Low-density Lipoprotein Fatty Acid Research Articles

LDL fatty acids composition as a risk biomarker of cardiovascular disease

ObjectiveFatty acid composition of Low-density lipoprotein (LDL) particle is an effective factor in LDL oxidation and atherosclerotic plaques formation. This study evaluates the relationship between LDL fatty acid composition and coronary artery disease (CAD). Methods42 men with coronary artery disease (CAD-group) and 40 men without coronary artery disease (non-CAD-group) were selected. LDL fatty acid composition of blood samples was measured by gas chromatography. ResultsOx-LDL was significantly high in CAD-group. Poly unsaturated fatty acids (PUFA) and PUFA/MUFA (Mono unsaturated fatty acids), linoleic acid and arachidonic acid were significantly higher in CAD-group than in non-CAD-group. In CAD-group, a reverse correlation was observed between oleic acid concentrations and ox-LDL levels and a direct correlation was seen between arachidonic acid concentrations and ox-LDL levels. ConclusionComposition of LDL is related to atherosclerosis and CAD. High levels of arachidonic and linoleic acids could increase LDL oxidation and atherosclerotic plaques formation. In addition, LDL arachidonic acid levels could be a better predictor of CAD.

Flaxseed Lignan Complex Consumption Thus Far Fails to Change Plasma Total Peroxyl Radical-Trapping Potential and Two LDL Oxidation Measures in Older Patients with Type 2 Diabetes—More Study Required

Plasma low-density lipoprotein(LDL) oxidation substantially exacerbates atherosclerosis in type 2 diabetes(T2D). The impact of antioxidant-containing flaxseed lignan complex (FLC) consumption on LDL fatty acid conjugated diene (LDL-CD), oxidized low-density lipoprotein protein (LDLox) and total peroxyl radical-trapping antioxidant potential (TRAP) levels has never been examined in persons with T2D. It was hypothesized that FLC relative to placebo would decrease LDL-CD and LDLox via increased TRAP levels. The objective was to test this hypothesis.

Oxidative stress in diabetes – circulating advanced glycation end products, lipid oxidation and vascular disease

Individuals with both Type 1 and Type 2 diabetes show vascular complications that may remain undetected for many years until the disease is at an advanced stage. Clinical trials to date have been unsuccessful in identifying a therapeutic approach that addresses both the underlying problem of poor glycaemic control in diabetes and the high incidence of microvascular disease. Oxidative stress, an imbalance of oxidants and antioxidants in the favour of oxidants, has been thought to play a central part in the complications of diabetes arising from protein glycation. Neutralization of oxidants by increased antioxidant availability has been considered as one possible way to mitigate oxidative stress. Indeed, several human intervention studies have been undertaken to determine whether dietary antioxidants can exert beneficial effects for patients with Type 2 diabetes. Chronically elevated concentrations of glucose increase the frequency of non-enzymatic glucose adduction with proteins, lipids and DNA to form advanced glycation end products (AGEs). One of the major plasma proteins that can undergo secondarymodification by glucose or oxidised lipids is the cholesterolcarrying low density lipoprotein (LDL). In Type 2 diabetes, LDL is more glycated and more susceptible to oxidation, increasing its clearance bymacrophages in a nonregulated manner and increasing foam cell formation. Complications such as albuminuria are associated with renal protein oxidation, which is often preceded by LDL fatty acid oxidation. The initiator is H2O2 produced from protein glycation, auto-oxidation of homocysteine and increased metabolism of arachidonic acid towards its pro-inflammatory eicosanoids. The backdrop of increased oxidative stress promotes a state of diffuse vasculopathy. In both Type 1 and Type 2 diabetes, there is an increased risk of cognitive impairment in later life. In the glucose control intervention study, cognitive function was an independent predictor of glycaemic control, but the risk of cognitive decline or dementia was not decreased by improving glycaemic control. AGEs, carbonylation of LDL, which is indicative of oxidative stress, and glycation are shared common risk factors for both diabetes and cognitive impairment.

