Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 23
Filter
1.
Arterioscler Thromb Vasc Biol ; 21(12): 2051-8, 2001 Dec.
Article in English | MEDLINE | ID: mdl-11742884

ABSTRACT

The insulin resistance syndrome, consisting of resistance to insulin and several metabolic abnormalities, is associated with an increased risk of symptomatic coronary artery disease. Asymptomatic persons with increased coronary calcification have increased coronary plaque and an increased likelihood of future cardiovascular events. Electron-beam computed tomography-derived coronary artery calcium scores, metabolic and anthropometric parameters, and fasting and stimulated concentrations of glucose and insulin were measured in 1160 asymptomatic men and women. Coronary artery calcium scores were positively correlated with glucose, insulin, and homeostasis model assessment (HOMA) insulin resistance. Calcium scores were positively correlated with intra-abdominal adiposity, age, total cholesterol/high density lipoprotein (HDL) ratio, low density lipoprotein, triglycerides, blood pressure, and HOMA beta cell function and inversely correlated with HDL and peripheral fat. These correlations, except for 2-hour glucose, remained significant for all subjects with fasting serum glucose <126 mg/dL or all subjects with fasting serum glucose 110 mg/dL. In a multivariate analysis, age, sex, family history of premature coronary artery disease, intra-abdominal adiposity, low density lipoprotein, and smoking independently predicted calcium scores. Blood pressure, HDL, triglycerides, glucose, insulin, and HOMA insulin resistance or beta cell function were not independently correlated with coronary artery calcium scores. Asymptomatic individuals with insulin resistance have elevated coronary calcium scores. The association between insulin resistance and coronary calcification persists with impaired glucose tolerance and normal fasting serum glucose. Central/visceral adiposity may be a determinant of insulin resistance and atherosclerosis even in asymptomatic nondiabetic persons.


Subject(s)
Coronary Artery Disease/diagnostic imaging , Coronary Artery Disease/epidemiology , Diabetes Mellitus, Type 2/epidemiology , Adipose Tissue/metabolism , Comorbidity , Diabetes Mellitus/epidemiology , Female , Humans , Insulin Resistance , Male , Middle Aged , Multivariate Analysis , New York City/epidemiology , Obesity , Prevalence , Risk Factors , Skinfold Thickness , Tomography, X-Ray Computed
3.
Control Clin Trials ; 22(5): 553-72, 2001 Oct.
Article in English | MEDLINE | ID: mdl-11578788

ABSTRACT

Early detection of asymptomatic subjects who are at risk for future cardiovascular events may allow for earlier medical treatment in order to prevent disease progression and future events. Electron-beam computed tomography accurately identifies people with increased coronary calcification, which is correlated with increased coronary plaque mass, increased likelihood of obstructive coronary disease, and increased likelihood of future cardiovascular events. The St. Francis Heart Study is a single-center combination study of men and women 50-70 years old that includes a natural history study of the relation between calcium scores and cardiovascular events (n = 5582), the association of calcium scores with traditional and nontraditional coronary disease risk factors (n = 1160), and a randomized clinical trial designed to assess the benefit of combination treatment with atorvastatin, vitamin C, and vitamin E, as compared to placebos, in subjects with elevated age- and gender-adjusted coronary calcification (n = 1007). Mean follow-up duration will be 4 years. The study is proceeding on schedule with anticipated completion by August 2002. It should provide important information regarding the benefits of treating asymptomatic men and women who have elevated coronary artery calcium, using cholesterol reduction and antioxidant therapy. The article describes the design of the St. Francis Heart Study.


Subject(s)
Patient Selection , Randomized Controlled Trials as Topic/methods , Research Design , Aged , Antioxidants/administration & dosage , Antioxidants/therapeutic use , Atorvastatin , Calcinosis/drug therapy , Coronary Disease/drug therapy , Drug Therapy, Combination , Female , Heptanoic Acids/administration & dosage , Heptanoic Acids/therapeutic use , Humans , Hydroxymethylglutaryl-CoA Reductase Inhibitors/administration & dosage , Hydroxymethylglutaryl-CoA Reductase Inhibitors/therapeutic use , Male , Middle Aged , Pyrroles/administration & dosage , Pyrroles/therapeutic use
4.
Curr Cardiol Rep ; 3(5): 408-15, 2001 Sep.
Article in English | MEDLINE | ID: mdl-11504578

