201
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Whitman SC, Sawyez CG, Miller DB, Wolfe BM, Huff MW. Oxidized type IV hypertriglyceridemic VLDL-remnants cause greater macrophage cholesteryl ester accumulation than oxidized LDL. J Lipid Res 1998. [DOI: 10.1016/s0022-2275(20)33868-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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202
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Miller M, Seidler A, Moalemi A, Pearson TA. Normal triglyceride levels and coronary artery disease events: the Baltimore Coronary Observational Long-Term Study. J Am Coll Cardiol 1998; 31:1252-7. [PMID: 9581716 DOI: 10.1016/s0735-1097(98)00083-7] [Citation(s) in RCA: 128] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
OBJECTIVES This study sought to evaluate long-term predictors of coronary events in men and women with arteriographically defined coronary artery disease (CAD). BACKGROUND There is conflicting evidence of the role of triglycerides (TGs) as a prognosticator of CAD, and no studies have examined the long-term outcome of "normal" levels in predicting new coronary events. METHODS This was a retrospective cohort study that evaluated 740 consecutive patients presenting for diagnostic coronary arteriography between 1977 and 1978. Beginning in 1988, patients with arteriographic CAD (n=350) were recontacted and asked to complete detailed medical questionnaires. Case and control patients were stratified by development of new coronary events, including death from ischemic heart disease, nonfatal myocardial infarction and revascularization. RESULTS There were 199 events during the 18-year follow-up period. The mean high density lipoprotein cholesterol (HDL-C) was significantly lower (35 vs. 39 mg/dl; p=0.002) and TGs higher (160 vs. 137 mg/dl; p=0.03) in case patients than in control patients; After adjusting for age, gender and beta-adrenergic blocking agent use, multiple logistic regression analysis revealed the following independent predictors of CAD events: diabetes mellitus (relative risk [RR] 2.1, 95% confidence interval [CI] 1.4% to 3.1%), HDL-C <35 mg/dl (RR 1.5, 95% CI 1.1% to 2.00) and TGs >100 mg/dl (RR 1.5, 95% CI 1.1% to 2.1%). A Kaplan-Meier analysis revealed significantly reduced survival from CAD events in patients with baseline TG levels > or = 100 mg/dl compared with TG levels <100 mg/dl (p=0.008). CONCLUSIONS TG levels previously considered "normal" are predictive of new CAD events. The cutpoints established by the National Cholesterol Education Program for elevated TGs (>200 mg/dl) may need to be refined.
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Affiliation(s)
- M Miller
- Division of Cardiology, University of Maryland School of Medicine, Baltimore 21201-1595, USA.
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203
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Devaraj S, Vega G, Lange R, Grundy SM, Jialal I. Remnant-like particle cholesterol levels in patients with dysbetalipoproteinemia or coronary artery disease. Am J Med 1998; 104:445-50. [PMID: 9626027 DOI: 10.1016/s0002-9343(98)00089-8] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
PURPOSE Several studies have provided support for a proatherogenic role for remnant lipoproteins. Thus, the aim of this study was to compare remnant-like particle (RLP) cholesterol levels in patients with coronary artery disease who were normolipidemic with those in controls of similar age and gender. We also assessed the usefulness of measuring RLP-cholesterol levels in patients with type III dyslipidemia. SUBJECTS AND METHODS Remnant-like particle cholesterol levels were measured in 63 normolipidemic men with coronary artery disease and 23 male controls of similar age as well as in 15 patients with type III dyslipidemia and 103 controls, using an immunoaffinity method. RESULTS Remnant-like particle cholesterol levels were significantly increased in men with coronary artery disease compared with controls (7.6 +/- 3.8 mg/dL versus 5.7 +/- 1.9 mg/dL, P < 0.01). In patients with coronary artery disease, RLP-cholesterol levels were correlated with total triglyceride and nonhigh-density-lipoprotein (HDL) cholesterol levels, but not with HDL-cholesterol levels. RLP-cholesterol levels were significantly elevated in patients with type III dyslipidemia (median 119, range 31 to 240 mg/dL) compared with controls (median 5.6, range 2.2 to 10.5 mg/dL, P < 0.001). CONCLUSION Normolipidemic men with coronary artery disease have increased levels of RLP-cholesterol that is not detected with conventional lipid screening. The RLP-cholesterol assay is a simple method for detecting high concentrations of remnant lipoproteins in patients with type III dyslipidemia.
