Paraoxonase activity in high-density lipoproteins: a comparison between healthy and obese females

Paraoxonase, an enzyme associated with high-density lipoprotein (HDL-PON), exerts a protective effect against oxidative damage of circulating cells and lipoproteins, modulates the susceptibility of HDL to atherogenic modifications such as glycation and homocysteinylation, and even exerts an antiinflammatory role. The aim of the present study was to investigate the relationship between lipoprotein oxidative stress and the activity of HDL-PON in healthy and obese subjects. Therefore, the activity of HDL-PON and the levels of lipid hydroperoxides in HDL and low-density lipoprotein (LDL) isolated from plasma of obese females (n = 12) and age-sex-matched controls (n = 31) were compared. Our results demonstrated for the first time that the activity of HDL-PON in obese subjects was significantly lower compared with that in controls (P < 0.001). Moreover, our results showed a significant increase in the levels of lipid hydroperoxides in HDL and LDL isolated from obese subjects (P < 0.001). The negative correlations established between HDL-PON activity and the levels of lipid hydroperoxides associated with HDL and LDL confirm the relationship between paraoxonase activity and lipid peroxidation of lipoproteins. Plasma levels of leptin correlated negatively with HDL-PON activity and positively with levels of lipid hydroperoxides in HDL and LDL of obese subjects, suggesting a relationship between leptin and oxidative damage of lipoproteins. In conclusion, our study demonstrated that the increase in oxidative stress in LDL and HDL of obese subjects is associated with a decrease in HDL-PON activity. The lower paraoxonase activity and the compositional changes in HDL and LDL could contribute to the greater risk of cardiovascular disease associated with obesity.     

Alpha-tocopherol supplementation decreases the oxidative susceptibility of LDL in renal failure patients on dialysis therapy

Atherosclerotic cardiovascular disease is the leading cause of death in patients with end stage renal disease (ESRD) who have undergone dialysis treatment. The oxidation of low density lipoprotein (LDL) appears to be a crucial step in the pathogenesis of atherosclerosis. The increased oxidative stress and attendant increased oxidizability of lipoproteins, such as LDL could contribute to the accelerated atherosclerosis in dialysis patients. Since alpha-tocopherol (AT) is the major antioxidant in LDL, the aim of the present study was to test the effectiveness of RRR-AT supplementation (800 I.U. per day) for 12 weeks on the susceptibility of LDL to oxidation. The study subjects comprised patients with chronic renal failure on hemodialysis (HD), peritoneal dialysis (PD), and age and sex matched controls (C). Plasma fatty acids, lipoproteins and AT levels were measured in these subjects before and after supplementation. Also, LDL AT and oxidizability was studied. LDL was isolated by ultracentrifugation at baseline and after 12 weeks of supplementation, and subjected to a 5-h time course of copper catalyzed oxidation. Oxidation was measured by the formation of conjugated dienes (CD) and lipid peroxides (LP). Supplementation with AT did not alter the plasma lipid or lipoprotein profile of these subjects. Plasma lipid-standardized AT and LDL AT concentrations were not different among the groups at baseline. AT supplementation significantly increased plasma lipid-standardized AT (C=150%, HD=149%, PD=217%, P<0.001) and LDL AT concentrations (C=94%, HD=94%, PD=135%, P<0.003). AT enrichment of LDL resulted in a significant prolongation in conjugated diene lag phase in all groups (C=34%, HD=21%, PD=54%, P<0.02). Lipid peroxide lag phase was also increased significantly in C (27%,) and PD (40%) groups after AT supplementation (P<0.01). There was a significant positive correlation between plasma lipid standardized AT and lag phase (r=0. 54, P=0.0003). Overall, AT decreased the susceptibility of LDL to oxidation in patients with chronic renal failure but the benefit appears to be greater in patients on PD. Therefore, AT supplementation may also provide a measure of protection against CAD in patients with chronic renal failure on dialysis therapy.     