ABSTRACT

Deficiencies in traditional cardiovascular risk-factor assessment in asymptomatic individuals have led to the use of electron beam computed tomography (CT) scanning as a screening test for coronary artery disease. This novel approach is based on a secure pathologic foundation: the risk of coronary disease events is proportional to the severity and extent of underlying coronary atherosclerosis, and in middle-aged and elderly adults, calcified plaque is closely related to total plaque. Electron beam CT measures coronary calcium quickly, easily, accurately, and with a high degree of reproducibility. Coronary calcium is three to nine times higher in persons with fatal or nonfatal myocardial infarction than in age-matched controls, and four observational outcomes studies have demonstrated that the electron beam CT-derived coronary calcium score predicts fatal and nonfatal myocardial infarction. In symptomatic persons undergoing cardiac catheterization, electron beam CT is more closely associated with the severity of coronary atherosclerosis than are standard coronary risk factors. Preliminary evidence in asymptomatic persons indicates that the coronary calcium score also predicts coronary disease events more accurately than standard risk factors.


Subject(s)
Calcium/metabolism , Coronary Disease/prevention & control , Coronary Vessels/metabolism , Hypolipidemic Agents/therapeutic use , Adult , Calcinosis , Coronary Artery Disease , Coronary Disease/diagnostic imaging , Coronary Disease/drug therapy , Humans , Myocardial Infarction , Predictive Value of Tests , Tomography, X-Ray Computed
5.
J Am Coll Cardiol ; 36(4): 1253-60, 2000 Oct.
Article in English | MEDLINE | ID: mdl-11028480

ABSTRACT

OBJECTIVES: We sought to determine the prognostic accuracy of electron beam computed tomographic (EBCT) scanning of the coronary arteries at three to four years. BACKGROUND: Coronary artery calcium scores determined by EBCT correlate with the severity of coronary artery disease. However, previous reports of the prognostic accuracy of EBCT scanning for coronary events in asymptomatic individuals are conflicting. METHODS: Asymptomatic men and women undergoing coronary EBCT completed initial and follow-up evaluations, which included past medical history, the Rose angina questionnaire and interim cardiovascular events. Reported coronary events (death, nonfatal myocardial infarction [MI] and revascularization procedures) were confirmed without knowledge of the scan results. RESULTS: Information was obtained in 1,172 (99.6%) of 1,177 eligible subjects (baseline age 53 +/- 11 years, 71% men). During an average follow-up of 3.6 years, 39 subjects sustained coronary events: three coronary deaths, 15 nonfatal MIs and 21 coronary artery revascularization procedures. The mean coronary artery calcium score was 764 +/- 935 among subjects with events as compared with 135 +/- 432 among those without events (p < 0.0001). For the prediction of all coronary events and of nonfatal MIs and deaths, the areas under the receiver-operator characteristics curve were 0.84 and 0.86, respectively, and a coronary calcium score > or =160 was associated with odds ratios of 15.8 and 22.2, respectively. The odds ratios for all events remained high (14.3 to 20.2) after adjustment for self-reported cardiovascular risk factors. CONCLUSIONS: In asymptomatic adults, EBCT of the coronary arteries predicts coronary death and nonfatal MI and the need for revascularization procedures.


Subject(s)
Coronary Artery Disease/diagnostic imaging , Tomography, X-Ray Computed , Adult , Aged , Angina Pectoris/diagnostic imaging , Angina Pectoris/etiology , Angina Pectoris/mortality , Cause of Death , Coronary Artery Disease/complications , Coronary Artery Disease/mortality , Female , Humans , Male , Middle Aged , Myocardial Infarction/diagnostic imaging , Myocardial Infarction/etiology , Myocardial Infarction/mortality , Prognosis , ROC Curve , Reproducibility of Results , Retrospective Studies , Survival Rate
6.
Curr Pharm Des ; 5(1): 1-10, 1999 Jan.
Article in English | MEDLINE | ID: mdl-10066880

ABSTRACT

Coronary artery disease (CAD) ranks as the leading cause of death in the Western world. The most widely used therapeutics utilized for the treatment of CAD are the lipid-lowering drugs, which lower plasma cholesterol. However lowering cholesterol alone may not be sufficient to provide benefit to all patient populations at risk for CAD. This creates an unmet medical need. Emerging knowledge of the genesis, progression and regression of atherosclerosis, that leads to CAD permits evaluation of other therapeutic strategies. This review will evaluate two such naturally occurring paradigms, the nitric oxide pathway and the high-density lipoprotein system which are nature's defense mechanisms against atherosclerosis and may lead to next generation therapeutics against CAD.


