The Effect of Diet on Cardiovascular Disease, Heart Disease, and Blood Vessels.

The Effect of Diet on Cardiovascular Disease, Heart Disease, and Blood Vessels [...].

Desmodium gyrans dc modulates lipid trafficking in cultured macrophages and improves functional high-density lipoprotein in male wistar rats.

OBJECTIVE: High-density lipoprotein (HDL) cholesterol-mediated atherosclerotic plaque regression has gained wide therapeutic attention. The whole plant methanolic extract of the medicinal plant Desmodium gyrans Methanolic Extract (DGM) has shown to mitigate hyperlipidemia in high fat- and-cholesterol fed rats and rabbits with significant HDL enhancing property. The study aimed to assess the functionality and mechanistic basis of HDL promoting effect of DGM. MATERIALS AND METHODS: Macrophage cholesterol efflux and foam cell formation assays were performed in THP-1 macrophages. Male Wistar rats were given DGM extract over 1 month and assessed the serum HDL, Apolipoprotein A1 (Apo-A1), and paraoxonase activity. Quantitative Polymerase chain reaction was carried out to assess the expression level of Apo-A1, SR-B1 (Scavenger receptor B1), and Cholesteryl ester transfer protein (CETP) on cDNA of HepG2 cells exposed to DGM. RESULTS: Pretreatment of DGM inhibited uptake of oxidized lipids and enhanced the lipid efflux by THP-1-derived macrophages. Oral administration of DGM (100 and 250 mg/kg) progressively enhanced the serum HDL, Apo-A1 level, and associated paraoxonase activity in normal male Wistar rats. In support to this, DGM exposed HepG2 cells documented dose-dependent increase in the expression of SR-B1 and Apo-A1 mRNA, while reduced the CETP expression. CONCLUSION: Overall the results indicated that DGM modulates lipid trafficking and possesses functional HDL enhancing potential through increased Apo-A1 levels and paraoxonase activity. Further, reduced CETP expression and increased expression of SR-B1 suggest the reverse cholesterol transport promoting role of DGM.

Ethnicity and coronary artery disease: the role of high-density lipoprotein - a change in paradigm.

Cardiovascular disease (CVD) is the number one killer of men and women across ethnic groups in the USA. Health disparities in CVD, especially coronary artery disease (CAD), are well documented in the diverse American population. Despite efforts taken toward reducing cardiovascular health disparities, there are still gaps in its diagnosis and management. Current risk assessment guidelines consider high high-density lipoprotein (HDL) levels a protective factor against CAD, although its significance across races remains poorly understood. Recent clinical trials focused on increasing HDL levels have been disappointing. In this article, the authors have explored the role of HDL in CAD, have analyzed its significance across gender and ethnic groups and have challenged the broad application of widely used HDL level cutoffs in CAD risk assessment tools across these vulnerable groups. The current evidence suggests a paradigm change from HDL quantity to quality and function in future CVD risk research. This may better explain why some ethnic minority groups with a seemingly more benign lipid profile experience a higher CAD burden.

High-density lipoprotein subfractions--what the clinicians need to know.

Although the inverse relationship between plasma levels of high-density lipoprotein (HDL) and cardiovascular disease has been largely demonstrated, many observations have suggested that the assessment of HDL functionality might be more informative than a simple measurement of HDL-cholesterol plasma levels. HDLs are a class of structurally and functionally heterogeneous particles; in atherosclerosis-related diseases, changes in HDL subfraction levels and functions are frequently observed. Circulating levels of large HDL particles are decreased in dyslipidaemic conditions, while levels of small dense HDL particles are increased in patients with coronary heart disease. Furthermore, specific genetic defects in proteins involved in HDL metabolism significantly impact the distribution of HDL subpopulations. Finally, many drugs used for dyslipidaemia induce changes in HDL subfractions strictly related to cardiovascular disease. Although several methods exist to evaluate HDL subclass levels, most of them are not easily applicable in clinical practice, due to the costs and high variability. However, the possibility to measure the levels of specific HDL subfractions in patients with atherosclerosis-related diseases might help to better define their cardiovascular risk.

Brazil nut ingestion increased plasma selenium but had minimal effects on lipids, apolipoproteins, and high-density lipoprotein function in human subjects.

