Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.1.34 (lipoprotein lipase)
7,025 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Apolipoprotein C-II (apoC-II), which is known to activate lipoprotein lipase (LPL), was identified by ordered differential display (ODD)-polymerase chain reaction (PCR) as a cDNA fragment exhibiting a distinct increase in expression during 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced differentiation of promonocytic U937 cells into monocytes and macrophages. The amount of apoC-II mRNA expression detectable in U937 cells significantly increased and reached a maximum 24-48 h after treatment with 32 nM TPA. apoC-II mRNA was also detected in monocytic THP-1 cells but was not detected in promyelocytic HL-60 cells. In healthy human tissues, the most significant expression of apoC-II mRNA was in the liver. Although apoC-II mRNA expression was markedly up-regulated during the induced differentiation of HL-60 cells into monocytes and macrophages with 32 nM TPA, such expression was not induced during the differentiation of HL-60 cells into granulocytes with 1.25% dimethyl sulfoxide. These results suggest that human apoC-II expression is induced at the transcription level during myelomonocytic differentiation and may confer an important role to macrophages involved in normal lipid metabolism and atherosclerosis.
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PMID:Expression of the apolipoprotein C-II gene during myelomonocytic differentiation of human leukemic cells. 1131 Aug 52

3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) are drugs very effective to decrease low-density lipoprotein (LDL) cholesterol. In addition, a number of studies suggest that statins have other beneficial clinical effects beyond cholesterol lowering. We recently reported that statins decrease nuclear factor kappa B (NF-kappaB) binding activity in monocytes and vascular smooth muscle cells. We now explored the effect of two different statins, simvastatin and atorvastatin, in the activation of the octamer transcription factor Oct-1 on the monocytic cell line THP-1. Oct-1 is a nuclear factor that represses the transcription of proinflammatory genes such as interleukin-8, CD11c/CD18, vascular cell adhesion molecule-1 (VCAM-1) and platelet endothelial cell adhesion molecule-1 (PECAM-1). Low concentrations of both statins increased Oct-1 DNA binding activity (electrophoretic mobility shift assay) that was resolved into two specific bands. The upper one was supershifted by preincubation of nuclear extracts with anti-Oct-1 antibody. The lower one was supershifted by preincubation of nuclear extracts with an anti-Oct-2 antibody, also partially competed with 100 mol/l excess of cold activator protein-1 (AP-1) and attenuated by anti-c-Jun antibody. Both statins increased Oct-1 and Oct-2 nuclear protein levels (Western blot). In contrast, neither had any effect on PMA-differentiated cells, suggesting a distinct sensitivity between circulating monocytes and resident tissular macrophages. In addition, statins did not increase Oct-lipoprotein lipase binding activity that contains an Oct-1 binding element. The mRNA expression of interleukin-8, a chemokine containing Oct sites in its promoter, was diminished by statin pretreatment. Our results indicate that simvastatin and atorvastatin increase the activity of the transcriptional repressor Oct-1 in mononuclear cells, and could thus contribute to decrease the activation of these cells. These data suggest a possible novel mechanism supporting a certain anti-inflammatory effect of these two 3-hydroxy-3-methylglutaryl-CoA reductase inhibitors.
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PMID:3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors increase the binding activity and nuclear level of Oct-1 in mononuclear cells. 1214 30

Peroxisome proliferator-activated receptors (PPARs) are transcriptional factors which mediate pleiotropic effects including regulation of genes involved in lipid metabolism and control of inflammation. In the present study, we measured the in vitro effects of PPAR alpha and gamma ligands on macrophage lipoprotein lipase (LPL) expression. Human monocyte-derived macrophages (MDM) were cultured for 1-3 days in the presence of PPAR alpha and gamma ligands. At the end of these incubation periods, extracellular LPL immunoreactive mass/activity and LPL mRNA levels were measured. Incubation of human MDM with PPAR alpha and gamma ligands stimulated, in a time- and dose-dependent manner, human MDM LPL mass and activity. These agents also significantly increased macrophage LPL mRNA expression. In THP-1 cells treated with PPAR alpha and gamma ligands, enhanced nuclear protein binding to the peroxisome proliferator responsive element (PPRE) of the human LPL promoter was observed. Furthermore, in these cells, a decreased rate of decay of LPL mRNA was documented. Overall, these results demonstrate that PPAR alpha and gamma activators increase macrophage LPL secretion. Given the proatherogenic effect of vascular wall LPL, better understanding of the role of PPARs in the regulation of macrophage LPL expression could lead to the development of new approaches in the prevention and treatment of atherosclerosis.
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PMID:Peroxisome proliferator-activated receptor alpha and gamma agonists upregulate human macrophage lipoprotein lipase expression. 1220 75