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Affiliation(s)
- S Devaraj
- Department of Pathology, University of Texas Southwestern Medical Center, Dallas 75235-9073, USA
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204
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Boquist S, Ruotolo G, Hellénius ML, Danell-Toverud K, Karpe F, Hamsten A. Effects of a cardioselective beta-blocker on postprandial triglyceride-rich lipoproteins, low density lipoprotein particle size and glucose-insulin homeostasis in middle-aged men with modestly increased cardiovascular risk. Atherosclerosis 1998; 137:391-400. [PMID: 9622282 DOI: 10.1016/s0021-9150(97)00278-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Beta-adrenergic receptor-blocking agents are commonly used for treatment of hypertension, angina pectoris and arrhythmias and as secondary prevention after myocardial infarction. The modest protection against myocardial infarction conferred by these compounds in primary-preventive studies has suggested that beneficial effects of beta-blockade are counteracted by known adverse influences on lipid and glucose metabolism. As most beta-blockers increase plasma triglycerides and decrease the high density lipoprotein (HDL) cholesterol concentration, a randomized, double-blind, cross-over study was conducted to evaluate whether a 12-week treatment with metoprolol (100 mg o.d.) or placebo affected the metabolism of postprandial triglyceride-rich lipoproteins in 15 middle-aged men with a modestly increased cardiovascular risk. Metoprolol treatment significantly increased the postprandial responses of very low density lipoprotein (VLDL) and VLDL remnants to a mixed meal-type of oral fat tolerance test. The effect was particularly prominent for larger (Svedberg flotation rate (Sf) > 400 and Sf 60-400) particle species (P < 0.001 in repeated measures ANOVA), whereas the smaller (Sf 20-60) particles were less affected (P < 0.05). The changes in the postprandial responses of the different VLDL species were mainly related to an effect on the fasting plasma concentrations, with limited or no influences on VLDL catabolism during the postprandial state. In contrast, metoprolol treatment did not significantly influence the postprandial responses of chylomicrons and chylomicron remnants. Notably, the enhanced fasting and postprandial triglyceridaemia during metoprolol treatment was neither accompanied by a rise in fasting or postprandial free fatty acid concentrations, nor by alterations of the glucose and insulin responses to a standard oral glucose challenge. The ensuing shift in the LDL particle size distribution towards smaller particles was limited (fraction small LDL: metoprolol 22.8 +/- 15.7% versus placebo 19.3 +/- 15.0%, P < 0.05). In conclusion, metoprolol treatment primarily enhances fasting and postprandial triglyceridaemia in middle-aged men by increasing the basal hepatic production of VLDL.
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Affiliation(s)
- S Boquist
- Department of Emergency and Cardiovascular Medicine, Karolinska Institute, Karolinska Hospital, Stockholm, Sweden
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205
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Abstract
Atherosclerosis is characterized by the presence of lipid-loaded cells which are derived from macrophages and smooth muscle cells. Several lipoprotein receptors may be involved in cellular lipid uptake. These receptors include: scavenger receptor(s); LDL receptor-related protein/alpha2-macroglobulin receptor (LRP); LDL receptor; and VLDL receptor. With the exception of the LDL receptor, all of these receptors are expressed in atherosclerotic lesions. While scavenger receptors are mostly expressed in macrophages, the LRP and VLDL receptor may play an important role in mediating lipid uptake in smooth muscle cells. It is evident that no single receptor pathway is solely responsible for the increased lipid uptake in lesion cells but several redundant mechanisms may contribute to the uptake and degradation of lipoproteins in atherosclerotic lesions.