The Brazil nut (Bertholletia excelsa) of the Amazon region is consumed worldwide. It is rich in both monounsaturated fatty acids and polyunsaturated fatty acids and is known for its high selenium content. This study tested the hypothesis whether the consumption of this nut could affect the plasma lipids and apolipoproteins and some functional properties of the antiatherogenic high-density lipoprotein (HDL). Fifteen normolipidemic subjects aged 27.3 +/- 3.9 years and with body mass index of 23.8 +/- 2.8 kg/m(2) consumed 45 g of Brazil nuts per day during a 15-day period. On days 0 and 15, blood was collected for biochemical analysis, determination of HDL particle size, paraoxonase 1 activity, and lipid transfer from a lipoprotein-like nanoparticle to the HDL fraction. Brazil nut ingestion did not alter HDL, low-density lipoprotein cholesterol, triacylglycerols, apolipoprotein A-I, or apolipoprotein B concentrations. HDL particle diameter and the activity of antioxidative paraoxonase 1, mostly found in the HDL fraction, were also unaffected. Supplementation increased the reception of cholesteryl esters (P < .05) by the HDL yet did not alter the reception of phospholipids, free cholesterol, or triacylglycerols. As expected, plasma selenium was significantly increased. However, the consumption of Brazil nuts for short duration by normolipidemic subjects in comparable amounts to those tested for other nuts did not alter serum lipid profile. The only alteration in HDL function was the increase in cholesteryl ester transfer. This latter finding may be beneficial because it would improve the nonatherogenic reverse cholesterol transport pathway.

Mechanisms involved in vitamin E transport by primary enterocytes and in vivo absorption.

It is generally believed that vitamin E is absorbed along with chylomicrons. However, we previously reported that human colon carcinoma Caco-2 cells use dual pathways, apolipoprotein B (apoB)-lipoproteins and HDLs, to transport vitamin E. Here, we used primary enterocytes and rodents to identify in vivo vitamin E absorption pathways. Uptake of [(3)H]alpha-tocopherol by primary rat and mouse enterocytes increased with time and reached a maximum at 1 h. In the absence of exogenous lipid supply, these cells secreted vitamin E with HDL. Lipids induced the secretion of vitamin E with intermediate density lipoproteins, and enterocytes supplemented with lipids and oleic acid secreted vitamin E with chylomicrons. The secretion of vitamin E with HDL was not affected by lipid supply but was enhanced when incubated with HDL. Microsomal triglyceride transfer protein inhibition reduced vitamin E secretion with chylomicrons without affecting its secretion with HDL. Enterocytes from Mttp-deficient mice also secreted less vitamin E with chylomicrons. In vivo absorption of [(3)H]alpha-tocopherol by mice after poloxamer 407 injection to inhibit lipoprotein lipase revealed that vitamin E was associated with triglyceride-rich lipoproteins and small HDLs containing apoB-48 and apoA-I. These studies indicate that enterocytes use two pathways for vitamin E absorption. Absorption with chylomicrons is the major pathway of vitamin E absorption. The HDL pathway may be important when chylomicron assembly is defective and can be exploited to deliver vitamin E without increasing fat consumption.

Oral synthetic phospholipid (DMPC) raises high-density lipoprotein cholesterol levels, improves high-density lipoprotein function, and markedly reduces atherosclerosis in apolipoprotein E-null mice.

BACKGROUND: Lecithin has been widely sold as a dietary supplement. 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) is a phospholipid that does not exist in nature and has been used in vitro to study lipid binding. We tested DMPC in vivo in apolipoprotein (apo) E-null mice. METHODS AND RESULTS: DMPC or soy or egg lecithin at 1.0 mg/mL was added to the drinking water of 4-week-old apoE-null female mice. Eight weeks later, HDL cholesterol levels and apoA-I levels were markedly increased in the mice that received DMPC. HDL function was also dramatically improved in the mice receiving DMPC, and there was a significant reduction in aortic lesions (P=0.021) in the DMPC mice but not in those receiving lecithin. Adding 1.0 mg/mL of DMPC to the drinking water of 10-month-old apoE-null female mice for 5 weeks caused regression of aortic sinus lesions (P=0.003). Adding 1.0 mg/mL DMPC to the drinking water of 6-month-old apoE-null male mice for 8 weeks significantly reduced aortic sinus lesion area (P=0.0031) and en face whole aorta lesion area (P=0.001), whereas adding the same concentrations of soy or egg lecithin did not significantly alter lesion area. Jejunal apoA-I synthesis and plasma apoA-I levels were increased 2- to 3-fold in mice receiving DMPC but not soy or egg lecithin. CONCLUSIONS: DMPC (but not lecithin) raises HDL cholesterol and apoA-I, improves HDL function, and prevents lesions or causes their regression in apoE-null mice.

Effects of high density lipoprotein containing high or low beta-carotene concentrations on progesterone production and beta-carotene uptake and depletion by bovine luteal cells.