It is well known that raised plasma triglycerides (TG) are positively linked to the development of coronary heart disease. However, triglycerides circulate in a range of distinct lipoprotein subfractions and the relative atherogenicity of these subfractions is not clear. In this study, three fractions of triglyceride rich lipoprotein (TRL) were isolated from normolipidaemic males according to their differing Svedberg flotation (S(f)) rates: chylomicron (CM, S(f)>400), very low-density lipoprotein (VLDL)-1 (S(f) 60-400) and VLDL-2 (S(f) 20-60). These fractions were incubated with THP-1 monocyte-derived macrophages for determination of cholesterol and TG accumulation, in the presence and absence of the lipoprotein lipase (LPL) inhibitor orlistat. Expression of LDL receptor related protein (LRP) and apolipoprotein B48 receptor (apoB48R) was also examined in both differentiating monocytes, and monocyte-derived macrophages, incubated with TRL. VLDL-1 caused a significantly greater accumulation of TG within macrophages compared to VLDL-2. Binding studies also tended to show a greater preference for VLDL-1. No change in expression of LRP or apoB48R was observed in fully differentiated macrophages incubated with VLDL-1, VLDL-2 or CM, although a greater expression of LRP mRNA was observed in differentiating monocytes exposed to VLDL-1, compared to those incubated with CM or VLDL-2. TG loading in response to all three TRL fractions was blocked by orlistat, suggesting that it is likely that the major pathway for uptake of TG was hydrolysis by LPL. Calculations suggested that direct uptake of particles accounts for between 12 and 25% of total TAG uptake. In conclusion, THP monocyte-derived macrophages demonstrate a preference for VLDL-1, both through the LPL pathway and by direct uptake of whole particles.
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PMID:Differential uptake of subfractions of triglyceride-rich lipoproteins by THP-1 macrophages. 1591 Aug 48

Salacia oblonga (SO) root is an Ayurvedic medicine with anti-diabetic and anti-obese properties. Peroxisome proliferator-activated receptor (PPAR)-alpha, a nuclear receptor, plays an important role in maintaining the homeostasis of lipid metabolism. Here, we demonstrate that chronic oral administration of the water extract from the root of SO to Zucker diabetic fatty (ZDF) rats, a genetic model of type 2 diabetes and obesity, lowered plasma triglyceride and total cholesterol (TC) levels, increased plasma high-density lipoprotein levels and reduced the liver contents of triglyceride, non-esterified fatty acids (NEFA) and the ratio of fatty droplets to total tissue. By contrast, the extract had no effect on plasma triglyceride and TC levels in fasted ZDF rats. After olive oil administration to ZDF the extract also inhibited the increase in plasma triglyceride levels. These results suggest that SO extract improves postprandial hyperlipidemia and hepatic steatosis in ZDF rats. Additionally, SO treatment enhanced hepatic expression of PPAR-alpha mRNA and protein, and carnitine palmitoyltransferase-1 and acyl-CoA oxidase mRNAs in ZDF rats. In vitro, SO extract and its main component mangiferin activated PPAR-alpha luciferase activity in human embryonic kidney 293 cells and lipoprotein lipase mRNA expression and enzyme activity in THP-1 differentiated macrophages; these effects were completely suppressed by a selective PPAR-alpha antagonist MK-886. The findings from both in vivo and in vitro suggest that SO extract functions as a PPAR-alpha activator, providing a potential mechanism for improvement of postprandial hyperlipidemia and hepatic steatosis in diabetes and obesity.
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PMID:Salacia oblonga root improves postprandial hyperlipidemia and hepatic steatosis in Zucker diabetic fatty rats: activation of PPAR-alpha. 1597 14