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Affiliation(s)
- T P Hiltunen
- Department of Medical Biochemistry, Tampere University Medical School and University Hospital, Finland
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206
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Abstract
There is increasing evidence that alterations in metabolism of triglyceride-rich lipoproteins are of importance in the pathogenesis of atherosclerosis and its clinical consequences. Particles with the characteristics of triglyceride-rich lipoprotein remnants have been related to the extent and severity of atherosclerosis in humans and in animal models. These particles can be identified using ultracentrifugal procedures as small, very low-density lipoprotein (VLDL) and intermediate-density lipoprotein (IDL) with Svedberg flotation rates (Sf) of 12-60. Postprandial triglyceride levels also have been related to risk of coronary artery disease, consistent with a pathologic role for remnant lipoproteins. In studies in which measurements of lipoprotein subfractions have been carried out, levels of IDL have been more predictive than low-density lipoprotein (LDL) of atherosclerosis progression as assessed by coronary artery angiography or carotid artery ultrasonography. These findings suggest that a considerable portion of the coronary disease risk attributed to LDL may be accounted for by the IDL particles included in standard LDL measurements. Other metabolic changes associated with increased levels of plasma triglyceride may also adversely affect cardiovascular disease risk. These include reductions in HDL-cholesterol and apoprotein A1, increased levels of small dense LDL particles, redistribution of apoC-III from HDL to apoB-containing lipoproteins, diminished insulin sensitivity, and procoagulant changes, including increased levels of the fibrinolysis inhibitor, plasminogen-activator inhibitor-1 (PAI-1). A predominance of small dense LDL (subclass pattern B) is a discrete marker for this cluster of interrelated abnormalities and is found in 40-50% of patients with coronary artery disease. Therapeutic interventions with favorable effects on components of this dysmetabolic profile appear to be of value in decreasing atherosclerosis risk in a substantial proportion of the population.
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Affiliation(s)
- R M Krauss
- Donner Laboratory, Lawrence Berkeley National Laboratory, University of California, Berkeley 94720, USA
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207
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Transient triglyceridemia in healthy normolipidemic men increases cellular processing of large very low density lipoproteins by fibroblasts in vitro. J Lipid Res 1998. [DOI: 10.1016/s0022-2275(20)33903-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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208
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Schissel SL, Jiang X, Tweedie-Hardman J, Jeong T, Camejo EH, Najib J, Rapp JH, Williams KJ, Tabas I. Secretory sphingomyelinase, a product of the acid sphingomyelinase gene, can hydrolyze atherogenic lipoproteins at neutral pH. Implications for atherosclerotic lesion development. J Biol Chem 1998; 273:2738-46. [PMID: 9446580 DOI: 10.1074/jbc.273.5.2738] [Citation(s) in RCA: 256] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The subendothelial aggregation and retention of low density lipoprotein (LDL) are key events in atherogenesis, but the mechanisms in vivo are not known. Previous studies have shown that treatment of LDL with bacterial sphingomyelinase (SMase) in vitro leads to the formation of lesion-like LDL aggregates that become retained on extracellular matrix and stimulate macrophage foam cell formation. In addition, aggregated human lesional LDL, but not unaggregated lesional LDL or plasma LDL, shows evidence of hydrolysis by an arterial wall SMase in vivo, and several arterial wall cell types secrete a SMase (S-SMase). S-SMase, however, has a sharp acid pH optimum using a standard in vitro SM-micelle assay. Thus, a critical issue regarding the potential role of S-SMase in atherogenesis is whether the enzyme can hydrolyze lipoprotein-SM, particularly at neutral pH. We now show that S-SMase can hydrolyze and aggregate native plasma LDL at pH 5.5 but not at pH 7.4. Remarkably, LDL modified by oxidation, treatment with phospholipase A2, or enrichment with apolipoprotein CIII, which are modifications associated with increased atherogenesis, is hydrolyzed readily by S-SMase at pH 7.4. In addition, lipoproteins from the plasma of apolipoprotein E knock-out mice, which develop extensive atherosclerosis, are highly susceptible to hydrolysis and aggregation by S-SMase at pH 7.4; a high SM:PC ratio in these lipoproteins appears to be an important factor in their susceptibility to S-SMase. Most importantly, LDL extracted from human atherosclerotic lesions, which is enriched in sphingomyelin compared with plasma LDL, is hydrolyzed by S-SMase at pH 7.4 10-fold more than same donor plasma LDL, suggesting that LDL is modified in the arterial wall to increase its susceptibility to S-SMase. In summary, atherogenic lipoproteins are excellent substrates for S-SMase, even at neutral pH, making this enzyme a leading candidate for the arterial wall SMase that hydrolyzes LDL-SM and causes subendothelial LDL aggregation.