Hepatic and very low-density lipoprotein fatty acids in obese offspring of overfed dams

The combined effects of developmental programming and high-fat feeding at weaning on fatty acid metabolism of the offspring are not well known. In the present study, we aim at characterizing the influence of maternal and offspring's own diets on liver and very low-density lipoprotein (VLDL) lipids; fatty acid profiles of VLDL and liver phospholipids, triglycerides, and cholesteryl esters; and hepatic enzyme activities. Twenty obese male rats born to cafeteria diet–fed dams and 20 control rats born to control diet–fed dams were selected. At weaning, 10 rats of each group were fed control or cafeteria diet. Obese rats had a significant increase in serum glucose, insulin, leptin, VLDL apolipoprotein B100 and lipid levels, and hepatic fatty acid synthase and a reduction in acyl–coenzyme A oxidase and dehydrogenase activities compared with control pups at day 21 and day 90. Hepatic steatosis was apparent only at day 90. The proportions of saturated fatty acids and monounsaturated fatty acids and the oleic to stearic acid ratio were significantly increased, whereas polyunsaturated fatty acids and the arachidonic to linoleic acid ratio were decreased, in liver and VLDL lipids of obese pups compared with controls. The cafeteria diet at weaning induced more severe abnormalities in obese rats. In conclusion, maternal cafeteria diet induced a permanent reduction in hepatic β-oxidation and an increase in hepatic lipogenesis that caused liver steatosis and VLDL and fatty acid alterations in adult offspring. These preexisting alterations in offspring were worsened under a high-fat diet from weaning to adulthood. Nutritional recommendations in obesity must then target maternal and postnatal nutrition, especially fatty acid composition.

Evaluation of the Effect of Dietary Virgin Olive Oil on Blood Pressure and Lipid Composition of Serum and Low-Density Lipoprotein in Elderly Type 2 Diabetic Subjects

Dietary virgin olive oil may help to reduce blood pressure in hypertensive individuals, but little is known about the effect on type 2 diabetic patients. For the present study, 17 type 2 diabetic elderly subjects and 23 healthy elderly controls received a diet rich in virgin olive oil for 4 weeks. Blood pressure, biochemical parameters, low-density lipoprotein (LDL), and oxidized LDL lipids and fatty acids were measured. Systolic blood pressure was reduced after virgin olive oil consumption in both controls and diabetic patients. Although the biochemical parameters were not modified, the intervention protected LDL from oxidation and restored the levels of dihomo-gamma-linolenic acid (20:3, n-6) in serum cholesterol esters and phospholipids of diabetic patients. In conclusion, the present study provides new evidence of the effects of dietary virgin olive oil on blood pressure and LDL oxidation in type 2 diabetics. It is likely that the components responsible for the observed effects are the monounsaturated fatty acids and the presence of antioxidants in the oil, but this needs further investigation.

Low-Density Lipoprotein Oxidizability and the Alteration of Its Fatty Acid Content in Renal Transplant Recipients Treated With Cyclosporine/Tacrolimus

Renal transplantation is widely used to treat patients with end-stage renal disease. Atherosclerosis is an important posttransplantation risk factor for renal transplant recipients. Subsequent to transplantation low-density lipoprotein (LDL) particles become susceptible to oxidative modification, which results in atherosclerosis. Therefore, the aim of our study was to investigate differences in the susceptibility of LDL particles to oxidation by analyzing LDL fatty acid levels among renal transplant recipients. The changes in lag phases and fatty acid levels of LDL were observed over 4 months among renal transplant recipients treated with Cyclosporine (CsA; n = 7) or Tacrolimus (FK-506; n = 9). We also analyzed cholesterol and triglyceride levels of patients and healthy controls. The lag phase at the 60th day after transplantation was significantly shorter than the results either before transplantation or among control subjects. In conclusion, a similar decrease in lag phase was observed in both above groups, but the FK-506–treated group showed a better lipid profile than the CsA-treated group.

