Diabetic state induces lipid loading and altered expression and secretion of lipoprotein lipase in human monocyte-derived macrophages.
(2000)
Journal - Atherosclerosis (IRELAND )
Abstract :
Non-insulin-dependent diabetes mellitus (NIDDM) is frequently associated with macroangiopathies and coronary heart diseases. Lipoprotein lipase (LPL), an enzyme known to undergo significant functional alterations in diabetic state, is also a potential atherogenic protein. Since, to the best of our knowledge, there are no data concerning LPL secreted by macrophages of NIDDM patients we conducted a study to assess the expression and activity of LPL secreted by monocyte-derived macrophages from NIDDM patients with cardiovascular complications versus cardiovascular patients without diabetes (controls). Isolated cells from NIDDM patients, after 7 days in culture in the presence of 20% autologous serum, readily exhibit a foam cell phenotype, in contrast to the cells from controls. Macrophages were mainly loaded with triglycerides, whose cellular amount was well correlated to triglyceridemia of NIDDM subjects. Concomitantly, macrophages from NIDDM patients displayed a approximately six-fold decrease of mRNA expression and a approximately two-fold reduction of the activity of secreted LPL, as compared to control cells. These data suggest that in complicated diabetic state, macrophage loading leading to foam cell formation is accelerated, at least in part, due to a diminished expression and activity of LPL. These observations add and extend the data that may explain the occurrence of accelerated atherogenesis and of the atherosclerotic complications associated with diabetes.
| ISSN : | 0021-9150 |
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| Mesh Heading : | Adult Cardiovascular Diseases Cell Line Cells, Cultured Diabetes Mellitus, Type 2 Diabetic Angiopathies Female Foam Cells Humans Lipoprotein Lipase Macrophages Male Microscopy, Electron Monocytes RNA, Messenger metabolism pathology pathology metabolism pathology pathology genetics pathology pathology metabolism |
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| Mesh Heading Relevant : | Lipid Metabolism metabolism metabolism metabolism |
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Increased macrophage uptake of irreversibly glycated albumin modified-low density lipoproteins of normal and diabetic subjects is mediated by non-saturable mechanisms.
(1996)
Journal - Biochimica et biophysica acta (NETHERLANDS )
Abstract :
Diabetes mellitus is known as an independent risk factor in atherosclerosis. Among the prominent biochemical changes that occur in diabetic state, are the enhanced formation of advanced glycosylation end products (AGE) (especially linked to albumin and collagen) and the impaired oxidative-antioxidative balance. Previously, we have shown that AGE-albumin (AGE-Alb) significantly alters the physico-chemical characteristics of low density lipoproteins of normal (nLDL) and diabetic (dLDL) subjects. In this study we tried to establish if incubation of nLDL or dLDL, with AGE-Alb in autoxidative conditions, modifies the rate and/or the pathway of their uptake by macrophages. To this purpose, nLDL and dLDL were exposed to AGE-Alb, and after re-isolation and radiolabeling the lipoproteins were incubated with U937 or peritoneal macrophages (for various time and concentrations), in the absence or presence of different competitors (native LDL, acetylated LDL, AGE-Alb, mannan) or cytochalasin D. As controls, nLDL and dLDL, maintained in similar conditions, but without AGE-Alb, were used. The results showed that preincubation for 24 h and 72 h with AGE-Alb augmented the macrophage uptake for both nLDL and dLDL (1.7-fold). Either pre-incubated or not with AGE-Alb, dLDL was taken up at a constantly higher rate than nLDL; the difference appeared more prominent at 72 h (1.5 vs. 4 micrograms LDL protein/mg cell protein). The increased level of glycation of native dLDL as compared to native nLDL (266 +/- 35 vs. 160 +/- 24 mmol HMF/mol apoB) as well as of the lipid peroxides (1.34 +/- 0.47 vs. 0.3 +/- 0.09 nmol MDA/mg apoB) could account for the greater uptake of dLDL at any preincubation time. Competition experiments indicated that, generally, incubation with AGE-Alb diminished the apo B100,E receptor-mediated uptake in favour of 'scavenger' receptor pathway and phagocytosis. Macrophage uptake of AGE-Alb modified dLDL was reduced approximately 30% by native nLDL, approximately 70% by acetylated LDL and approximately 38% by cytochalasin D. Together, these data suggest that the consequence of the alterations induced by AGE-Albumin on LDL is the increased macrophage uptake, via non-saturable pathways, that ultimately may lead to accelerated formation of atherosclerotic plaques in diabetics.
| ISSN : | 0006-3002 |
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| Mesh Heading : | Adult Aged Animals Cell Line Cholesterol Cytochalasin D Diabetes Mellitus, Type 2 Humans Lipoproteins, LDL Macrophages, Peritoneal Mannans Microscopy, Electron Middle Aged Phagocytosis Rats Serum Albumin Thiobarbituric Acid Reactive Substances blood pharmacology pharmacology pharmacology metabolism |
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| Mesh Heading Relevant : | metabolism metabolism metabolism pharmacology |
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Irreversibly glycated albumin alters the physico-chemical characteristics of low density lipoproteins of normal and diabetic subjects.
