Studies of aortic plaque reveal the presence of tissue macrophages filled with cholesteryl esters. To study lipoprotein metabolism of in vivo, maturated human macrophages, I isolated cells from human peritoneal effluent. Population analysis using cytochemistry showed substantial numbers of acid-esterase positive monocytic cells, lymphocytes, leukocytes and erythrocytes. Substantial variation in cell populations existed among patients. Human peritoneal cells degraded low density lipoproteins (LDL) and acetylated LDL (AcLDL) by high affinity, receptor-mediated processes. AcLDL degradation saturated at 15 ug protein/ml and LDL degradation saturated at 11 ug protein/ml. Positive correlation of the percentages of monocytic cells with the degradation values (LDL, r =.710; AcLDL, r =.725) and a degradation assay using cells isolated by Lymphoprep showed that the monocytic cells substantially contributed to the degradation of LDL. AcLDL degradation was calcium independent and inhibited by fucoidin. LDL degradation was calcium dependent and very low density lipoprotein and apoE-containing high density lipoprotein (HDL) competed with LDL for receptor uptake; apoE-free HDL, AcLDL and fucoidin did not reduce LDL degradation. Both receptors were pronase-sensitive and degradation was dependent upon lysosomal activity. ACAT activity analysis showed that pre-incubation of cells with LDL or AcLDL stimulated ACAT activity. ACAT activity was greatest for cells preincubated using AcLDL and fresh medium was necessary to maintain the ACAT activity values beyond 24 hrs. LDL-stimulated ACAT activity declined as time was increased above 24 hrs. Flow cytometry analysis of a total cell population and the Lymphoprep-isolated cells revealed a heterogenous T cell population, the presence of monocyte/macrophages, suggested that some of the cells present were activated and confirmed cytochemistry analysis demonstrating that Lymphoprep concentrated the mononuclear cells. Human peritoneal macrophages formed foam cells when incubated in the presence of AcLDL or LDL for 72 hrs. The formation of foam cells in the presence of LDL was dependent upon cell exposure time to the medium. Foam cell formation in the presence of LDL was accompanied by dense vacuolization and in the demonstrated absence of the oxidation of LDL the oil red O stainable material collected outside the vacuoles.

by Alexandra M. Leung. / Thesis (M. Phil.)--Chinese University of Hong Kong, 1981. / Bibliography: leaves 208-224.

Thesis (Ph. D.)--Ohio State University, 2006. / Available online via OhioLINK's ETD Center; full text release delayed at author's request until 2007 Aug 10

The physical properties (i.e., mass, particle diameter and composition) of apolipoprotein B (apoB)-containing lipoproteins (apoB-LP) are a major determinant of atherosclerotic cardiovascular disease (ASCVD) risk. The objective of this research was to investigate how nascent apoB-LP physical properties affect circulating lipoprotein profiles and risk of disease. Relationships between apoB-LP physical properties and arterial plaque formation in four genotypes of mice with apoB isoform specific clearance defects were investigated. Multivariate statistical analysis found that arterial lesions were most closely related to genetic background and apoB concentration related to delayed clearance rate. For defining the dietary effects on circulating lipoprotein profiles, the physical properties of lipoproteins in hamsters fed high-carbohydrate diets containing either 60% fructose or 60% cornstarch for 2 wk were studied. Fructose increased very low-density lipoprotein (VLDL) particle diameter and decreased low-density lipoprotein (LDL) particle diameter. Elevations in all high-density lipoprotein (HDL) fractions were observed in the fructose-fed group. Further investigation was made of whether changes to the physical properties in circulating lipoproteins resulted from changes to nascent particles in the assembly and secretion processes. Intermediate particles used for lipoprotein assembly were isolated from rough endoplasmic reticulum of hamster liver, and nascent VLDL were isolated from plasma after Triton WR-1339 injection of hamsters. A large, TG-rich apoB-deficient particle and a small, lipid-poor apoB-containing particle were isolated in each dietary setting. The diameter of first-step particles was larger in fructose feeding, which indicated that apoB degradation decreases and provides the basis for apoB oversecretion. Fructose feeding significantly increased the concentrations recovered from liver for these two particles and for nascent particles compared with chow or starch feeding. Collectively, these results demonstrate: 1) genetic factors can dictate metabolism, and metabolic conditions can critically affect the physical properties and further atherogenicity of apoB-LP; 2) changes in physical properties of circulating apoB-LP are derived from changes to the nascent particles; and 3) dietary factors can influence the assembly, secretion, and metabolism of apoB-LP. The findings of the research may provide a metabolic basis for the recognition of new targets that could regulate apoB-LP metabolism to prevent and treat ASCVD.