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Affiliation(s)
- S L Schissel
- Department of Anatomy, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA
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209
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Atherogenic Lipoproteins Support Assembly of the Prothrombinase Complex and Thrombin Generation: Modulation by Oxidation and Vitamin E. Blood 1998. [DOI: 10.1182/blood.v91.2.508] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractThe importance of lipoproteins in the etiology of atherosclerosis is well established. Evidence is now accumulating to implicate thrombin in the pathogenesis of atherosclerosis. We have investigated whether atherogenic lipoproteins can support thrombin generation. In the absence of platelets or endothelial cells, both very low-density lipoprotein (VLDL) and oxidized low-density lipoprotein (LDL) support assembly of the prothrombinase complex and generation of thrombin. Thrombin generation (per μg of apolipoprotein) supported by VLDL was 19.4-fold greater than that supported by high-density lipoprotein (HDL), P < .00001, and 11.7-fold greater than that supported by LDL, P < .00001. Oxidation of LDL increased lipoprotein-supported thrombin generation 12-fold compared to unmodified LDL, P < .0001. We have shown that the phenomenon of lipoprotein-supported thrombin generation is mediated predominantly by specific phospholipids and is enhanced by oxidation of these phospholipids. The addition of vitamin E (α-tocopherol) markedly reduced the increase in thrombin generation observed after oxidation of LDL (822 ± 57 v 138 ± 47 nmol/L;P < .0001). These effects suggest that lipoproteins are important in the production of thrombin and that vitamin E may confer protection from the detrimental effects of lipoprotein oxidation by limiting thrombin formation. These results suggest that atherogenic lipoproteins are linked to the development of atherosclerosis in part by their capacity to support thrombin generation.
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210
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Atherogenic Lipoproteins Support Assembly of the Prothrombinase Complex and Thrombin Generation: Modulation by Oxidation and Vitamin E. Blood 1998. [DOI: 10.1182/blood.v91.2.508.508_508_515] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The importance of lipoproteins in the etiology of atherosclerosis is well established. Evidence is now accumulating to implicate thrombin in the pathogenesis of atherosclerosis. We have investigated whether atherogenic lipoproteins can support thrombin generation. In the absence of platelets or endothelial cells, both very low-density lipoprotein (VLDL) and oxidized low-density lipoprotein (LDL) support assembly of the prothrombinase complex and generation of thrombin. Thrombin generation (per μg of apolipoprotein) supported by VLDL was 19.4-fold greater than that supported by high-density lipoprotein (HDL), P < .00001, and 11.7-fold greater than that supported by LDL, P < .00001. Oxidation of LDL increased lipoprotein-supported thrombin generation 12-fold compared to unmodified LDL, P < .0001. We have shown that the phenomenon of lipoprotein-supported thrombin generation is mediated predominantly by specific phospholipids and is enhanced by oxidation of these phospholipids. The addition of vitamin E (α-tocopherol) markedly reduced the increase in thrombin generation observed after oxidation of LDL (822 ± 57 v 138 ± 47 nmol/L;P < .0001). These effects suggest that lipoproteins are important in the production of thrombin and that vitamin E may confer protection from the detrimental effects of lipoprotein oxidation by limiting thrombin formation. These results suggest that atherogenic lipoproteins are linked to the development of atherosclerosis in part by their capacity to support thrombin generation.
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211
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Malloy MJ, Kane JP. Aggressive medical therapy for the prevention and treatment of coronary artery disease. Dis Mon 1998. [DOI: 10.1016/s0011-5029(98)90000-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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212
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Grainger DJ, Byrne CD, Witchell CM, Metcalfe JC. Transforming growth factor beta is sequestered into an inactive pool by lipoproteins. J Lipid Res 1997. [DOI: 10.1016/s0022-2275(20)34948-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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213
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Kazdová L, Zák A, Vrána A. Increased lipoprotein oxidability and aortic lipid peroxidation in an experimental model of insulin resistance syndrome. Ann N Y Acad Sci 1997; 827:521-5. [PMID: 9329783 DOI: 10.1111/j.1749-6632.1997.tb51863.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- L Kazdová
- Department of Metabolic Research, Institute for Clinical and Experimental Medicine, Prague, Czech Republic
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214
