMed2006

Molecular characterization of lipoprotein lipase, hepatic lipase and pancreatic lipase genes: effects of fasting and refeeding on their gene expression in red sea bream Pagrus major.

To investigate the nutritional regulation of lipid metabolism in fish, molecular characterization of lipases was conducted in red sea bream Pagrus major, and the effects of fasting and refeeding on their gene expression was examined. Together with data from a previous study, a total of four lipase genes were identified and characterized as lipoprotein lipase (LPL), hepatic lipase (HL) and pancreatic lipase (PL). These four lipase genes, termed LPL1, LPL2, HL and PL, share a high degree of similarity. LPL1 and LPL2 genes were expressed in various tissues including adipose tissue, gill, heart and hepatopancreas. HL gene was exclusively expressed in hepatopancreas. PL gene expression was detected in hepatopancreas and adipose tissue. Red sea bream LPL1 and LPL2 gene expression levels in hepatopancreas were increased during 48 h of fasting and decreased after refeeding, whereas no significant change in the expression levels of LPL1 and LPL2 was observed in adipose tissue, indicating that LPL1 and LPL2 gene expression is regulated in a tissue-specific manner in response to the nutritional state of fish. HL and PL gene expression was not affected by fasting and refeeding. The results of this study suggested that LPL, HL and PL gene expression is under different regulatory mechanisms in red sea bream with respect to the tissue-specificities and their nutritional regulation.

Amino Acid Sequence↗

PubMed1979

Effects of unsaturated fatty acids in phospholipids on the in vitro activation of the lipoprotein lipase and the triglyceride lipase.

The effects of different types of phospholipids on the lipoprotein lipase (LPL) and on the hepatic triglyceride lipase (TGLH) were studied by comparative in vitro incubation. Substrates were prepared by homogenization in glycerol of 3H-labelled triolein plus phosphatidylcholine (either dipalmitoyl PC, or ovolecithin or highly unsaturated PC, EPL Nattermann). Enzymes were obtained from rat adipose tissue, myocardium, lungs and liver and human adipose tissue and post-heparin plasma, respectively. The enzyme activities as determined in mmol/ml medium showed differences of highly statistical significance (p less than 0.001). In any tissue investigated the enzyme activities of LPL or TGLH followed the sequence: highly unsaturated PC (EPL) greater than ovo-lecithin greater than dipalmitoyl-lecithin. This was true for the enzymes of rat and human origin as well. It was concluded that the observed LPL and TGLH activation may account for the beneficial therapeutic effects of highly unsaturated phosphatidylcholine (EPL) in human hyperglyceridemias.

Adipose Tissue↗

PubMed2001

Polymorphisms in the lipoprotein lipase and hepatic lipase genes and plasma lipid values in the Czech population.

We have determined the genotypes of two common polymorphisms in the lipoprotein lipase (S447X) and hepatic lipase (-480C/T) genes in a cohort of 285 representative selected Czech probands (131 male and 154 female), examined in 1988 and reinvestigated in 1996. The genotype distributions of both polymorphisms were in Hardy-Weinberg equilibrium and did not differ between male and female subjects. The rare allele frequency of the lipoprotein lipase polymorphism did not differ significantly from the other European populations. Compared to the German populations, the frequency of the hepatic lipase -480T allele was significantly higher in the Czech group (20% vs. 36%, p<0.0001). There were no significant associations between the lipoprotein lipase gene variants and lipid parameters measured either in 1988, or in 1996 or with changes of lipid parameters over the 8-year period. The carriers of the T-480 allele of the hepatic lipase polymorphism were found to have higher HDL cholesterol levels (p=0.02). However, this difference was confined to female subjects only. The male carriers of the -480T allele had higher concentrations of total cholesterol (p=0.03) as compared to CC-480 subjects. Both associations were observed in 1996 only. In the Slavic Czech population, a common polymorphism in the hepatic lipase gene (-480C/T), but not in the lipoprotein lipase gene (S447X), is a significant determinant of plasma HDL cholesterol in females and plasma total cholesterol in males and indicates the importance of gender-associated effects in the genetic determinations of plasma lipids.

Adult↗

PubMed1980

Characteristics of triacylglycerol and partial acylglycerol hydrolysis by human plasma lipoprotein lipase.