The physical properties (i.e., mass, particle diameter and composition) of apolipoprotein B (apoB)-containing lipoproteins (apoB-LP) are a major determinant of atherosclerotic cardiovascular disease (ASCVD) risk. The objective of this research was to investigate how nascent apoB-LP physical properties affect circulating lipoprotein profiles and risk of disease. Relationships between apoB-LP physical properties and arterial plaque formation in four genotypes of mice with apoB isoform specific clearance defects were investigated. Multivariate statistical analysis found that arterial lesions were most closely related to genetic background and apoB concentration related to delayed clearance rate. For defining the dietary effects on circulating lipoprotein profiles, the physical properties of lipoproteins in hamsters fed high-carbohydrate diets containing either 60% fructose or 60% cornstarch for 2 wk were studied. Fructose increased very low-density lipoprotein (VLDL) particle diameter and decreased low-density lipoprotein (LDL) particle diameter. Elevations in all high-density lipoprotein (HDL) fractions were observed in the fructose-fed group. Further investigation was made of whether changes to the physical properties in circulating lipoproteins resulted from changes to nascent particles in the assembly and secretion processes. Intermediate particles used for lipoprotein assembly were isolated from rough endoplasmic reticulum of hamster liver, and nascent VLDL were isolated from plasma after Triton WR-1339 injection of hamsters. A large, TG-rich apoB-deficient particle and a small, lipid-poor apoB-containing particle were isolated in each dietary setting. The diameter of first-step particles was larger in fructose feeding, which indicated that apoB degradation decreases and provides the basis for apoB oversecretion. Fructose feeding significantly increased the concentrations recovered from liver for these two particles and for nascent particles compared with chow or starch feeding. Collectively, these results demonstrate: 1) genetic factors can dictate metabolism, and metabolic conditions can critically affect the physical properties and further atherogenicity of apoB-LP; 2) changes in physical properties of circulating apoB-LP are derived from changes to the nascent particles; and 3) dietary factors can influence the assembly, secretion, and metabolism of apoB-LP. The findings of the research may provide a metabolic basis for the recognition of new targets that could regulate apoB-LP metabolism to prevent and treat ASCVD.

Thesis (Ph. D.)--University of California, San Diego and San Diego State University, 2004. / Vita. Includes bibliographical references (leaves 181-227).

Thesis (Ph. D.)--University of Missouri--Columbia, 2000. / "December 2000." Typescript. Vita. Includes bibliographical references (leaves 120-131). Also available on the Internet.

Lectin-like oxidized low density lipoprotein receptor-1 (LOX-1) is a recently identified scavenger receptor expressed in endothelial cells and mediates the uptake of oxidized LDL (oxLDL). LOX-1 expression is increased in atherosclerotic lesions in animals and humans. Recent evidence has suggested that LOX-1 is involved in the development and progression of atherosclerosis. In addition to endothelial cells, it has also been reported that LOX-1 is also expressed by other cell types like macrophages. It is a multi-ligand class E scavenger receptor and cellular expression of LOX-1 can be induced by many of its ligands. The concentration of some of these ligands like oxLDL and advanced glycation end products (AGEs) are increased in the diabetic milieu. My hypothesis is that LOX-1 expression is increased in diabetes mellitus and LOX-1 activation may play a role in the development of micro- and/or macrovascular complications of diabetes. The objective of this thesis is to elucidate the role of LOX-1 in type 2 diabetes mellitus and its complications. The effect of modified LDL and AGEs on LOX-1 expression and the cellular response upon LOX-1 activation was investigated. In vitro studies have shown that both AGEs and oxLDL can activate and increase cellular expression of LOX-1 and the soluble form of LOX-1 (sLOX-1) in cultured endothelial cells. In addition, LDL modified by glycoxidation, is also a ligand of LOX-1 and glycoxidized LDL is even more potent than oxLDL in inducing LOX-1 expression. In patients with type 2 diabetes, serum level of sLOX-1 was significantly higher than non-diabetic normal control, indicating that LOX-1 expression was increased in diabetes. Serum levels of AGEs and glycoxidized LDL were important determinants of serum sLOX-1 level, and lowering serum AGEs led to a beneficial reduction in serum sLOX-1 concentration. Hence, AGEs was clearly an important ligand of LOX-1 in diabetes mellitus, and experiments were performed to further elucidate the underlying signaling pathway involved in the up-regulation of LOX-1 by AGEs. This was mediated by ligation of AGEs to the receptor for advanced glycation end products (RAGE) and activation of phosphoinositide 3-kinase. Mammalian target of rapamycin was a found to be a key downstream intermediary in AGEs-inducible LOX-1 expression in endothelial cells. I further demonstrated that LOX-1 was also expressed in human renal mesangial cells, and expression was at a low level at basal state but inducible by its ligands. Up-regulation of LOX-1 expression in activated mesangial cells resulted in increased oxidative stress, as well as increased production of proinflammatory cytokines, chemokines and growth factors. These experimental findings would suggest that LOX-1 might potentially be involved in renal inflammation and diabetic nephropathy. The above results collectively suggest that diabetes is associated with increased LOX-1 activation, and LOX-1 may play a role in the development of diabetic complications. Hence, LOX-1 might represent a suitable target for the future development of new strategies for treating and preventing diabetic vascular complications. / published_or_final_version / Medicine / Doctoral / Doctor of Philosophy