Bariatric Surgery Improves Atherogenic LDL Profile by Triglyceride Reduction

Small dense low-density lipoprotein (LDL) are atherogenic particles frequently observed in obese patients. Fatty acids modulate LDL. Objective of this study was to determine the relations between plasma phospholipid fatty acid composition and the presence of small dense LDL particles in morbidly obese patients treated with laparoscopic gastric banding (LAGB). Small dense LDL, plasma lipids, lipoproteins, apoproteins, and phospholipid fatty acid composition (a marker of dietary fatty acid intake) were quantified before and 12 months after surgery in four men and 11 women who were morbidly obese and (BMI > 40 kg/m(2)) eligible for surgery, consecutively treated with LAGB at the Department of Medical and Surgical Sciences of the University of Padova. BMI was 48.3 +/- 4.8 kg/m(2) before and 36.1 +/- 5.5 kg/m(2) after LAGB. Plasma triglycerides and apoprotein E levels significantly decreased, while HDL cholesterol significantly increased after LAGB. A reduction of small dense LDL with an increase of LDL relative flotation (0.34 +/- 0.04 before vs 0.38 +/- 0.03 after LAGB, p < 0.001) was also observed. These modifications were neither related to weight reduction nor to changes in phospholipid fatty acid composition, but they were associated to triglyceride reduction, which explained 76.7% of the LDL relative flotation variation. Weight loss obtained by LAGB in morbidly obese subjects was accompanied by triglyceride reduction, high-density lipoprotein increase, and an improvement of the atherogenic LDL profile. Triglyceride reduction, but not the extent of weight loss or dietary fatty acid modifications, is the determinant of modifications of LDL physical properties in these patients.

Supplementation of hydrogen-rich water improves lipid and glucose metabolism in patients with type 2 diabetes or impaired glucose tolerance

Oxidative stress is recognized widely as being associated with various disorders including diabetes, hypertension, and atherosclerosis. It is well established that hydrogen has a reducing action. We therefore investigated the effects of hydrogen-rich water intake on lipid and glucose metabolism in patients with either type 2 diabetes mellitus (T2DM) or impaired glucose tolerance (IGT). We performed a randomized, double-blind, placebo-controlled, crossover study in 30 patients with T2DM controlled by diet and exercise therapy and 6 patients with IGT. The patients consumed either 900 mL/d of hydrogen-rich pure water or 900 mL of placebo pure water for 8 weeks, with a 12-week washout period. Several biomarkers of oxidative stress, insulin resistance, and glucose metabolism, assessed by an oral glucose tolerance test, were evaluated at baseline and at 8 weeks. Intake of hydrogen-rich water was associated with significant decreases in the levels of modified low-density lipoprotein (LDL) cholesterol (ie, modifications that increase the net negative charge of LDL), small dense LDL, and urinary 8-isoprostanes by 15.5% (P < .01), 5.7% (P < .05), and 6.6% (P < .05), respectively. Hydrogen-rich water intake was also associated with a trend of decreased serum concentrations of oxidized LDL and free fatty acids, and increased plasma levels of adiponectin and extracellular-superoxide dismutase. In 4 of 6 patients with IGT, intake of hydrogen-rich water normalized the oral glucose tolerance test. In conclusion, these results suggest that supplementation with hydrogen-rich water may have a beneficial role in prevention of T2DM and insulin resistance.

Hypolipidemic Effect of Triphala in Experimentally Induced Hypercholesteremic Rats

Hypercholesteremia is one of the risk factors for coronary artery disease. The present study highlights the efficacy of Ayurvedic herbal formulation Triphala (Terminalia chebula, Terminalia belerica, and Emblica officinalis) on total cholesterol, Low density lipoprotein (LDL), Very low density lipoprotein (VLDL), High density lipoprotein (HDL) and free fatty acid in experimentally induced hypercholesteremic rats. Four groups of rats were employed namely control, Triphala treated, hypercholesterolemia rats (4% Cholesterol + 1% cholic acid + egg yolk) and Triphala pre-treatment in hypercholesteremic rats. Results showed significant increase in the total cholesterol, LDL, VLDL, and free fatty acid in hypercholesteremic rats were significantly reduced in Triphala treated hypercholesteremic rats. The data demonstrated that Triphala formulation was associated with hypolipidemic effects on the experimentally induced hypercholesteremic rats.