Luteal cells were isolated from mid-luteal heifer ovaries by collagenase digestion. Cells were cultured with DMEM/Ham's F12 medium in serum pre-treated plastic culture dishes for periods of up to 11 days. As beta-carotene is almost completely insoluble in all polar solvents, it was added to cultures in either dimethyl sulphoxide (DMSO), tetrahydrofuran (THF) or as high-density lipoprotein (HDL) containing high or low beta-carotene concentrations. Medium was replaced after 24 h, thereafter medium was changed every 48 h. Treatment of cells with DMSO alone or with beta-carotene (5 micromol/l) in DMSO both resulted in significant (P<0.01) stimulation of progesterone production. beta-Carotene (5 micromol/l) in THF did not alter progesterone production but 50 micromol/l beta-carotene in THF resulted in significant inhibition (P<0.02) of progesterone production on days 3 and 7. Cultures were also supplemented with bovine HDL preparations containing equal concentrations of cholesterol (25 microg/ml) but high or low beta-carotene (12.4 or 0.44 microg/mg of cholesterol). Both HDL preparations significantly stimulated progesterone production (P<0. 001) but the high beta-carotene HDL was significantly (P<0.02) more effective than the low beta-carotene HDL. However, when given together with bovine luteinizing hormone (bLH) or dibutyryl cAMP (dbcAMP), the high beta-carotene HDL stimulated progesterone production less than did the low HDL (P<0.01). Uptake and depletion of beta-carotene by luteal cells were also examined in culture. beta-Carotene supplementation increased luteal cell beta-carotene from an initial level of 373 ng per 10(6) cells to 2030 ng per 10(6) cells by day 6. In contrast, the levels in control cells decreased to 14% of starting values during the same period. Cells treated with HDL containing high beta-carotene on day 1 or days 1 and 3 were then incubated with or without bLH or dbcAMP for a further 2 days to investigate the effect of bLH and dbcAMP on depletion of beta-carotene by luteal cells. beta-Carotene depletion in the luteal cells was significantly higher (P<0.05) in LH- and dbcAMP-treated cells than in the control cells in both groups. These results indicate that the use of solvents such as DMSO or THF may have undesirable effects due to alteration of cell membrane permeability. Supplementation with bLH or dbcAMP may increase the metabolism of beta-carotene in luteal cells. bLH or dbcAMP together with high beta-carotene HDL may, when combined with the effect of increased beta-carotene metabolism, give less stimulation than with low beta-carotene HDL.

Oxidation of low density lipoproteins in the pathogenesis of atherosclerosis.

Malondialdehyde (MDA)-modified and oxidized low density lipoproteins (LDL) have been demonstrated in atherosclerotic lesions. Elevated titers of autoimmune antibodies specific for MDA-modified LDL predicted the progression of carotid atherosclerosis and of myocardial infarction. Recently, elevated levels of MDA-modified LDL were detected in the plasma of patients with ischemic heart disease, whereas, elevated levels of oxidized LDL were detected in the plasma of patients with ischemic heart disease and of heart transplant patients with post-transplant cardiovascular disease. Although increased levels of autoimmune antibodies against oxidatively modified LDL and increased levels of oxidized LDL antigen appear to be associated with atherosclerotic cardiovascular disease, there is to date no direct proof of the causal role of oxidized LDL in atherothrombosis. However, the decreased risk of cardiovascular disease associated with the administration of antioxidants (e.g. vitamin E), estrogen supplementation and increased levels of high density lipoproteins (HDL) may, at least partially, be due to the inhibition of oxidation of LDL or to the reversal of the atherothrombotic effects of oxidized LDL.

High-density lipoprotein from hypercholesterolemic animals has peroxidized lipids and oligomeric apolipoprotein A-I: its putative role in atherogenesis.

Oxidized lipoproteins have been involved in the pathogenesis of atherosclerosis and atherosclerotic lesions contain oxidized low density lipoprotein. Conversely, the presence of oxidized high density lipoprotein (HDL) in vivo has not been clearly established. Oxidation of HDL in vitro models produces an increase in peroxidized lipids and the appearance of apolipoprotein A-I (apo A-I) oligomers. We investigated the oxidative status of HDL in an in vivo model: the hypercholesterolemic chicken. The HDLs from control and hyperlipemic animals were analyzed for the content of lipid peroxides employing spectroscopic and fluorescence techniques, for the level of apo A-I oligomerization, and for susceptibility to in vitro oxidation. HDL from hypercholesterolemic chickens was more peroxidized (as detected by fluorescence), had higher amount of oligomeric apo A-I, and was oxidized to a greater extent by uv irradiation than that of control animals. We speculate that apo A-I oligomerization could be a key step in the atheroma formation.