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Nordestgaard BG, Agerholm-Larsen B, Mortensen A, Fischer Hansen B, Fischer Hansen J, Ibsen P, Kjeldsen K. Intermediate density lipoprotein cholesterol as the best lipoprotein predictor of atherosclerosis severity in the Watanabe Heritable Hyperlipidemic rabbit. Atherosclerosis 1997; 132:119-22. [PMID: 9247367 DOI: 10.1016/s0021-9150(97)00051-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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215
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Affiliation(s)
- F Karpe
- King Gustaf V Research Institute, Department of Medicine, Karolinska Hospital, Stockholm, Sweden
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216
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Shoji T, Nishizawa Y, Kawagishi T, Tanaka M, Kawasaki K, Tabata T, Inoue T, Morii H. Atherogenic lipoprotein changes in the absence of hyperlipidemia in patients with chronic renal failure treated by hemodialysis. Atherosclerosis 1997; 131:229-36. [PMID: 9199276 DOI: 10.1016/s0021-9150(97)00054-3] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We compared plasma lipid and lipoprotein parameters between 210 chronic renal failure patients treated by hemodialysis and 223 age- and sex-matched healthy control subjects to examine whether atherogenic lipoprotein changes were present in hemodialysis patients in the absence of hyperlipidemia. The hemodialysis group showed higher levels of plasma triglycerides, very low density lipoprotein (VLDL) cholesterol, and intermediate density lipoprotein (IDL) cholesterol and a lower level of high density lipoprotein (HDL) cholesterol. Low density lipoprotein (LDL) cholesterol of the hemodialysis group was not elevated but their LDL was significantly more triglyceride-enriched than that of controls. Subjects were then divided into five categories according to their plasma triglyceride levels at an interval of 50 mg/dl, and comparison was made between the two groups in the same range of plasma triglycerides. Hemodialysis patients again showed higher levels of VLDL- and IDL-cholesterol, and lower levels of HDL-cholesterol than the control group even in the plasma triglycerides-matched comparisons. Similarly, higher VLDL- and IDL-cholesterol levels in hemodialysis patients were significant in plasma total cholesterol-matched subgroup comparisons. Multiple regression analysis indicated that the relationship between plasma lipid concentrations and individual lipoprotein levels were substantially altered in uremic state. The 95th percentile level of IDL-cholesterol in the nonuremic controls was 15 mg/dl, and 45% of hemodialysis patients exceeded this level. Decreased HDL-cholesterol levels < or = 35 mg/dl were seen in 6% of the control and 38% of the hemodialysis group. Elevated IDL-cholesterol and decreased HDL-cholesterol were persistently found in hemodialysis patients with normal lipid levels. It is concluded that hemodialysis patients exhibited more atherogenic lipoprotein profile than nonuremic subjects with comparable levels of plasma triglycerides and total cholesterol. Especially, increased IDL- and decreased HDL-cholesterol levels in hemodialysis patients persisted even at very low levels of plasma lipids. Since elevated IDL and decreased HDL-cholesterol are implicated in the progression of atherosclerosis, these findings are of clinical importance in the diagnosis of lipoprotein disorder in chronic renal failure.
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Affiliation(s)
- T Shoji
- Second Department of Internal Medicine, Osaka City University Medical School, Abeno-ku, Osaka, Japan
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217
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Mallampalli RK, Salome RG, Bowen SL, Chappell DA. Very low density lipoproteins stimulate surfactant lipid synthesis in vitro. J Clin Invest 1997; 99:2020-9. [PMID: 9109447 PMCID: PMC508027 DOI: 10.1172/jci119370] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Surfactant synthesis is critically dependent on the availability of fatty acids. One fatty acid source may be circulating triglycerides that are transported in VLDL, and hydrolyzed to free fatty acids by lipoprotein lipase (LPL). To evaluate this hypothesis, we incubated immortalized or primary rat alveolar pre-type II epithelial cells with VLDL. The cells were observed to surface bind, internalize, and degrade VLDL, a process that was induced by exogenous LPL. LPL induction of lipoprotein uptake significantly increased the rates of choline incorporation into phosphatidylcholine (PC) and disaturated PC, and these effects were associated with a three-fold increase in the activity of the rate-regulatory enzyme for PC synthesis, cytidylyltransferase. Compared with native LPL, a fusion protein of glutathione S-transferase with the catalytically inactive carboxy-terminal domain of LPL did not activate CT despite inducing VLDL uptake. A variant of the fusion protein of glutathione S-transferase with the catalytically inactive carboxy-terminal domain of LPL that partially blocked LPL-induced catabolism of VLDL via LDL receptors also partially blocked the induction of surfactant synthesis by VLDL. Taken together, these observations suggest that both the lipolytic actions of LPL and LPL-induced VLDL catabolism via lipoprotein receptors might play an integral role in providing the fatty acid substrates used in surfactant phospholipid synthesis.