Cholesteryl ester hydroperoxide lability is a key feature of the oxidative susceptibility of small, dense LDL

Abundant evidence has been provided to substantiate the elevated cardiovascular risk associated with small, dense, low density lipoprotein (LDL) particles. The diminished resistance of dense LDL to oxidative stress in both normolipidemic and dyslipidemic subjects is established; nonetheless, the molecular basis of this phenomenon remains indeterminate. We have defined the primary molecular targets of lipid hydroperoxide formation in light, intermediate, and dense subclasses of LDL after copper-mediated oxidation and have compared the relative stabilities of the hydroperoxide derivatives of phospholipids and cholesteryl esters (CEs) as a function of the time course of oxidation. LDL subclasses (LDL1 through LDL5) were isolated from normolipidemic plasma by isopycnic density gradient ultracentrifugation, and their content of polyunsaturated molecular species of phosphatidylcholine (PC) and CE and of lipophilic antioxidants was quantified by reverse-phase high-performance liquid chromatography. The molar ratio of the particle content of polyunsaturated CE and PC species containing linoleate or arachidonate relative to alpha-tocopherol or beta-carotene did not differ significantly between LDL subspecies. Nonetheless, dense LDL contained significantly less polyunsaturated CE species (400 mol per particle) compared with LDL1 through LDL4 (range, approximately 680 to 490 mol per particle). Although the formation of PC-derived hydroperoxides did not vary significantly between LDL subspecies as a function of the time course of copper-mediated oxidation, the abundance of the C18:2 and C20:4 CE hydroperoxides was uniquely deficient in dense LDL (23 and 0.6 mol per particle, respectively, in LDL5; 47 to 58 and 1.9 to 2.3 mol per particle, respectively, in other LDL subclasses) at propagation half-time. When expressed as a lability ratio (mol hydroperoxides formed relative to each 100 mol of substrate consumed) at half-time, the oxidative lability of CE hydroperoxides in dense LDL was significantly elevated (lability ratio <25:100) relative to that in lighter, larger LDL particle subclasses (lability ratio >40:100) throughout the oxidative time course. We conclude that the elevated lability of CE hydroperoxides in dense LDL underlies the diminished oxidative resistance of these particles. Moreover, this phenomenon appears to result not only from the significantly elevated PC to free cholesterol ratio (1.54:1) in dense LDL particles (1.15:1 to 1.25:1 for other LDL subclasses) but also from their unique structural features, including a distinct apoB100 conformation, which may facilitate covalent bond formation between oxidized CE and apoB100.     

Gastrointestinal glutathione peroxidase prevents transport of lipid hydroperoxides in CaCo-2 cells

BACKGROUND & AIMS: Gastrointestinal glutathione peroxidase (GI-GPx), 1 of the 4 types of selenium-dependent glutathione peroxidases, is expressed exclusively in the gastrointestinal system and has therefore been suggested to function as a barrier against the absorption of dietary hydroperoxides. METHODS: The selenium-dependent expression of GI-GPx and cytosolic GPx (cGPx) was analyzed by Western blotting. Transport of 13-hydroperoxy octadecadienoic acid (13-HPODE) was investigated in a CaCo-2 cell monolayer modulated in GI-GPx and cGPx by selenium restriction or repletion. Localization of GI-GPx in rat intestine was visualized by immunohistochemistry. RESULTS: Low but significant GI-GPx levels were detected in selenium-deficient CaCo-2 cells and in the gastrointestinal tract of selenium-deficient rats, whereas cGPx was completely absent. Selenium supplementation of CaCo-2 cells resulted in a 5-fold increase of GI-GPx protein, whereas total GPx activity increased by a factor of 13, with most of the GPx activity under selenium-adequate conditions being cGPx. Irrespective of the selenium status, 13-HPODE did not reach the basolateral side of an intact CaCo-2 cell monolayer. Depending on the selenium status, hydroperoxides damaged the monolayer as evidenced by loss of transepithelial resistance and paracellular diffusion of lucifer yellow. Only under these conditions was unmetabolized 13-HPODE detectable at the basolateral side. CONCLUSIONS: Low GI-GPx levels, as present in selenium deficiency, suffice to prevent transport of 13-HPODE. GI-GPx may thus function as a barrier against hydroperoxide absorption. cGPx contributes to balance major oxidative challenge.     

