bluuebunny/crossref_metadata_2025 huggingface dataset:
Lipoprotein lipase activity in skeletal muscle is related to insulin sensitivity.
Authors: Pollare T , Vessby B , Lithell H
Published: June 2011

The relative effects of obesity, alone or in combination with insulin resistance and hyperinsulinemia (with or without diabetes), on lipoprotein concentrations, blood pressure, and other risk factors for cardiovascular disease were investigated in 28 men (mean age, 63 years). Special attention was given to lipoprotein lipase (LPL) activity in tissues and to postheparin plasma LPL activity and hepatic lipase activity and their relation to insulin resistance. The 28 men fulfilled the entrance criteria of the study so that they could be allocated to one of the four groups (seven in each group): 1) normal body weight, normal fasting insulin level, and normal glucose tolerance (controls); 2) the same as in group 1 but with moderate obesity; 3) the same as in group 2 but with fasting hyperinsulinemia; 4) the same as in group 3 but with non-insulin-dependent diabetes mellitus. Glucose infusion rate for the control group was 8.1 +/- 2.1 mg/kg body wt/min (mean +/- SD) at an insulin infusion rate of 56 milliunits/m2/min. The average values in groups 2, 3, and 4 were 6.0 +/- 0.7, 3.2 +/- 0.5, and 1.9 +/- 1.0 mg/kg body wt/min, respectively. Concentrations of very low density lipoproteins as well as blood pressure and urate concentrations were highest and those of high density lipoproteins were lowest in the two hyperinsulinemic groups (groups 3 and 4). Skeletal muscle LPL activity was 46 +/- 23, 41 +/- 25, 23 +/- 6, and 31 +/- 13 milliunits/g wet wt (mean +/- SD) in the four groups, respectively. There was a positive correlation between glucose infusion rate and muscle LPL activity (r = 0.58, p less than 0.0001). The hepatic lipase activity was positively correlated with the insulin area under the curve of the intravenous glucose tolerance test (r = 0.35, p = 0.02). Furthermore, blood pressure, free fatty acid concentration, liver enzymes, and urate concentrations were significantly correlated with glucose infusion rate at the clamp test. These data give further support for insulin resistance as an important factor behind the observed lipoprotein abnormalities and blood pressure elevations as part of the insulin resistance syndrome characteristic for obese and diabetic patients.
Guar gum and plasma cholesterol. Effect of guar gum and an oat fiber source on plasma lipoproteins and cholesterol in hypercholesterolemic adults.
Authors: Spiller G A , Farquhar J W , Gates J E , Nichols S F
Published: June 2011

The hypolipidemic effect of guar gum (GG, 15 g/day) was compared with that of an oat fiber source (OFS, 77 g/day). Both treatments supplied the same amount of total dietary fiber (11 g/day) and were taken with water three times a day for 3 weeks at mealtime. Thirteen free-living adult men and women participated in the study. Their total plasma cholesterol (TC) was 244 +/- 21 mg/dl (mean +/- SD), and plasma triglycerides (TGLYs) were 149 +/- 93 mg/dl before the intervention. Diets were monitored to ensure that no changes occurred other than the replacement of carbohydrate calories for the 200 kcal/day supplied by the OFS. Combined averages for both of the crossover phases showed that GG induced a reduction in TC of 26 +/- 10 mg/dl and in low density lipoprotein cholesterol of 25 +/- 9 mg/dl. The OFS induced a reduction in TC of 9 +/- 13 mg/dl and in low density lipoprotein cholesterol of 11 +/- 4 mg/dl. Although both treatments were effective in reducing elevated TC, GG at the levels fed was significantly more effective (p less than 0.001) in reducing TC. Neither treatment induced significant changes in high density lipoprotein cholesterol or very low density lipoprotein cholesterol.
Reduction in thrombus formation by PG-1 F(ab')2, an anti-guinea pig platelet glycoprotein Ib monoclonal antibody.
Authors: Miller J L , Thiam-Cisse M , Drouet L O
Published: June 2011

We have recently demonstrated that intraperitoneal injection into guinea pigs of F(ab')2 fragments of PG-1, a murine monoclonal antibody recognizing the guinea pig homologue of human platelet glycoprotein Ib, produces virtually complete functional block of the platelet von Willebrand factor receptor without inducing a hemorrhagic state. To assess the ability of this antibody to protect against thrombosis resulting from laser-induced injury to mesenteric small arteries, we injected guinea pigs with either PG-1 F(ab')2 (2.3 mg/kg) or with buffer alone 24 hours before study. For each animal, four mesenteric vessels were studied consecutively for 15 minutes each. The number of thrombi, time to first thrombus, and time to embolization of first thrombi were recorded. In the control animals most individual vessels had three to four thrombi, whereas in the antibody-treated animals, vessels most frequently had only a single thrombus or even none at all. The mean number of thrombi per vessel in the antibody-treated animals (1.125) was significantly lower than the mean in the control animals (3.40), with p less than 0.001. However, there was no significant difference between groups with respect to time to first thrombus after laser injury. Detachment of thrombi in the control animals occurred in an easily recordable, discrete fashion, with 75% of first thrombi embolizing in less than 5 minutes. In the antibody-treated animals, gradual dissolution rather than discrete detachment was typically observed. In 31% of the vessels studied in these animals, no embolus occurred; for the remaining vessels only 9% of thrombi were observed to embolize within 5 minutes of their formation.(ABSTRACT TRUNCATED AT 250 WORDS)
Both circulating and clot-bound plasminogen activator inhibitor-1 inhibit endogenous fibrinolysis in the rat.
Authors: Reilly C F , Fujita T , Mayer E J , Siegfried M E
Published: June 2011

