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At least 1,315 records · Page 73Linked to original sources
PubMed1992

Human lipoprotein lipase: relationship of activity, heparin affinity, and conformation as studied with monoclonal antibodies.

The objective of this study was to investigate how a conformational change in lipoprotein lipase (LPL) affects its molecular functions. Monoclonal antibodies (MAbs) were raised against purified bovine milk lipoprotein lipase. MAb 5D2 bound to human and bovine LPL both before and after denaturation of LPL. MAb 5F9 also recognized LPL from both species, but only after denaturation of the antigen, suggesting that a conformational change led to exposure of a previously hidden epitope. The MAbs were used in two sandwich enzyme-linked immunosorbent assays (ELISAs). One ELISA used the same MAb (5D2) to coat the plate and detect the bound antigen. This ELISA thus required the same epitope to be present in duplicate for detection (as would be the case with a dimeric antigen). The second ELISA used MAb 5F9 to coat the plate and MAb 5D2 to detect the antigen. This ELISA detected LPL only after it had been denatured. By measuring the same sample before and after denaturation with guanidine hydrochloride (GuHCl) in the 5F9 ELISA, and subtracting one from the other, a measure of native LPL was obtained. In inactivation experiments using human LPL, activity and the measure of LPL mass obtained in the 5D2 ELISA decreased and were related inversely to the measured mass obtained in the 5F9 ELISA which increased, indicating that loss of activity is closely linked to dimer dissociation and loss of native conformation. The effect of conformation and dimeric structure on LPL-heparin interaction was studied by heparin-Sepharose chromatography.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Decreased susceptibility of glycated very low density lipoproteins to lipoprotein lipase in vitro and prevention by glutathione.

In vitro glycation of very low density lipoprotein (VLDL) reduced the susceptibility to lipoprotein lipase (LPL) as the level of glycation increased. Addition of reduced glutathione to an incubation medium of serum and glucose interfered with glycation of serum proteins when the concentration of reduced glutathione was higher than 10 mM. At concentrations higher than 25 mM, it also significantly prevented the glycation induced reduction of fatty acid releases from VLDL by LPL. There were no such effects on glycation of serum protein and the fatty acid release from the addition of aminoguanidine. By contrast, addition of D-lysine enhanced glycation of serum proteins by glucose and further decreased fatty acid release from VLDL by LPL. From these results, it is suggested that glycation of VLDL decreases the susceptibility of VLDL to LPL. Delayed catabolism of VLDL in diabetic patients is considered partly caused by glycation of apoproteins, which renders VLDL less sensitive to LPL, in addition to the decreased LPL activity in diabetes mellitus.

Catalysis↗
PubMed1992

Selective measurement of lipoprotein lipase and hepatic triglyceride lipase in heparinized plasma from horses.

Affinity chromatography on heparin sepharose was used to identify 2 lipolytic enzymes in heparinized plasma from horses. One enzyme was typical of hepatic triglyceride lipase (HTGL), because it was resistant to inactivation by high concentrations of NaCl, and it did not require the addition of serum for activity. The other enzyme was identified as lipoprotein lipase (LPL), because of its inactivation at NaCl concentrations in excess of 0.2M, and its dependency on addition of serum as a source of apolipoprotein C-II activator. The enzymes were purified by 347-(HTGL) and 442- (LPL) fold, with yields of 54 and 58%, respectively. The partially purified enzymes were used to design incubation conditions that gave optimal activities for each enzyme in vitro. A selective assay was then developed for direct measurement of LPL and HTGL activities in heparinized plasma from horses. Analysis of HTGL took advantage of the almost complete inactivation of LPL when serum cofactor was excluded from the assay at the NaCl concentration that gave optimal HTGL activity. Prior incubation of heparinized plasma with sodium dodecyl sulfate to inhibit HTGL was necessary for measurement of LPL, because HTGL retained 67% of its activity at the NaCl concentration required for optimal LPL activity. Activity of each enzyme was measured in heparinized plasma from 12 Shetland ponies. The mean activity +/- SD for LPL was 3.22 +/- 1.04 mumol of fatty acids/ml of heparinized plasma/h (mumol of FA/ml/h. The mean activity for HTGL was 4.9 +/- 1.56 mumol of FA/ml/h. The performance of the assay was assessed by replicate analysis of pools of each enzyme with high and low activities.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1996

Muscle-specific overexpression of lipoprotein lipase in transgenic mice results in increased alpha-tocopherol levels in skeletal muscle.