The rates of reaction of human lipoprotein lipase (EC 3.1.1.34) with triacylglycerol and partial acylglycerol substrates have been compared as a function of the concentration of lipase cofactor protein (apolipoprotein C-II). The data indicate that the dissociation constant for monoacylglycerol is approximately three orders of magnitude greater than for diacylglycerols, indicating that only when the concentrations of higher acylglycerols become vanishingly small will significant monoacylglycerol hydrolysis (from 1-monoacylglycerol generated by isomerization of the 2-substituted primary product) be mediated by the lipase. This is in spite of the fact that maximal reaction velocities with each of the potential substrates are similar. A 'lipolytic cycle' is proposed to explain binding and dissociation of substrates with cofactor-lipase complex during catabolism of triacylglycerols.

Apolipoproteins↗

PubMed1980

Effects of metabolic inhibitors on the synthesis and release of lipoprotein lipase in cultured cells derived from the stromal-vascular fraction of rat adipose tissue.

Cultured cells derived from the stromal-vascular fraction of rat epididymal adipose tissue have been used to study the release of lipoprotein lipase in response to heparin. In the presence of heparin, lipoprotein lipase appeared in the medium biphasically, with an initial rapid rise followed by a slower linear release. The initial increase in activity in the medium was paralleled by a decrease in cell-associated activity. Over the course of the slower phase of release, cell-associated lipoprotein lipase levels remained constant. Treatment of cultures with cycloheximide or 2-deoxyglucose eliminated the second phase of release as well as cell-associated lipoprotein lipase activity. Treatment of cultures with Colcemid decreased the second phase of release but increased cell-associated lipoprotein lipase activity. These data suggest that exposure to heparin results in a rapid release of pre-formed enzyme and that continued release is dependent on both protein synthesis and transport of the enzyme to the cell surface.

Adipose Tissue↗

PubMedDate not supplied

Cytochemical studies of lipid metabolism: immunogold probes for lipoprotein lipase and cholesterol.

In this article, cytochemical methods are presented for the study of lipid metabolism both in normal cells and in mutant cells with genetic disorders characterized by abnormal lipid metabolism. The benefit of using an immunocytochemical approach to the study of lipase in tissues is discussed, and a review is presented of the results on immunolocalization of lipoprotein lipase in cardiac tissue of normal mice. Immunocytochemical techniques are applied to the study of lysosomal proliferation in hepatocytes from liver of mutant mice with a genetic defect responsible for the lack of hepatic lipase and lipoprotein lipase activity in these animals. Localization of lipids in tissues with structural techniques has been an area of great interest to our laboratory for many years. Attention is called to the development of a technique for the visualization of fatty acids as a function of their ionization state and the production of fatty-acid myelin figures in membranes. Results on the use of filipin to detect unesterified cholesterol in membranes are reviewed. Filipin produces fluorescent filipin-cholesterol complexes but also perturbs cell membranes. Application of this cytochemical probe, in combination with immunocytochemistry of lysosomes, produced useful information on defects in low-density lipoprotein-derived cholesterol translocation in mutant human fibroblasts. Initial results on the application of immunological techniques to the study of cholesterol in lipid model systems indicate a novel approach, which may be applicable to specialized cell systems. Recent advances in cryoultramicrotomy and development of immunoprobes present valuable opportunities for the structural assessment of lipids and lipases in cell organelles and cell membranes.

Animals↗

PubMed1980

Lipoprotein lipase and adipose tissue and plasma triglyceride clearance in patients with primary hypertriglyceridaemia.

1. The activity of lipoprotein lipase (E.C.3.1.1.3) extracted and released from adipose tissue has been measured in obese subjects with mild or severe hypertriglyceridaemia. The Intralipid tolerance test has been studied as a measure of in vivo clearance of exogenous triglyceride from plasma. 2. Plasma triglyceride clearance was reduced in patients with severe hypertriglyceridaemia (> 4 mmol/l) and this was associated with reduced activities of extracted lipoprotein lipase in adipose tissue compared to patients with mild hypertriglyceridaemia (2--4 mmol/l). 3. A course of insulin therapy (20 u/day) for 1 week increased the extracted, but not the released component of the enzyme from adipose tissue of hypertriglyceridaemic patients. 4. Serum (25% v/v) potentiated the release of lipoprotein lipase from adipose tissue of normo- but not hypertriglyceridaemic patients. 5. The effect of serum on enzyme release was abolished if lipoprotein-deficient serum was used. Addition of very low density lipoprotein (VLDL) or high density lipoprotein (HDL) restored the ability of delipidated serum to augment release of enzyme from adipose tissue, but this was not observed with low density lipoprotein (LDL). 6. It is suggested that a defect in the release of lipoprotein lipase activity in adipose tissue may contribute to the development of hypertriglyceridaemia in this group of patients.

