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PubMed1977

Lipoprotein lipase. Isolation and characterization of a second enzyme species from postheparin plasma.

A lipoprotein lipase species (mol wt 69 250) has been isolated from rat postheparin plasma, which differs from the low-molecular-weight species previously characterized in its amino acid composition and hexosamine content, and in its lower affinity for triglyceride-rich lipoprotein substrates. However, both enzymes are activated by the same coprotein (C-terminal glutamic acid, apo-C-2) from human very low density lipoprotein and have a similar specificity for lipid esters. Neither purified enzyme is activated by heparin. Both are inhibited by molar sodium chloride. Both enzyme species can be recovered from the same plasma samples. The possible relationship of these proteins to the different functional lipoprotein lipase activities of muscle and adipose tissues is discussed.

Amino Acids↗

PubMed2000

PLTP activity in premenopausal women. Relationship with lipoprotein lipase, HDL, LDL, body fat, and insulin resistance.

Plasma phospholipid transfer protein (PLTP) is thought to play a major role in the facilitated transfer of phospholipids between lipoproteins and in the modulation of high density lipoprotein (HDL) particle size and composition. However, little has been reported concerning the relationships of PLTP with plasma lipoprotein parameters, lipolytic enzymes, body fat distribution, insulin, and glucose in normolipidemic individuals, particularly females. In the present study, 50 normolipidemic healthy premenopausal females were investigated. The relationships between the plasma PLTP activity and selected variables were assessed. PLTP activity was significantly and positively correlated with low density lipoprotein (LDL) cholesterol (r(s) = 0.53), apoB (r(s) = 0.44), glucose (r(s) = 0.40), HDL cholesterol (r(s) = 0.38), HDL(3) cholesterol (r(s) = 0.37), lipoprotein lipase activity (r(s) = 0.36), insulin (r(s) = 0.33), subcutaneous abdominal fat (r(s) = 0.36), intra-abdominal fat (r(s) = 0.29), and body mass index (r(s) = 0.29). HDL(2) cholesterol, triglyceride, and hepatic lipase were not significantly related to PLTP activity. As HDL(2) can be decreased by hepatic lipase and hepatic lipase is increased in obesity with increasing intra-abdominal fat, the participants were divided into sub-groups of non-obese (n = 35) and obese (n = 15) individuals and the correlation of PLTP with HDL(2) cholesterol was re-examined. In the non-obese subjects, HDL(2) cholesterol was found to be significantly and positively related to PLTP activity (r(s) = 0.44). Adjustment of the HDL(2) values for the effect of hepatic lipase activity resulted in a significant positive correlation between PLTP and HDL(2) (r(s) = 0.41), indicating that the strength of the relationship between PLTP activity and HDL(2) can be reduced by the opposing effect of hepatic lipase on HDL(2) concentrations. We conclude that PLTP-facilitated lipid transfer activity is related to HDL and LDL metabolism, as well as lipoprotein lipase activity, adiposity, and insulin resistance.

Adipose Tissue↗

PubMed1985

Is muscle lipoprotein lipase inactivated by ordinary amounts of dietary carbohydrates?

Lipoprotein metabolism was investigated in 12 patients, healthy except for renal stone disease, who received a high-protein experimental diet for 2 weeks under metabolic ward conditions. The results were compared with those after 2 weeks on a control diet of ordinary composition. The patients were randomly allocated to begin with the control or experimental diet. The energy contributions from protein, carbohydrate and fat were 12, 48 and 41 per cent in the control diet and 29, 31 and 41 per cent in the experimental diet, respectively. Fasting concentrations of very-low-density lipoprotein (VLDL) triglycerides and cholesterol were lower with the high-protein than with the control diet (0.69 vs 1.4 mmol/l, P less than 0.0001, and 0.33 vs 0.47 mmol/l P less than 0.01, respectively). High-density lipoprotein cholesterol tended to be higher (0.05 less than P less than 0.10) with the high-protein diet. Lipoprotein-lipase (LPL) activity in skeletal muscle and the fractional catabolic rate constant of an intravenous fat tolerance test were higher with the high-protein than with the control diet (38 vs 21 mU/l, P less than 0.01, and 5.1 vs 3.6 mU/l, P less than 0.001, respectively). Neither fasting blood glucose, intravenous glucose tolerance nor insulin concentrations differed between the two dietary periods. These findings indicate that an 'ordinary' intake of refined carbohydrates has an inhibitory effect on the muscle LPL activity, thereby increasing the VLDL level and slightly decreasing the level of high-density lipoproteins, which may be of relevance for the atherosclerotic process.

