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PubMed2006

[Associations between Ser447Ter gene polymorphism of lipoprotein lipase and atherosclerotic cerebral infarction].

OBJECTIVE: To investigate the relationship between lipoprotein lipase (LPL) gene Ser447Ter polymorphism and atherosclerotic cerebral infarction (CI), and to investigate the effect of Ser447Ter polymorphism on plasma lipids, carotid intima-media thickness (IMT) and carotid artery plaque (CAP) in patients with CI. METHODS: PCR-restriction fragment lengh polymorphism (PCR-RFLP) technique was used to detect LPL gene Ser447Ter polymorphism in 166 patients with CI (CI group) and 72 healthy subjects (control group). Carotid IMT and CAP were measured with carotid color ultrasonographic doppler for the patients and the controls. RESULTS: CG+GG carriers had lower plasma triglyceride (TG) levels and higher high density lipoprotein cholesterol (HDL-C) levels than CC carriers in CI group (P=0.001 and P=0.007 respectively). CG+GG carriers had lower plasma TG levels than CC carriers in control group (P=0.041). The frequency of G allele in CI patients was significantly lower than that in control subjects (P= 0.014). There was no statistical correlation between LPL Ser447Ter gene polymorphism and carotid IMT and CAP. CONCLUSION: The Ser447Terls polymorphism of LPL gene is significantly associated with plasma lipids and CI. G allele genotype may lead to decrease of plasma TG and increase of plasma HDL-C. G allele may be a protective genotype of CI.

Adult↗
PubMed1999

Lipolysis-induced iron release from diferric transferrin: Possible role of lipoprotein lipase in LDL oxidation.

Conditions leading to oxidation of LDL in vivo are still unknown. While the occurrence of oxidized lipoproteins and catalytic free iron in advanced atherosclerotic lesions has been demonstrated, the origin of both is unclear. In vivo, iron metabolism is tightly regulated by iron-binding proteins that ensure that virtually no free iron exists. We examined whether physiological events such as lipolysis might reduce pH, facilitate iron release from transferrin (Tf), and promote low density lipoprotein (LDL) oxidation. Lipolysis is brought about by lipoprotein lipase (LpL), a triglyceride hydrolase present on endothelial cell surfaces and in atherosclerotic lesions. LpL hydrolysis of Intralipid lowered pH from 7.40 to 7.00 in 10% human serum and from 7.40 to 6.88 in phosphate-buffered saline. Similar decreases in pH were also observed when very low density lipoproteins were hydrolyzed by LpL. Lipolysis was accompanied by a 2-fold increase in the release of 59Fe from Tf. Tf binding to subendothelial matrix (SEM), a site of key events in atherosclerosis, increased 2-fold as the pH decreased from 7.40 to 6.00. More free iron also bound to SEM as the pH decreased below 7.40. We next tested whether a reduction in pH promotes LDL oxidation. More oxidation products were found in LDL incubated at low pH for 24 h in 10% human serum. Malonaldehyde contents (nmol/mg protein), measured as TBARS, were 7.11 +/- 0.34 at pH 7.40, 7.65 +/- 0.49 at pH 7.00, 9.00 +/- 1.18 at pH 6.50, and 11. 54 +/- 0.63 at pH 6.00. Based on these results, we hypothesize that lipolysis-induced acidic conditions enhance iron release from Tf and increase formation of oxidized LDL.

Animals↗
PubMed1977

[Elective induction in mice of solid and ascitic carcinoma of the exocrine pancreas by the repeated doses of antibodies against a lipoprotein lipase fraction].

Small doses, repeated for months of anti-esterase-lipoprotein antibodies, from several antisera raised against a crude lipoprotein-lipase from Rabbit adipose tissue (2), induce exocrine pancreatic carcinomas in mice, without any specific barrier. This seems to be the first case of a quite elective carcinogenic process of the pancreas, by an immunological mechanism, with a very high incidence, up to 100%. Such carcinomas are highly metastatic, produce a pancreatic carcinomatous ascites, and are deadly. This immunological pathogeny is discussed., more particulary on an action of immuno-complexes in an abnormal physiological environment.

Animals↗
PubMed1994

[Primary lipoprotein lipase deficiency: clinical and genetic aspects].