(1995)
Journal - Biochimica et biophysica acta (NETHERLANDS )
Abstract :
In diabetic plasma, glycated albumin and glycated LDL coexist with augmented levels of peroxides, conditions frequently associated with the development of accelerated atherosclerosis. The direct interaction between irreversibly glycated albumin, LDL and oxidation have not been explored yet. We tried to elucidate whether irreversibly glycated albumin (AGE-Alb) induces changes in the chemistry and morphology of LDL particle, and if AGE-Alb has the ability to scavenge free radicals, as reported for native albumin. LDL isolated from normal (nLDL) or diabetic human subjects (dLDL) was incubated in vitro with AGE-Alb in conditions of autoxidation (37 degrees C, 24-48 h in the absence of oxidation inhibitors) or of Cu2+ induced-oxidation. The results showed that, especially in the latter condition, AGE-Alb induced marked physico-chemical modifications of both nLDL and dLDL without significant changes in the level of peroxides. Incubation with AGE-Alb decreased the cholesteryl esters/unesterified cholesterol ratio of nLDL by 30% and of dLDL by approximately 50%. Concomitantly, in oxidative conditions a marked increase (approximately 3-fold) in the lysophosphatidylcholine/phosphatidylcholine ratio of dLDL was detected. Apolipoprotein B integrity as well as the morphology of the lipoprotein particles were drastically affected. To a lesser extent, these modifications occurred also in the presence of inhibitors of oxidation at 37 degrees C, but not at 4 degrees C. The above described effects were constantly more pronounced in the case of dLDL. These results indicated that in the absence of other plasma or vascular tissue components (e.g., endothelial cells, extracellular matrix) AGE-Alb by itself induces alterations in the chemistry and morphology of LDL, especially of glycated LDL, modifications that may account for the occurrence of accelerated atherogenesis in diabetes.
| ISSN : | 0006-3002 |
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| Mesh Heading : | Arteriosclerosis Diabetes Mellitus Humans Lipid Peroxidation Lipoproteins, LDL Serum Albumin Thiobarbituric Acid Reactive Substances metabolism drug effects blood ultrastructure analysis |
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| Mesh Heading Relevant : | metabolism chemistry pharmacology |
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In vitro formation of oxidatively-modified and reassembled human low-density lipoproteins: antioxidant effect of albumin.
(1993)
Journal - Biochimica et biophysica acta (NETHERLANDS )
Abstract :
In early atherogenesis, excess plasma lipoproteins accumulate into the arterial lesion-prone areas as modified and reassembled lipoproteins (MRLp) appearing mostly as lipid droplets and vesicles. In the present study we produced such MRLp, in a cell-free system, devoid of any component of extracellular matrix, by subjecting in vitro human low-density lipoproteins (LDL) to autoxidation or copper-induced oxidation, for up to 96 h. As visualized by negative staining electron microscopy, a large number of lipoprotein particles (Lp) were progressively transformed into aggregates (ALp), fused particles (FLp) and vesicles (VLp). These modifications were paralleled by peroxidation of the samples as revealed by chemical analysis of each MRLp fraction isolated by a three-step purification procedure. LDL peroxidation in the above conditions was inhibited by the presence of albumin as assessed by TBARS and lipid analysis, and by the lack of MRLp formation. This protective effect was independent of albumin source (bovine, human, rabbit) and occurs at an albumin/LDL ratio of 1 when Cu2+ was present, and at a ratio of 0.25 in autoxidative conditions. The results show that: (i) in vitro LDL autoxidation or copper-induced peroxidation in a cell-free system can generate modified and reassembled lipoproteins similar to those detected in vivo in the arterial intima at the inception of atherogenesis; (ii) Lp particles appear to be sequentially transformed in self-aggregates, droplets and vesicles; (iii) serum albumin can completely prevent these LDL alterations.
| ISSN : | 0006-3002 |
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| Mesh Heading : | Antioxidants Cell-Free System Chemical Fractionation Humans Immunoglobulins Lipid Peroxidation Lipoproteins, LDL Oxidation-Reduction Particle Size Serum Albumin pharmacology chemistry ultrastructure |
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| Mesh Heading Relevant : | pharmacology isolation & purification pharmacology |
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