Adult↗

PubMed1980

[Lipoprotein lipase. Interest in clinical biochemistry (author's transl)].

Lipoprotein lipase (LPL) is an enzyme which hydrolyses triglycerides especially VLDL and chylomicrons triglycerides. The measurement of LPL can be of interest in clinical biochemistry. There is no LPL in blood circulation, but it is possible to release it by heparin intravenous injection. However, heparin releases also other enzymes, particularly hepatic triglyceride lipase (HTGL). It is then post-heparin lipolytic activity (PHLA) which is determined. It is possible to measure separately LPL and HTGL, by using antibodies or inhibitors so chosen to be specific to one or the other enzyme. The main variations of LPL and HTGL in various diseases or treatments at present known are reported. LPL has also been recently involved in atherosclerosis pathogeny.

Adipose Tissue↗

PubMed1987

Effect of dibutyryl cyclic AMP and theophylline on lipoprotein lipase secretion by human monocyte-derived macrophages.

The effect of dibutyryl cyclic AMP and theophylline on lipoprotein lipase secretion was investigated after a 24 h pretreatment of human monocyte-derived macrophages. Both the effectors decreased in a dose-dependent manner the enzyme activity recovered in the culture medium. The decrease in lipoprotein lipase activity appeared to be related to reduced enzyme synthesis without apparent modification of its stability and half-life and was conversely associated with an increase of lysosomal acid hydrolase activities. This effect was reversible on removal of the nucleotide. The present findings suggest that cyclic AMP may play a role in lipoprotein lipase expression in human macrophages and therefore may participate in the regulation of lipoprotein uptake by these cells, which are strongly implicated in the atherogenic process.

Bucladesine↗

PubMed1992

Prevalence, geographical distribution and genealogical investigations of mutation 188 of lipoprotein lipase gene in the French Canadian population of Québec.

Familial lipoprotein lipase deficiency (FLD) is of particular interest to the French Canadian population of Québec since the largest concentration of homozygotes and carriers of this genetic disease in the world resides in this area. We have previously described a missense mutation (M-188) in the lipoprotein lipase (LPL) gene which was present in FLD patients belonging to different ancestries, including a number of French Canadians (Monsalve MV et al. J Clin Invest 1990: 86: 728-734). In the present report, we show that this mutation, although found in largest absolute numbers among French Canadians as compared to other groups in the world, accounts for only a small proportion (24%) of all the LPL mutant alleles in this population. The M-188 occurs either in the homozygote state or as a compound heterozygote with another LPL mutation. Analysis of geographic distribution indicates that the M-188 is more prevalent in western Québec, with the highest carrier rate in the Mauricie region. Genealogical reconstruction leads to the recognition of four founders for M-188, all emigrants from France to Québec in the 17th century.

Base Sequence↗

PubMed1983

Rapid preparation of a relatively stable, partially purified lipoprotein lipase from perfused rat heart.

Rat hearts, extensively washed with cold 0.15 M NaCl solution, were perfused with 5 ml of 0.15 M NaCl containing 16 U of heparin and 10% glycerol to release endothelium-bound lipoprotein lipase. Approximately 100 mU of enzyme activity could be released from each heart (weighing about 1.7 g). Several hearts could be sequentially perfused with the same heparin solution to enrich it in lipase activity. When compared with other equally rapid and frequently used sources of rat lipoprotein lipase (such as heart acetone powder or postheparin plasma), our enzyme preparation had a much higher specific activity suggesting that a greater purification level had been already achieved in a single step. In addition, this lipoprotein lipase preparation contained only trace amounts of lipids, was stable for an hour at 37 degrees C and retained 75% of its activity after 10 days at 4 degrees C. The described procedure is a quick way to prepare a soluble, partially purified and relatively stable lipoprotein lipase that may be useful especially for the in vitro preparation of triacylglycerol-rich lipoprotein remnants.

Animals↗

PubMed1983

Adipose tissue and skeletal muscle lipoprotein lipase and hepatic lipase activities in cholesterol-fed guinea pigs.

In control and in cholesterol-fed (1%) guinea pigs, the lipoprotein lipase activities of adipose tissue and skeletal muscle and the hepatic lipase activity were assayed after elution of the enzymes from tissues by heparin. The lipoprotein lipase activities were similar in the two groups of animals; the hepatic lipase activity was found be significantly increased in the animals fed cholesterol.