Subject(s)
Arteriosclerosis/drug therapy , Coronary Disease/drug therapy , Lipoproteins, HDL/therapeutic use , Nitric Oxide/physiology , Animals , Arteriosclerosis/etiology , Coronary Disease/blood , Humans , Lipoproteins, HDL/metabolism , Lipoproteins, LDL/blood
7.
Coron Artery Dis ; 9(8): 513-8, 1998.
Article in English | MEDLINE | ID: mdl-9847983

ABSTRACT

BACKGROUND: The amount of coronary artery calcification, measured using electron beam computed tomography, is correlated with the volume of coronary artery atherosclerotic plaque, the severity of stenosis by angiography, and with the likelihood of future cardiovascular events. The deposition of calcium in atherosclerotic plaques may also be influenced by determinants of calcium metabolism, thus contributing to the variance of the relation between coronary artery calcification and extent of atherosclerosis. Our objective was to determine whether this variance could be explained by differences in the parameters of calcium metabolism. DESIGN AND METHODS: We measured serum concentrations of calcium, 1,25(OH)2 vitamin D and parathyroid hormone (PTH) in 50 subjects undergoing angiography for clinical indications, and evaluated the correlations between these concentrations and calcium deposition in the coronary arteries, and the ratio of calcium deposition to extent of atherosclerosis using coronary angiography. RESULTS AND CONCLUSIONS: Serum concentrations of calcium 1,25(OH)2 vitamin D and PTH were not correlated with coronary calcification or the ratio of coronary calcification to the extent of coronary stenosis. We conclude that, in subjects undergoing coronary angiography, the variance of the relationship between coronary atherosclerosis and coronary calcium is not a result of differences in serum concentrations of calcium, 1,25(OH)2 vitamin D or PTH.


Subject(s)
Calcitriol/blood , Calcium/blood , Coronary Artery Disease/blood , Parathyroid Hormone/blood , Aged , Coronary Angiography , Coronary Artery Disease/diagnostic imaging , Coronary Vessels/pathology , Female , Humans , Male , Middle Aged , Tomography, X-Ray Computed
8.
J Am Coll Cardiol ; 32(3): 673-9, 1998 Sep.
Article in English | MEDLINE | ID: mdl-9741510

ABSTRACT

OBJECTIVE: To determine whether electron beam computed tomography (CT) adds to conventional risk factor assessment in the prediction of angiographic coronary artery disease. BACKGROUND: Electron beam CT scanning can be used to predict the severity of coronary atherosclerosis, but whether it does so independently of conventional risk factors is unclear. METHODS: Electron beam CT scans were performed and conventional risk factors were measured in 290 men and women undergoing coronary arteriography for clinical indications. The association of the electron beam CT-derived coronary artery calcium score and conventional risk factors with the presence and severity of angiographically defined coronary atherosclerosis was analyzed by logistic regression and receiver-operator characteristics analysis. RESULTS: Age, the ratio of total cholesterol to high-density lipoprotein (HDL) cholesterol and the coronary calcium score were significantly and independently associated with the presence of any coronary disease and obstructive coronary disease. In association with any coronary disease, odds ratios for age, the ratio of total cholesterol to HDL cholesterol and calcium score, highest quartile vs. lowest quartile, were 6.01 (95% confidence interval 2.87 to 12.56), 3.14 (1.56 to 6.31) and 94.08 (21.06 to 420.12), respectively. For obstructive coronary disease, highest quartile vs. lowest quartile, the respective odds ratios for age, the ratio of total cholesterol to HDL and calcium score were 3.86 (1.86 to 8.00), 4.11 (1.98 to 8.52) and 34.12 (12.67 to 91.86). Male gender was also significantly associated with any coronary disease (odds ratio 2.19, p=0.04) and obstructive coronary disease (odds ratio 2.07, p=0.04). Cigarette smoking was significantly associated with any coronary disease (odds ratio=2.74, p=0.004), and diabetes was significantly associated with obstructive disease (odds ratio 3.16, p=0.01). After adjustment for the coronary calcium score and other risk factors, it was determined that triglycerides, family history and hypertension were not significantly associated with any disease state. A coronary calcium score >80 (Agatston method) was associated with an increased likelihood of any coronary disease regardless of the number of risk factors, and a coronary calcium score > or = 170 was associated with an increased likelihood of obstructive coronary disease regardless of the number of risk factors (p < 0.001). CONCLUSIONS: Electron beam CT scanning offers improved discrimination over conventional risk factors in the identification of persons with any angiographic coronary disease or angiographic obstructive coronary disease.