Lipoprotein lipase (LPL) has been implicated in the delivery of chylomicron-located alpha-tocopherol (alpha-TocH) to peripheral tissues. To investigate the role of LPL in the cellular uptake of alpha-TocH in peripheral tissue in vivo, three lines of transgenic mice [mouse creatine kinase- (MCK) L, MCK-M and MCK-H] expressing various amounts of human LPL were compared with regard to alpha-TocH levels in plasma, skeletal muscle, cardiac muscle, adipose tissue and brain. Depending on the copy number of the transgene, LPL activity was increased 3- to 27-fold in skeletal muscle and 1.3- to 3.7-fold in cardiac muscle. The intracellular levels of alpha-TocH in skeletal muscle were significantly increased in MCK-M and MCK-H animals and correlated highly with the tissue-specific LPL activity (r = 0.998). The highest levels were observed in MCK-H (21.4 nmol/g) followed by MCK-M (13.3 nmol/g) and MCK-L (8.2 nmol/g) animals when compared with control mice (7.3 nmol/g). Excellent correlation was also observed between intracellular alpha-TocH and non-esterified fatty acid (NEFA) levels (r = 0.998). Although LPL activities in cardiac muscle were also increased in the transgenic mouse lines, alpha-TocH concentrations in the heart remained unchanged. Similarly, alpha-TocH levels in plasma, adipose tissue and brain were unaffected by the tissue specific over-expression of LPL in muscle. The transgenic model presented in this report provides evidence that the uptake of alpha-TocH in muscle is directly dependent on the level of LPL expression in vivo. Increased intracellular alpha-TocH concentrations with increased triglyceride lipolysis and NEFA uptake might protect the myocyte from oxidative damage during increased beta-oxidation.

Adipose Tissue↗
PubMed1998

Streptozotocin-induced diabetes enhances cardiac heparin-releasable lipoprotein lipase activity in spontaneously hypertensive rats.

Vascular endothelial-bound lipoprotein lipase (LPL), also known as heparin-releasable LPL, catalyzes the breakdown of the triglyceride component of lipoproteins and is rate-limiting for free fatty acid transport to tissues. We previously demonstrated that heparin-releasable LPL activity increases in diabetic Wistar rat hearts, whereas with the development of hypertension in spontaneously hypertensive rats (SHR), there is a concomitant and progressive reduction in LPL activity. The objective of the present study was to examine the regulation of cardiac LPL activity in SHR-diabetic rats. Heparin perfusion of the isolated Langendorff heart induced the release of LPL activity. SHR hearts demonstrated a reduction in peak heparin-releasable LPL activity, relative to Wistar controls. However, induction of streptozotocin-induced diabetes in SHR, as in Wistar rats, increased peak heparin-releasable LPL activity in perfused hearts. The elevated heparin-releasable LPL peak could not be accounted for by enhanced LPL synthesis in that both cellular and surface-bound LPL activities in myocytes from SHR-diabetic rats were low relative to control. Chronic (12-day) insulin treatment of SHR-diabetic rats reduced the augmented heparin-releasable LPL activity and increased cell-associated LPL activity. Moreover, acute (90-minute) treatment of SHR-diabetic rats with rapid-acting insulin also reduced the heparin-releasable LPL activity to normal, although it had no effect on the low cellular LPL activity. These results demonstrate that the diabetes-induced augmentation of cardiac LPL counteracts the reduction in enzyme activity associated with hypertension. This may serve to increase the delivery of free fatty acid to the heart, and the resultant metabolic changes may lead to the severe cardiomyopathy observed in the hypertensive-diabetic rat heart.

Animals↗
PubMed1987

Effect of amiodarone on serum lipids, lipoprotein lipase, and hepatic triglyceride lipase.

We have determined the effects of chronic amiodarone treatment on lipid metabolism and compared them with those of hypothyroidism in the rat. Serum triglyceride was lower in both amiodarone-treated and hypothyroid rats; total cholesterol was higher in hypothyroid rats, and serum high density lipoprotein cholesterol remained unchanged. Amiodarone increased adipose tissue lipoprotein lipase activity. Hepatic triglyceride lipase activity was decreased in both hypothyroid and amiodarone-treated groups. The effects of amiodarone on serum triglyceride and adipose tissue lipoprotein lipase were reversed by concomitant administration of T3. The activity of hepatic triglyceride lipase, however, was not increased. Our findings indicate that amiodarone causes marked changes in lipid metabolism which are similar to those found in hypothyroidism.

