Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.1.34 (lipoprotein lipase)
 7,025 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In type I (insulin-dependent) diabetic patients, peripheral hyperinsulinemia due to subcutaneous insulin treatment is associated with increased high-density lipoprotein (HDL) cholesterol, and also with an altered surface composition of HDL. Pancreas grafts also release insulin into the systemic rather than into the portal venous system, giving rise to pronounced peripheral hyperinsulinemia. We hypothesized that if peripheral hyperinsulinemia is responsible for high HDL cholesterol and/or altered surface composition of HDL in diabetic subjects, similar changes in the lipid profile should be present in pancreas-kidney transplant recipients (PKT-R). Using zonal ultracentrifugation, we isolated HDL2, HDL3, very-low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), and low-density lipoprotein (LDL) from fasting plasma of 14 type I diabetic PKT-R, eight nondiabetic kidney transplant recipients (KT-R), and 14 healthy control subjects and determined the level and composition of the above lipoproteins. HDL2 cholesterol was increased in PKT-R as compared with KT-R and healthy controls (both P < .05), whereas HDL3 cholesterol was unchanged. However, an altered lipoprotein surface composition was evident in PKT-R: HDL2, HDL3, and LDL were enriched in unesterified cholesterol ([UC] PKT-R v KT-R, P=.13, P < .005, and P < .05, respectively; PKT-R v controls, all P < .005); HDL2 was enriched in phospholipids; and LDL was depleted of phospholipid. KT-R, in contrast, showed no changes in lipoprotein surface composition but a substantial triglyceride enrichment of HDL2 as compared with PKT-R and healthy controls (both P < .05). LDL size as determined by gradient gel electrophoresis was increased in PKT-R compared with controls (P < .005). The plasma concentration of cholesteryl ester (CE) transfer protein (CETP), involved also in phospholipid transfer, was increased in both transplant groups compared with healthy controls (both P < .05). Insulin concentrations in fasting plasma were directly related to CETP levels and to the weight-percentage of UC in HDL3, and inversely to the weight-percentage of phospholipids in LDL (all P < .05). We explain the increase in HDL2 cholesterol and LDL size in PKT-R by their high lipoprotein lipase (LPL) activity conferring an excellent capacity to clear chylomicron triglycerides. Effective handling of postprandial triglycerides, high HDL2 cholesterol, and predominance of LDL pattern A, respectively, are established indicators of a low risk of atherosclerosis. However, it is presently unclear what effects the compositional changes on the surface of HDL and LDL may have on cardiovascular risk in clinically stable PKT-R.
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PMID:Effects of pancreas transplantation on distribution and composition of plasma lipoproteins. 869 21

Infection, inflammation and trauma induce marked changes in the plasma levels of a wide variety of proteins (acute phase response), and these changes are mediated by cytokines. The acute phase response is thought to be beneficial to the host. The host's response to injury also results in dramatic alterations in lipid metabolism and circulating lipoprotein levels which are mediated by cytokines. A large number of cytokines including TNF, the interleukins, and the interferons increase serum triglyceride levels. This rapid increase (1-2 h) is predominantly due to an increase in hepatic VLDL secretion while the late increase may be due to a variety of factors including increased hepatic production of VLDL or delayed clearance secondary to a decrease in lipoprotein lipase activity and/or apolipoprotein E levels on VLDL. In animals other than primates, cytokines also increase serum cholesterol levels, most likely by increasing hepatic cholesterol. Cytokines increase hepatic cholesterol synthesis by stimulating HMG CoA reductase gene expression and decrease hepatic cholesterol catabolism by inhibiting cholesterol 7 alpha-hydroxylase, the key enzyme in bile acid synthesis. Injury and/or cytokines also decrease HDL cholesterol levels and induce alterations in the composition of HDL. The content of SAA and apolipoprotein J increase, apolipoprotein A1 may decrease, and the cholesterol ester content decreases while free cholesterol increases. Additionally, key proteins involved in HDL metabolism are altered by cytokines; LCAT activity, hepatic lipase activity, and CETP levels decrease. These changes in lipid and lipoprotein metabolism may be beneficial in a number of ways including: lipoproteins competing with viruses for cellular receptors, apolipoproteins neutralizing viruses, lipoproteins binding and targeting parasites for destruction, apolipoproteins lysing parasites, redistribution of nutrients to cells involved in the immune response and/or tissue repair, and lipoproteins binding toxic agents and neutralizing their harmful effects. Thus, cytokines induce marked changes in lipid metabolism that lead to hyperlipidemia which represents part of the innate immune response and may be beneficial to the host.
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PMID:Beneficial effects of cytokine induced hyperlipidemia. 955 31