Subject(s)
Coronary Angiography , Coronary Artery Disease/diagnostic imaging , Tomography, X-Ray Computed , Adult , Aged , Calcinosis/diagnostic imaging , Cholesterol/blood , Cholesterol, HDL/blood , Female , Humans , Male , Middle Aged , Odds Ratio , Risk Factors , Sensitivity and Specificity
9.
Atherosclerosis ; 138(2): 319-27, 1998 Jun.
Article in English | MEDLINE | ID: mdl-9690915

ABSTRACT

We investigated the ability of NAC to inhibit in vitro LDL oxidation, and the effects of the timing of NAC addition, repeated additions of NAC, and the presence of preoxidized LDL, on the oxidation reaction. NAC inhibited in vitro LDL oxidation induced by copper sulfate, 2,2'-azobis(2-amidinopropane) dihydrochloride, and UV light, and protected LDL against depletion of antioxidant vitamins. Glutathione was similarly effective against copper-mediated LDL oxidation. NAC's effectiveness was inversely related to the timing of its addition. Sequential NAC additions prolonged the lag phase more effectively than initial addition of the same total dose. NAC reduced CD formation during the oxidation of native LDL by oxidized LDL. NAC's effectiveness as an inhibitor of in vitro LDL oxidation is dependent on the temporal sequence of the oxidation reaction, sequential additions, and the presence of previously oxidized LDL.


Subject(s)
Acetylcysteine/pharmacology , Free Radical Scavengers/pharmacology , Lipid Peroxidation/drug effects , Lipoproteins, LDL/metabolism , Acetylcysteine/metabolism , Free Radical Scavengers/metabolism , Humans , Oxidation-Reduction
11.
S Afr Med J ; 88(5): 558-63, 1998 May.
Article in English | MEDLINE | ID: mdl-9638124

ABSTRACT

Electron beam computed tomography (EBCT) of the heart is a new modality which will alter the way cardiology is practised. It allows for the detection of early coronary artery disease (CAD) in asymptomatic individuals, regardless of their level of risk as assessed by traditional risk factor analysis. Compared with risk analysis based on risk factors alone, an assessment which also utilises quantitative measurements of coronary artery plaque by EBCT allows for more precise determination of the need for medical therapy. Non-invasive intravenous contrast EBCT coronary angiography can identify significant obstructive CAD, and should reduce the need for conventional coronary angiography. Incorporation of EBCT into routine medical practice is more cost-effective than other modalities currently available. This paper reviews relevant original articles on EBCT and preventive cardiology published in peer-reviewed medical journals, and assesses the implications of EBCT for preventive cardiology.


Subject(s)
Calcinosis/diagnostic imaging , Coronary Disease/diagnostic imaging , Tomography Scanners, X-Ray Computed , Calcium/analysis , Coronary Angiography , Coronary Disease/economics , Cost-Benefit Analysis , Humans , ROC Curve , Sensitivity and Specificity , Time Factors , Tomography Scanners, X-Ray Computed/economics
12.
Atherosclerosis ; 136(2): 305-14, 1998 Feb.
Article in English | MEDLINE | ID: mdl-9543102

ABSTRACT

Oxidation of low-density lipoprotein (LDL) is postulated to be essential for the development of atherosclerosis. LY-139478 is a new non-steroidal potent estrogen analog, but its effects on in vitro LDL oxidation have not been completely elucidated. We investigated the ability of LY-139478 to inhibit in vitro copper sulfate-mediated LDL oxidation using several methods, including conjugated diene (CD) accumulation, relative electrophoretic mobility on agarose gel, thiobarbituric acid-reactive substances (TBARS) assay, and superoxide anions scavenging activity. The antioxidative potential of LY-139478 was compared to testosterone (T), 17-alpha-estradiol (17alphaE), 17-beta-estradiol (17betaE), dehydroepiandrosterone (D), and dehydroepiandrosterone-3-sulfate (DS). LY-139478 was superior to 17alphaE and 17betaE in prolonging the lag phase and decreasing the slope and peak concentration of the conjugated diene accumulation, decreasing the rate of migration of LDL on agarose gel electrophoresis, and inhibiting the production of melonyldialdehyde (MDA) in the TBARS assay. T, D and DS were ineffective in all three assays. It was previously shown that when native LDL is oxidized by previously oxidized LDL (secondary oxidation) the lag phase is lost (Schnitzer et al. Free Rad Res 1995;23:137). LY-139478 was at least 15-fold more effective than 17alphaE, and 17betaE in slowing the propagation phase and reducing CD accumulation in this secondary oxidation, with 50% inhibition at 10 microM and 98% inhibition at 100 microM. However, none restored the lag phase. T, D and DS were ineffective. Superoxide anion generation was inhibited only by DS at high doses (500 microM). These results demonstrate that LY-139478 is an effective inhibitor of LDL oxidation and is superior to natural steroidal hormones, including 17betaE, in protecting against primary and secondary LDL oxidation.


