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PubMed2002

Lipoprotein lipase: structure, function, regulation, and role in disease.

Lipoprotein lipase (LPL) catalyses the hydrolysis of the triacylglycerol component of circulating chylomicrons and very low density lipoproteins, thereby providing non-esterified fatty acids and 2-monoacylglycerol for tissue utilisation. Research carried out over the past two decades have not only established a central role for LPL in the overall lipid metabolism and transport but have also identified additional, non-catalytic functions of the enzyme. Furthermore, abnormalities in LPL function have been found to be associated with a number of pathophysiological conditions, including atherosclerosis, chylomicronaemia, obesity, Alzheimer's disease, and dyslipidaemia associated with diabetes, insulin resistance, and infection. Advances have also been made in relating the various domains in the protein to different functions, and in understanding the mechanisms that are responsible for the changes in LPL expression seen in response to nutritional and other physiological changes, and during disease. This review summarises recent findings in relation to the structure, function, and regulation of LPL along with its important role in disease.

Animals↗
PubMed1986

Iodine-125-labeled lipoprotein lipase as a tool to detect and study spontaneous lipolysis in bovine milk.

The distribution of lipoprotein lipase among cream, casein, and milk serum can be evaluated by addition of a trace amount of 125I-labeled lipoprotein lipase to milk. Radioactive lipase was distributed in parallel to endogenous lipase under several conditions. In some milk samples, binding of lipase to cream increased when the milk was cooled. Correlation was good between bound labeled lipase and degree of cold-induced lipolysis in corresponding milk samples. Binding of lipase to cream or to casein was not saturable by addition of two-to threefold more lipase than is normally present in milk. In milk with a relatively high fraction of lipase bound to cream, a correspondingly lower fraction was associated with casein, whereas the fraction of lipase in milk serum was similar in all milk samples. Cold-induced binding of lipoprotein lipase to cream was not fully reversed when the milk was warmed again. Heparin released lipase from casein and increased the amount of lipase bound to cream after cooling.

Animals↗
PubMed1986

Comparison of apolipoprotein C-II-deficient triacylglycerol-rich lipoproteins and trioleoylglycerol/phosphatidylcholine-stabilized particles as substrates for lipoprotein lipase.

The effect of apolipoproteins C-II and C-III on the lipoprotein lipase-catalyzed hydrolysis of apolipoprotein C-II-deficient triacylglycerol-rich lipoproteins and particles of trioleoylglycerol stabilized with a phosphatidylcholine monolayer was investigated. For both triacylglycerol-rich lipoproteins and artificial lipid particles, maximal lipoprotein lipase activity occurred at a constant apolipoprotein C-II/phospholipid mol ratio of 2.0 X 10(-4) and was independent of particle size, indicating that the amount of apolipoprotein C-II bound to the surface of the substrate is important for enzyme activation. The effect of apolipoprotein C-II on lipoprotein lipase activity with apolipoprotein C-II-deficient lipoproteins as substrate was to decrease the apparent Michaelis constant (Kmapp) from 7.1 to 1.0 mM with minor changes on the apparent maximal velocity (Vmax) (22.2 mmol free fatty acid released/h per mg enzyme). In contrast, apolipoprotein C-II increased the apparent Vmax from 2.4 to 20.0 mmol free fatty acid/h per mg enzyme for the lipoprotein lipase-catalyzed hydrolysis of trioleoylglycerol/phospholipid particles with little change in Kmapp (1.0 mM). Addition of apolipoprotein C-II-deficient triacylglycerol-rich lipoproteins or high-density lipoproteins to trioleoylglycerol/phospholipid particles in the presence of apolipoprotein C-II inhibited lipoprotein lipase activity. Lipoprotein lipase activity was also inhibited by the addition of a large excess of lipid-free apolipoprotein C-III to the artificial particles. The decrease in lipoprotein lipase activity correlated with the amount of bound apolipoprotein C-II. We suggest that the reported discrepancies on the effect of apolipoproteins C-II and C-III on lipoprotein lipase catalysis is related to differences in substrates and to the amount of added apolipoproteins.