Primary deficiency of the enzyme lipoprotein lipase (LPL) is an autosomal recessive disorder characterized by chylomicronemia, recurrent pancreatitis and xanthomas. In recent years, a growing number of mutations have been identified in patients with this inherited disorder and molecular defects include insertions and deletions, splicing defects, and nonsense and missense mutations. Most of these mutations are clustered in the region encoded by exon 4, 5 and 6 which forms the catalytic domain of LPL. The study of these mutations also contributes to our understanding of the structure, function relationships of the enzyme.

Adult↗
PubMed2006

Enhancement of serum lipoprotein lipase mass levels by intensive insulin therapy.

We previously reported that lipoprotein lipase mass level in preheparin serum (preheparin LPL mass) was significantly lower in type 2 diabetes mellitus compared to healthy subjects and increased by conventional insulin therapy using NPH (intermediate-acting) insulin. The aim of this study was to investigate the effects of intensive insulin therapy on preheparin LPL mass. Thirty-two subjects (total group) with type 2 diabetes receiving treatment by NPH insulin injection twice a day in the morning and evening were switched to basal bolus insulin (BBI) therapy (fast-acting insulin after each meal and NPH insulin before bedtime). In 14 subjects, the total daily insulin dose was not change after switching to BBI therapy (iso-dose group). After 3 months of BBI therapy, preheparin LPL mass increased significantly from 47 to 56 ng/ml in total group. Glycosylated hemoglobin and serum triglyceride levels decreased significantly, and high-density lipoprotein-cholesterol increased significantly. Low-density lipoprotein levels did not changed but increase in size was suggested by PAG disc electrophoresis. Similar changes were observed in the iso-dose group. These results suggest that BBI therapy enhances preheparin LPL mass, accompanied by antiatherogenic changes in glucose and lipid metabolism.

Body Mass Index↗
PubMed1999

Partial hepatectomy and/or surgical stress provoke changes in the expression of lipoprotein lipase and actin in liver and extrahepatic tissues.

The expression of lipoprotein lipase (LPL) and actin genes was examined in heart, muscle and white adipose tissue (WAT) and the expression of albumin and actin genes was examined in regenerating liver after 2/3 hepatectomy. Both surgical stress and partial hepatectomy (PH) affected LPL and actin mRNA levels in muscle and WAT, but not in heart. The changes in LPL mRNA suggest transcriptional regulation of the enzyme during hepatic regeneration. Our results show for the first time that the LPL gene expression in the different tissues studied is altered not only by the surgical stress, but also by PH per se. Actin expression is also affected in some tissues. In liver, PH and surgical stress altered the expression of albumin and total mRNA. The total mRNA of the other tissues studied did not change. The changes observed in LPL in different tissues, especially in WAT and muscle, may be responsible for some of the changes in lipidic metabolism, thus allowing for some plasma lipoproteins to be used as substrates by the LPL activity that arises in the liver during hepatic regeneration. The fatty acids derived from these lipoproteins would constitute not only an energy source but also the building material needed in the process of restoration of the lost hepatic mass. It is suggested that hormonal changes taking place after surgery are responsible for the variation in the levels of the different mRNAs studied.

Actins↗
PubMed2002

Association between preheparin serum lipoprotein lipase mass and acute myocardial infarction in Japanese men.

A sensitive immunoassay system using a specific monoclonal antibody against lipoprotein lipase (LPL) recently demonstrated the presence of an LPL mass in preheparin serum. We reported that a preheparin serum LPL mass (pre-LPL mass) reflected the level of functioning LPL activity in the whole body and could be deeply involved in the progression of coronary atherosclerosis of stable organic angina pectoris. We examined the relation between the pre-LPL mass and acute myocardial infarction (AMI). We studied 44 males with AMI (AMI group) and 16 males with a normal coronary artery (NCA group), and measured the pre-LPL mass by enzyme-linked immunosorbent assay. Coronary risk factors including the pre-LPL mass were compared between the two groups and multiple regression analysis was performed for AMI. There were no significant differences in the lipid data, but the pre-LPL mass level was significantly low in the AMI group (52 +/- 16 vs 41 +/- 14 ng/ml, p = 0.01), and a low pre-LPL mass concentration was observed in the small sized LDL group and/or the Midband positive group. Multiple regression analysis revealed that a low pre-LPL mass and hypertriglyceridemia were independent risk factors for AMI (t value = 2.1, 2.4). The result indicates that a low pre-LPL mass may be an important risk factor for AMI and stable organic angina pectoris.