Subject(s)
Estrogen Antagonists/pharmacology , Gonadal Steroid Hormones/pharmacology , Lipoproteins, LDL/metabolism , Pyrrolidines/pharmacology , Thiophenes/pharmacology , Antioxidants/pharmacology , Copper Sulfate/pharmacology , Dehydroepiandrosterone/pharmacology , Dehydroepiandrosterone Sulfate/pharmacology , Dose-Response Relationship, Drug , Electrophoresis, Agar Gel , Estradiol/pharmacology , Humans , In Vitro Techniques , Malondialdehyde/metabolism , Oxidation-Reduction , Superoxides/metabolism , Testosterone/pharmacology , Thiobarbituric Acid Reactive Substances/metabolism
13.
J Comput Assist Tomogr ; 22(2): 207-11, 1998.
Article in English | MEDLINE | ID: mdl-9530380

ABSTRACT

PURPOSE: Electron beam CT (EBCT)-derived coronary artery calcium scores correlate with the extent of atherosclerosis, but there is a substantial variance about the general relationship between coronary calcification and coronary atherosclerosis. The relationship between calcification and atherosclerosis may also differ in various arteries. This study was designed to evaluate whether the relation between carotid artery intima-media thickness (IMT) and carotid artery calcium could be used as a correction factor to improve the correlation between coronary calcification and coronary atherosclerosis. METHOD: We measured atherosclerosis in the coronary and carotid arteries by angiography and ultrasonography, respectively, and quantified coronary and carotid calcium deposition with EBCT in 50 subjects. The correlation between the findings in the carotid and coronary arteries was investigated. RESULTS: Coronary artery calcium score correlated with coronary angiography and with carotid calcium score. Coronary stenosis correlated with carotid IMT. There was no meaningful correlation of carotid IMT and carotid calcium. CONCLUSION: There is an intraindividual variation in the relationship of plaque mass to calcification among different vessels. The relation between carotid artery calcification and carotid IMT is not predictive of the relation between coronary artery calcification and coronary obstruction.


Subject(s)
Calcinosis/diagnostic imaging , Carotid Arteries/diagnostic imaging , Carotid Artery Diseases/diagnostic imaging , Coronary Angiography/methods , Coronary Artery Disease/diagnostic imaging , Tomography, X-Ray Computed/methods , Aged , Coronary Angiography/instrumentation , Coronary Angiography/statistics & numerical data , Coronary Vessels/diagnostic imaging , Electrons , Female , Humans , Male , Middle Aged , Regression Analysis , Tomography, X-Ray Computed/instrumentation , Tomography, X-Ray Computed/statistics & numerical data , Ultrasonography
14.
Circulation ; 93(11): 1951-3, 1996 Jun 01.
Article in English | MEDLINE | ID: mdl-8640967

ABSTRACT

BACKGROUND: Coronary electron beam computed tomography (EBCT) detects atherosclerotic coronary artery disease by measuring calcium deposition in the walls of coronary arteries. EBCT-derived coronary artery calcium (CAC) scores correlate with the severity of underlying coronary artery disease. METHODS AND RESULTS: We followed 1173 asymptomatic patients who underwent EBCT between September 1993 and March 1994. During average follow-up of 19 months, 18 subjects had 26 cardiovascular events: 1 death, 7 myocardial infarctions, 8 coronary artery bypass graft procedures, 9 coronary angioplasties, and 1 nonhemorrhagic stroke. For CAC score thresholds of 100, 160, and 680, EBCT had sensitivities of 89%, 89%, and 50% and specificities of 77%, 82%, and 95%, respectively. Odds ratios ranged from 20.0 to 35.4 (P < .0001 for all). CONCLUSIONS: Coronary EBCT predicts future atherosclerotic cardiovascular disease events in asymptomatic subjects.