Influence of three rapeseed oil-rich diets, fortified with α-linolenic acid, eicosapentaenoic acid or docosahexaenoic acid on the composition and oxidizability of low-density lipoproteins: results of a controlled study in healthy volunteers

To compare the individual effects of dietary alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) on low-density lipoprotein (LDL) fatty acid composition, ex vivo LDL oxidizability and tocopherol requirement. A randomized strictly controlled dietary study with three dietary groups and a parallel design, consisting of two consecutive periods. Sixty-one healthy young volunteers, students at a nearby college, were included. Forty-eight subjects (13 males, 35 females) completed the study. Subjects received a 2-week wash-in diet rich in monounsaturated fatty acids (21% energy) followed by experimental diets enriched with about 1% of energy of ALA, EPA or DHA for 3 weeks. The omega-3 (n-3) fatty acids were provided with special rapeseed oils and margarines. The wash-in diet and the experimental diets were identical, apart from the n-3 fatty acid composition and the tocopherol content, which was adjusted to the content of dienoic acid equivalents. Ex vivo oxidative susceptibility of LDL was highest after the DHA diet, indicated by a decrease in lag time (-16%, P<0.001) and an increase in the maximum amount of conjugated dienes (+7%, P<0.001). The EPA diet decreased the lag time (-16%, P<0.001) and the propagation rate (-12%, P<0.01). Tocopherol concentrations in LDL decreased in the ALA group (-13.5%, P<0.05) and DHA group (-7.3%, P<0.05). Plasma contents of tocopherol equivalents significantly decreased in all three experimental groups (ALA group: -5.0%, EPA group: -5.7%, DHA group: -12.8%). The content of the three n-3 polyunsaturated fatty acid differently increased in the LDL: on the ALA diet, the ALA content increased by 89% (P<0.001), on the EPA diet the EPA content increased by 809% (P<0.001) and on the DHA diet, the DHA content increased by 200% (P<0.001). In addition, the EPA content also enhanced (without dietary intake) in the ALA group (+35%, P<0.01) and in the DHA group (+284%, P<0.001). Dietary intake of ALA, EPA or DHA led to a significant enrichment of the respective fatty acid in the LDL particles, with dietary EPA preferentially incorporated. In the context of a monounsaturated fatty acid-rich diet, ALA enrichment did not enhance LDL oxidizability, whereas the effects of EPA and DHA on ex vivo LDL oxidation were inconsistent, possibly in part due to further changes in LDL fatty acid composition.

Plasma asymmetric dimethylarginine (ADMA), nitrate and the indices of low-density lipoprotein oxidation

Background Oxidative modification of low-density lipoprotein (LDL) is an important contributor to atherosclerosis. Also, oxidized LDL is suspected to cause accumulation of asymmetric dimethylarginine (ADMA), an endogenous competitive nitric oxide synthase inhibitor, which is suggested to be an independent risk factor for atherosclerosis. This study was performed to evaluate how plasma ADMA is related to plasma nitric oxide production, oxidized LDL and ex vivo susceptibility of LDL to oxidation in mildly hypercholesterolemic otherwise healthy subjects. Methods Plasma ADMA was determined using high performance liquid chromatography tandem mass spectrometry. LDL oxidation was estimated by the lag time and rate of copper-induced LDL oxidation. The nitric oxide production in plasma was estimated based on nitrate (NO 3 −) determination and plasma oxidized LDL was determined by a capture ELISA. Results Low ADMA was a significant determinant for high LDL oxidation rate and concentration of plasma ADMA was associated with nitrate levels. Conclusions There may be an interplay between LDL fatty acid oxidation rate and plasma ADMA and nitrate. We hypothesize that plasma ADMA has a bivalent role: high ADMA may have a protective role in decelerating LDL fatty acid oxidation and also a risk factor for endothelial dysfunction by decreasing availability of nitric oxide.