Adipose Tissue↗
PubMed1975

Effect of ethanol on the activity of lipoprotein lipase in adipose tissue of male and female rats.

The effect of a single large dose of ethanol on the activity of lipoprotein lipase in adipose tissue of previously fasted male and female rats was followed over a 16-hour period. Feeding of ethanol caused an increase in the plasma triacylglycerol concentration in both male and female rats. This has previously been attributed to an increased secretion of triacylglycerols from the liver into the plasma. The present results show that there is probably not any significant increase in the uptake of triacylglycerols in adipose tissue after ethanol feeding in male and female rats, since there was no major increase in the activity of lipoprotein lipase in adipose tissue. This may be a prerequisite for the ethanol-induced increase in the plasma triacylglycerol concentration and shows the unphysiological nature of ethanol as a source of energy.

Adipose Tissue↗
PubMed1981

Influence of two non-steroidal anti-inflammatory drugs on lipolysis and on plasma post-heparin lipoprotein lipase activity in normal man.

Indomethacin 50 mg i.v. or p.o. and diclofenac sodium 50 mg p.o. produced a prompt and significant increase in plasma free fatty acid concentration. In 10 subjects who took indomethacin 150 mg/d p.o. for 3 days, plasma post-heparin lipoprotein lipase activity was also significantly increased. The same effect occurred in 9 subjects treated for 3 days with diclofenac sodium 50 mg t.d.s. Since both indomethacin and diclofenac sodium are potent inhibitors of prostaglandin synthetase, these findings are consistent with the hypothesis tht prostaglandins are involved in the feed-back regulation of lipolysis, and mediate the inhibitory effect of lipolysis on lipoprotein lipase activity.

Adult↗
PubMed1996

HindIII DNA polymorphism in the lipoprotein lipase gene and plasma lipid phenotypes and carotid artery atherosclerosis.

Lipoprotein lipase (LPL) is the rate limiting enzyme in the hydrolysis of core triglyceride in chylomicron and very low density lipoprotein (VLDL) thus affecting a broad spectrum of plasma lipid levels. In this paper, we investigated the association of a HindIII polymorphism in the LPL gene with plasma lipid levels and carotid artery wall thickness measured by B-mode ultrasonography. A total of 238 Caucasian subjects were selected from the Atherosclerosis Risk In Community (ARIC) study (male = 1.31, female = 107) based on their fasting triglyceride and LDL-cholesterol levels: normolipidemic (n = 48), hypertriglyceridemic (n = 44), hypercholesterolemic (n = 36), and hypertriglyceridemic-hypercholesterolemic (n = 110) groups. We observed a marginally significant association between lipid phenotypes and HindIII genotypes (P = 0.04) in males, with the hypertriglyceridemic and hypercholesterolemic groups having a higher frequency (0.65) of the H+H+ genotype than the other two groups (pooled: 0.55). In males, there was also a significant association between HindIII genotypes and carotid artery wall thickness after considering the effects of age, body mass index, cigarette smoking, lipid phenotype and diabetes status (P = 0.013), with the H+H+ genotype having a higher average value of carotid artery wall thickness (0.84 +/- 0.15 mm) than the other two genotype groups (0.76 +/- 0.14 mm in H+H(+)-genotype class, 0.75 +/- 0.13 mm in H-H- genotype class). In females, no significant associations among LPL HindIII genotype, lipid phenotype and carotid artery wall thickness were observed. These results suggest that the LPL HindIII polymorphism influences LPL-catalyzed, triglyceride-rich lipoprotein metabolism and carotid artery atherosclerosis in a gender-specific manner.

Adult↗
PubMed1988

Use of a fluorescent radiolabeled triacylglycerol as a substrate for lipoprotein lipase and hepatic triglyceride lipase.

A fluorescent radiolabeled triacylglycerol has been synthesized by using a fluorescent fatty acid (pyrene decanoic acid) and a radiolabeled oleic acid. This analog of the natural substrate, 1(3)pyrene decanoic-2,3 (1,2)-dioleoyl-sn-glycerol, has been tested as substrate for determining lipoprotein lipase and hepatic triacylglycerol lipase activities in post-heparin plasma. Optimal conditions for the determination of the two post-heparin plasma lipases were similar to those using radiolabeled triolein. Using this substrate, both post-heparin lipases exhibited their characteristic properties (pH optimum and effect of inhibitors) and attacked external ester bonds (1 or 3) containing pyrene decanoic and oleic acids at a similar rate.