Peroxisome proliferator-activated receptor (PPAR)-gamma activators are widely used in the treatment of type 2 diabetes because they improve the sensitivity of insulin receptors. Punica granatum flower (PGF) has been used as an anti-diabetic medicine in Unani medicinal literature. The mechanism of actions is, however, unknown. In the current study, we demonstrated that 6-week oral administration of methanol extract from PGF (500 mg/kg, daily) inhibited glucose loading-induced increase of plasma glucose levels in Zucker diabetic fatty rats (ZDF), a genetic animal model for type 2 diabetes, whereas it did not inhibit the increase in Zucker lean rats (ZL). The treatment did not lower the plasma glucose levels in fasted ZDF and ZL rats. Furthermore, RT-PCR results demonstrated that the PGF extract treatment in ZDF rats enhanced cardiac PPAR-gamma mRNA expression and restored the down-regulated cardiac glucose transporter (GLUT)-4 (the insulin-dependent isoform of GLUTs) mRNA. These results suggest that the anti-diabetic activity of PGF extract may result from improved sensitivity of the insulin receptor. From the in vitro studies, we demonstrated that the PGF extract enhanced PPAR-gamma mRNA and protein expression and increased PPAR-gamma-dependent mRNA expression and activity of lipoprotein lipase in human THP-1-differentiated macrophage cells. Phytochemical investigation demonstrated that gallic acid in PGF extract is mostly responsible for this activity. Thus, our findings indicate that PPAR-gamma is a molecular target for PGF extract and its prominent component gallic acid, and provide a better understanding of the potential mechanism of the anti-diabetic action of PGF.
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PMID:Anti-diabetic action of Punica granatum flower extract: activation of PPAR-gamma and identification of an active component. 1610 67

The pathogenesis of Mycoplasma pneumoniae infection is considered to be in part attributed to excessive immune responses. Recently, lipoproteins from mycoplasmas have been reported to induce NF-kappaB activation. In this study, we examined the ability of lipoproteins from M. pneumoniae to activate NF-kappaB, and the active component responsible for the NF-kappaB activation was identified. Lipid-associated membrane proteins from M. pneumoniae were found to induce NF-kappaB through TLR 2 in a human monocytic cell line, THP-1. The active component of the Lipid-associated membrane proteins was a subunit b of F0F1-type ATPase (F0F1-ATPase). The F0F1-ATPase is assumed to contain two palmitic acids. The activation of NF-kappaB by the F0F1-ATPase was inhibited by a dominant negative construct of TLR1 and TLR6. These results indicate that the activation of NF-kappaB by F0F1-ATPase is dependent on TLR1, TLR2, and TLR6. The activity of the F0F1-ATPase was decreased with pretreatment of lipoprotein lipase but not protease, indicating that the lipid moiety of the F0F1-ATPase was important for the NF-kappaB activation. Thus, a dipalmitoylated lipoprotein from M. pneumoniae was found to activate NF-kappaB through TLR1, TLR2, and TLR6.
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PMID:A dipalmitoylated lipoprotein from Mycoplasma pneumoniae activates NF-kappa B through TLR1, TLR2, and TLR6. 1617 10

We have previously identified four novel isoforms of PPAR-gamma transcripts in monkey macrophages (J. Zhou, K.M. Wilson, J.D. Medh, Genetic analysis of four novel peroxisome proliferator receptor-gamma splice variants in monkey macrophages. Biochem. Biophys. Res. Commun., 293 (2002) 274-283). The purpose of this study was to ascertain that these isoforms are also present in humans. Specific primers were designed to amplify individual isoform transcripts. The presence of PPAR-gamma4, PPAR-gamma5, and PPAR-gamma7 transcripts in human THP-1 macrophages was confirmed by RT-PCR and sequencing. A transcript corresponding to PPAR-gamma6 was not detected. The presence of novel full-length transcripts and protein was also ascertained by Northern and Western blot analysis. Treatment of THP-1 cells with 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2) resulted in more than 20% induction in the expression of PPAR-gamma5 and PPAR-gamma7 transcripts by both Northern blot analysis and RT-PCR. Another PPAR-gamma ligand, troglitazone, induced expression of only PPAR-gamma5. Both ligands inhibited the expression of PPAR-gamma1 and PPAR-gamma2. Additionally, 15d-PGJ2 and troglitazone increased the level of apolipoprotein E transcript by 60% but decreased lipoprotein lipase expression by 15% in THP-1 cells. The differential regulation of PPAR-gamma transcripts suggests that each transcript isoform may contribute to macrophage function.
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PMID:Identification and regulation of novel PPAR-gamma splice variants in human THP-1 macrophages. 1654 39