The effects of both clot-bound and circulating plasminogen activator inhibitor-1 (PAI-1) on endogenous fibrinolysis were investigated in a rat model of pulmonary embolism. Iodine-125 fibrin(ogen)-labeled blood-clot homogenates were delivered through the left jugular vein to the lung microvasculature, and the subsequent extent of the clot lysis was monitored by measuring the release of 125I-fibrin degradation products (FDPs) into the blood. Clots that had incorporated activated PAI-1 ex vivo were subsequently protected from dissolution in vivo in a dose-responsive manner (half-maximal concentration [IC50] = 4.3 micrograms/ml). PAI-1-containing clots also resisted lysis, as measured by the release of the specific FDP D-dimer. Plasma levels of plasminogen activator (PA) and PAI activity were unaltered by administration of PAI-1-containing clots, and the clot-protective effects of clot-bound PAI-1 were reversed by exogenous tissue-type plasminogen activator administration. Clot lysis was also inhibited in a dose-responsive manner (IC50 = 58 micrograms/kg) by intravenous bolus delivery of activated PAI-1 to the circulation. The clot-protective effects of circulating PAI-1 were correlated with dose-dependent increases in plasma PAI-1 antigen and activity levels and decreases in plasma PA levels (IC50 = 37 micrograms/ml). There was no evidence of any accumulation of circulating PAI-1 in the lungs. Latent PAI-1, whether delivered with or delivered after the clot homogenates, did not affect the clot-lytic process. Activated and latent PAI-1 was cleared from the circulation in a monophasic manner, with a half-life of approximately 32 and 7 minutes, respectively. The results indicate that both clot-bound and circulating PAI-1 are potent inhibitors of fibrinolysis in vivo. Clot-bound PAI-1 may inhibit PAs in the immediate vicinity of the clots, whereas circulating PAI-1 may act systemically by controlling overall levels of PAs present in the blood.
Effects of polymorphisms in apolipoproteins E, A-IV, and H on quantitative traits related to risk for cardiovascular disease.
Authors: Kaprio J , Ferrell R E , Kottke B A , Kamboh M I , Sing C F
Published: June 2011

The impact of the common alleles at structural loci coding for apolipoprotein (apos) A-IV, E, and H on 12 quantitative risk factors for cardiovascular disease (apos A-I, A-II, B, C-II, C-III, and E; total cholesterol; triglycerides; high density lipoprotein cholesterol; systolic blood pressure; diastolic blood pressure; and red blood cell sodium-lithium countertransport) was estimated in 453 unrelated individuals (227 men and 226 women) aged 26-63 years from the Rochester Family Heart Study, who were not using medications affecting lipid levels or blood pressure. Each risk factor was adjusted for concomitants (assay date, age, age, squared, height, weight and smoking status) before the genotypic effects on mean levels and variances were estimated. Allele frequencies were the same in men and women and were similar to those observed in other studies of US Caucasians. There were very different gender-specific estimates of the relative contribution of concomitants, measured genetic effects, and residual unexplained effects to the interindividual variation of particular traits. Allelic variation in apo E had effects on the greatest number of traits, namely apo E, apo B, apo C-II, and total cholesterol. An effect on triglycerides was dependent on the inclusion of hypertriglyceridemic subjects. Allelic effects of apo A-IV and apo H were much less than those estimated for the apo E polymorphism. A possible role for apo H in high density lipoprotein metabolism is suggested. This study indicates that variation in many genes may influence variation in a particular trait and that a particular gene may have pleiotropic effects on several traits.
Increased removal of beta-very low density lipoproteins after ethinyl estradiol is associated with increased mRNA levels for hepatic lipase, lipoprotein lipase, and the low density lipoprotein receptor in Watanabe heritable hyperlipidemic rabbits.
Authors: Demacker P N , Staels B , Stalenhoef A F , Auwerx J
Published: June 2011

The mechanism by which ethinyl estradiol (EE) decreases the concentration of lipids in the d less than 1.019 g/ml fraction (beta-very low density lipoprotein [beta-VLDL]) of homozygous Watanabe heritable hyperlipidemic (WHHL) rabbits was studied. Treatment with EE increased the activity of hepatic lipase (HL) twofold to threefold in postheparin plasma and in liver biopsies. Postheparin plasma and adipose tissue lipoprotein lipase (LPL) activities were also increased twofold to fourfold after EE. The effects of EE on HL and LPL activities were associated with a threefold to sixfold elevation in liver HL mRNA and a fourfold elevation in adipose tissue LPL mRNA steady-state levels, pointing to an effect of EE on HL and LPL gene transcription. EE also increased liver low density lipoprotein (LDL) receptor mRNA levels threefold to fivefold. These results suggest a concerted action of LPL, HL, and the LDL receptor in the removal of beta-VLDL in homozygous WHHL rabbits with a defective LDL receptor. In addition, the content of apolipoprotein E in the d less than 1.019 g/ml fraction changed toward normal after EE. Because the remaining particles contained apolipoprotein B-100 almost exclusively, it is likely that apolipoprotein E-containing beta-VLDLs are preferentially removed. This may be the result of the increased activity of LPL and HL influencing the conformation of apolipoprotein E on the beta-VLDL particle in such a way that it is directly removed from the circulation, possibly by the induced LDL receptor.
Hypercholesterolemia and atherosclerosis change vascular reactivity in rabbits by different mechanisms.
Authors: Galle J , Busse R , Bassenge E
Published: June 2011