The "Unexpected Role" of Vitamin E in Free Radical-Induced Hemolysis of Human Erythrocytes: α-Tocopherol-Mediated Peroxidation

Vitamin E involves a group of tocopherols and tocotrienols, in which alpha-tocopherol with the highest biological activity plays a more efficient role in advanced lesions with aged oxidized tissues. However, the results of the present study reveal that a large amount of endogenous alpha-tocopherol in human low-density lipoprotein (LDL) in the absence of any other antioxidants may initiate additional free radical propagation under low concentration of free radical initiator (i.e., 2,2'-azobis(2-amidinopropane hydrochloride) [AAPH], a water-soluble free radical source) to peroxide polyunsaturated fatty acids in LDL in the manner of alpha-tocopherol-mediated peroxidation (TMP). Whether the addition of high concentration of exogenous alpha-tocopherol to human erythrocytes under low concentration of AAPH can also drive TMP is the concern in this research work. Moreover, the hemolysis extent of human erythrocytes peroxidized by AAPH is followed easily by the determination of the hemoglobin outside the erythrocytes. A series of observations on various concentrations of AAPH-induced hemolysis in the presence of various concentrations of exogenous alpha-tocopherol demonstrates that the high concentration of exogenous alpha-tocopherol, coupled with low concentration of AAPH, can initiate TMP in the free-radical-induced peroxidation of human erythrocytes system as well. This result provides direct evidence to support TMP theory and expands its application into in vitro erythrocyte system.

Low density lipoprotein non-esterified fatty acids and lipoprotein lipase in diabetes

Objectives: Fatty acid metabolism is disturbed in poorly controlled diabetes. Low density lipoprotein (LDL) oxidation, thought to be an atherogenic modification, is partly dependent on LDL fatty acid content whether it be in the form of cholesteryl ester, phospholipids, triglyceride or non-esterified fatty acid (NEFA). Lipoprotein lipase (LPL) is deficient in diabetic patients. Lipoprotein lipase bound to LDL may facilitate cholesterol accumulation in the artery wall through the attachment of LDL to the proteoglycans expressed on endothelial cells and collagen. The purpose of this study was to examine the degree of binding of fatty acids and lipoprotein lipase to LDL in type 2 diabetic patients and to examine the relationship between non-esterified fatty acids attached to LDL and LDL oxidisability. Subjects and methods: Eight type 2 diabetic patients and eight control subjects were examined fasting and at 4 and 6 h following a high fat meal. Six control subjects were examined fasting and 30 min after intravenous heparin. LDL was isolated by sequential ultracentrifugation. Individual LDL non-esterified fatty acids were measured by gas–liquid chromatography following transmethylation. LPL and oxidised LDL were measured by ELISA. Results: The diabetic patients had HbA1c of 7.8 ± 0.5% confirming moderate diabetic control. There was a large increase in the mean non-esterified fatty acids on LDL from diabetic subjects (0.66 ± 0.40 mg/mg versus 0.06 ± 0.02 mg/mg LDL protein, p < 0.01). Mean LDL cholesterol ester fatty acids were also significantly increased in the diabetic subjects (1.47 ± 0.58 mg/mg versus 0.57 ± 0.40 mg/mg LDL protein, p < 0.01). There was a significant increase in oxidised LDL (31.2 ± 24 mg/mg versus 7.7 ± 4.5 mg/mg LDL protein, p < 0.01) and a significant correlation between postprandial non-esterified fatty acid and LDL oxidation ( r = 0.69, p < 0.05). LPL was significantly increased on the LDL but not in the plasma of diabetic subjects. Acute elevation in non-esterified fatty acids produced by heparin in control subjects did not increase LDL non-esterified fatty acids. Conclusions: This study demonstrates that the disturbance in fatty acid metabolism found in type 2 diabetic subjects is associated with a significant increase in non-esterified fatty acids attached to LDL. This may account, at least in part, for the increased oxidation of the LDL and therefore its atherogenicity. The finding of an increase in the amount of LPL bound to LDL suggests an important mechanism to facilitate the uptake of diabetic LDL by endothelial proteoglycans and collagen in the atherosclerotic plaque.