Subject(s)
Calcinosis/diagnostic imaging , Coronary Angiography/methods , Coronary Artery Disease/diagnostic imaging , Coronary Vessels/pathology , Myocardial Infarction/epidemiology , Angioplasty/statistics & numerical data , Brain Ischemia/epidemiology , Calcium/analysis , Coronary Artery Bypass/statistics & numerical data , Coronary Artery Disease/complications , Coronary Vessels/chemistry , Death, Sudden, Cardiac/epidemiology , Death, Sudden, Cardiac/etiology , Disease Progression , Female , Follow-Up Studies , Humans , Male , Mass Screening , Myocardial Infarction/etiology , Myocardial Infarction/prevention & control , ROC Curve , Sensitivity and Specificity
15.
J Biol Chem ; 269(1): 511-9, 1994 Jan 07.
Article in English | MEDLINE | ID: mdl-8276844

ABSTRACT

We compared the effect of lipid composition and particle size of triglyceride-rich low density lipoprotein (LDL) upon apoprotein B conformation and binding to the LDL receptor. Three groups of triglyceride-rich LDL were studied: (a) LDL isolated from chronic hypertriglyceridemic individuals (HTG-LDL); (b) normal LDL made triglyceride-rich by in vitro incubation with triglyceride emulsion and the neutral lipid transfer protein (R-LDL); and (c) LDL from normolipidemic individuals made acutely hypertriglyceridemic by intravenous infusion of 10% Intralipid (IV-LDL). HTG-LDL was small and dense, whereas R-LDL and IV-LDL had normal size. HTG-LDL, but not R-LDL or IV-LDL, exhibited decreased binding to the LDL receptor on human skin fibroblasts in studies at 4 degrees C and reduced degradation at 37 degrees C. Apoprotein B conformation was assessed by circular dichroism and by analyzing the immunoreactivity of different monoclonal antibodies. HTG-LDL but not R-LDL or IV-LDL showed a change in the CD spectra and a consistent decrease in the immunoreactivity of monoclonal antibody 3F5 (2.5-fold) which recognizes an epitope adjacent to the receptor binding domain of apoprotein B. These findings suggest that in triglyceride-rich LDL, the relative content of neutral lipid in the core of LDL in the absence of changes in the size of the particle does not significantly affect apoprotein B conformation or its affinity for the LDL receptor.


Subject(s)
Apolipoproteins B/metabolism , Lipoproteins, LDL/metabolism , Triglycerides/metabolism , Antibodies, Monoclonal , Apolipoproteins B/chemistry , Apolipoproteins B/immunology , Cells, Cultured , Circular Dichroism , Humans , Immunohistochemistry , Lipoproteins, LDL/chemistry , Lipoproteins, LDL/ultrastructure , Microscopy, Electron , Particle Size , Protein Conformation , Receptors, LDL/metabolism
16.
J Clin Invest ; 90(4): 1504-12, 1992 Oct.
Article in English | MEDLINE | ID: mdl-1401083

ABSTRACT

Lipoprotein lipase (LPL), the rate limiting enzyme for hydrolysis of lipoprotein triglyceride, also mediates nonenzymatic interactions between lipoproteins and heparan sulfate proteoglycans. To determine whether cell surface LPL increases LDL binding to cells, bovine milk LPL was added to upregulated and nonupregulated human fibroblasts along with media containing LDL. LDL binding to cells was increased 2-10-fold, in a dose-dependent manner, by the addition of 0.5-10 micrograms/ml of LPL. The amount of LDL bound to the cells in the presence of LPL far exceeded the capacity for LDL binding via the LDL receptor. Treatment of fibroblasts with heparinase and heparitinase resulted in a 64% decrease in LPL-mediated LDL binding. Compared to studies performed without LPL, more LDL was internalized and degraded in the presence of LPL, but the time course was slower than that of classical lipoprotein receptor mediated pathways. In LDL receptor negative fibroblasts, LPL increased surface bound LDL > 140-fold, intracellular LDL > 40-fold, and LDL degradation > 6-fold. These effects were almost completely inhibited by heparin and anti-LPL monoclonal antibody. LPL also increased the binding and uptake by fibroblasts of apolipoprotein-free triglyceride emulsions; binding was increased > 8-fold and cellular uptake was increased > 40-fold with LPL. LPL increased LDL binding to THP-1 monocytes, and increased LDL uptake (4.5-fold) and LDL degradation (2.5-fold) by THP-1 macrophages. In the absence of added LPL, heparin and anti-LPL monoclonal antibodies decreased LDL degradation by > 40%, and triglyceride emulsion uptake by > 50%, suggesting that endogenously produced LPL mediated lipid particle uptake and degradation. We conclude that LPL increases lipid and lipoprotein uptake by cells via a pathway not involving the LDL receptor. This pathway may be important for lipid accumulation in LPL synthesizing cells.