Background Over the past few years, results refuting the causal role of HDL cholesterol (HDL-c) have been reported by a number of randomized controlled trials (RCTs) testing different ways of modifying HDL-c. Results from Mendelian randomization studies showed no difference in cardiovascular disease (CVD) risk among individuals with genetically different serum levels of HDL-c. The causal role of HDL-c in CVD is thus uncertain, raising the question as to whether HDL-c is a worthwhile target of public health interventions and medical treatments. The objective of these meta-analyses is to explore whether changes in HDL-c are symptomatic of prior causes instead of being a causal factor for CVD by first identifying two possible candidates—androgens and zinc—for the investigation of associations. Experimental evidence would then be investigated for whether either of them might underlie (i.e. confound) the observed association of HDL-c with CVD risk factors. Methods This study followed the PRISMA statement. A literature search was conducted through PUBMED, MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials. Keywords of “androgens/testosterone”, “HDL”, “high-density lipoprotein”, “lipid”, “cholesterol”, “lipoprotein”, “CVD”, “cardiovascular”, “heart”, “cardiovascular disease” were used with the search period limited to January 2000 – June 2013 with only human RCTs conducted and reported in English. For locating studies concerning the effect of zinc, the keyword “zinc” was used instead of “androgens/testosterone”. Inclusion and exclusion criteria were applied during study screening and selection. The Cochrane Collaboration’s tool for assessing risk of bias was used for quality assessment. Heterogeneity across included studies was measured using I2 statistic and publication bias was assessed via funnel plots and the Begg’s Rank Correlation test. The “trim and fill” method was also used for the correction of funnel plot asymmetry. The meta-analyses were performed using The Comprehensive R Archive Network Program (Version R 3.0.0), using the function “metacont” from the “meta” package, where the pooled intervention effects were displayed using forest plots, with inverse variance weighting and random effects model. Results A total of twelve and ten RCTs were identified and included in the meta-analyses of androgens and zinc respectively. There were no consistent beneficial effects of androgens on CVD observed, as the results from CVD surrogate markers were inconclusive, despite showing significant overall reduction in HDL-c levels. However, as current findings suggest that lower HDL-c levels are associated with higher cardiovascular risk, it is possible that androgens may increase that risk by influencing HDL metabolism. On the other hand, zinc was associated with healthier CVD profile. This supports the notion of zinc as a cardioprotective agent. Nonetheless, conclusion failed to be drawn concerning the effect of zinc on HDL-c as there were contradictory results across included studies. Conclusion The meta-analyses suggest that androgens could be a factor which lowers HDL-c and thus increases cardiovascular risk, rather than HDL-c being the direct causative agent. This research may serve as a template for more extensive search for other potentially better candidates in this new study focus in cardiovascular epidemiology. / published_or_final_version / Community Medicine / Master / Master of Public Health

Studies have shown that hypercholesterolemia is a risk for cardiovascular disease; however, some normocholesterolemic individuals still develop coronary atherosclerosis. This project was undertaken to investigate the association of abnormalities of low density lipoprotein (LDL) metabolism, in the absence of hypercholesterolemia, with the development of coronary artery disease (CAD). Mononuclear leukocytes (MNL), HL-60 cells and 1,25-dihydroxyvitamin D₃-induced HL-60 macrophages were used as model systems to study the effect of an altered LDL composition on cellular lipoprotein and sterol metabolism. LDL and MNL were isolated from patients with and without CAD. The mean rate of LDL degradation was 1.7-fold higher in CAD-MNL than in control-MNL (P < 0.05), independent of the LDL source. The increased LDL degradation rate in CAD-MNL appeared to be due to an increased LDL receptor activity of CAD-MNL and not to an increased CAD-LDL interaction with the receptor since LDL isolated from patients with and without CAD had similar in vitro degradation rates by HL-60 cells and D₃-induced HL-60 macrophages. LDL from CAD patients (CAD-LDL) contained significantly less cholesteryl ester per particle than LDL from control subjects (Control-LDL). The ability of CAD-LDL and Control-LDL to regulate sterol and lipoprotein metabolism was compared in HL-60 cells. The results indicate that CAD-LDL exhibited reduced abilities to suppress receptor-mediated LDL degradation and to activate acyl-CoA:cholesterol acyltransferase as compared to Control-LDL. There was no significant difference in the rate of sterol synthesis between cells treated with CAD-LDL and Control-LDL. The data support the hypothesis that cholesteryl ester-poor CAD-LDL exhibits a decreased ability to down-regulate LDL receptor activity which could in part account for the observed increase in LDL degradation by MNL from CAD patients. A noncompetitive enzyme-linked immunosorbent assay (ELISA) was developed to measure plasma apolipoproteins (apo) A-I and B. The results indicate that a reduced plasma apo A-I level was associated with CAD patients even if there were no significant differences in the levels of high density lipoprotein cholesterol when compared with individuals without CAD.