Adipose Tissue↗

PubMed1983

Experimental hyperthyroidism in man: effects on plasma lipoproteins, lipoprotein lipase and hepatic lipase.

We have studied the effects of triiodothyronine administration (20-40 micrograms three times daily over one week) in six healthy young men, on the activities of lipoprotein lipase and hepatic lipase and on plasma lipoprotein concentrations. Hepatic lipase activity in post-heparin plasma rose by 46 +/- 25% (p less than 0.025), whereas the activity of lipoprotein lipase did not change significantly. Plasma cholesterol concentrations decreased by about 20% (p less than 0.025), whereas there was no change in plasma triglyceride levels. The fall in plasma cholesterol could be accounted for by a reduction of HDL cholesterol (-11%, p less than 0.025) as well as LDL cholesterol (-27%, p less than 0.025). The data emphasize the role of hepatic lipase in the lipoprotein alterations associated with thyroid dysfunction.

Adult↗

PubMed1995

Absence of N-glycosylation at asparagine 43 in human lipoprotein lipase induces its accumulation in the rough endoplasmic reticulum and alters this cellular compartment.

Lipoprotein lipase (LPL) is the enzyme responsible for the hydrolysis of plasma triglycerides from apolipoprotein C-II-containing lipoproteins at the capillary endothelium and it is synthesized in parenchymal cells of several tissues. Intracellular LPL processing is a major aspect of LPL regulation. The present study aims to determine the intracellular accumulation site of the LPL that is not glycosylated at Asn43. Human LPL (hLPL) cDNA was mutated by site-directed mutagenesis. An Ala residue was substituted for Asn at position 43 of the protein generating N43A hLPL. Wild type hLPL and the mutant hLPL were expressed in COS1 cells. Using immunofluorescence and immunoelectron microscopy we found that wild type hLPL in addition to being secreted into the medium was present in the rough endoplasmic reticulum (ER), Golgi compartments, and vesicles. Neither LPL activity nor protein was found in medium of cells expressing the mutant hLPL and all detectable protein was present exclusively in the ER identified witha specific antibody against the protein disulfide isomerase (PDI), an ER marker. In addition, the intracellular distribution of the ER of the cells that expressed the mutant protein was grossly altered. Treatment of COS1 cells with tunicamycin for 24 h had the same effect on wild type hLPL processing and edoplasmic reticulum distribution. Next, we investigated the influence of the accumulation of mutant hLPL on the intracellular transport of three other proteins that are N-glycosylated before reaching the plasma membrane: the related Bo,+ amino acid transporter (rBAT), the insulin-regulated glucose transporter (GLUT4), and the placental alkaline phosphatase (PLAP) protein. Coexpression of the mutant hLPL (but not wild type) caused the accumulation of rBAT and GLUT4 in the ER while PLAP reached the plasma membrane. Our findings demonstrate that glycosylation of Asn43 of human lipoprotein lipase in the endoplasmic reticulum is essential for its efflux from this compartment and that the retention of the non-glycosylated LPL induces morphological changes in the ER that could also affect its ability to modify the transport of other proteins.

Asparagine↗

PubMed1992

Free fatty acids do not release lipoprotein lipase from isolated cardiac myocytes or perfused hearts.

Lipoprotein lipase (LPL), located at the vascular endothelium, catalyzes the hydrolysis of plasma triacylglycerols to fatty acids and 2-monoacylglycerol. In the heart, LPL is synthesized in cardiac myocytes and then translocated to the vascular endothelium. We investigated whether lipolytic products could displace LPL from the cell surface of cardiac myocytes isolated from adult rat hearts. Incubation of myocytes with 0.15-0.9 mM oleic acid or 0.1 mM monoolein did not produce a significant increase in LPL activity in the medium. LPL on the cell surface of intact myocytes hydrolyzed exogenous [3H]triolein, but there was no associated increase in LPL activity measured in the medium. Perfusion of isolated hearts with heparin (5 U/ml) resulted in displacement of LPL from the capillary endothelium. Addition of 0.9 mM oleic acid to the perfusion medium did not increase perfusate LPL activity with perfused hearts from either control or fasted rats. Therefore lipolytic products do not release active LPL from binding sites at the surface of isolated cardiac myocytes or capillary endothelial cells in perfused hearts.

Animals↗

PubMed1990

Lipoprotein lipase activity in white adipose tissue of rats subjected to exercise--rest cycles.