Improvement of the omega 3 index of healthy subjects does not alter the effects of dietary saturated fats or n-6PUFA on LDL profiles

Background and AimsDietary fat composition is known to modulate circulating lipid and lipoprotein levels. Although supplementation with long chain omega-3 polyunsaturated fatty acids (LCn-3PUFA) has been shown to reduce plasma triglyceride levels, the effect of the interactions between LCn-3PUFA and the major dietary fats consumed has not been previously investigated.MethodsIn a randomized controlled parallel design clinical intervention, we examined the effect of diets rich in either saturated fatty acids (SFA) or omega-6 polyunsaturated fatty acids (n-6PUFA) on plasma lipid levels and lipoprotein profiles (lipoprotein size, concentration and distribution in subclasses) in subjects with an adequate omega 3 index. Twenty six healthy subjects went through a four-week pre-supplementation period with LCn-3PUFA and were then randomized to diets rich in either n-6PUFA or SFA both supplemented with LCn-3PUFA.ResultsThe diet rich in n-6PUFA decreased low density lipoprotein (LDL) particle concentration (− 8%, p = 0.013) and LDL cholesterol (LDL-C) level (− 8%, p = 0.021), while the saturated fat rich diet did not affect LDL particle concentration or LDL-C levels significantly. Nevertheless, dietary saturated fatty acids increased LCn-3PUFA in plasma and tissue lipids compared with n-6PUFA, potentially reducing other cardiovascular risk factors such as inflammation and clotting tendency.ConclusionImprovement on the omega 3 index of healthy subjects did not alter the known effects of dietary saturated fats and n-6PUFA on LDL profiles.     

Postprandial antioxidant effect of the Mediterranean diet supplemented with coenzyme Q10 in elderly men and women

Postprandial oxidative stress is characterized by an increased susceptibility of the organism towards oxidative damage after consumption of a meal rich in lipids and/or carbohydrates. We have investigated whether the quality of dietary fat alters postprandial cellular oxidative stress and whether the supplementation with coenzyme Q(10) (CoQ) lowers postprandial oxidative stress in an elderly population. In this randomized crossover study, 20 participants were assigned to receive three isocaloric diets for periods of 4 week each: (1) Mediterranean diet supplemented with CoQ (Med+CoQ diet), (2) Mediterranean diet (Med diet), and (3) saturated fatty acid-rich diet (SFA diet). After a 12-h fast, the volunteers consumed a breakfast with a fat composition similar to that consumed in each of the diets. CoQ, lipid peroxides (LPO), oxidized low-density lipoprotein (oxLDL), protein carbonyl (PC), total nitrite, nitrotyrosine plasma levels, catalase, superoxide dismutase (SOD), and glutathione peroxidase (GPx) activities and ischemic reactive hyperaemia (IRH) were determined. Med diet produced a lower postprandial GPx activity and a lower decrease in total nitrite level compared to the SFA diet. Med and Med+CoQ diets induced a higher postprandial increase in IRH and a lower postprandial LPO, oxLDL, and nitrotyrosine plasma levels than the SFA diet. Moreover, the Med+CoQ diet produced a lower postprandial decrease in total nitrite and a greater decrease in PC levels compared to the other two diets and lower SOD, CAT, and GPx activities than the SFA diet.In conclusion, Med diet reduces postprandial oxidative stress by reducing processes of cellular oxidation and increases the action of the antioxidant system in elderly persons and the administration of CoQ further improves this redox balance.     

The correlation between markers of oxidative stress and risk factors of coronary artery disease in Thai patients

An imbalance between oxidative damage and antioxidative protection in association with the pathophysiology of atherosclerosis has been suggested. The aim of our study was to investigate the relationship between plasma lipids, the antioxidant system and oxidative damage in Thai patients with stable coronary artery disease (CAD). Sixty-one patients (40 males, 21 females), who were angiographically defined as having CAD and were clinically stable, participated in this study. Thirty-two healthy subjects (20 males, 12 females) served as normal controls. The investigation included the measurements of plasma lipid profiles and plasma total antioxidative status (TAS) such as plasma vitamin E erythrocyte glutathione (GSH) and glutathione peroxidase (GPx), as well as malondialdehyde (MDA) and total plasma total protein thiols (P-SH). In patients with CAD, erythrocyte GSH and GPx were significantly lower than those found in controls. However plasma TAS and vitamin E were not significantly different between groups. Patients with CAD also had higher MDA and lower P-SH levels than the controls, which represents the oxidative damage products of lipid and proteins. Multiple regression analysis revealed negative correlations between GSH and cholesterol, GSH and low density lipoprotein (LDL), vitamin E and MDA, as well as P-SH and MDA. This study demonstrated the status of oxidative stress in patients with stable CAD. Since oxidative stress is the imbalance between the total oxidants and antioxidants in the body, any single oxidant/antioxidant parameter may not reflect the overall oxidative stress system. Thus, in patients with CAD, diets with various types of antioxidants may be more beneficial in increasing antioxidant activity than any particular antioxidant supplementation.     