Vasomotor reactivity was assessed in vitro in arterial segments obtained from rabbits with different stages of atherosclerosis. Rabbits were fed a standard chow diet (controls) or a cholesterol-enriched diet to induce hypercholesterolemia and atherosclerosis. A third group received the hydroxymethylglutaryl coenzyme A reductase inhibitor, lovastatin, simultaneously with the cholesterol diet. Contractile responses of thoracic aortas to norepinephrine, serotonin, and potassium-rich solution, as well as endothelium-dependent dilations to acetylcholine, were compared after 2 and 4 months on the respective diet. Additionally, plasma cholesterol levels and the amount of plaques covering the intimal surface (as a percentage of the intimal surface) were determined; transmission electron microscopy of atherosclerotic arteries was also performed. After 2 months, the only difference was an enhancement of contractile responses to serotonin in the cholesterol-fed versus the control group. After 4 months on the diet, contractile responses to serotonin were further enhanced, and norepinephrine- and potassium-induced vasoconstrictions were now also significantly enhanced in cholesterol-fed animals versus controls. Endothelium-dependent vasodilations were simultaneously reduced in cholesterol-fed animals. These alterations were partly prevented in cholesterol-fed and lovastatin-treated animals. Suppression of nitric oxide synthesis in control aortas by NG-nitro-L-arginine did not reveal any significant increases in contractile responses. Contractile responses to serotonin were enhanced after 2 months on the diet but before the appearance of intimal plaques, whereas attenuation of endothelium-dependent dilations, as well as the further enhancement of contractile responses to serotonin and to other agonists, were closely correlated with the degree of intimal plaques after 4 months on the diet.(ABSTRACT TRUNCATED AT 250 WORDS)
Molecular cloning, sequence, and expression of cynomolgus monkey cholesteryl ester transfer protein. Inverse correlation between hepatic cholesteryl ester transfer protein mRNA levels and plasma high density lipoprotein levels.
Authors: Pape M E , Rehberg E F , Marotti K R , Melchior G W
Published: June 2011

A cDNA clone containing the coding region for cynomolgus monkey cholesteryl ester transfer protein (CETP) was isolated by the polymerase chain reaction with primers based on the human CETP cDNA sequence and cDNA synthesized from liver poly (A+) RNA. Analysis of that cDNA indicated that the nucleotide and amino acid sequences of cynomolgus monkey CETP were greater than 95% homologous with the human sequences. A fragment of the cDNA was used to develop an internal-standard/RNAse protection assay that allowed precise quantification of CETP mRNA levels. Analysis of total RNA from various tissues with this assay revealed that the liver and thoracic aorta expressed high levels of CETP mRNA; the mesenteric fat, adrenal gland, spleen, and abdominal aorta had low but detectable levels of the mRNA; and the brain, kidney, intestine, and skeletal muscle had undetectable levels of that mRNA. When the monkeys were made hypercholesterolemic by a high-fat, high-cholesterol (HFHC) diet, hepatic levels of CETP mRNA increased from 1.6 +/- 0.4 pg/micrograms total RNA (mean +/- SEM) to 4.1 +/- 0.8 pg/micrograms (p less than 0.005); mesenteric fat CETP mRNA increased from 0.4 +/- 0.1 pg/micrograms total RNA to 5.3 +/- 2.2 pg/micrograms (p less than 0.05); and plasma CET activity increased approximately fourfold. The CETP mRNA levels in the thoracic and abdominal aortas were not significantly increased in monkeys fed the HFHC diet, even though those animals had gross atherosclerosis. The apoprotein E mRNA levels, however, were markedly increased in the aortas of monkeys with atherosclerosis, with the largest increase occurring in the abdominal aorta. Taken together, these data suggest that lipid deposition in the artery was not accompanied by increased expression of the CETP gene in that tissue. Statistical analysis showed that a strong, negative correlation existed between hepatic CETP mRNA levels and both high density lipoprotein cholesterol (r = -0.85, p less than 0.001) and apoprotein A-I (r = -0.84, p less than 0.001). These data suggest that HFHC diet-induced changes in high density lipoprotein metabolism may be linked to altered expression of a function CETP gene.
Transient increase of plasma lipoprotein(a) in patients with unstable angina pectoris. Does lipoprotein(a) alter fibrinolysis?
Authors: Oshima S , Uchida K , Yasu T , Uno K , Nonogi H , Haze K
Published: June 2011

It has been shown that lipoprotein(a) (Lp[a]) may interfere with the fibrinolytic system and that the Lp(a) level in an individual remains constant. To evaluate the effects of Lp(a) on the fibrinolytic system in patients with unstable angina, we measured plasma levels of Lp(a), the alpha 2-plasmin inhibitor-plasmin complex, and the thrombin-antithrombin III complex. The latter is a marker of thrombin generation, and the alpha 2-plasmin inhibitor-plasmin complex is an indicator of plasminogen activation. Venous plasma samples were taken from 18 patients with unstable angina and 18 patients with stable exertional angina who had been matched for clinical variables. On admission, plasma levels of Lp(a) were significantly higher in patients with unstable angina than in those with stable exertional angina (319 +/- 193 mg/l versus 191 +/- 141 mg/l, respectively; p less than 0.05). On admission, plasma levels of the alpha 2-plasmin inhibitor-plasmin complex and of the thrombin-antithrombin III complex were also significantly higher in patients with unstable angina than in those with stable exertional angina (0.78 +/- 0.42 micrograms/ml and 3.6 +/- 1.3 ng/ml versus 0.41 +/- 0.13 micrograms/ml and 1.9 +/- 0.5 ng/ml, respectively; p less than 0.01). In nine of the 18 patients with unstable angina, serial changes of plasma levels of Lp(a), the alpha 2-plasmin inhibitor-plasmin complex, the thrombin-antithrombin III complex, and the acute-phase proteins C-reactive protein and alpha 1-antitrypsin were examined for 3 weeks after admission.(ABSTRACT TRUNCATED AT 250 WORDS)
Lipoproteins enhance fibronectin binding to adherent cells.
Authors: Checovich W J , Schultz R L , Mosher D F
Published: June 2011