Very low (VLDL) and low density lipoproteins (LDL) were isolated from plasma of patients with the E3/3 phenotype which were divided into three groups based on their plasma triglyceride content: low (TG<200 mg/dl, TG(l)), intermediate (200<300 mg/dl, TG(i)300 mg/dl, TG(h)). The protein density (PD) on the VLDL and LDL surface was calculated from lipoprotein composition and protein location was studied by tryptophan fluorescence quenching by I(-) anions at 25 degrees C and 40 degrees C. A comparison of the TG(h) with the TG(l) group revealed a significant (<0.05) increase of the PD parameter as much as 21% for VLDL, but not for LDL where this parameter did not change for any group; generally, PD(LDL) values were 3.2-3.8-fold lower than PD(VLDL). In accordance with this difference, the tryptophan accessibility f in VLDL vs. LDL was lower at both temperatures. There were temperature-induced changes of the f parameter in opposite directions for these lipoproteins. The difference in f value gradually decreased for VLDL in the direction TG(l)TG(i)TG(h) while for LDL there was a U-shaped dependence for these groups. The Stern-Volmer quenching constant K(S-V) which is sensitive to both temperature and viscosity, did not change for VLDL, but K(S-V)(LDL) was 2-3-fold higher for the TG(i) group compared to the other two. The efficiencies of VLDL and LDL binding to the LDL receptor (LDLr) in vitro were compared by solid-phase assay free of steric hindrance observed in cell binding. The maximal number of binding sites did not change for either type of particles and between groups. The association constant K(a) and apolipoprotein (apo) E/apoB mole ratio values all increased significantly for VLDL, but not for LDL, in comparison of the TG(i+h) with the TG(l) group. Based on VLDL and LDL concentrations in serum and on the affinity constant values obtained in an in vitro assay, VLDL concentrations corresponding to 50% inhibition of LDL binding (IC(50)) were calculated in an assumption of the competition of both ligands for LDLr in vivo; the mean values of IC(50) decreased 2-fold when plasma TG exceeded 200 mg/dl. The functional dependences of K(a)(VLDL), IC(50) and apoE content in VLDL (both fractional and absolute) and in serum on TG content in the whole concentration range studied were fitted to a saturation model. For all five parameters, the mean half-maximum values TG(1/2) were in the range 52-103 mg/dl. The efficiency of protein-protein interactions is suggested to differ in normolipidemic vs. HTG-VLDL and apoE content and/or protein density on VLDL surface may be the primary determinant(s) of the increased binding of HTG-VLDL to the LDL receptor. ApoCs may compete with apoE for the binding to the VLDL lipid surface as plasma triglyceride content increases. The possible competition of VLDL with LDL for the catabolism site(s) in vivo, when plasma TG increases, could explain the atherogenic action of TG-rich lipoproteins. Moreover, the 'dual action' hypothesis on anti-atherogenic action of apoE-containing high density lipoproteins (HDL) in vivo is suggested: besides the well-known effect of HDL as cholesteryl ester catabolic outway, the formation of a transient complex of apoE-containing discs appearing at the site of VLDL TG hydrolysis by lipoprotein lipase with VLDL particles proposed in our preceding paper promotes the efficient uptake of TG-rich particles; in hypertriglyceridemia due to the diminished HDL content this uptake seems to be impaired which results in the increased accumulation of the remnants of TG-rich particles. This explains the observed increase in cholesterol and triglyceride content in VLDL and LDL, respectively, due to the CETP-mediated exchange of cholesteryl ester and triglyceride molecules between these particles.
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PMID:Structural peculiarities of the binding of very low density lipoproteins and low density lipoproteins to the LDL receptor in hypertriglyceridemia: role of apolipoprotein E. 1068 28