Apolipoprotein C-II↗
PubMed1982

Adipose tissue lipoprotein lipase activity in Plasmodium chabaudi and Plasmodium vinckei rodent malaria.

Adipose tissue lipoprotein lipase activity (LPL) falls dramatically during experimental infection of mice by Plasmodium chabaudi. The decrease in this activity accounts for the seric accumulation of triacyl-glyceride-rich lipoproteins (chylomicrons mainly and Very Low Density Lipoproteins (VLDL) partly). This loss of tissue LPL enzyme activity is moreover enhanced, in capillary vessels, by a simultaneous decrease in the activatory power of serum towards the enzyme. This phenomenon is mainly related to the presence of Very Low Density Lipoproteins. In the mouse VLDL apoprotein composition is supposed to be modified. On the contrary, in fatal infection of mice by P. vinckei the adipose tissue lipoprotein lipase (LPL) activity is normal or even increased.

Adipose Tissue↗
PubMed1980

Lipoprotein lipase activity in F1 heart cell cultures. Effect of dialyzable serum factors on enzyme stability and enzyme synthesis.

F1 heat cell cultures were grown in F-10 medium containing 20% fetal calf and horse serum and after 6-7 days showed high activity of lipoprotein lipase. When the culture medium contained 20% serum which had been dialyzed against F-10 medium, a 75% decline in lipoprotein lipase activity occurred after 3 h of incubation. Cultures incubated with 20% dialyzed serum and dialysate, obtained after 24 h dialysis of serum against F-10 medium, retained full enzyme activity. Restoration of enzyme activity, lost upon incubation with dialyzed serum, became apparent only 2 h after incubation of the cells with dialysate and dialyzed serum and was complete after 24 h. The effectiveness of the dialysate was not affected by trichloroacetic acid precipitation, ether extraction, exposure to pronase or to 80 degrees C for 10 min; it was retained after chromatography of DEAE cellulose but was lost after elution from CM cellulose colums. Addition of spermidine and spermine to culture media containing dialyzed serum did prevent partially the decline in lipoprotein lipase activity of the heart cell cultures. These polyamines were also able to stabilize lipoprotein lipase activity of heart homogenates incubated at 37 degrees C. However, these compounds were not effective in resoration of enzyme activity of cultured cells lost after exposure to dialyzed serum. It appears that positively charged low molecular weight molecules present in sera of various species are required for the stabilization and synthesis of lipoprotein lipase in heart cell cultures.

Animals↗
PubMed2004

HDL metabolic activities in a boy with lipoprotein lipase deficiency and his family.

BACKGROUND: Lipoprotein lipase (LPL) deficiency is a rare autosomal recessively inherited disease characterized by elevated triglyceride, low total cholesterol and quantitative and qualitative alterations of high-density lipoprotein (HDL). The aim of the present study was to explore HDL metabolic activities in a patient with LPL deficiency and in his family (n = 11). MATERIALS AND METHODS: Subjects were divided into four groups: proband (Ser447Stop/Arg170Leu carrier), Ser447Stop carriers, Arg170Leu carriers and silent mutation/wild-type carriers (controls). Cholesterol efflux from Fu5AH cells, lecithin:cholesterol acyltransferase (LCAT), cholesteryl ester transfer protein (CETP), paraoxonase 1 (PON1) and platelet-activating factor acetylhydrolase (PAF-AH) activities were evaluated. RESULTS: Comparison between the proband and the control group revealed that the boy had significantly reduced cholesterol efflux (P < 0.001), conserved LCAT activity (P > 0.05) and increased CETP activity (P < 0.001). As regards antioxidant enzymes, while PON1 activity was higher in the proband than in the controls (P < 0.0001), PAF-AH activity was reduced (P < 0.05). The other groups did not show relevant differences in comparison with controls. CONCLUSIONS: The presence of one mutation was not enough to introduce important modifications in HDL functions. Markedly reduced HDL levels can keep certain normal enzymatic activities, which probably tend to counteract the deleterious effects of LPL deficiency.