We have identified very low density (VLDL) and low density (LDL) lipoproteins as blood plasma components that enhance the binding and deposition of fibronectin into the extracellular matrices of cultured MG-63 osteosarcoma cells and human fibroblasts. The lipoproteins increased the binding and deposition of iodinated fibronectin by MG-63 cells threefold over control levels. LDL also increased the deposition of multimeric fibronectin into extracellular matrix as assessed by gel electrophoresis and fluorescence microscopy. High density lipoprotein (HDL) and the d > 1.21 g/ml nonlipoprotein fraction had less activity. Enhancement of binding of fibronectin was observed within 15 minutes, when binding was largely reversible. LDL also increased the binding of a fragment containing the 70-kd amino-terminal region of fibronectin that is primarily responsible for the reversible binding of fibronectin to cell layers. LDL had to be present simultaneously with radiolabeled fibronectin to exert an effect on fibronectin binding. LDL enhanced fibronectin binding equally well to normal skin fibroblasts and to familial hypercholesterolemic fibroblasts lacking the LDL receptor. Acetylation of LDL, performed to block its interaction with the LDL receptor, did not diminish the enhancement of fibronectin binding to MG-63 cells. These results indicate that LDL and VLDL interact with fibronectin to potentiate binding to monolayer cells through a pathway that does not involve the LDL receptor.
Familial combined hyperlipidemia and abnormal lipoprotein lipase.
Authors: Babirak S P , Brown B G , Brunzell J D
Published: June 2011

A previous study reported that heterozygotes for lipoprotein lipase (LPL) deficiency have reduced LPL, the lipoprotein pattern classified as familial combined hyperlipidemia (FCHL), elevated apolipoprotein (apo) B levels, and reduced high density lipoprotein (HDL) levels. These findings suggest that subjects with reduced LPL may form one subset of the FCHL population. The purpose of the present study is to determine whether a subset of patients with FCHL have reduced LPL. Three patient populations with FCHL were studied: 1) subjects with the diagnosis of FCHL (n = 9) established by previous family studies, 2) clinic patients with a tentative diagnosis of FCHL (n = 14), and 3) subjects undergoing angiography who had coronary artery disease (CAD) and a diagnosis of FCHL by family study (n = 33). Two of nine subjects with the established diagnosis of FCHL, five of the 14 FCHL clinic patients, and 13 of the 33 CAD subjects with FCHL had reduced LPL activity in the same range as do individuals who are obligate heterozygotes for LPL deficiency. Subjects with FCHL and reduced LPL had higher plasma triglyceride (p < 0.01) and lower HDL cholesterol (p < 0.025) levels than did the subjects with FCHL and normal LPL levels (327 +/- 201 versus 210 +/- 122 mg/dl [mean +/- SD] and 36 +/- 7 versus 44 +/- 13 mg/dl, respectively). Thus, in all three groups of patients with apparent FCHL, 20 of 56 subjects (36%) had reduced LPL, suggesting that one subset of the FCHL population may be identified by an abnormality in LPL activity that is associated with lipoprotein abnormalities.
Modulation of fibrinolytic response to venous occlusion in humans by a combination of low-dose aspirin and n-3 polyunsaturated fatty acids.
Authors: Iacoviello L , Amore C , De Curtis A , Tacconi M T , de Gaetano G , Cerletti C , Donati M B
Published: June 2011

Aspirin at high but not at low doses reduces the fibrinolytic response to venous occlusion. Inhibition of vascular prostacyclin synthesis could be involved in this effect. Fish oil supplementation may redirect prostanoid metabolism toward an overall "antithrombotic" condition but with controversial effects on prostacyclin formation. In this study we investigated the effect of low-dose aspirin together with n-3 polyunsaturated fatty acid (PUFA) supplementation on the fibrinolytic response to venous occlusion. Following a double-blind, randomized, crossover design, six healthy volunteers (three men and three women, 24-37 years old) were given for 29 days 5.3 g eicosapentaenoic and docosahexaenoic acids or a corresponding dose of n-6 PUFAs as control; aspirin (40 mg/day) was then added for an additional 14 days. A 2-month washout period was allowed before the crossover. Blood was collected before and after venous stasis on days 0, 29, and 43 of each test period. A combination of aspirin with n-3 PUFAs reduced the fibrinolytic response to venous occlusion in all subjects, the mean value of fibrinolytic activity after stasis being 240 +/- 40 mm2, a value significantly lower than at baseline (366 +/- 51 mm2, mean +/- SEM, p < 0.05). Similarly, the tissue-type plasminogen activator (t-PA) antigen level was lower in the aspirin + PUFA-treated group. Plasminogen activator inhibitor activity before stasis was enhanced by n-3 PUFA supplementation (from 7.5 +/- 2 to 14.8 +/- 3 IU/ml, p < 0.05), an effect not affected by aspirin.(ABSTRACT TRUNCATED AT 250 WORDS)
Contribution of the endothelium to intimal thickening in normocholesterolemic and hypercholesterolemic rabbits.
Authors: Kisanuki A , Asada Y , Hatakeyama K , Hayashi T , Sumiyoshi A
Published: June 2011