There are no definitive explanations as to why individuals with hypercholesterolemia, a major cardiovascular risk factor, respond differently to dietary change. Fifty five free-living individuals completed a double crossover trial with two dietary regimens, a high saturated fat diet (providing 21% energy from saturated fat and 3% energy from polyunsaturated fat) and a high polyunsaturated fat diet (providing 11% energy as saturated fat and 10% energy as polyunsaturated fat), each phase continuing for 4 weeks. Extensive genotyping and several measures of dietary compliance have provided further insights regarding the determinants of extent of cholesterol response to changes in the nature of dietary fat. Individuals with the CETP B1B1 genotype and the LPL X447+ allele showed an average 0. 44 (95% CI: 0.22, 0.66) and 0.45 (95% CI: 0.18, 0.72) mmol/l greater change in total cholesterol, respectively, than those with one or more CETP B2 allele or homozygous for the LPL S447 allele when comparing diets high and low in saturated fat. Indices of dietary compliance including changes in reported saturated and polyunsaturated fat intake and change in triglyceride linoleate were not significantly different between the CETP genotypes. Change in reported saturated (r=0.36, P=0.04) and polyunsaturated (r=0.22, P=0. 05) fat intake and change in triglyceride linoleate (reflecting polyunsaturated fat intake) (r=0.21, P=0.07), also predicted total cholesterol response to dietary fat changes. In multivariate analyses, variation in the cholesterol ester transfer protein and lipoprotein lipase genes predicted response independent of measures of dietary compliance, suggesting that these two genes are important determinants of variation in cholesterol response to dietary change in free-living individuals.
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PMID:Variants in the cholesterol ester transfer protein and lipoprotein lipase genes are predictors of plasma cholesterol response to dietary change. 1099 60

Low density lipoprotein (LDL) particle size is a genetically influenced trait associated with coronary heart disease (CHD). This study investigates the effects of genetic variation in plasma factors with important roles in lipoprotein metabolism on LDL heterogeneity. Common variants in the cholesteryl ester transfer protein (CETP-629C/A), lipoprotein lipase (LPL S447X), hepatic lipase (HL-480C/T) and apolipoprotein E (apoE e2/e3/e4) genes were studied in relation to LDL particle size distribution in 377 healthy, middle-aged men. A high-resolution polyacrylamide gradient gel electrophoresis technique was used to measure plasma concentrations of four LDL subfractions. The CETP-629A and LPL 447X alleles were associated with moderately increased LDL peak particle size. In contrast, the apoE e4 allele was associated with a marked reduction in LDL peak particle size and an increased relative proportion and plasma concentration of small, dense LDL. An interaction between the HL-480C/T and apo E polymorphisms contributed significantly to increased plasma concentration of small, dense LDL (LDL-III) in HL-480T carriers. In summary, the investigated polymorphisms were associated with diverse effects on the LDL particle size distribution, consistent with respect to protein function and proposed association with CHD risk. The observed associations were further modulated by gene-gene and gene-environment interactions.
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PMID:Influence of common variants in the CETP, LPL, HL and APO E genes on LDL heterogeneity in healthy, middle-aged men. 1281 14