Liver X receptor (LXR) activation represents a mechanism to prevent macrophage foam cell formation. Previously, we demonstrated that partial inhibition of oxidosqualene:lanosterol cyclase (OSC) stimulated synthesis of the LXR agonist 24(S),25-epoxycholesterol (24(S),25-epoxy) and enhanced ABCA1-mediated cholesterol efflux. In contrast to a synthetic, nonsteroidal LXR activator, TO-901317, triglyceride accumulation was not observed. In the present study, we determined whether endogenous 24(S),25-epoxy synthesis selectively enhanced expression of macrophage LXR-regulated cholesterol efflux genes but not genes that regulate fatty acid metabolism. THP-1 human macrophages incubated with the OSC inhibitor (OSCi) RO0714565 (15 nM) significantly reduced cholesterol synthesis and maximized synthesis of 24(S),25-epoxy. Endogenous 24(S),25-epoxy increased ABCA1, ABCG1, and APOE mRNA abundance and consequently increased cholesterol efflux to apoAI. In contrast, OSCi had no effect on LXR-regulated genes LPL (lipoprotein lipase) and FAS (fatty acid synthase). TO-901317 (>or=10 nM) significantly enhanced expression of all genes examined. OSCi and TO-901317 increased the mRNA and precursor form of SREBP-1c, a major regulator of fatty acid and triglyceride synthesis. However, conversion of the precursor to the active form (nSREBP-1c) was blocked by OSCi-induced 24(S),25-epoxy but not by TO-901317 (>or=10 nm), which instead markedly increased nSREBP-1c. Disruption of nSREBP-1c formation by 24(S),25-epoxy accounted for diminished FAS and LPL expression. In summary, endogenous synthesis of 24(S),25-epoxy selectively up-regulates expression of macrophage LXR-regulated cholesterol efflux genes without stimulating genes linked to fatty acid and triglyceride synthesis.
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PMID:Selective up-regulation of LXR-regulated genes ABCA1, ABCG1, and APOE in macrophages through increased endogenous synthesis of 24(S),25-epoxycholesterol. 1718 44

Large-scale epidemiological studies have revealed a strong association between hypertriglyceridemia and coronary arteriosclerotic disease. However, there are conflicting reports whether the severe hypertriglyceridemia caused by lipoprotein lipase (LPL) deficiency is pro- or antiatherogenic. To determine the effect of LPL deficiency on atherosclerosis, we pursued long-term observation of the development of atherosclerotic lesions in an LPL gene deficient mouse model. At 4 months of age, homozygous LPL-deficient mice exhibited severe hypertriglyceridemia but no signs of aortic atherosclerotic lesions. At >15 months of age, these mice developed foam cell-rich atherosclerotic lesions at the aortic root, whereas wild-type and heterozygous mice were lesion-free at the same age. Further investigation revealed that plasma malondialdehyde levels in >15-month-old LPL-deficient mice were significantly higher than those of heterozygous and wild-type mice. Electron spin resonance analysis showed a marked increase in oxidative susceptibility of chylomicrons from the aged LPL-deficient mice. Incubation of chylomicrons from >15-month-old LPL-deficient mice with cultured human umbilical vein endothelial cells showed significantly increased upregulation of vascular cell adhesion molecule-1 and monocyte chemoattractant protein-1, markers of enhanced endothelial activation, and enhanced adherence of human THP-1 mononuclear cells. These results clearly demonstrate the occurrence of spontaneous atherosclerosis in aged LPL-deficient mice mediated by the oxidation of chylomicrons and the activation of vascular endothelial cells.
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PMID:Spontaneous atherosclerosis in aged lipoprotein lipase-deficient mice with severe hypertriglyceridemia on a normal chow diet. 1853 62


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