This study was conducted to determine serum lipid levels and the activity of lipoprotein lipase in epididymal white adipose tissue of rats undergoing exercise training. During the 8-week period of treatment, one group of rats was kept sedentary and the remaining animals were exercise trained either continually (1 h of daily treadmill running) or intermittently (alternate weeks of daily running and inactivity). Exercise training, either continual or intermittent, decreased postprandial serum total and high-density lipoprotein cholesterol concentrations, which returned to sedentary levels in the intermittently trained animals following a week of rest. Lipoprotein lipase activity in whole epididymal adipose pad was lower in rats trained continually than in the sedentary group at the end of the treatment. The intermittent training program elicited large fluctuations in both the specific (per milligram of protein) and total (per tissue) activity of lipoprotein lipase in white adipose tissue. During rest periods, enzyme activity rose to levels that were higher than those of sedentary rats, whereas lipase activity was below that of sedentary animals following a week of running. In the last exercise--rest cycle, body weight gain of the intermittently trained rats was nearly abolished during the week of running, but it increased above that of sedentary animals during weeks of rest. The present results suggest that the modulation of lipoprotein lipase activity in white adipose tissue is one of the adaptations that take place to accommodate the fluctuations in the rate of energy deposition that occur in the rat during an intermittent training program.

Adipose Tissue↗

PubMed1993

Lipoprotein lipase mass and activity in severe hypertriglyceridemia.

To clarify the role of defective lipoprotein lipase (LPL) in hypertriglyceridemia, the LPL masses and LPL activities in post-heparin plasma (PHP) were studied in severe hypertriglyceridemias. The developed sandwich enzyme immunoassay for the LPL was sensitive from 0.5 to 20 ng/ml of LPL in human PHP. The plasma LPL mass increased by heparin injection (30 USP units/kg) and was found to positively correlate with LPL activity. The mean LPL activity from PHP of normal controls was 2,960 +/- 1,057 nmol/ml/h. The mean LPL masses from human pre- and 15-min post-heparin plasma from normal subjects were 25 +/- 5 ng/ml and 224 +/- 60 ng/ml, respectively. Thus the specific activity of LPL from PHP of normal controls was calculated to be 13.3 mumol FFA released/h/microgram LPL. Among hypertriglyceridemic patients with over 1,000 mg/dl of serum triglyceride, the incidence of patients with LPL masses less than -2 standard deviations (S.D.) of those of average normal control subjects was found to be 27%. Seventy percent of patients showed specific activities within + 2 S.D. of those of average control LPL, and 30% showed significantly low specific activities less than -2 S.D. despite the fact that LPL masses were not less than -2 S.D. of the average normal controls. These results suggest that the evaluation of LPL masses in PHP would be useful for finding functionally defective LPL in patients with hypertriglyceridemia, and that up to 30% severe hypertriglyceridemias may have functionally defective LPL.

Adult↗

PubMed1990

Adaptive regulation of lipoprotein lipase and salt-resistant lipase activities in essential fatty acid deficiency: an experimental study in the rat.

Lipoprotein lipase (LPL) activities of postheparin plasma, heart, lungs, and adipose tissue, and salt-resistant lipase (hepatic lipase, SRL) activities of postheparin plasma, liver, and adrenals were examined in essential fatty acid deficient (EFAD) rats and in age-matched controls. The LPL activity of heart was higher in the deficient than in the control rats, but did not differ in the other tissues. The SRL activity of postheparin plasma was twofold higher, and that of liver and adrenals approximately 50% higher in the group with EFA deficiency. It is suggested that SRL exhibits an adaptive up-regulation in EFA deficiency. This up-regulation may be linked to a role for the enzyme in the transport of polyenoic fatty acids.

Adaptation, Physiological↗

PubMed1993

Alcoholic hypertriglyceridemia with decreased activity of lipoprotein lipase and hepatic triglyceride lipase.

A 35-year-old male with alcoholic hypertriglyceridemia due to decreased lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL) activities is reported. The patient had been drinking about 180 ml of whiskey (equivalent to 80 g of 100% ethanol) every day for the last 17 years, and the highest levels of serum triglyceride (TG) and cholesterol were 5,120 mg/dl and 506 mg/dl, respectively. Serum TG level returned to normal levels after complete alcohol abstinence. Further intake of ethanol resulted in an increase in serum TG to 326 mg/dl with a concomitant decrease in the serum levels of LPL and HTGL activities.

Adult↗

PubMed1979

Lipoprotein lipase of goat mammary tissue: comparison of extraction methods.