Endothelial cell injury is considered to be a primary event in the pathogenesis of atherosclerosis. In this study, we investigated the aortic intimal lesion after balloon catheterization in hypercholesterolemic and normocholesterolemic rabbits with or without probucol, an antioxidant. After deendothelialization, the rabbits were divided into four groups: 1) a control group fed a standard diet; 2) a probucol-treated group; 3) a cholesterol-fed group; and 4) a group fed a mixed cholesterol and probucol diet. Four animals from each group were killed at 2, 4, and 8 weeks after deendothelialization. The aortic segments of nonendothelialized areas, borderline areas, and uninjured areas were histologically and immunohistochemically examined. Deendothelialized areas showed various degrees of intimal thickening, which was mainly composed of smooth muscle cells in rabbits from groups 1 and 2. The intimal thickness of group 3 was significantly larger than that of other groups in any area examined. The intimal thickness of group 4 was less than that of group 3 despite the hypercholesterolemic state in the former group. The intima of borderline areas was generally thicker than that of nonendothelialized areas. Although the borderline lesions of groups 3 and 4 contained numerous macrophages, the number of macrophages was lower in the nonendothelialized compared with the reendothelized lesion. These data indicate that endothelial cell injuries can cause intimal thickening. The regenerated endothelial covering is favorable for monocyte migration and attachment. This process, together with the proliferation of smooth muscle cells, greatly contributes to the progression of atherosclerosis, which appears to involve lipid oxidation. Probucol prevented intimal thickening to a certain degree in this experiment in the normocholesterolemic as well as the hypercholesterolemic state.
Effect of atherosclerosis on responses of the perfused rabbit carotid artery to human platelets.
Authors: Kaul S , Padgett R C , Waack B J , Brooks R M , Heistad D D
Published: June 2011

Vascular responses to intraluminal and abluminal activation of human platelets were examined in carotid arteries from normal and atherosclerotic rabbits. The carotid artery was perfused in vitro, platelets were activated with thrombin (0.1 unit/ml), and changes in diameter were measured. In vessels from normal animals, intraluminal activation of platelets produced dilatation of preconstricted arteries. The dilator response was attenuated by N omega-nitro-L-arginine (10(-5) M), an inhibitor of synthesis of endothelium-derived relaxing factor-nitric oxide (EDRF-NO), and augmented by LY53,857 (10(-5) M), a 5-HT2-serotonergic antagonist. Abluminal activation of platelets produced modest constriction in quiescent arteries, which was inhibited by LY53,857. Intraluminal but not abluminal ADP produced pronounced dilatation of preconstricted arteries. In vessels from atherosclerotic animals, endothelium-dependent dilatation to intraluminal activation of platelets and to ADP was impaired and dilator responses to sodium nitroprusside were normal. These experiments indicate that 1) intraluminal activation of human platelets produces endothelium-dependent dilatation in perfused carotid arteries, whereas abluminal activation of human platelets produces vasoconstriction, which is mediated primarily by serotonin, and 2) atherosclerosis markedly impairs vasodilator responses to activation of human platelets, probably because vasodilatation to ADP released from platelets is impaired.
Monoclonal antibodies against LDL further enhance macrophage uptake of LDL aggregates.
Authors: Khoo J C , Miller E , Pio F , Steinberg D , Witztum J L
Published: June 2011

Self-aggregates of low density lipoprotein (LDL) are taken up and degraded more rapidly by macrophages than is native LDL. That enhanced uptake is attributable in part to phagocytosis via the LDL receptor pathway. However, arterial macrophages appear to express little LDL receptor activity. The present studies demonstrate an alternative mechanism by which LDL aggregates could contribute to foam cell formation. This could occur by the formation of large immune complexes that are taken up by macrophages via the Fc receptor. When immune complexes were formed with native, soluble LDL and MB47, a monoclonal antibody specific to the apoprotein B domain recognized by the LDL receptor, the subsequent uptake and degradation of the LDL by macrophages were inhibited 50-80% compared with native LDL alone. In contrast, when aggregated LDL was bound to MB47 at a similar molar ratio, the subsequent degradation of the insoluble immune complexes was two- to fivefold greater than that of aggregated LDL alone. The enhanced uptake was abolished when Fab or F(ab')2 fragments of MB47 were substituted for the intact antibody, indicating that the increased uptake was via the Fc receptor pathway. Furthermore, the uptake of the immune complexes of aggregated LDL was reduced by competition for the Fc receptor with heat-aggregated immunoglobulin. There was also an increase in the rate of cellular cholesterol esterification and an increase in macrophage cholesteryl ester mass. Since aggregates of LDL as well as autoantibodies against modified LDL have been demonstrated in atherosclerotic lesions, it is possible that immune complexes of aggregates of modified LDL may be generated in the intima.(ABSTRACT TRUNCATED AT 250 WORDS)
Upper-body fat distribution: a hyperinsulinemia-independent predictor of coronary heart disease mortality. The Paris Prospective Study.
Authors: Casassus P , Fontbonne A , Thibult N , Ducimetière P , Richard J L , Claude J R , Warnet J M , Rosselin G , Eschwège E
Published: June 2011

The Paris Prospective Study is a long-term investigation of the factors predicting coronary heart disease in a large population of middle-aged men. The first follow-up examination involved 7,152 subjects, who were natives of metropolitan France and were free of any cardiovascular history. At that time, the usual cardiovascular risk factors and plasma insulin levels were recorded. An index of body fat distribution, the iliac-to-thigh ratio, was entered into the list of predictive variables, despite the fact that it had been measured 1 year before the first follow-up examination. After 11 years of mean follow-up, 129 of the men had died of coronary heart disease. Univariate analysis showed that the iliac-to-thigh ratio (p < 0.0001) and plasma insulin level (both fasting [p < 0.003] and 2-hour postload [p < 0.02]), as well as the four major risk factors of coronary heart disease (age, smoking, blood pressure, and plasma cholesterol level) were significantly higher in subjects who died of coronary heart disease compared with those who had died of another cause or were alive at the end of follow-up. In multivariate stepwise logistic regression, the iliac-to-thigh ratio appeared as an independent predictor of coronary heart disease death, thereby causing the removal of fasting insulin level from the list of significant independent predictors. Nevertheless, in a model that entered 2-hour postload insulin in two classes (high or low), both the insulin level and iliac-to-thigh ratio were found as significant independent predictors.(ABSTRACT TRUNCATED AT 250 WORDS)
Familial correlations of HDL subclasses based on gradient gel electrophoresis.
Authors: Williams P T , Vranizan K M , Austin M A , Krauss R M
Published: June 2011