Effect of genistein supplementation on tissue genistein and lipid peroxidation of serum, liver and low-density lipoprotein in hamsters

The aim of this study was to investigate the effects of genistein supplementation in a vitamin E-deficient diet on the genistein concentrations and the lipid oxidation of serum, liver and low-density lipoprotein (LDL) of hamsters. Thirty-six male hamsters were randomly divided into three groups and fed a vitamin E-deficient semisynthetic diet (AIN-76) containing different levels of genistein, i.e., G0 (control group, genistein-free diet), G50 (50 mg genistein/kg diet) and G200 (200 mg genistein/kg diet) for 5 weeks. The concentrations of genistein in serum and liver significantly increased with the increase of genistein supplementation. The vitamin E contents in LDL were higher in hamsters fed G50 or G200 diets than in hamsters fed genistein-free diet. Genistein supplementation to hamsters significantly reduced the propagation rate during conjugated diene formation of LDL oxidation, and the lag time of LDL oxidation in hamsters fed G200 diets was significantly lower than that of G0 diets. In addition, genistein supplementation significantly raised serum total antioxidant capacity and decreased the thiobarbituric acid-reactive substances (TBARS) of LDL and liver in hamsters. However, no significant differences in TBARS were found in serum, irrespective of genistein addition. On the other hand, the relative contents of polyunsaturated fatty acids in LDL were decreased after genistein supplementation. There was a negative correlation between lag time and P/S ratio, and a positive correlation between lag time and vitamin E contents. These data demonstrate that genistein supplementation markedly increased its concentrations in body tissues and reduced oxidative stress of lipid oxidation of serum, liver and LDL.

Differential recruitment of the coactivator proteins CREB-binding protein and steroid receptor coactivator-1 to peroxisome proliferator-activated receptor gamma/9-cis-retinoic acid receptor heterodimers by ligands present in oxidized low-density lipoprotein.

Peroxisome proliferator-activated receptor gamma (PPARgamma) colocalizes with oxidized low-density lipoprotein (LDL) in foam cells in atherosclerotic lesions. We have explored a potential role of oxidized fatty acids in LDL as PPARgamma activators. LDL from patients suffering from intermittent claudication due to atherosclerosis was analyzed using HPLC and gas chromatography/mass spectrophotometry and found to contain 9-hydroxy and 13-hydroxyoctadecadienoic acid (9- and 13-HODE), as well as 5-hydroxy-, 12-hydroxy- and 15-hydroxyeicosatetraenoic acid (5-, 12- and 15-HETE respectively). PPARgamma was potently activated by 13(S)-HODE and 15(S)-HETE, as judged by transient transfection assays in macrophages or CV-1 cells. 5(S)- and 12(S)-HETE as well as 15-deoxy-Delta(12,14)-prostaglandin J(2) also activated PPARgamma but were less potent. Interestingly, the effect of the lipoxygenase products 13(S)-HODE and 15(S)-HETE as well as of the drug rosiglitazone were preferentially enhanced by the coactivator CREB-binding protein, whereas the effect of the cyclooxygenase product 15-deoxy-Delta(12,14)-prostaglandin J(2) was preferentially enhanced by steroid receptor coactivator-1. We interpret these results, which may have relevance to the pathogenesis of atherosclerosis, to indicate that the lipoxygenase products on the one hand and the cyclooxygenase product on the other exert specific effects on the transcription of target genes through differential coactivator recruitment by PPARgamma/9-cis retinoic acid receptor heterodimer complexes.

Increased Levels of Low-Density Lipoprotein Oxidation in Patients with Familial Hypercholesterolemia and in End-Stage Renal Disease Patients on Hemodialysis