A high-density-lipoprotein receptor appears to mediate the transfer of essential fatty acids from high-density lipoprotein to lymphocytes.

It has been shown previously that a specific high-density lipoprotein (HDL) receptor exists on human lymphocytes that recognizes apoprotein (apo) A1 as its ligand, and may be responsible for utilization of HDL lipids to respond optimally to mitogenic stimulation when cultured in serum-free medium supplemented with HDL. To clarify further the relationship between various HDL lipids used by lymphocytes and HDL receptor activity, the lipid composition of the cells and the regulation of HDL and low-density lipoprotein (LDL) receptors on freshly isolated lymphocytes and mitogen-activated T-blasts after treatment with lipoproteins, liposomes or fatty acids were investigated. Our data show that the linear increase in cell proliferation correlates with the presence of HDL in fatty-acid-free culture medium in the concentration range of HDL receptor saturation. Decreased binding/uptake of dioctadecylindocarbocyanine (DiI)-fluorescence-labelled HDL by freshly isolated lymphocytes was observed in the presence of unlabelled HDL in 4-day culture, whereas T-blast binding/uptake was down-regulated by preincubation not only with HDL but also with LDL. T-blasts pretreated with HDL showed increased cellular contents of phosphatidylcholine, oleic acid (C18:1,n-9) and linoleic acid (C18:2,n-6), which are essential for optimal proliferation of mitogen-stimulated lymphocytes. Furthermore, DiI-HDL binding on lymphocytes was down-regulated by up to 20% (resting T cells) and 50% (T-blasts) when cultured in the presence of apoA1-phosphatidylcholine liposomes (T-blasts only), oleic acid or linoleic acid, but not by stearic acid (C18:0). The results indicate that HDL provide lymphocytes with essential fatty acids, which in turn regulate HDL receptor activity.

Phosphatidyl choline and the growth in serum-free medium of vascular endothelial and smooth muscle cells, and corneal endothelial cells.

Liposomes made by sonication of egg yolk phosphatidyl choline support the proliferation of low-density bovine vascular and corneal endothelial cells, and vascular smooth muscle cells maintained on basement laminacoated dishes and exposed to a defined medium supplemented with transferrin. The optimal growth-promoting effect of phosphatidyl choline was observed at concentrations of 25 micrograms/ml for low-density cultures of vascular smooth muscle cells, and 100 micrograms/ml for vascular and corneal endothelial cells. The growth rate and final cell density of vascular endothelial cells exposed to a synthetic medium supplemented with transferrin and either high-density lipoproteins or phosphatidyl choline has been compared. Although cultures exposed to phosphatidyl choline reached a final cell density similar to that of cultures exposed to high-density lipoproteins, they had a longer average doubling time (17 h vs. 12 h) during their logarithmic growth phase and a shorter lifespan (17 generations vs. 30 generations). Similar observations were made in the case of vascular smooth muscle cells or bovine corneal endothelial cells maintained in medium supplemented with transferrin, fibroblast growth factor (FGF) or epidermal growth factor (EGF), and insulin and exposed to either high-density lipoproteins or phosphatidyl choline. Since phosphatidyl choline can, for the most part, replace high-density lipoproteins in supporting the proliferation of various cell types, it is likely that the growth stimulating signal conveyed by high-density lipoproteins is associated with its polar lipid fraction, which is composed mostly of phosphatidyl cholines.

Nonimmunological host defenses: a review.

Nonimmunological defenses are very diverse in type. Some are directed against already transformed cells and belong to mechanisms of containment. Others exert a surveillance by preventing or inhibiting initial events of carcinogenesis. Chalones and oncolytic factors in sera and exudates are agents of containment. Under appropriate circumstances, the autoxidation of thiols and the formation of mixed disulfides lead to destruction of tumor cells in vitro and in vivo. Both processes involve the generation of superoxide radicals and of hydrogen peroxide which, in turn, activate the peroxide:peroxidase:halide system. Thiol:disulfide ratios and interchange codetermine the antioxidative activity of cellular membranes, thus bearing on carcinogenesis. Many aliphatic and aromatic antioxidants are endowed with anticarcinogenic properties. The fact that they are inhibitors of free radical processes corroborates the increasingly evident role of free radicals in carcinogenesis. Endogenous antioxidants and exogenous ones in foods are agents of surveillance. Antioxidant activity, linked with the ergastoplasm, points to a homeostatic mechanism that prevents self-accelerating chain reactions from leading to membrane damage or to carcinogenesis. Carcinogens can also be inactiviated by microsomal enzymes belonging to an overall mechanism of detoxification. Activity levels of these systems depend on diet and state of nutrition. They may be naturally very low, but they can be increased with various inducers.