We used nondenaturing polyacrylamide gradient gel electrophoresis to examine the familial correlations of high density lipoprotein (HDL) subclasses for 150 offspring in 47 nuclear families. The absorbance of protein stain was used as an index of mass concentrations at intervals of 0.01 nm within five HDL subclasses: HDL3c (7.2-7.8 nm), HDL3b (7.8-8.2 nm), HDL3a (8.2-8.8 nm), HDL2a (8.8-9.7 nm), and HDL2b (9.7-12 nm). Parent-offspring correlations were computed for two different characterizations of the parents: 1) by sex (i.e., mother versus father) and 2) by their relative values (highest versus lowest HDL). Sibling resemblance was assessed by using the intraclass correlations coefficient. Family members were significantly related for the following subclasses: HDL3c (sibling and father-offspring), HDL3b (sibling), HDL3a (sibling and mother-offspring), HDL2a (mother-offspring), and HDL2b (sibling, father-offspring, and mother-offspring). The offsprings' HDL3c and HDL2b values were more strongly related to their fathers' than to their mothers' values, whereas their HDL2a levels were more strongly related to their mothers' than their fathers' values. In addition, fathers' HDL2b levels were inversely correlated with the offsprings' HDL3b. The parents' HDL subclass levels were more strongly related to subclass levels of their younger (< or = 20 years) than their older offspring. Among all subclasses, HDL2b showed the strongest parent-offspring relation, with the parents' HDL values accounting for over 30% of the variance in offsprings' HDL2b.(ABSTRACT TRUNCATED AT 250 WORDS)
Fasting blood coagulation and fibrinolysis of young adults unchanged by reduction in dietary fat content.
Authors: Marckmann P , Sandström B , Jespersen J
Published: June 2011

Low-fat, high-fiber diets may influence the variables of blood coagulation and fibrinolysis associated with cardiovascular morbidity. Dietary fat content has been suggested as the important determinant. This hypothesis was tested in a strictly controlled dietary study of 13 healthy individuals. They were fed two experimental diets in a 2 x 2-week crossover trial. The diets differed in fat content (39% versus 31% of total energy), whereas the fatty acid composition and the fiber content were virtually identical. We observed no significant differences between diets in terms of fasting plasma levels of factor VII coagulant activity, fibrinogen, euglobulin fibrinolytic activity, tissue-type plasminogen activator (t-PA) activity, t-PA antigen, plasminogen activator inhibitor type 1 (PAI-1) antigen, or PAI activity. Serum levels of total cholesterol, high density lipoprotein cholesterol, and triglycerides were also unaffected. In conclusion, a moderate reduction in dietary fat intake, at a fixed fatty acid composition and dietary fiber intake, did not significantly influence blood coagulation, fibrinolysis, or blood lipids in the fasting state.
Pathogenesis of carbohydrate-induced hypertriglyceridemia using HepG2 cells as a model system.
Authors: Cianflone K , Dahan S , Monge J C , Sniderman A D
Published: June 2011

This study compares the effects of glucose and fatty acid on hepatic lipid synthesis and apolipoprotein (apo) B secretion. To do so, varying concentrations of either glucose or oleic acid were added to the medium in which HepG2 cells were being incubated. Intracellular triacylglycerol and cholesteryl ester synthesis and secretion were measured by addition of radioisotopic tracers and by determination of mass, whereas apo B concentration in the medium was measured by a specific enzyme-linked immunosorbent assay. The data indicate that increasing concentrations of glucose in the medium resulted in increased synthesis of triacylglycerol within the cell and increased secretion of triacylglycerol into the medium. Apo B secretion into the medium, however, did not change, and intracellular synthesis and secretion of cholesteryl ester did not change as well. By contrast, addition of oleic acid to the medium resulted in increased synthesis and secretion of both cholesteryl ester and triacylglycerol, and this was associated with increased secretion of apo B into the medium. Thus, a carbohydrate load resulted in secretion of normal numbers of triacylglycerol-enriched apo B particles by this hepatocyte cell line, whereas a fatty acid load led to the secretion of increased numbers of apo B particles, which were essentially normal in composition.
High density lipoprotein-binding proteins in porcine liver. Isolation and histological localization.
Authors: de Crom R P , van Haperen R , Willemsen R , van der Kamp A W
Published: June 2011

The antiatherogenic properties of high density lipoproteins (HDLs) are thought to reside in their involvement in the reverse cholesterol transport pathway. Specific HDL-binding proteins could play a key role in this process. Two HDL-binding proteins of approximately 90 and 180 kd were identified in porcine liver by ligand blotting and were purified to apparent homogeneity by a combination of protein extraction, DEAE-cellulose chromatography, Con A-Sepharose chromatography, and preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Binding of 125I-HDL by these proteins could be actively competed for by unlabeled HDL but not by low density lipoprotein. Polyclonal antisera have been raised against these two proteins. Each antiserum recognized only one of the HDL-binding proteins, indicating that they are not immunologically related. Moreover, striking differences in localization were observed in immunohistochemical studies. The 90-kd protein is located within the hepatocellular plates, while the 180-kd protein is present along the lining of the sinusoids. These results suggest functional differences between the two HDL-binding proteins described.
Effect of dietary supplementation with n-3 polyunsaturated fatty acids on physical properties and metabolism of low density lipoprotein in humans.
Authors: Nenseter M S , Rustan A C , Lund-Katz S , Søyland E , Maelandsmo G , Phillips M C , Drevon C A
Published: June 2011