Mammary lipoprotein lipase of lactating goats was extracted by 3 methods: homogenization of tissue acetone-ether powders; aqueous homogenization of crude tissue using an Ultra-Turrax apparatus; aqueous homogenization of crude tissue using a Sorvall Omni-mixer microhomogenizer. Although there were differences between absolute values obtained by the 3 methods, each type of homogenate had a lipolytic activity with lipoprotein lipase characteristics (i.e. more than 90% inhibition by serum omission or NaCl addition). Furthermore, the 3 methods were highly correlated and presented similar variations with the stage of lactation, in parallel with long-chain fatty acid secretion into milk. Repeatability of the measure of homogenate lipolytic activities was about 8%, whereas day-to-day repeatability of enzyme extraction and assay was about 20% for each method.

Animals↗

PubMed2001

Effect of 6 dietary fatty acids on the postprandial lipid profile, plasma fatty acids, lipoprotein lipase, and cholesterol ester transfer activities in healthy young men.

BACKGROUND: There is increasing evidence that postprandial triacylglycerol-rich lipoproteins may be related to atherogenic risk. OBJECTIVE: The objective was to investigate the effect of individual fatty acid intakes on postprandial plasma lipoprotein triacylglycerol and cholesterol concentrations, plasma fatty acids, and preheparin lipoprotein lipase and cholesterol ester transfer protein (CETP) activities. DESIGN: Six test fats high (approximately 43% by wt) in stearic acid, palmitic acid, palmitic + myristic acid, oleic acid, elaidic acid (trans 18:1), and linoleic acid were produced by interesterification. After having fasted for 12 h, 16 healthy young men were served the individual test fats incorporated into meals (1 g fat/kg body wt) in random order on different days separated by washout periods. Blood samples were drawn before and 2, 4, 6, and 8 h after the meals. RESULTS: Different responses to the test-fat meals were observed for plasma lipoprotein triacylglycerol and cholesterol concentrations, plasma fatty acid concentrations, and lipoprotein lipase and CETP activities (diet x time interaction: 0.001 < P < 0.05). Intake of the long-chain saturated fatty acids stearic and palmitic acids resulted in a relatively lower lipemic response than did intake of the unsaturated fatty acids, probably because the saturated fatty acids were absorbed less and at a lower rate; therefore, the lipemic response took longer to return to postabsorptive values. CONCLUSIONS: Fatty acid chain length and degree of saturation appear to affect the extent and duration of lipemia and affect hepatic output indirectly. These effects may not be mediated via effects on lipoprotein lipase and CETP activities.

Adult↗

PubMedDate not supplied

Enhanced lipolysis in normal mice expressing liver-derived human lipoprotein lipase after adenoviral gene transfer.

The authors previously demonstrated that the gene for human lipoprotein lipase (hLPL), an enzyme crucial to the breakdown of triglyceride (TG)-rich dietary fats, corrects the hypertriglyceridemia in lipoprotein lipase (LPL)-deficient knockout mice after adenoviral (Ad)-mediated LPL gene transfer. They have now extended their observations to primary cultured mouse hepatocytes and intact animals of normal LPL genotype, and confirm effective overexpression of hLPL from the liver and a sustained TG-lowering effect in plasma over 60 days. A typical first-generation Ad-vector containing the hLPL cDNA (Ad-LPL) resulted in efficient gene transfer into isolated mouse hepatocytes and significant de novo synthesis of active hLPL protein. In this experiment, 5 x 10(9) viral particles (5 x 10(7) pfu) of either Ad-LPL or an Ad-LacZ control vector were injected into CD1 mice of normal LPL genotype. Hepatic expression of hLPL was confirmed at Day 7 postinjection by in situ hybridization and direct measurement of LPL in the liver. This correlated with a total LPL activity (human + mouse) in postheparin plasma (PHP) of 1020.5 standard deviation [SD] 93.6 mU/mL, versus 479.5 SD 129.7 mU/mL (p < 0.001) in Ad-LacZ controls at Day 7. Respective hLPL activity comprised 49% of the total. Significantly raised levels of hLPL protein mass persisted until Day 60. Corresponding plasma TGs decreased to 39% of Ad-LacZ controls at Day 7, and, despite absent hLPL activity from Day 28 on, serum TGs remained significantly lower in Ad-LPL mice up to Day 42. Fast phase liquid chromatography analysis showed a dramatic depletion in TG-rich lipoproteins, mainly very low density lipoproteins (VLDL) and chylomicron fractions. Therefore, Ad-mediated overexpression of hepatic LPL was found to significantly decrease plasma TG levels unrelated to primary LPL deficiency.

Adenoviridae↗