Subject(s)
Fibroblasts/metabolism , Lipoprotein Lipase/pharmacology , Lipoproteins, LDL/metabolism , Macrophages/metabolism , Animals , Cattle , Cells, Cultured , Emulsions , Heparin Lyase , Humans , Polysaccharide-Lyases/pharmacology , Receptors, LDL/physiology , Triglycerides/metabolism
17.
J Lipid Res ; 33(10): 1551-61, 1992 Oct.
Article in English | MEDLINE | ID: mdl-1431579

ABSTRACT

The ability to preserve low density lipoprotein (LDL) preparations frozen for weeks and months without changes in structure or biological properties is of potential use in long-term comparative studies of LDL. We demonstrate that freeze-thawing of LDL causes marked alterations in its structure and biological behavior, and that such changes can be prevented by the addition of sucrose to the LDL solution prior to freezing. Freezing LDL at -70 degrees C in the absence of sucrose resulted in aggregation and fusion of particles as measured by electron microscopy, spectrophotometric absorption, and column gel filtration. This was associated with increased binding affinity of monoclonal antibodies at epitopes distant from the receptor binding region. Functional changes induced by freezing included 3- to 10-fold increases in binding at 4 degrees C and 37 degrees C, and uptake of LDL in fibroblasts, attributable mainly to increases in nonspecific binding processes. Cryopreservation of LDL in 10% sucrose (w/v) completely prevented the structural and functional changes incurred after short-term freezing, and LDL cryopreserved in sucrose for as long as 18 months displayed cell binding, uptake, and degradation very similar to that of freshly obtained LDL.


Subject(s)
Cryopreservation/methods , Lipoproteins, LDL/blood , Sucrose/pharmacology , Drug Stability , Humans , Iodine Radioisotopes , Microscopy, Electron , Radioimmunoassay , Specimen Handling , Spectrophotometry
18.
Metabolism ; 41(5): 487-93, 1992 May.
Article in English | MEDLINE | ID: mdl-1588827

ABSTRACT

We have previously reported decreased production rates of the major apolipoprotein B (apoB)-containing lipoproteins, very-low-density lipoproteins (VLDL), and low-density lipoproteins (LDL) in patients with combined hyperlipidemia (CHL) during treatment with lovastatin. In the present study, we determined the effects of lovastatin therapy on VLDL triglyceride (TG) metabolism. Plasma VLDL turnover was determined in six CHL patients, before and during lovastatin therapy. 3H-triglyceride-glycerol-specific activity data derived from injection of 3H-glycerol were analyzed by compartmental modeling. The effects of lovastatin on VLDL TG metabolism were compared with those previously determined on VLDL apoB metabolism in these subjects. Lovastatin therapy was associated with decreased concentrations of VLDL TG in five of six patients and decreased VLDL apoB concentrations in all six. VLDL TG production rates (PR) decreased in five patients, with the mean for the group decreasing from 14.1 +/- 7.1 to 10.3 +/- 4.0 mg/kg/h (P less than .05). VLDL apoB PR also decreased in five patients, with the mean decreasing from 21.8 +/- 20.3 to 12.2 +/- 9.0 mg/kg/d (P = .11). Changes in VLDL TG concentrations during lovastatin treatment were correlated with changes in VLDL apoB concentrations (r = .74, P = .09) and in VLDL TG PR (r = .91, P = .01). Changes in VLDL TG PR were also related to changes in VLDL apoB PR (r = .62, P = NS). There were no consistent changes in the fractional catabolic rates of either VLDL TG or VLDL apoB during lovastatin therapy.(ABSTRACT TRUNCATED AT 250 WORDS)