LDL oxidation by platelets propagates platelet activation via an oxidative stress-mediated mechanism

Objectives

Platelets generate oxidized LDL (ox-LDL) via NOX2-derived oxidative stress. We investigated if once generated by activated platelets ox-LDL can propagate platelet activation.

Methods

Experiments were performed in platelets from healthy subjects (HS), hyper-cholesterolemic patients and patients with NOX2 hereditary deficiency.

Results

Agonist-stimulated platelets from HS added with LDL were associated with a dose-dependent increase of reactive oxidant species and ox-LDL. Agonist-stimulated platelets from HS added with a fixed dose of LDL (57.14 μmol/L) or added with homogenized human atherosclerotic plaque showed enhanced ox-LDL formation (approximately +50% and +30% respectively), which was lowered by a NOX2 inhibitor (approximately −35% and −25% respectively). Compared to HS, ox-LDL production was more pronounced in agonist-stimulated platelet rich plasma (PRP) from hyper-cholesterolemic patients but was almost absent in PRP from NOX2-deficient patients.Platelet aggregation and 8-iso-PGF2α−ΙΙΙ formation increased in LDL-treated washed platelets (+42% and +53% respectively) and PRP (+31% and +53% respectively). Also, LDL enhanced platelet-dependent thrombosis at arterial shear rate (+33%) but did not affect platelet activation in NOX2-deficient patients. Platelet activation by LDL was significantly inhibited by CD36 or LOX1 blocking peptides, two ox-LDL receptor antagonists, or by a NOX2 inhibitor. LDL-added platelets showed increased p38MAPK (+59%) and PKC (+51%) phosphorylation, p47^phox translocation to platelet membrane (+34%) and NOX2 activation (+30%), which were inhibited by ox-LDL receptor antagonists.

Conclusion

Platelets oxidize LDL, which in turn amplify platelet activation via specific ox-LDL receptors; both effects are mediated by NOX2 activation.     

Selenium and antioxidant defenses as major mediators in the development of chronic heart failure

Increased oxidative stress is involved in the pathogenesis of chronic heart failure (CHF), the common end result of most cardiac diseases. Selenium is an “essential” trace element, which means that it must be supplied by our daily diet and that its blood and tissue concentrations are extremely low. Selenium has a variety of functions. It is a key component of several functional selenoproteins required for normal health. The best known of these are the antioxidant glutathione peroxidase (GPx) enzymes, which remove hydrogen peroxide and the harmful lipid hydroperoxides generated in vivo by oxygen-derived species. GPx deficiency exacerbates endothelial dysfunction, a major contributing factor in the severity of CHF symptoms, in various conditions such as hyperhomocysteinemia. This suggests that homocysteine may be involved in the CHF associated endothelial dysfunction through a peroxide-dependent oxidative mechanism. Selenium also plays a role in the control of thyroid hormone metabolism and in protection against organic and inorganic mercury. One possible additional mechanism by which low selenium may compromise cardiovascular condition may be through the effect of selenium on the synthesis and activity of deiodinases, enzymes converting thyroxin into the biologically active triiodothyronine. Selenium and iodine actually interact in cardiovascular physiology, and further studies are needed to examine their role, in isolation and in association, in the development of CHF. Thus, selenium (through its role in selenoenzymes, thyroid hormones, and interactions with homocysteine and endothelial function) appears to be a major mediator in several pathways potentially contributing to CHF development.     

Atherogenic lipoprotein phenotype and LDL size and subclasses in women with gestational diabetes