Adult↗
PubMed2002

Virolytic action of lipoprotein lipase on hepatitis C virus in human sera.

In most sera of hepatitis C virus (HCV)-infected patients beta-lipoproteins are bound to HCV RNA-carrying material, most often simultaneously with immunoglobulins (IgG, IgM) and sometimes additionally with high-density lipoproteins, forming complexes of low density (1.04-1.06 g/ml). To separate HCV particles from bound material, we tried to destroy the lipoprotein enzymatically by incubating HCV-positive human sera with lipoprotein lipase derived from Pseudomonas spp. (LPL-Ps). After this treatment, titers of HCV RNA in human sera (determined by a simple semiquantitative reverse transcription-PCR assay) were strongly reduced, regardless of whether primers of the NTR or NS5 region were used. Inactivation of HCV RNA could be inhibited by the addition of RNAguard to the serum-enzyme mixture. The lytic effect of the LPL-Ps preparation could be inhibited by tetrahydrolipstatin. Hence LPL-Ps seems to disrupt the HCV particle structure, including the putative core of the virus, and makes HCV RNA sensitive for RNase present in the reaction mixture. HBV was not destroyed by LPL-Ps. Porcine pancreatic lipase had no effect on HCV. The implications of these observations for the structure and biology of HCV and for its stability and inactivation in human sera are discussed.

Animals↗
PubMed1997

Recent polymorphic insertion of an Alu repeat in the baboon lipoprotein lipase (LPL) gene.

We have identified a polymorphic insertion in the lipoprotein lipase (LPL) gene in a captive baboon colony. Mapping and nucleotide (nt) sequence analysis of the polymorphism showed that it is due to the presence or absence of an Alu repetitive element in intron 7 of the baboon LPL gene. This polymorphic Alu repeat has not been reported in humans, and we did not detect the repeat in a survey of the LPL intron 7 gene region in other non-human primates. Comparison of nt at diagnostic positions in this Alu insertion with different Alu subfamily consensus sequences showed that it most closely resembles the young AluY subfamily. These data suggest that this polymorphic Alu repeat inserted independently in the baboon lineage.

Alleles↗
PubMed1999

[A gene analysis of familial lipoprotein lipase deficiency in China].

OBJECTIVE: To investigate the gene mutation of lipoprotein lipase(LPL) of familial LPL deficiency in China. METHODS: The DNA sequencing of LPL gene of the patients was performed with the dideoxy method based on the polymerase chain reaction amplification using the genomic DNA as a template. RESULTS: It was identified that a missense mutation in exon 6 of LPL gene (6G(979)-->A) resulted in the substitution of Glu(242) by Lys in a heterozygous state. CONCLUSION: The missense mutation of LPL may play a key role in the decrease of LPL activity. This is the first report about the gene mutation of LPL at this site in familial LPL deficiency. Moreover, it contributes to the elucidation of the pathophysiological mechanisms of atherosclerosis and some metabolic diseases.

Adult↗
PubMed1977

The effect of treatment with clofibrate on hepatic triglyceride and lipoprotein lipase activities of post heparin plasma in male patients with hyperlipoproteinemia.

Twelve male patients with hyperlipoproteinemia were treated with clofibrate, 1 g twice daily. Serum triglyceride concentration decreased on the average 28 +/- 6%. No significant change of serum cholesterol concentration occurred. Post heparin plasma lipoprotein lipase activity isolated and partially purified by heparin Sepharose affinity chromatography was determined quantitatively. During the clofibrate treatment this enzyme activity increased 48 +/- 9%. The post heparin hepatic triglyceride lipase did not change significantly. The possibility that the serum triglyceride-lowering effect of clofibrate might partly be explained by an increased removal rate of triglyceride rich lipoproteins through increased lipoprotein lipase activity is discussed.

Adult↗
PubMed1995

Regulation of lipoprotein lipase translation by epinephrine in 3T3-L1 cells. Importance of the 3' untranslated region.