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Affiliation(s)
- R K Mallampalli
- Department of Internal Medicine, Department of Veterans Affairs Medical Center, The University of Iowa College of Medicine, Iowa City 52242, USA
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218
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Isherwood SG, Williams CM, Gould BJ. Apolipoprotein B-48 as a marker for chylomicrons and their remnants: studies in the postprandial state. Proc Nutr Soc 1997; 56:497-505. [PMID: 9168557 DOI: 10.1079/pns19970050] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- S G Isherwood
- Nutrition Research Group, University of Surrey, Guildford
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219
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220
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Garner B, Baoutina A, Dean RT, Jessup W. Regulation of serum-induced lipid accumulation in human monocyte-derived macrophages by interferon-gamma. Correlations with apolipoprotein E production, lipoprotein lipase activity and LDL receptor-related protein expression. Atherosclerosis 1997; 128:47-58. [PMID: 9051197 DOI: 10.1016/s0021-9150(96)05979-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The demonstration of lipid loaded macrophages in atherosclerotic tissue has led to the development of in vitro systems to elucidate the mechanisms involved in lipid accumulation. Here we have characterised the changes which occur in human monocyte-derived macrophage (MDM) lipids during culture in either human serum (HS) or foetal calf serum (FCS). MDM cultured in HS were rapidly converted to lipid filled foam cells, as assessed using HPLC analysis and oil red-O staining and compared with the same cells grown in FCS. However, the lipids which accumulated were predominantly triglycerides with smaller amounts of unesterified cholesterol (UC) and only traces of cholesteryl esters (CE). alpha-Tocopherol (alpha-TocH) was present at higher levels in MDM cultured in HS compared to the same cells grown in FCS. MDM lipid accumulation was dependent on the triglyceride-rich lipoprotein (TGRL) fraction of human serum; accordingly, supplementation of FCS with human TGRL also induced MDM lipid accumulation. The relationships between cellular lipid accumulation and secretion of apolipoprotein E (apo E) and lipoprotein lipase (LPL) as well as expression of the low density lipoprotein receptor-related protein (LRP) were also examined. MDM lipid accumulation was associated with increased apo E secretion but did not alter extracellular LPL activity. The lipid accumulation which was induced by HS was potently inhibited (but not reserved) by the inflammatory cytokine interferon-gamma (IFN gamma), and this was associated with decreased apo E production, LPL secretion and expression of LRP. These studies reveal striking differences in the lipid composition of MDM cultured in either HS or FCS, and indicate that oil red-O staining is not necessarily associated with cholesteryl ester accumulation in human macrophages. Furthermore, the effect that serum-induced lipid accumulation has on the specific MDM functions studied should be appreciated when developing in vitro macrophage models.
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Affiliation(s)
- B Garner
- Cell Biology Unit, Heart Research Institute, Sydney, NSW, Australia.
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221
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Is Hypertriglyceridemia always a Risk Factor? Vasc Med 1997. [DOI: 10.1007/978-94-009-0037-0_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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222
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Affiliation(s)
- H S Kruth
- Section of Experimental Atherosclerosis, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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223
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Korhonen T, Savolainen MJ, Koistinen MJ, Ikäheimo M, Linnaluoto MK, Kervinen K, Kesäniemi YA. Association of lipoprotein cholesterol and triglycerides with the severity of coronary artery disease in men and women. Atherosclerosis 1996; 127:213-20. [PMID: 9125311 DOI: 10.1016/s0021-9150(96)05958-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The differences between the lipid profiles of male and female patients and the effect of plasma lipids on the extent of coronary artery disease were evaluated in 122 angiographically assessed coronary artery disease patients (95 males and 27 females) and 60 controls. Both male and female patients had lower HDL-cholesterol and higher total cholesterol, LDL-cholesterol, triglyceride, VLDL-cholesterol and VLDL-triglyceride concentrations than the controls. The VLDL lipid values did not differ significantly between the male patients with different extent of CAD, whereas the VLDL lipid values of female patients tended to increase with an increasing severity of CAD. High Lp(a) (> or = 35 mg/dl) values were more prevalent in patients with > 50% coronary stenosis compared to patients with < 50% stenosis and the controls (29%, 17% and 12%, respectively). The apolipoprotein E phenotypes and epsilon allele frequencies were similar in the patients and the controls. Low HDL-cholesterol and high LDL-cholesterol are CAD risk factors for both sexes. For women, elevated VLDL-triglycerides seem to be an additional risk factor for CAD.