The effects of marine n-3 polyunsaturated fatty acids were investigated in relation to the chemical and physical properties of low density lipoprotein (LDL) and how these changes affected LDL metabolism in humans. The subjects received supplements of six capsules daily, each capsule containing 1 g of either highly concentrated ethyl esters of n-3 fatty acids (85% eicosapentaenoic acid and docosahexaenoic acid) (n = 12) or corn oil (56% linoleic and 26% oleic acid) (n = 11). After 4 months of oil supplementation, the following changes were observed in the lipid moiety of the n-3-enriched LDL particles compared with LDL from the corn oil group: LDL cholesteryl ester, as well as the amount of total lipids of LDL, was significantly lower (0.97 +/- 0.12 versus 1.19 +/- 0.23 mg/mg protein and 1.88 +/- 0.40 versus 2.45 +/- 0.31 mg/mg, respectively; mean +/- SD, n = 6, p less than 0.05); the amount of eicosapentaenoic and docosahexaenoic acids and the unsaturation index increased (104.0 versus 29.4 micrograms/mg protein and 6.64 versus 5.49, respectively); and differential scanning calorimetry showed that LDL cholesteryl ester melting temperature was lowered by 2 degrees C (27.6 +/- 0.8 degrees versus 29.5 +/- 0.2 degrees C). The only effect observed on the protein moiety was an increase in the ratio of apolipoprotein (apo) B to cholesterol (0.66 +/- 0.17 versus 0.82 +/- 0.14 mg/mg cholesterol; p less than 0.05). Circular dichroism spectra of LDL indicated an alpha-helix content of 46 +/- 5% in apo B from both groups. No difference was observed by 13C nuclear magnetic resonance spectroscopy in the ratio of "active" to "normal" lysine residues of apo B. No detectable differences in the size of n-3 fatty acid-enriched LDL particles versus control LDL could be measured by either electron microscopy of negatively stained LDL (24.5 +/- 2.0 versus 25.0 +/- 1.5 nm) or dynamic light scattering (24.9 +/- 0.9 versus 24.9 +/- 0.4 nm). LDL from the fish oil and corn oil groups showed similar susceptibility to Cu(2+)-catalyzed lipid peroxidation, as indicated by the amount of lipid peroxides formed during the oxidation time, and degradation of oxidatively modified LDL in J774 macrophages as a function of Cu2+ oxidation time. No effect of n-3 fatty acids was observed on LDL metabolism. Specific uptake and degradation of n-3 fatty acid-enriched LDL were similar to those for control LDL in HepG2 cells as well as in human skin fibroblasts, and they showed the same ability to stimulate cholesteryl ester synthesis.(ABSTRACT TRUNCATED AT 400 WORDS)
Accumulation of 125I-tyramine cellobiose-labeled low density lipoprotein is greater in the atherosclerosis-susceptible region of White Carneau pigeon aorta and further enhanced once atherosclerotic lesions develop.
Authors: Schwenke D C , St Clair R W
Published: June 2011

Previous studies have suggested that greater arterial concentrations of undegraded low density lipoprotein (LDL) and/or greater arterial rates of LDL degradation may play role(s) in determining regional differences in arterial susceptibility to atherosclerosis in rabbits (Schwenke and Carew, Arteriosclerosis 1989;9:895-918). The White Carneau (WC) pigeon is also useful for investigating potential mechanism(s) that might account for regional variation in arterial susceptibility to atherosclerosis because atherosclerosis develops predictably in the aorta at the level of the celiac bifurcation (atherosclerosis-susceptible celiac site). In this study we sought to determine whether the 125I-tyramine cellobiose (125I-TC) content 1 day after injecting 125I-TC-LDL ("125I-TC-LDL accumulation") would be greater in the celiac site in arteries of WC pigeons and whether 125I-TC-LDL accumulation would be exaggerated by cholesterol feeding. Because 125I-TC remains trapped in cells after cellular degradation, arterial sites that either degrade LDL at higher rates or contain higher concentrations of undegraded LDL or both will demonstrate greater 125I-TC-LDL accumulation. Young WC pigeons were studied while consuming a cholesterol-free diet and after consuming a cholesterol-containing diet for 1, 2, 4, and 8 weeks. In pigeons fed a cholesterol-free diet, 125I-TC-LDL accumulation in the celiac site was equivalent to 0.24 +/- 0.02 micrograms LDL cholesterol/cm2 aortic surface/day compared with only 0.14 +/- 0.02 micrograms LDL cholesterol/cm2/day for the adjacent aorta, which is resistant to atherosclerosis (atherosclerosis-resistant site) (p less than 0.025). In atherosclerotic lesions excised from the celiac site, 125I-TC-LDL accumulation was equivalent to 21 +/- 10 micrograms LDL cholesterol/cm2 aortic surface/day compared with 0.66 +/- 0.17 micrograms LDL cholesterol/cm2/day for the adjacent atherosclerosis-resistant site (p less than 0.001). During cholesterol feeding, 125I-TC-LDL cholesterol accumulation in the celiac site as a whole increased 30-fold compared with a fivefold increase in plasma LDL cholesterol. In comparison, 125I-TC-LDL cholesterol accumulation in the adjacent atherosclerosis-resistant arterial site increased at the same rate as the plasma LDL cholesterol, while 125I-TC-LDL cholesterol accumulation in two other relatively atherosclerosis-resistant arterial sites that we studied increased relatively little during cholesterol feeding. The results of this study suggest that differences in arterial 125I-TC-LDL accumulation, both those present in normal animals and those induced by cholesterol feeding, may contribute to the characteristic regional variation in arterial susceptibility to atherosclerosis in WC pigeons.(ABSTRACT TRUNCATED AT 400 WORDS)
Ontogenetic regulation of apolipoprotein B mRNA editing during human and rat development in vivo.
Authors: Patterson A P , Tennyson G E , Hoeg J M , Sviridov D D , Brewer H B
Published: June 2011