Apolipoprotein A-I↗
PubMed1990

Effects of Spirulina platensis on plasma lipoprotein lipase activity in fructose-induced hyperlipidemic rats.

The effects of Spirulina platensis on lipoprotein lipase activity and hepatic triglyceride lipase activity in post-heparin plasma were studied in fructose-induced hyperlipidemic rats. Male Wistar rats aged 3 weeks old (body weight, 54 g) were fed on the high-fructose diet (68%) or the high-fructose diets containing Spirulina at the level of 5, 10, and 15%, respectively, for 4 weeks. The dietary hyperlipidemia caused by the high-fructose diet was improved by Spirulina feeding, accompanied by a significant increase in the lipoprotein lipase activity in post-heparin plasma.

Animals↗
PubMed1995

Analysis of ligand binding to the alpha 2-macroglobulin receptor/low density lipoprotein receptor-related protein. Evidence that lipoprotein lipase and the carboxyl-terminal domain of the receptor-associated protein bind to the same site.

The endocytic alpha 2-macroglobulin receptor/low density lipoprotein receptor-related protein (alpha 2MR/LRP) binds several classes of extracellular ligands at independent sites. In addition, alpha 2MR/LRP can bind multiple copies of the 39-40-kDa receptor-associated protein (RAP). Both amino-terminal and carboxyl-terminal fragments of RAP exhibit affinity, and the fragments apparently bind to different sites on the receptor. RAP completely inhibits the binding of all presently known extracellular ligands, whereas several ligands such as alpha 2-macroglobulin and tissue-type plasminogen activator are poor inhibitors of RAP binding. Since RAP is largely an intracellular molecule that normally does not occupy alpha 2MR/LRP at the cell surface, we hypothesized that an established extracellular ligand might bind to those sites on the receptor capable of binding the RAP fragments. We found complete cross-competition between carboxyl-terminal RAP fragments and fragments of lipoprotein lipase containing the recently identified binding domain for alpha 2MR/LRP (Nykjaer, A., Nielsen, M., Lookene, A., Meyer, N., Røigaard, H., Etzerodt, M., Beisiegel, U., Olivecrona, G., and Gliemann, J. (1994) J. Biol. Chem. 269, 31747-31755). Moreover, the lipoprotein lipase fragment completely inhibited the binding of several alpha 2MR/LRP ligands in a pattern similar to that of carboxyl-terminal RAP fragments. On the other hand, the amino-terminal RAP fragment was a poor competitor of binding of the lipoprotein lipase fragment, whereas it competed effectively with pro-uPA for binding to the receptor. The results provide evidence that lipoprotein lipase binds to the site on alpha2MR/LRP also available for binding of the carboxyl-terminal domain of RAP and suggest that pro-uPA may bind to or overlap the site available for the amino-terminal domain of RAP.

Amino Acid Sequence↗
PubMed2000

The lipoprotein lipase activator, NO-1886, suppresses fat accumulation and insulin resistance in rats fed a high-fat diet.