Adipose Tissue↗

PubMed2005

Gene therapy for genetic lipoprotein lipase deficiency: from promise to practice.

Lipoprotein lipase (LPL) deficiency is a rare, hereditary disorder of lipoprotein metabolism characterised by severely increased triglyceride levels, and associated with an increased risk for pancreatitis. Since no adequate treatment modality is available for this disorder, we set out to develop an LPL gene therapy protocol. This paper focuses on the clinical presentation of LPL deficiency, summarises the preclinical investigations in animal models and describes the rationale to evaluate gene therapy for this monogenetic disorder of lipid metabolism in humans.

Animals↗

PubMed1967

Tissue lipoprotein lipase in normal individuals and in individuals with exogenous hypertriglyceridemia and the relationship of this enzyme to assimilation of fat.

Lipoprotein lipase activity (LLA) was measured in the adipose tissue of six healthy subjects and five members of a family in whom the trait for familial exogenous hypertriglyceridemia was segregating. The lipase activity measured was characteristic of lipoprotein lipase: increased by feeding, dependent on the presence of serum, and inhibited by sodium chloride and protamine sulfate. When compared with lipase activity in healthy individuals, LLA was grossly deficient in two siblings with postabsorptive chylomicronemia and was intermediate in both parents and one sibling, who had normal postabsorptive triglycerides. These findings are compatible with autosomal recessive inheritance. The hormone-sensitive lipolytic enzyme responsible for mobilization of free fatty acids from adipose storage was normal in the hyperlipemic subjects. After a 104-g fat meal, the serum triglyceride increased more in subjects heterozygotic for LLA deficiency than in the healthy subjects, and there was a relatively greater increase in chylomicrons and very low density lipoproteins in the affected individuals. These observations demonstrate the physiologic importance of lipoprotein lipase in removal of these lipoprotein groups and further clarify the differences between endogenous and exogenous hypertriglyceridemia.

Adipose Tissue↗

PubMed1996

Very-low-density lipoprotein of uremic patients is a poor substrate for bovine lipoprotein lipase in vitro.

Very-low-density lipoprotein (VLDL) from 10 hemodialysis patients and 10 healthy controls was studied with respect to the substrate characteristics for bovine milk lipoprotein lipase (LPL). Compared with the control subjects, the hemodialysis patients had significantly higher serum triglyceride and apolipoprotein B-associated apolipoprotein CIII concentrations (1.03 +/- 0.31 v 1.98 +/- 0.86 mmol/L and 0.004 +/- 0.002 v 0.011 +/- 0.005 g/L, respectively), lower serum high-density lipoprotein (HDL) cholesterol and apolipoprotein AI concentrations (1.33 +/- 0.37 v 0.95 +/- 0.31 mmol/L and 1.29 +/- 0.25 v 1.09 +/- 0.23 g/L, respectively), and lower postheparin plasma LPL activity (82 +/- 24 v 35 +/- 14 milliU/milliL). There were also significant increases in the relative fat content and diameter of VLDL particles from patients versus controls. VLDL was labeled with a fluorescent phospholipid analog, DHPE, and the rate of the lipolytic reaction with purified bovine milk LPL was estimated from the increase in fluorescence intensity at 490 nm. There was no significant difference between initial reaction velocities in the study groups, but VLDL particles from hemodialysis patients were lipolyzed to a significantly lesser extent than those from healthy controls (mean increase in fluorescence intensity after completion of the reaction, 95 +/- 36 v 140 +/- 43 arbitrary units). These results are in accordance with the accumulation of remnant particles reported to occur in uremia despite only a moderately increased serum triglyceride concentration.

Adolescent↗