Lipoprotein lipase (LPL) is a central enzyme in lipoprotein metabolism and is in part responsible for adipocyte lipid accumulation. Catecholamines are known to decrease the activity of LPL in adipocytes, and we have previously demonstrated that this inhibition occurs posttranscriptionally, with a prominent inhibition of LPL translation. To better characterize the inhibition of LPL translation, 3T3-L1 cells were differentiated into adipocytes, and exposed to epinephrine. Epinephrine induced a dose-dependent decrease in LPL synthesis using [35S]methionine incorporation, with no change in LPL mRNA levels, demonstrating translational regulation of LPL in this cell line. The poly A-enriched RNA from epinephrine-treated cells was translated well in vitro, and there was no difference in the polysome profiles from control and epinephrine-treated cells, suggesting that epinephrine did not affect mRNA editing, and did not induce an inhibition of translation initiation. To obtain evidence for the presence of an inhibitory factor, a cytoplasmic extract from control, and epinephrine-treated adipocytes was human. When compared to the control cell extract, the epinephrine-treated cell extract sharply inhibited LPL translation in vitro, yet had no effect on the translation of other mRNAs. Epinephrine-treated cells had fourfold more of this inhibitor activity than control cells, and this translation inhibition was partially reversed by heat treatment. To determine what region of the LPL mRNA was involved in the translation inhibition, different LPL constructs were synthesized. The inhibitory effect of the epinephrine-treated cell extract was dependent on the presence of the first 40 nucleotides of the 3' (untranslated region UTR) (nucleotides 1599-1638), whereas deletion of the 5' UTR and other areas of the 3' UTR had no effect on translation inhibition. When a sense RNA strand corresponding to this region was added to the in vitro translation reaction, it restored translation towards normal, suggesting that the sense strand was competing for a transacting binding protein. Thus, epinephrine-treated adipocytes produced a transacting factor, probably a protein, that interacted with a region on the LPL mRNA between nucleotides 1599 and 1638, resulting in an inhibition of translation. These studies add new insight into the hormonal regulation of LPL.

3T3 Cells↗
PubMed1997

Lipoprotein lipase activity in rat cardiomyocytes is stimulated by insulin and dexamethasone.

Lipoprotein lipase (LPL) activity was studied in rat cardiomyocytes after overnight culture (16 h) in the presence of insulin (100 nM) and/or dexamethasone (100 nM). Insulin in combination with dexamethasone (INS/DEX) increased heparin-releasable LPL activity by 71% over the control level (566+/-85 versus 331+/-48 nmol/h.mg cell protein). This was accompanied by a 61% increase in total cellular LPL activity (914+/-89 versus 567+/-64 nmol/h.mg cell protein). The increase in LPL activity occurred at sub-nanomolar concentrations of the hormones, but neither hormone was effective alone. LPL protein mass, quantified by ELISA, was the same in both control and INS/DEX-treated cells (27.7 versus 28.6 ng/mg cell protein, respectively), thus LPL specific activity in cardiomyocytes was increased by INS/DEX treatment (0.113 versus 0.069 mU/ng LPL protein). These findings emphasize the importance of hormonal interactions in the regulation of LPL in heart tissue.

Analysis of Variance↗
PubMed1990

Intracellular regulation of lipoprotein lipase in human monocyte-derived macrophages.

The intracellular pathway of lipoprotein lipase (LPL) has been examined in human monocyte-derived macrophages in culture. These cells were previously shown to synthesize and constitutively secrete LPL. The secretion is dependent on new enzyme synthesis. 6-d-old human monocytes have stores of mRNA for linear release of LPL up to 24 h. Enzyme activity in cells and in culture medium was almost completely inhibited by 24 h treatment with tunicamycin, an inhibitor of glycosylation. In monensin-treated cells a pronounced increase in enzyme activity was found, whereas the secreted activity was markedly reduced. This indicates that LPL in human monocytes is processed through a pH sensitive part of the Golgi complex and that the terminal glycosylation is not needed for the expression of its catalytic activity. Our results suggest that lysosomal function is not important in secretion of the enzyme, whereas vesicular transport seem to be involved in regulating LPL in human monocyte-derived macrophages in culture.

Cell Differentiation↗
PubMed2004

Lipoprotein lipase protects bovine endothelial cells from human NK cytotoxic activity.