Polymorphisms in genes involved in HDL-cholesterol (HDL-C) metabolism influence plasma HDL-C concentrations. We examined whether dietary fat intake modified relations between HDL-C and polymorphisms in hepatic lipase (LIPC-514C-->T), cholesteryl ester transfer protein (CETP TaqIB), and lipoprotein lipase (LPL S447X) genes. Diet (food frequency questionnaire), plasma lipids, and LIPC, CETP, and LPL genotypes were assessed in approximately 12,000 White and African American adults. In both races and all genotypes studied, minor allele homozygotes had highest HDL-C concentrations compared to the other genotypes (P<0.001). However, main effects were modified by usual dietary fat intake. In African Americans - women somewhat more strongly than men -LIPC TT homozygotes with fat intake >or=33.2% of energy had approximately 3-4 mg/dL higher HDL-C concentrations than CC and CT genotypes. In contrast, when fat intake was <33.2% of energy, TT homozygotes had HDL-C concentrations approximately 3.5mg/dL greater than those with the CC genotype but not different from those with the CT genotype (P(interaction)=0.013). In Whites, LPLGG homozygotes had greatest HDL-C at lower total, saturated, and monounsaturated fat intakes but lowest HDL-C at higher intakes of these fats (P(interaction)<or=0.002). Dietary fat did not modify associations between CETP and HDL-C. In conclusion, these data show that plasma HDL-C differs according to LIPC, LPL, and CETP genotypes. In the case of LIPC and LPL, data suggest dietary fat modifies these relations.
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PMID:Associations between HDL-cholesterol and polymorphisms in hepatic lipase and lipoprotein lipase genes are modified by dietary fat intake in African American and White adults. 1715 61

Genes coding for proteins involved in lipid metabolism and, in women, menopausal status are independently associated with high-density lipoprotein cholesterol (HDL-c) and low-density lipoprotein cholesterol (LDL-c) levels. We examined whether the association between common functional genetic polymorphisms of apolipoprotein E (apoE Cys112Arg and Arg158Cys) gene and LDL-c levels, as well as the associations between the cholesteryl ester transfer protein (CETP TaqIB), hepatic lipase (LIPC C-514T), and lipoprotein lipase (LPL Ser447Stop) genes and HDL-c levels are significantly modified by menopausal status. Plasma lipid concentrations, genotype, and menopausal status were assessed across four examinations in a sample of Caucasian and African-American women (n=4652-4876) who were aged 45-64 years at baseline from the Atherosclerosis Risk in Communities (ARIC) Study. The association between LDL-c levels and the apoE gene, and HDL-c levels and the LIPC and LPL genes were not modified by menopausal status. The only statistically significant gene by menopause interaction was with the CETP gene on HDL-c concentrations (p=0.04). However, the significant CETP gene by menopause interaction was possibly due to chance because of multiple testing. Postmenopausal women who were carriers of the A allele of the CETP gene had approximately 0.7 mg/dL lower HDL-c levels than pre-/perimenopausal counterparts, whereas the opposite pattern of HDL-c (0.4 mg/dL higher HDL-c postmenopausally) was observed for the GG genotype. Overall, our data suggest that the decrease in endogenous estrogen as a result of menopause may independently affect lipoprotein concentration, but does not alter the effect on plasma lipids of some common genetic polymorphisms that regulate lipoprotein metabolism.
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PMID:Low-density lipoprotein and high-density lipoprotein cholesterol levels in relation to genetic polymorphisms and menopausal status: the Atherosclerosis Risk in Communities (ARIC) Study. 1827 64

The changes of total lipids, lipoproteins and their fractions, free fatty acids, triacylglyceroles, free and esterified cholesterol levels and parameters of its metabolism in the blood serum and liver, glucose-6-phosphate dehydrogenase and lysosomal lipase activity in the liver, and also post-heparin lipases activity in blood of hamsters with chronic social stress are investigated. Is has been shown, that in stressed animals the prevalence in early terms of chronic stress lipolysis above lipogenesis is observed. In later terms of chronic stress the lipogenesis activation is also observed which, alongside with active lipolysis, can cause hyperlipidemia in blood. The latter phenomenon is obviously more characteristic of males, while in females the main source of fatty acids in blood is probably lipolysis in the liver. Proatherogenic redistribution of lipoprotein fractions, which was observed at chronic stress, becomes complicated by changes of their transformations processes under blood lipases action, in particular, lipases disbalance: by increasing of hepatic lipase activity without lipoprotein lipase activity increase. The increase of CETP activity in HDL, which is observed at stress, can be accompanied by atherogenic LDLB accumulation in the blood plasma. The chronic social stress is proatherogenic owing to lipid and lipoprotein metabolism changes, which lead to the shift of balance during lipids transport and their use by tissues.
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PMID:[Effect of chronic social stress on lipid metabolism in golden Syrian hamsters]. 1914 Apr 58