Aims Women with gestational diabetes are more likely to develop Type 2 diabetes and cardiovascular disease after pregnancy; however, the exact nature of the lipid alterations present is not clear. In Mediterranean women with gestational diabetes, we measured low‐density lipoprotein (LDL) size and all seven subclasses, as well as the ‘atherogenic–lipoprotein phenotype’[ALP, e.g. concomitant presence of elevated triglycerides, reduced high‐density lipoprotein (HDL)‐cholesterol and increased small, dense LDL]. Methods In 27 women with gestational diabetes and 23 healthy pregnant women matched for age, weeks of gestation and body mass index, we measured plasma lipids and LDL size and subclasses by gradient gel electrophoresis between 24 and 28 weeks of gestation. Results Although no significant differences were found in the concentrations of any of the plasma lipids, compared with control subjects women with gestational diabetes had lower LDL size (P = 0.0007) due to reduced LDL‐I (P = 0.0074) and increased LDL‐IVA (P = 0.0146) and ‐IVB (P < 0.0001) subclasses. Correlation analysis revealed that fasting glucose, homeostasis model assessment and glycated haemoglobin were inversely correlated with LDL‐I and positively with LDL‐IVA and ‐IVB (all P < 0.05). ALP due to high HDL‐cholesterol levels was not seen in either group, whereas elevated small, dense LDL were more common in women with gestational diabetes than control subjects (33% vs. 4%, P = 0.0107). Conclusions Increased levels of small, dense LDL are common in Mediterranean women with gestational diabetes. Whether these findings affect the atherogenic process and clinical end‐points in these women remains to be determined by future prospective studies.     

Bariatric surgery in morbidly obese patients improves the atherogenic qualitative properties of the plasma lipoproteins

Objective

The purpose of this study was to evaluate the effect of weight loss induced in morbidly obese subjects by Roux-en-Y gastric bypass bariatric surgery on the atherogenic features of their plasma lipoproteins.

Methods

Twenty-one morbidly obese subjects undergoing bariatric surgery were followed up for up to 1 year after surgery. Plasma and lipoproteins were assayed for chemical composition and lipoprotein-associated phospholipase A2 (Lp-PLA2) activity. Lipoprotein size was assessed by non-denaturing polyacrylamide gradient gel electrophoresis, and oxidised LDL by ELISA. Liver samples were assayed for mRNA abundance of oxidative markers.

Results

Lipid profile analysis revealed a reduction in the plasma concentrations of cholesterol and triglycerides, which were mainly associated with a significant reduction in the plasma concentration of circulating apoB-containing lipoproteins rather than with changes in their relative chemical composition. All patients displayed a pattern A phenotype of LDL subfractions and a relative increase in the antiatherogenic plasma HDL-2 subfraction (>2-fold; P < 0.001). The switch towards predominantly larger HDL particles was due to an increase in their relative cholesteryl ester content. Excess weight loss also led to a significant decrease in the plasma concentration of oxidised LDL (∼−25%; P < 0.01) and in the total Lp-PLA2 activity. Interestingly, the decrease in plasma Lp-PLA2 was mainly attributed to a decrease in the apoB-containing lipoprotein-bound Lp-PLA2.

Conclusion

Our data indicate that the weight loss induced by bariatric surgery ameliorates the atherogenicity of plasma lipoproteins by reducing the apoB-containing Lp-PLA2 activity and oxidised LDL, as well as increasing the HDL-2 subfraction.     

Oxidative Modification of Low-Density Lipoprotein and Atherogenetic Risk in beta -Thalassemia

We investigated the oxidative state of low-density lipoprotein (LDL)in patients with -thalassemia to determine whether there was anassociation with atherogenesis. Conjugated diene lipid hydroperoxides(CD) and the level of major lipid antioxidants in LDL, as well asmodified LDL protein, were evaluated in 35 -thalassemia intermediapatients, aged 10 to 60, and compared with age-matched healthycontrols. Vitamin E and -carotene levels in LDL from patients were45% and 24% of that observed in healthy controls, respectively. Incontrast, the mean amount of LDL-CD was threefold higher and lysilresidues of apo B-100 were decreased by 17%. LDL-CD in thalassemiapatients showed a strong inverse correlation with LDL vitamin E (r = 0.784; P < .0001), while a negative trend was observedwith LDL--carotene (r = 0.443; P = .149). In theplasma of thalassemia patients, malondialdehyde (MDA), a byproduct oflipid peroxidation, was increased by about twofold, while vitamin Eshowed a 52% decrease versus healthy controls. LDL-CD were inverselycorrelated with plasma vitamin E (r = 0.659; P < .0001)and correlated positively with plasma MDA (r = 0.621; P < .0001). Plasma ferritin was positively correlated with LDL-CD (r = 0.583; P =.0002). No correlation was found between the age ofthe patients and plasma MDA or LDL-CD. The LDL from thalassemiapatients was cytotoxic to cultured human fibroblasts and cytotoxicityincreased with the content of lipid peroxidation products. Clinicalevidence of mild to severe vascular complications in nine of thepatients was then matched with levels of LDL-CD, which were 36% to118% higher than the mean levels of the patients. Our results couldaccount for the incidence of atherogenic vascular diseases oftenreported in -thalassemia patients. We suggest that the level ofplasma MDA in -thalassemia patients may represent a sensitive indexof the oxidative status of LDL in vivo and of its potentialatherogenicity.     