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Affiliation(s)
- T Korhonen
- Department of Internal Medicine, University of Oulu, Finland
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224
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Schissel SL, Tweedie-Hardman J, Rapp JH, Graham G, Williams KJ, Tabas I. Rabbit aorta and human atherosclerotic lesions hydrolyze the sphingomyelin of retained low-density lipoprotein. Proposed role for arterial-wall sphingomyelinase in subendothelial retention and aggregation of atherogenic lipoproteins. J Clin Invest 1996; 98:1455-64. [PMID: 8823312 PMCID: PMC507573 DOI: 10.1172/jci118934] [Citation(s) in RCA: 263] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Aggregation and retention of LDL in the arterial wall are key events in atherogenesis, but the mechanisms in vivo are not known. Previous work from our laboratories has shown that exposure of LDL to bacterial sphingomyelinase (SMase) in vitro leads to the formation of LDL aggregates that can be retained by extracellular matrix and that are able to stimulate macrophage foam cell formation. We now provide evidence that retained LDL is hydrolyzed by an arterial-wall SMase activity. First, we demonstrated that SMase-induced aggregation is caused by an increase in particle ceramide content, even in the presence of excess sphingomyelin (SM). This finding is compatible with previous data showing that lesional LDL is enriched in SM, though its ceramide content has not previously been reported. To address this critical compositional issue, the ceramide content of lesional LDL was assayed and, remarkably, found to be 10-50-fold enriched compared with plasma LDL ceramide. Furthermore, the ceramide was found exclusively in lesional LDL that was aggregated; unaggregated lesional LDL, which accounted for 20-25% of the lesional material, remained ceramide poor. When [3H]SM-LDL was incubated with strips of rabbit aorta ex vivo, a portion of the LDL was retained, and the [3H]SM of this portion, but not that of unretained LDL, was hydrolyzed to [3H]ceramide by a nonlysosomal arterial hydrolase. In summary, LDL retained in atherosclerotic lesions is acted upon by an arterial-wall SMase, which may participate in LDL aggregation and possibly other SMase-mediated processes during atherogenesis.
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Affiliation(s)
- S L Schissel
- Department of Anatomy & Cell Biology, College of Physicians & Surgeons, Columbia University, New York 10032, USA
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225
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Medh JD, Bowen SL, Fry GL, Ruben S, Andracki M, Inoue I, Lalouel JM, Strickland DK, Chappell DA. Lipoprotein lipase binds to low density lipoprotein receptors and induces receptor-mediated catabolism of very low density lipoproteins in vitro. J Biol Chem 1996; 271:17073-80. [PMID: 8663292 DOI: 10.1074/jbc.271.29.17073] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Lipoprotein lipase (LPL), the major enzyme responsible for the hydrolysis of plasma triglycerides, promotes binding and catabolism of triglyceride-rich lipoproteins by various cultured cells. Recent studies demonstrate that LPL binds to three members of the low density lipoprotein (LDL) receptor family, including the LDL receptor-related protein (LRP), GP330/LRP-2, and very low density lipoprotein (VLDL) receptors and induces receptor-mediated lipoprotein catabolism. We show here that LDL receptors also bind LPL and mediate LPL-dependent catabolism of large VLDL with Sf 100-400. Up-regulation of LDL receptors by lovastatin treatment of normal human foreskin fibroblasts (FSF cells) resulted in an increase in LPL-induced VLDL binding and catabolism to a level that was 10-15-fold greater than in LDL receptor-negative fibroblasts, despite similar LRP activity in both cell lines. This indicates that the contribution of LRP to LPL-dependent degradation of VLDL is small when LDL receptors are maximally up-regulated. Furthermore studies in LRP-deficient murine embryonic fibroblasts showed that the level of LPL-dependent degradation of VLDL was similar to that in normal murine embryonic fibroblasts. LPL also promoted the internalization of protein-free triglyceride emulsions; lovastatin-treatment resulted in 2-fold higher uptake in FSF cells, indicating that LPL itself could bind to LDL receptors. However, the lower induction of emulsion catabolism as compared with native VLDL suggests that LPL-induced catabolism via LDL receptors is only partially dependent on receptor binding by LPL and instead is primarily due to activation of apolipoproteins such as apoE. A fusion protein between glutathione S-transferase and the catalytically inactive carboxyl-terminal domain of LPL (GST-LPLC) also induced binding and catabolism of VLDL. However GST-LPLC was not as active as native LPL, indicating that lipolysis is required for a maximal LPL effect. Mutations of critical tryptophan residues in GST-LPLC that abolished binding to VLDL converted the protein to an inhibitor of lipoprotein binding to LDL receptors. In solid-phase assays using immobilized receptors, LDL receptors bound to LPL in a dose-dependent manner. Both LPL and GST-LPLC promoted binding of VLDL to LDL receptor-coated wells. These results indicate that LPL binds to LDL receptors and suggest that the carboxyl-terminal domain of LPL contributes to this interaction.