Subject(s)
Hyperlipidemia, Familial Combined/blood , Lipoproteins, VLDL/blood , Lipoproteins/blood , Lovastatin/therapeutic use , Triglycerides/blood , Apolipoproteins B/blood , Humans , Hyperlipidemia, Familial Combined/drug therapy , Hyperlipidemia, Familial Combined/metabolism , Kinetics , Lipoproteins/metabolism , Lipoproteins, VLDL/metabolism , Osmolar Concentration , Triglycerides/metabolism
19.
J Lipid Res ; 31(6): 1031-42, 1990 Jun.
Article in English | MEDLINE | ID: mdl-2373953

ABSTRACT

Radiolabeling of whole lipoproteins or individual apolipoproteins has been an essential tool for the determination of the kinetics of apolipoprotein metabolism in vivo. Mathematical analysis of specific radioactivity (SA) or total radioactivity data has demonstrated the existence of significant complexity in the plasma decay curves of several apolipoproteins. Results obtained during development of methods to study the metabolism of apolipoprotein B (apoB) in very low density lipoprotein (VLDL) subclasses isolated according to flotation (Sf) rates from whole radiolabeled (d less than 1.006 g/ml) VLDL suggested nonuniform radiolabeling of apoB in the three Sf subclasses being studied. We therefore determined apoB SA in VLDL Sf subclasses in ten hypertriglyceridemic and five normal subjects. After radioiodination of apoB in whole VLDL, different apoB SA were found in Sf 400-100, Sf 100-60, and Sf 60-20. The pattern of labeling was quite variable among subjects. On average, apoB SA in the VLDL tracer was greatest in Sf 400-100, and least in Sf 60-20. Nonuniform labeling could also be demonstrated in five studies in which samples were obtained 3 min after intravenous injection of the tracer into subjects with a wide range of plasma triglycerides. Nonuniform labeling of apoB in whole VLDL was also demonstrated in two of the subjects by isolating subclasses of their VLDL that did not bind to an anti-apolipoprotein E immunoaffinity column. These results indicate that the usual assumption of homogeneous labeling of apoB may be erroneous. We have derived a simple mathematical formula to study the consequences of this assumption in estimating kinetic parameters. It is shown that an erroneous assumption of homogeneous tracer labeling may significantly underestimate or overestimate the true production rate, even in a simple two-pool model. Identification of labeling characteristics and incorporation of this information into the mathematical analysis of the plasma radioactivity data can improve the accuracy of the analysis as well as the sensitivity of compartmental models generated by such data.


Subject(s)
Apolipoproteins B/blood , Hypertriglyceridemia/blood , Lipoproteins, VLDL/blood , Apolipoproteins B/metabolism , Evaluation Studies as Topic , Humans , Isotope Labeling , Lipoproteins, VLDL/metabolism , Models, Biological
20.
Int J Obes ; 14(5): 457-63, 1990 May.
Article in English | MEDLINE | ID: mdl-2143499

ABSTRACT

To assess the effects of dehydroepiandrosterone (DHEA) on weight and body fat mass in young obese men, six obese (body mass index, 31.5 +/- 2.9 (s.e.] men were studied at baseline, after 28 days of placebo administration, and again after 28 days of DHEA (1600 mg/day) administration. Body fat mass was assessed on each occasion by three separate methods: hydrostatic weighing, impedance plethysmography, and skinfold measurements at four body sites. Waist-to-hip ratios were recorded. In addition, tissue sensitivity to insulin was determined using the modified minimal model technique, and serum lipids were assayed. Serum DHEA-sulfate levels rose from 7.4 +/- 1.7 mumol/l at baseline to 39.8 +/- 11.9 mumol/l after DHEA administration (P less than 0.05). Although body fat mass was reduced in two of the six men following DHEA administration, for the group as a whole neither total body weight, body fat mass, or waist-to-hip ratio changed significantly during the study. No change in either tissue insulin sensitivity or serum lipids was observed. These observations suggest that, at a daily dose of 13.4-19.7 mg/kg, short-term DHEA administration does not affect the total weight, body fat mass, fat distribution, insulin sensitivity, or lipid status of obese young men.


Subject(s)
Dehydroepiandrosterone/therapeutic use , Lipids/blood , Obesity/drug therapy , Adipose Tissue/metabolism , Adult , Body Mass Index , Dehydroepiandrosterone/administration & dosage , Drug Administration Schedule , Drug Evaluation , Humans , Insulin/metabolism , Lipid Metabolism , Male , Obesity/metabolism
SELECTION OF CITATIONS
SEARCH DETAIL
...