AIMS/HYPOTHESIS: Fat balance is critical in the aetiology of obesity and related diseases. Lipoprotein lipase is of major importance in lipid metabolism. The aim of this study was to investigate the long-term effects of the lipoprotein lipase activator, NO-1886, on substrate utilisation, adiposity and insulin action in rats fed a high-fat diet. METHODS: Male, Sprague-Dawley rats were fed for 10 weeks on a chow diet or a high-fat diet with, or without, NO-1886 (50 mg x kg(-1) x day(-1)). Weight gain, fat accumulation and both hormone-sensitive and lipoprotein, lipase activities were measured. Insulin action was assessed by the euglycaemic hyperinsulinaemic clamp and metabolic rate/substrate utilisation by open-circuit respirometry. RESULTS: Compared with chow-fed controls, a high-fat diet increased weight gain, an effect lessened by NO-1886 [weight gain (g): chow, 37 +/- 3, high-fat, 222 +/- 9; high-fat + NO-1886, 109 +/- 6, all groups differed p < 0.001]. A similar pattern existed for fat accumulation [visceral fat (g): chow, 35.9 +/- 3.2; high-fat, 81.9 +/- 6.6; high-fat + NO-1886, 52.3 +/- 4.7, p < 0.01 high-fat vs the other groups]. A high-fat diet induced wholebody insulin resistance (clamp glucose infusion rate: 4.8 +/- 1.3 mg x kg(-1) x min(-1) vs 10.6 +/- 1.1 for the chow group, p < 0.01) with NO-1886 lessening this effect (8.3 +/- 0.5, p < 0.05 vs high-fat). The 24-h respiratory quotient was lower in the high-fat + NO-1886 group (0.825 +/- 0.010) compared with high-fat alone (0.849 +/- 0.004, p < 0.05). A high-fat diet increased lipoprotein and hormone-sensitive, lipase activities in epididymal fat, an effect not altered by NO-1886. In myocardium and skeletal muscle a high-fat diet lowered lipoprotein lipase activity, an effect lessened by NO-1886. CONCLUSION/INTERPRETATION: Lipoprotein lipase activators could have potential benefits for the treatment of obesity by increasing fat utilisation.

Adipose Tissue↗
PubMed1977

Lack of fatty acid specificity in the lipolysis of oligo and polyunsaturated triacylglycerols by milk lipoprotein lipase.

Native soybean and rapeseed oils and native and rearranged cod liver and peanut oils were subjected to partial hydrolysis with milk lipoprotein lipase and the fatty acid composition and molecular association in the substrates and lipolysis products were determined. In both native and rearranged oils the lack of significant differences in the fatty acid composition and molecular association between the residual and total triacylglycerols suggested that all triacylglycerols were attacked by the lipoprotein lipase at about the same rate. Any enrichment of a specific fatty acid in the diacyl- or monoacylglycerol products of a native oil generally reflected the preferential association of the fatty acid with the 2-position, and to a lesser extent the sn-3-position of the glycerol molecule and was accompanied by a decreased level of the corresponding free fatty acid product. In general, the products of the rearranged oils closely resembled the original triacylglycerols in the fatty acid composition. It is concluded that lipoprotein lipase does not show any detectable specificity for the unsaturated and polyunsaturated fatty acids with double bonds located at carbons 3 to 19 from the carboxyl end of the fatty acid molecules. These findings are compatible with the possible binding of the substrate to lipoprotein lipase through atoms involved in the acyl ester groups of the triacylglycerol molecules.

Animals↗
PubMed2006

Plasma triglyceride and HDL-cholesterol concentrations in Vietnamese girls are affected by lipoprotein lipase, but not apolipoprotein CIII polymorphism.

Lipoprotein lipase (LPL) and apolipoprotein CIII (apoCIII) play an important role in HDL-cholesterol and triglyceride metabolism. This study examined the effects of LPL S447X and apoCIII SstI polymorphisms on the plasma lipid and lipoprotein concentrations in Vietnamese girls. Three hundred and fifty-one Vietnamese girls, from 7 to 9 y of age, were randomly selected from the urban and rural areas of Ho Chi Minh City, Vietnam. The presence of LPL S447X and apoCIII polymorphism was determined using the Invader assay, and the plasma lipid concentrations were measured by an enzymatic method. Dietary intakes and anthropometrics were assessed for each child. The frequencies of LPL 447X (11.9%) and apoCIII S2 (32.6%) polymorphisms in the Vietnamese were similar to those of other Asian populations. The frequency of LPL 447X was the same as that in Caucasians but the frequency of apoCIII S2 was approximately 3.8 times that in Caucasians. Overall, LPL 447X polymorphism was associated with a higher HDL-cholesterol concentration (7.4%, P = 0.007) and a lower triglyceride concentration (-13.6%, P = 0.04) than LPL 447S. The apoCIII S2 polymorphism was not associated with an increase in the plasma triglyceride concentration in Vietnamese girls with a low fat intake. However, due to the high frequency of the apoCIII SstI polymorphism and the increasingly westernized diet in Vietnam, attention should be paid to the interaction of genotype with the Vietnamese diet.