Animals↗
PubMed1996

Ginsenosides increase secretion of lipoprotein lipase by 3T3-L1 adipocytes.

Treatment of 3T3-L1 adipocytes with either an oleanolic acid glycoside or a 20(S)-protopanaxatriol glycoside increased the secretion of lipoprotein lipase activity into the medium dose-dependently. At a concentration of 100 micrograms/ml, ginsenosides Ro, Re, Rg1, and Rh1 increased the secretion of lipase activity into the medium by 119, 107, 56, and 32%, respectively. The ratio of lipase activity in the medium to cellular lipase activity was 4.7% in control cells and 8.6% in ginsenoside Ro-treated cells, 8.3% in ginsenoside Re-treated cells, 7.0% in ginsenoside Rg1-treated cells, and 6.3% in ginsenoside Rh1-treated cells. Ginsenoside Rb2, which is a 20(S)-protopanaxadiol glycoside, increased the secretion of lipase activity by 16% at 25 micrograms/ml, and the ratio of lipase activity in the medium to cellular lipase activity was higher in ginsenoside Rb2-treated cells than in control cells. However, at 100 and 200 micrograms/ml, ginsenoside Rb2 decreased the secretion of lipase activity in parallel with cellular lipase activity. Ginsenoside Rd also decreased the secretion of lipase activity in the same dose-dependent manner. Thus, the effective dose for the secretion of lipoprotein lipase activity with ginsenosides varies with their aglycone structure.

3T3 Cells↗
PubMed1993

Tissue-specific lipoprotein lipase: relationships to body composition and body fat distribution in normal weight humans.

Twenty-six normal weight subjects (22 female, 4 male) were studied to determine the relationships of fasting levels of lipoprotein lipase in gluteal adipose tissue (ATLPL) and skeletal muscle (SMLPL) to body composition and body fat distribution. No relationship was found between fasting gluteal ATLPL and percent (%) body fat. There was, however, an inverse relationship between fasting SMLPL (from the vastus lateralis) and %body fat (p=0.005). A strong inverse correlation was also seen between fasting ATLPL and waist/hip ratio (p=0.0006), a measurement of body fat distribution. These relationships existed with or without the male subjects included. The tissue-specific relationships of lipoprotein lipase to body composition and body fat distribution could relate to the development of obesity or the maintenance of normal body weight by the effects of the lipase on the partitioning of lipoprotein triglyceride fatty acids.

Adipose Tissue↗
PubMed1985

Synthesis and secretion of lipoprotein lipase by human monocyte-derived macrophages.

Human monocytes isolated from either defibrinated blood or buffy coat were shown to produce and secrete lipoprotein lipase during culture. The secretion occurred constitutively. Low levels of enzyme activity in the medium from freshly isolated cells increased with time of incubation, and maximal activity was attained after 9 days. The addition of heparin resulted in a substantial increase of enzyme activity in the culture medium. The optimal concentration of heparin was about 2 U/ml. The production of lipoprotein lipase was dependent on the presence of serum in the culture medium, and the optimal supplementation of serum was 25-50%.

Cells, Cultured↗
PubMed1960

Changes in blood coagulation during the clearing of lipid emulsions by lipoprotein lipase.

The clearing of lipid emulsions by postheparin plasma from rabbits or human beings was accompanied regularly by a sharp reduction in the recalcification time of the plasma. No change in blood coagulation took place when the activity of lipoprotein lipase, the clearing enzyme, was inhibited by means of heat or the action of a surface-active agent. In control studies, the recalcification time of postheparin plasma was not altered by the addition of glycerol, free fatty acids, or the products of hydrolysis of a lipid emulsion. Taken together, the findings indicated that a heat-labile factor was released during the course of clearing which was capable of inactivating reversibly the anti-coagulant properties of heparin.

Animals↗
PubMed2000

Type I hyperlipoproteinemia due to a novel loss of function mutation of lipoprotein lipase, Cys(239)-->Trp, associated with recurrent severe pancreatitis.