The solubilization and delivery of lipids in plasma rely on both forms of apolipoprotein B (apo B): apo B-100 and apo B-48. Apo B-48 is the translational product of apo B-100 mRNA that undergoes peritranscriptional conversion of C----U, replacing codon CAA (glutamine 2,153) with the inframe stop codon (UAA). We examined mRNA editing activity in the human and the rat by reverse transcription-polymerase chain reaction primer-extension analysis of intestine and liver total RNA. In rat intestine the percentage of apo B transcripts that undergo editing increases dramatically the day before birth (from approximately 1% to 80%), whereas the rat liver acquires an adult level of editing activity during the third postnatal week (rising from approximately 8% to 30%), when weaning is completed, bile acid composition matures, and plasma thyroid hormone levels peak. In contrast to the rat, the human intestine acquires adult levels of apo B mRNA editing relatively early in fetal development, rising from 10% at 10 weeks to approximately 80% by the end of the second trimester. Our results establish that apo B mRNA editing is 1) developmentally regulated in a tissue- and species-specific manner; 2) fully developed prenatally in both human and rat intestine, suggesting a crucial role of apo B-48 in mammalian fetal adaptation to extrauterine life; and 3) acquired early in human fetal intestine, implying a potential role for apo B-48 in prenatal lipid metabolism.
Structure of the murine tissue factor gene. Chromosome location and conservation of regulatory elements in the promoter.
Authors: Mackman N , Imes S , Maske W H , Taylor B , Lusis A J , Drake T A
Published: June 2011

Tissue factor (TF) is a transmembrane glycoprotein that mediates cellular initiation of the coagulation serine protease cascades. Moreover, expression of TF in human atherosclerotic plaques is likely to play a significant role in the thrombotic complications associated with plaque rupture. In this study the complete murine TF gene, Cf-3, was isolated from mouse NIH 3T3 cells and was found to consist of six exons spanning about 11 kilobase pairs (kbp) of DNA. A major transcriptional start site was located 24 bp downstream of a TATA box. Cf-3 was mapped to chromosome 3 by analysis of an intersubspecies test cross. Conserved transcription factor-binding sites were identified by comparison of 5' flanking regions of the murine and human TF genes. A region of the TF promoter required for constitutive expression exhibited 85% identity in DNA sequence and included two conserved binding sites for Sp1. Furthermore, two AP-1 sites and an NF-kappa B site were conserved in a 56-bp region necessary for transcriptional activation in response to bacterial lipopolysaccharide. These highly conserved regions of the TF promoter, which contain several binding sites for well-characterized transcription factors, are likely to be functionally important in the complex pattern of TF gene expression observed in a variety of cell types.
Scavenger receptor-independent stimulation of cholesterol esterification in macrophages by low density lipoprotein extracted from human aortic intima.
Authors: Steinbrecher U P , Lougheed M
Published: June 2011

There is a growing body of evidence that suggests that modification of low density lipoprotein (LDL) in the artery wall may contribute to atherogenesis. A number of physiologically plausible modifications have been studied in vitro, including oxidation, aggregation, formation of complexes with glycosaminoglycans, and generation of LDL-immune complexes. Several studies of the properties of LDL extracted from the aortic intima have been published, but these indicate disagreement about both the nature and the extent of modification of LDL in the artery wall. The objectives of the present study were to determine the nature and extent of modification of LDL extracted from both normal and diseased human aortic intimas and to correlate this with the rate of LDL uptake in cultured cells. Analyses were performed on LDLs isolated from aortic intimas obtained at autopsy or at the time of organ harvest from 33 subjects. LDL from normal intima showed no clear evidence of oxidation but had slightly increased electrophoretic mobility compared with native plasma LDL, whereas LDL from plaques or fatty streaks exhibited variable but usually modest signs of oxidative change. Aortic LDL was more rapidly degraded by cultured macrophages than was plasma LDL and resulted in a greater stimulation of cholesterol esterification. The degree of stimulation of cholesterol esterification was correlated with the extent of modification of LDL as reflected by the degree of apolipoprotein B fragmentation. However, in all aortic LDLs the extent of oxidative change, as assessed by electrophoretic mobility or other physical parameters, was less than that required for scavenger receptor-mediated uptake. In all cases where sufficient amounts of LDL were recovered to permit degradation experiments, the uptake of aortic LDL was nonsaturable and could not be inhibited by polyinosinic acid or acetylated LDL. Chromatography on Sepharose CL-4B showed that most LDLs isolated from plaque contained a fraction that eluted in the void volume, and the size of this void peak correlated well with the stimulation of cholesterol esterification. Electron microscopy showed that the high-molecular-weight fraction contained several different types of aggregates. Some appeared to be clusters of LDL-size particles, but large vesicular structures with numerous adherent LDL particles as well as lipid droplets were also identified. These results indicate that the accelerated uptake by macrophages of LDL isolated from the arterial intima can largely be attributed to phagocytosis of LDL-containing aggregates.(ABSTRACT TRUNCATED AT 400 WORDS)