Alleles↗
PubMed2000

Zinc deficiency and the activities of lipoprotein lipase in plasma and tissues of rats force-fed diets with coconut oil or fish oil.

The present study was performed to investigate the effect of zinc deficiency on the activities of lipoprotein lipase in postheparin serum and tissues of rats fed diets containing either coconut oil or fish oil as dietary fat, using a bifactorial experimental design. To ensure an adequate food intake, all the rats were force-fed by gastric tube. Experimental diets contained either 0.8 mg zinc/kg (zinc-deficient diets) or 40 mg zinc/kg (zinc-adequate diets). The effects of zinc deficiency on the activities of lipoprotein lipase in postheparin serum and postprandial triglyceride concentrations and distribution of apolipoproteins in serum lipoproteins depended on the type of dietary fat. Zinc-deficient rats fed the coconut oil diet exhibited a reduced activity of lipoprotein lipase in postheparin serum and adipose tissue, markedly increased concentrations of triglycerides in serum, and a markedly reduced content of apolipoprotein C in triglyceride-rich lipoproteins and high density lipoproteins compared with zinc-adequate rats fed coconut oil. By contrast, zinc-deficient rats fed the fish oil diet did not exhibit reduced activities of lipoprotein lipase in postheparin serum and adipose tissue and increased concentrations of serum lipids compared with zinc-adequate rats fed the fish oil diet. This study suggests that a reduced activity of lipoprotein lipase might contribute to increased postprandial concentrations of serum triglycerides observed in zinc-deficient animals. However, it also demonstrates that the effects of zinc deficiency on lipoprotein metabolism are influenced by dietary fatty acids.

Journal Article↗
PubMed1983

Soluble and membrane-bound forms of lipoprotein lipase in mouse lung tissue.

Homogenates of mouse lungs were separated by differential centrifugation into two fractions containing lipoprotein lipase, namely, a soluble and a membrane-bound fraction. Lipoprotein lipase was specifically identified by its inhibition by both protamine sulfate (3 mg/ml) and sodium chloride (0.9 mol/l). The enzymatic activity of each fraction was enhanced when serum was preincubated with the enzyme. Both enzyme fractions showed optimum activity at alkaline pH, but the membrane-bound enzyme showed a higher pH optimum. In addition, the apparent Km of the soluble enzyme was lower than that of the membrane-bound enzyme. It is concluded that there are two different forms of lipoprotein lipase in mouse lung tissue that differ in a number of aspects.

Animals↗
PubMed1986

Characterization of the lipoprotein lipase in the functional pool of rat heart by immunoblotting.

Rat hearts were perfused with heparin for 2 min at 4 degrees C. The lipoprotein lipase activity in the perfusate was inhibited by antiserum to rat adipose tissue lipoprotein lipase. By immunoblotting, the lipoprotein lipase derived from the functional pool of the heart was found to be a protein with an apparent Mr of 69 000. After incubation of the perfusate at 37 degrees C for 24 h an immunologically reactive protein with an apparent Mr of 28 000 was found. This protein is not a physiological derivative of the enzyme but a degradation product.

Animals↗
PubMed1981

Estradiol-induced changes in lipoprotein lipase, eating, and body weight in rats.