The CETP (cholesteryl ester transfer protein) is a plasma protein synthesized in several tissues, mainly in the liver; CETP reduces plasma HDL (high-density lipoprotein) cholesterol and increases the risk of atherosclerosis. The effect of CETP levels on postprandial intravascular metabolism of TAGs (triacylglycerols) is an often-overlooked aspect of the relationship between CETP and lipoprotein metabolism. Here, we tested the hypothesis that CETP delays the plasma clearance of TAG-rich lipoprotein by comparing human CETP expressing Tg (transgenic) and non-Tg mice. After an oral fat load, the postprandial triglyceridaemia curve was markedly increased in CETP-Tg compared with non-Tg mice (280+/-30 versus 190+/-20 mg/dl per 6 h respectively, P<0.02). No differences in intestinal fat absorption and VLDL (very-low-density lipoprotein) secretion rates were observed. Kinetic studies of double-labelled chylomicron-like EMs (emulsions) showed that both [(3)H]triolein and [(14)C]cholesteryl oleate FCRs (fractional clearance rates) were significantly reduced ( approximately 20%) in CETP-Tg mice. Furthermore, TAG from lipid EM pre-incubated with CETP-Tg plasma had plasma clearance and liver uptake significantly lower than the non-Tg plasma-treated lipid EM. In addition, reductions in post-heparin plasma LPL (lipoprotein lipase) activity (50%) and adipose tissue mRNA abundance (39%) were verified in CETP-Tg mice. Therefore we conclude that CETP expression in Tg mice delays plasma clearance and liver uptake of TAG-rich lipoproteins by two mechanisms: (i) transferring TAG to HDLs and increasing CE content of the remnant particles and (ii) by diminishing LPL expression. These findings show that the level of CETP expression can influence the responsiveness to dietary fat and may lead to fat intolerance.
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PMID:Cholesteryl ester transfer protein (CETP) increases postprandial triglyceridaemia and delays triacylglycerol plasma clearance in transgenic mice. 1919 59

The peroxisome proliferator-activated receptor alpha (PPARalpha) activator fenofibrate efficiently decreases plasma triglycerides (TG), which is generally attributed to enhanced very low density lipoprotein (VLDL)-TG clearance and decreased VLDL-TG production. However, because data on the effect of fenofibrate on VLDL production are controversial, we aimed to investigate in (more) detail the mechanism underlying the TG-lowering effect by studying VLDL-TG production and clearance using APOE*3-Leiden.CETP mice, a unique mouse model for human-like lipoprotein metabolism. Male mice were fed a Western-type diet for 4 weeks, followed by the same diet without or with fenofibrate (30 mg/kg bodyweight/day) for 4 weeks. Fenofibrate strongly lowered plasma cholesterol (-38%) and TG (-60%) caused by reduction of VLDL. Fenofibrate markedly accelerated VLDL-TG clearance, as judged from a reduced plasma half-life of glycerol tri[(3)H]oleate-labeled VLDL-like emulsion particles (-68%). This was associated with an increased post-heparin lipoprotein lipase (LPL) activity (+110%) and an increased uptake of VLDL-derived fatty acids by skeletal muscle, white adipose tissue, and liver. Concomitantly, fenofibrate markedly increased the VLDL-TG production rate (+73%) but not the VLDL-apolipoprotein B (apoB) production rate. Kinetic studies using [(3)H]palmitic acid showed that fenofibrate increased VLDL-TG production by equally increasing incorporation of re-esterified plasma fatty acids and liver TG into VLDL, which was supported by hepatic gene expression profiling data. We conclude that fenofibrate decreases plasma TG by enhancing LPL-mediated VLDL-TG clearance, which results in a compensatory increase in VLDL-TG production by the liver.
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PMID:Fenofibrate increases very low density lipoprotein triglyceride production despite reducing plasma triglyceride levels in APOE*3-Leiden.CETP mice. 2050 52


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