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Affiliation(s)
- J D Medh
- Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, Iowa 52242, USA
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226
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Assmann G, Schulte H, von Eckardstein A. Hypertriglyceridemia and elevated lipoprotein(a) are risk factors for major coronary events in middle-aged men. Am J Cardiol 1996; 77:1179-84. [PMID: 8651092 DOI: 10.1016/s0002-9149(96)00159-2] [Citation(s) in RCA: 305] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Cardiovascular risk factors were analyzed in 4,849 male participants, aged 40 to 65 years, in an 8-year follow-up of the Münster Heart Study (Prospective Cardiovascular Münster Study; PROCAM). One hundred eighty-one definite nonfatal myocardial infarctions, 49 fatal myocardial infarctions, and 28 sudden cardiac deaths were observed. Multiple logistic function analysis confirmed that age, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, systolic blood pressure, cigarette smoking, diabetes mellitus, angina pectoris, and family history of myocardial infarction were important cardiovascular risk factors. Interestingly, this analysis revealed a significant and independent association between serum levels of triglycerides and the incidence of major coronary events. The relation between lipoprotein(a) [Lp(a)] levels and the occurrence of major coronary events was analyzed in a subgroup of 878 men. Thirty-three probands with major coronary events had significantly higher geometric mean levels of Lp(a) than 828 men who did not experience major coronary events (0.09 vs 0.05 g/L; p <0.011). Thus, in addition to established risk for factors, serum levels of triglycerides and Lp(a) are sensitive indicators of increased risk major coronary events.
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Affiliation(s)
- G Assmann
- Institut für Arterioskleroseforschung an der Universität Münster, Münster, Germany
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227
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Goldberg IJ. Lipoprotein lipase and lipolysis: central roles in lipoprotein metabolism and atherogenesis. J Lipid Res 1996. [DOI: 10.1016/s0022-2275(20)37569-6] [Citation(s) in RCA: 323] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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228
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Affiliation(s)
- R J Havel
- Cardiovascular Research Institute, University of California, San Francisco 94143-0130, USA
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229
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Coleman T, Seip RL, Gimble JM, Lee D, Maeda N, Semenkovich CF. COOH-terminal disruption of lipoprotein lipase in mice is lethal in homozygotes, but heterozygotes have elevated triglycerides and impaired enzyme activity. J Biol Chem 1995; 270:12518-25. [PMID: 7759497 DOI: 10.1074/jbc.270.21.12518] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The role of the enzyme lipoprotein lipase (LPL) in atherosclerosis is uncertain. To generate an animal model of LPL deficiency, we targeted the LPL gene in embryonic stem cells with a vector designed to disrupt the COOH terminus of the protein and used these cells to generate LPL-deficient mice. Germ line transmission of the disrupted LPL allele was achieved with two chimeric males, and offspring from each of these animals were phenotypically identical. Pups homozygous (-/-) for LPL deficiency died within 48 h of birth with extreme elevations of serum triglycerides (13,327 mg/dl) associated with essentially absent LPL enzyme activity in heart and carcass. Newborn heterozygous (+/-) LPL-deficient pups had lower LPL enzyme activity and higher triglycerides (370 versus 121 mg/dl) than wild type (+/+) littermates. Adult heterozygotes had higher triglycerides than wild type mice with ad libitum feeding (236 mg/dl for +/- versus 88 mg/dl for +/+) and after fasting for 4 h (98 mg/dl for +/- versus 51 for +/+) or 12 h (109 mg/dl for +/- versus 56 mg/dl for +/+). Triglycerides were present as very low density lipoprotein particles and chylomicrons, but high density lipoprotein cholesterol levels were not decreased in +/- animals. Plasma heparin-releasable LPL activity was 43% lower in +/- versus +/+ adult animals. LPL activity, mRNA, and protein were lower in the tissues of +/- versus +/+ mice. Homozygous LPL deficiency caused by disruption of the COOH terminus of the enzyme is lethal in mice. Heterozygous LPL deficiency caused by this mutation is associated with mild to moderate hypertriglyceridemia without affecting static HDL cholesterol levels. Heterozygous LPL-deficient mice could be useful for determining if hypertriglyceridemia, independently or in combination with other discrete defects, influences atherosclerosis.
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Affiliation(s)
- T Coleman
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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