Daily injections of 5 micrograms estradiol benzoate (EB) for 1, 2, 3, and 12 days decreased parametrial and retroperitoneal adipose tissue lipoprotein lipase activity in ovariectomized rats. Nearly all of this decrease occurred within the 1st day. In contrast, EB-induced body weight loss and hypophagia were very slight during the 1st day after EB administration and increased substantially over the next 2 days. EB did not affect gastrocnemius muscle lipoprotein lipase activity over the first 3 days, but did decrease muscle lipoprotein lipase activity after 12 days. These changes in adipose and muscle lipoprotein lipase activity suggested that EB-induced redistribution of fuel would be greater after 3 days of treatment than after 12 days of treatment. Tests with two different in vivo triglyceride uptake methods confirmed this suggestion. EB-treated rats were hypertriglyceridemic after 12 days of treatment, but not after 3 days of treatment. Elevated plasma triglycerides were associated with an increased rate of triglyceride entry. These findings are consistent with the hypothesis that EB administration temporarily results in redistribution of triglyceride fuel from adipose tissue to muscle, resulting in a transient decrease in rate of weight gain.

Adipose Tissue↗
PubMed1982

Increase of postheparin plasma-lipoprotein-lipase activity in ventromedial-hypothalamic obesity in rats.

Postheparin plasma-lipoprotein lipase (LPL) and hepatic triglyceride lipase (H-TGL) were investigated in rats 1 week after ventromedial-hypothalamic lesions. The enzyme activities were measured using radio-labelled triolein as a substrate. Two lipases were measured separately using specific antiserum prepared against H-TGL. VMH-lesioned rats fed ad lib. showed an increase in plasma LPL with normal H-TGL activity and an elevation of plasma insulin. There was a positive correlation between plasma-LPL activity and insulin levels in VMH-lesioned rats. When rats were examined after overnight fast, VMH-lesioned rats again showed an increase in plasma LPL with normal H-TGL activity and an elevation of plasma insulin. There was also a positive correlation between plasma LPL activity and insulin levels. In order to examine the effect of insulin, rats were treated with daily doses of 3 units of insulin for 1 week. Rats fed ad lib. were insulin treatment showed an increase in plasma LPL with normal H-TGL activity. These results indicate that hyperinsulinemia which was produced by VMH lesions may increase postheparin plasma-LPL activity. We speculate that this increase in plasma-LPL activity mainly reflects that of adipose tissue. The increase of LPL activity can accelerate fat deposition into adipose tissue, contributing to one of the factors causing hypothalamic obesity.

Adipose Tissue↗
PubMed1987

Molecular cloning and sequence analysis of cDNA encoding lipoprotein lipase of guinea pig.

We have isolated and sequenced cDNA clones covering the entire coding sequence and short flanking regions of guinea pig lipoprotein lipase. The expression cDNA library used was constructed in lambda gt11 with mRNA derived from adipocytes. The deduced amino acid (aa) sequence starts with a stretch of 17 aa interpreted as a leader peptide. The open reading frame continues with 448 aa residues and ends with a TGA stop codon. Combined with previous data this information allows the assignment of domains in the lipase molecule. A likely candidate for the heparin-binding site is a 9-aa stretch containing five positive charges, analogous to the consensus sequence for receptor-binding sites on apolipoproteins E and B. A previously noted homology to pancreatic lipase is extended. Analysis of polyadenylated RNA from several tissues indicated a high level of expression in adipocytes, heart muscle and mammary gland. No lipoprotein lipase mRNA could be detected in liver. Northern blots revealed three major mRNAs with sizes corresponding to 3.8 kb, 3.3 kb and 2.1 kb, respectively. In adipocytes and heart muscle a fourth mRNA, with an estimated size of 4.5 kb, was also detected. Analysis of genomic DNA by Southern blotting indicated a single gene locus coding for lipoprotein lipase. Hence, modification of the primary transcript seems to be involved in the production of the various mRNAs.

Amino Acid Sequence↗