Human lipoprotein lipase (LPL), in a dose dependent fashion, significantly inhibited spontaneous human natural killer (NK) cells, but not lymphokine-activated killer (LAK) cytotoxic activity against bovine pulmonary endothelial cells. The effect was dependent on endothelial heparan sulfate (HS) sites, since heparitinase reverted it. When HS is added before LPL, NK and LAK cytotoxicity are markedly reduced. Endothelial and NK cell priming, with LPL and HS+LPL, significantly induced CD40 and CD154 expression, respectively. Furthermore, CD40 expression was inversely proportional to lytic units (R2 = 0.9, P < 0.001). Treating endothelial cells simultaneously with indomethacin, CD154 fusion protein, and Wortmanin prevented the CD40 effect increasing xenograft rejection. LPL and HS+LPL protect bovine endothelial cells from NK cytotoxicity by inducing CD40, CD154 expression, and secretion of soluble factors. The high, non-modulated expression of adhesion receptors and the low number of HS sites account for the minor effect of CD40 in LAK cytotoxic responses against bovine endothelial cells.

Animals↗
PubMed1978

Increased adipose tissue lipoprotein lipase activity during the development of the genetically obese rat (fa/fa).

Lipoprotein lipase (LPL) enzyme activity in epididymal adipose tissue from obese and lean Zucker rats was measured. At 5, 10, 13, and 20 wk of age obese rats have heavier fat pads, larger fat cells, and more LPL per epididymal fat pad and per fat cell than do their lean littermate controls. Although LPL per fat cell increased as fat cell size increased in lean rats, the increased LPL activity in the obese could not be attributed solely to increased fat cell size. When obese and lean rats had similar cell sizes, LPL per fat cell was still significantly increased in the obese compared to lean. Furthermore LPL activity was increased in "preobese" (fa/fa) rats compared to either lean genotype (Fa/fa or Fa/Fa) during the second postnatal week. The data suggest that early increments in LPL activity in adipose tissue of the "pre-obese" rat may significantly contribute to the early fat cell hypertrophy seen during the development of this genetic obesity. Furthermore, early increased LPL activity may prove useful as a predictor of the onset of obesity.

Adipose Tissue↗
PubMed1998

Ile225Thr loop mutation in the lipoprotein lipase (LPL) gene is a de novo event.

Mutations in the lipoprotein lipase (LPL) gene are the most important cause of familial chylomicronemia with over 70 mutations being recorded to date. Thus far de novo mutations have not been described. Here we report on the molecular analysis of the family of a patient previously reported to be LPL deficient on the basis of compound heterozygosity for the Arg243His and Ile225Thr mutations, the latter being the first and only mutation identified in the loop region of LPL. Both parents of the propositus were screened for the presence of these two mutations to confirm their status as obligate heterozygotes and to determine the mutation allocation. Although paternal inheritance of the Arg243His allele could be established, maternal DNA did not show carrier status for the Ile225Thr substitution. An examination of maternity, using LPL restriction fragment length polymorphisms four polymorphic CA repeats and ApoE genotypes, was consistent with correct biological parentage for the propositus. Therefore, we conclude that the Ile225Thr mutation constitutes a de novo event, the first to be reported in the LPL gene.

Adult↗
PubMed1998

Heparin-releasable lipoprotein lipase activity is increased in cardiomyocytes after culture.

The activity of lipoprotein lipase (LPL) in adult rat heart cardiomyocytes after overnight culture on laminin-coated plates for 18-22 h was compared with enzyme activity in freshly isolated cardiomyocytes. LPL activity in cellular homogenates from cultured cardiomyocytes and freshly isolated cells was 240 and 233 nmol oleate released h-1.mg-1 protein, respectively. LPL specific activity (mU/ng LPL protein) was 0.07 in cultured cells compared with 0.42 in freshly isolated cells, indicating an increased content of inactive LPL mass after overnight culture. The heparin-induced release of LPL activity into the medium of cultured cardiomyocytes (198 nmol.h-1.mg-1) was much greater than heparin-releasable LPL (HR-LPL) activity (59 nmol.h-1.mg-1) from freshly isolated cells. HR-LPL activity from cultured cardiomyocytes was dependent on serum (16.3-fold activation) and was inhibited by high ionic strength (1 M NaCl) and by a polyclonal antibody to LPL. Cultured cardiomyocytes also had more immunodetectable LPL on the cell surface compared with freshly isolated cardiomyocytes, consistent with increased HR-LPL activity. Therefore, overnight culture may permit cardiomyocytes time to recover from the stress of isolation by increasing the content of LPL on the cell surface.

Animals↗