Patients with familial hypercholesterolemia (FH) and patients with end-stage renal disease (ESRD) undergoing dialysis suffer from accelerated atherosclerosis. Oxidation of low-density lipoprotein (LDL) cholesterol is crucial in atherogenesis. In the present study, we determined the LDL oxidation level and oxidizability of isolated LDL of 11 male patients with FH, 15 male ESRD patients on hemodialysis, and 15 age-matched male normolipidemic healthy controls. FH patients were without lipid-lowering medication for at least 4 weeks and were reassessed after 2 years of cholesterol-lowering therapy (statins). LDL oxidation level was measured by ELISA using monoclonal antibody 4E6 to oxidized LDL (oxLDL) as the capture antibody and anti-human apoB antibody for detection; results were expressed as percentage oxLDL. In FH patients and in ESRD patients on hemodialysis, both groups having a higher percentage of cardiovascular disease, mean plasma LDL oxidation levels were significantly elevated compared with controls (4.9 ± 1.3; 3.7 ± 2.0; 1.7 ± 0.6%, respectively). Within each group of subjects, LDL oxidation level was not associated with history of cardiovascular disease. Furthermore, in neither group was a significant correlation found between plasma concentration of LDL cholesterol and LDL oxidation level. After cholesterol-lowering therapy, LDL oxidation level in FH patients had not changed significantly and remained elevated compared with controls, despite a reduction of LDL cholesterol by 55% on average. Also, absolute plasma oxLDL concentrations, obtained by multiplying LDL oxidation level with plasma LDL cholesterol concentration, were significantly higher in FH patients before and after cholesterol-lowering therapy and in ESRD patients on hemodialysis than in controls (489 ± 145; 189 ± 122; 100 ± 65; and 59 ± 27 μmoles/L, respectively). No correlation was found between plasma oxLDL concentration and parameters of LDL oxidizability, LDL fatty acids, and LDL alpha-tocopherol content. We conclude that cholesterol-lowering therapy does not normalize elevated LDL oxidation levels in FH patients and elevated LDL oxidation level in FH and in ESRD might mirror atherosclerosis.

Molecular mechanism of low density lipoprotein oxidation by 12-lipoxygenase-overexpressing macrophages

Oxidative modification of low-density lipoprotein (LDL) leads to foam cell formation in atherosclerosis. The involvement of 12- and 15-lipoxygenases in LDL oxidation has been implicated by enzymological and knockout mouse studies. However, the molecular basis of oxidized LDL formation in vivo has not yet been elucidated. We constructed expression vectors pEF-BOS for porcine leukocyte and human platelet 12-lipoxygenases exhibiting distinct activity toward esterified fatty acids in LDL. Macrophage-like J774A.1 cells were transfected with these expression vectors, transcription of which was driven by elongation factor-1α promoter. The established clones showed 12-lipoxygenase activity, while the original J774A.1 cells did not show any detectable enzyme activity. When the 12-lipoxygenase-expressing cells were incubated with LDL, their oxidation was markedly increased over mock-transfected cells as determined by the thiobarbituric acid reactive substance (TBARS). Furthermore, the cells expressing porcine 12-lipoxygenase generated more oxygenated products than the platelet enzyme. Most of the oxygenated derivatives were of an esterified form, and the major product was identified to be 13 S-hydroxy-octadeca-9 Z,11 E-dienoic acid. In addition, the oxidized LDL generated by the 12-lipoxygenase-expressing cells was recognized by a scavenger receptor as assessed by macrophage degradation assay. These results suggest that the intracellular 12-lipoxygenase of macrophages play an essential role in the oxygenation of esterified fatty acids in LDL.

Long chain polyunsaturated fatty acids may account for higher low-density lipoprotein oxidation susceptibility in Lithuanian compared to Swedish men

Objectives: Mortality in coronary heart disease among middle-aged men is four times higher in Lithuania than in Sweden. Traditional risk factors cannot account for this difference. We earlier reported that low-density lipoprotein (LDL) in Lithuanian men showed a lower resistance to oxidation, measured as LDL lag time during copper oxidation, than that in Swedish men. Serum concentrations of several fat-soluble antioxidant vitamins were lower among Lithuanian men. The aim of this study was to investigate whether differences in LDL fatty acid composition could account for the difference in LDL oxidation susceptibility between men in the two countries. Methods: This cross-sectional study included randomly selected healthy 50-year-old men from Vilnius, Lithuania (n = 50) and Linköping, Sweden (n = 50). Main outcome measures were fatty acids in LDL, phospholipid (PL) and cholesterol ester (CE) fractions of LDL and LDL oxidation susceptibility. Results: The mean proportions of PL 20:5n3 (eicosapentaenoic acid, EPA) were higher in Vilnius men (2.09 - 1.05 vs. 1.53 - 0.58%, p = 0.004). LDL lag time was shorter in Vilnius men, mean - SD (75.4 - 13.6 vs. 89.5 - 13.1 mins, p < 0.0001) than in Linköping men. Mean serum n -tocopherol was lower in Vilnius men (0.07 - 0.05 vs. 0.12 - 0.04 w g/mmol, p < 0.0001) but f -tocopherol did not differ. In a multiple regression analysis controlled for city, high PL-EPA, low alpha-tocopherol, and high plasma triglycerides significantly contributed to a short LDL lag time, r 2 = 0.53. Conclusions: Fat quality, i.e. poly unsaturated fatty acids, especially LDL-EPA, plasma triglycerides and antioxidative vitamins may partly account for the increased LDL oxidation susceptibility found in Vilnius men compared with Linköping men.