Lipoprotein lipase (LPL) is the major enzyme responsible for the hydrolysis of triglyceride-rich lipoproteins in plasma. The purpose of this study was to examine the molecular pathogenesis of type I hyperlipoproteinemia in a patient suffering from recurrent severe pancreatitis. Apolipoprotein (apo) CII concentration was normal as well as apo CII-activated LPL in an in vitro assay. In postheparin plasma neither LPL mass nor activity was detectable, whereas hepatic lipase activity was normal. Direct sequencing of all 10 exons of the LPL gene revealed that the patient was homozygous for a hitherto unknown mutation in exon 6, Cys(239)-->Trp. The mutation prevents the formation of the second disulfide bridge of LPL, which is an essential part of the lid covering the catalytic center. Consequently, misfolded LPL is rapidly degraded within the cells, causing the absence of LPL immunoreactive protein in the plasma of this patient. In conclusion, we have identified a novel loss of function mutation in the LPL gene (Cys(239)-->Trp) of a patient with type I hyperlipoproteinemia suffering from severe recurrent pancreatitis. After initiation of heparin therapy (10,000 U/day sc), the patient experienced no more episodes of pancreatitis, although heparin therapy did not affect serum triglyceride levels.

Amino Acid Substitution↗
PubMed2006

Association of two genetic variations of lipoprotein lipase, S447X and Hind III, with coronary artery disease and hypertriglyceridemia.

This study was performed to assess the effect of the S447X and Hind III lipoprotein lipase gene polymorphisms on development of coronary artery disease and hypertriglyceridemia. The study included 132 patients and 98 healthy control subjects of Croatian descent. The lipoprotein lipase S447X polymorphism was associated with coronary artery disease and hypertriglyceridemia, as indicated by the lower frequency of S447 allele in the patient group (p = 0.005) and odds ratio (O.R = 0.40, p = 0.006). The patient and control groups also showed a significant difference in the distribution of Hind III/S447X genotype combinations (p = 0.013). There were no significant associations with lipid parameters for any genotype or genotype combination in the patient group. Frequencies of the S447X polymorphism and S447X/Hind III combinations differed between the CAD/TG and control group, thus these polymorphisms may be associated with CAD and hypertriglyceridemia.

Adult↗
PubMed1993

Changes in lipoprotein lipase activity and plasma liver lipids in thiram intoxicated rats.

Acute thiram (tetramethyl-bis-thiocarbamyl disulphide) poisoning of rat (a single dose of 50% LD50) caused decreased lipoprotein lipase (LPL) activity in adipose tissue, the greatest inhibition being observed at 72 h after administration of the pesticide. Simultaneously, the levels of total plasma cholesterol, triacylglycerols and the high density lipoprotein (HDL) cholesterol were increased. On repeated pesticide administration (5% LD50) decreased LPL activity was observed after 14 and 30 days of poisoning, whereas after 90 days the LPL activity was distinctly increased. The levels of total cholesterol (in all periods of poisoning) and HDL cholesterol (only after 30 days of poisoning) became increased. These changes were accompanied by decreased content of free fatty acids and increase of hepatic triacylglycerols. The changes observed in the lipoprotein lipase activity of thiram-poisoned rats correspond to the profiles of plasma lipoproteins typical of thyroid hypofunction.

Adipose Tissue↗
PubMed1988

Effect of dichlorvos on the activity of lipoprotein lipase from adipose tissue, on plasma lipids and postheparin lipolytic plasma activity in rats.

The activity of lipoprotein lipase (LPL) from adipose tissue, the postheparin lipolytic activity (PHLA) in plasma, and the content of plasma lipoproteins were investigated in rats poisoned with dichlorvos (DDVP). Administration of a single dose (50% LD50) resulted in inhibition of LPL and PHLA; the greatest inhibition was observed at 24 and 48 h after administration of the posticide. The metabolism of serum lipoproteins was also altered; the content of triacylglycerols in very low density lipoproteins (VLDL) and low density lipoproteins (LDL) fractions was increased; the content of cholesterol was increased in VLDL and high density lipoproteins (HDL) fractions, and decreased in the LDL fraction. On repeated administration of small DDVP doses (5% LD50) the greatest changes were observed after 90 days of intoxication. The levels of all three determined lipoprotein fractions, as well as PHLA, were decreased. The LPL activity in adipose tissue was slightly raised. The results suggest that DDVP interferes with the metabolism of lipids.

Adipose Tissue↗