Composition of LDL as determinant of its susceptibility to in vitro oxidation in patients with well-controlled type 2 diabetes.

There is increasing evidence that oxidation of low-density lipoprotein (LDL) in the vascular wall plays an important role in the development of atherosclerosis. The present study was undertaken to characterise how different constituents of LDL contribute to its in vitro oxidisability. The LDL composition, i.e. lipids, antioxidants, fatty acids, plasmenylcholines, and baseline level of conjugated dienes (CD) of 94 well-controlled and normolipidaemic type 2 diabetic patients was measured. Two oxidisability indices were determined: the lag time, reflecting the resistance of LDL to copper-induced oxidation, and the amount of conjugated dienes formed during oxidation of LDL. The lag time was not related to the total level of saturated, monounsaturated, and polyunsaturated fatty acids, but a strong inverse relationship was observed with fatty acids with three or more double bonds (r = -0.56, p < 0.001). In addition, an inverse relation was observed between the lag time and LDL-plasmenylcholine (r = -0.35, p < 0.001). Although not related to lag time in univariate analysis, alpha-tocopherol was a significant determinant in multiple regression analysis. A multiple linear regression model with LDL polyunsaturated fatty acids with three or more double bonds, alpha-tocopherol, monounsaturated fatty acids, and plasmenylcholines as determinants explained 47% of the variation in lag time. CD production was negatively correlated to oleic acid and positively to linoleic acid (r = -0.45 and r = 0.73, respectively; p<0.001). Fatty acids with three or more double bonds were the most important predictor of LDL lag time, whereas oleic acid and linoleic acid were major determinants of the amount of CD formed during oxidation of LDL.

Ex vivo low-density lipoprotein oxidizability and in vivo lipid peroxidation in patients on CAPD

Chronic renal failure is associated with accelerated atherosclerosis and a high incidence of cardiovascular disease. Oxidative modification of low-density lipoprotein (LDL) is considered a key event in atherogenesis. We studied the ex vivo oxidizability of LDL exposed to Cu2+ ions (lag time, rate of propagation, maximum conjugated diene formation) and its relationship with LDL density, fatty acids, and antioxidants, along with plasma malondialdehyde (MDA) and autoantibodies against Cu2+-, MDA-, and hypochlorous acid-modified LDL and plasma antioxidants in 17 continuous ambulatory peritoneal dialysis (CAPD) patients and 21 healthy control subjects. LDL alpha- and gamma-tocopherol and total polyunsaturated fatty acid (PUFA) concentrations were significantly higher in the CAPD patients. LDL density was shifted to small, dense LDL. LDL oxidizability was comparable to that of healthy subjects. Lag time correlated positively with LDL alpha-tocopherol and inversely with both total PUFA concentrations and density; the rate of oxidation and LDL density correlated positively with total PUFA and total fatty acid concentrations, respectively. Ratios of autoantibody titers against oxidized to native LDL did not differ between the two groups. While plasma alpha- and gamma-tocopherol concentrations and tocopherol to cholesterol ratios were significantly higher, vitamin C concentrations were very low in the CAPD patients. MDA concentrations were 1.7 times higher than in healthy subjects. (1) Ex vivo LDL oxidizability is normal in CAPD patients as a result of efficient protection by LDL-associated lipophilic antioxidants, although the LDL composition is altered toward high oxidizability; and (2) the plasma antioxidant screen is insufficient due to impaired vitamin C status.