Influence of consumption of probiotics on the plasma lipid profile: a meta-analysis of randomised controlled trials

Aims

Human clinical studies have yielded mixed results on the effects of consumption of probiotics on the plasma lipid profile. We conducted a meta-analysis of randomised controlled trials that evaluated the effects of probiotics consumption on blood lipids.

Data Synthesis

A systematic literature search of Embase, Web of Science, PubMed and Cochrane Controlled Trials Registry was conducted for studies that investigated the efficacy of probiotics on the plasma lipid profile of subjects. With the help of Review Manager 4.2, data from 13 trials, which included 485 participants with high, borderline high and normal cholesterol levels, were examined. The pooled mean net change in total cholesterol for those treated with probiotics compared to controls was −6.40 mg dl⁻¹ (95% confidence interval (CI), −9.93 to −2.87), mean net change in low-density lipoprotein (LDL) cholesterol was −4.90 mg dl⁻¹ (95% CI, −7.91 to −1.90), mean net change in high-density lipoprotein (HDL) cholesterol was −0.11 mg dl⁻¹ (95% CI, −1.90–1.69) and mean net change in triglycerides was −3.95 mg dl⁻¹ (95% CI, −10.32–2.42).

Conclusion

These results indicate that a diet rich in probiotics decreases total cholesterol and LDL cholesterol concentration in plasma for participants with high, borderline high and normal cholesterol levels.     

Glucosylated glycerophosphoethanolamines are the major LDL glycation products and increase LDL susceptibility to oxidation: evidence of their presence in atherosclerotic lesions

Glycation of both protein and lipid components is believed to be involved in LDL oxidation. However, the relative importance of lipid and protein glycation in the oxidation process has not been established, and products of lipid glycation have not been isolated. Using glucosylated phosphatidylethanolamine (Glc PtdEtn) prepared synthetically, we have identified glycated diacyl and alkenylacyl species among the ethanolamine phospholipids in LDL. Accumulation of these glycation products in LDL incubated with glucose showed a time- and glucose concentration-dependent increase. LDL specifically enriched with Glc PtdEtn (25 nmol/mg protein) showed increased susceptibility to lipid oxidation when dialyzed against a 5-micromol/L Cu(2+) solution. The presence of this glucosylated lipid resulted in a 5-fold increase in production of phospholipid-bound hydroperoxides and 4-fold increase in phospholipid-bound aldehydes. Inclusion of glucosylated phosphatidylethanolamine in the surface lipid monolayer of the LDL resulted in rapid loss of polyunsaturated cholesteryl esters from the interior of the particle during oxidation. Glycated ethanolamine phospholipids were also isolated and identified from atherosclerotic plaques collected from both diabetic and nondiabetic subjects. The present findings provide direct evidence for the previously proposed causative effect of lipid glycation on LDL oxidation.     

Vitamin C protects human vascular smooth muscle cells against apoptosis induced by moderately oxidized LDL containing high levels of lipid hydroperoxides.

Vascular cell death is a key feature of atherosclerotic lesions and may contribute to the plaque "necrotic" core, cap rupture, and thrombosis. Oxidatively modified low-density lipoproteins (LDLs) are implicated in the pathogenesis of atherosclerosis, and dietary antioxidants are thought to protect the vasculature against LDL-induced cytotoxicity. Because LDL oxidative modification may vary within atherosclerotic lesions, we examined the effects of defined, oxidatively modified LDL species on human arterial smooth muscle cell apoptosis and the cytoprotective effects of vitamin C. Moderately oxidized LDL (0 to 300 microg protein/mL), which has the highest content of lipid hydroperoxides, induced smooth muscle cell apoptosis within 6 hours, whereas native LDL and mildly and highly oxidized LDL had no effect. Moderately oxidized LDL increased cellular DNA fragmentation, release of fragmented DNA into the culture medium, and annexin V binding and decreased mitochondrial dehydrogenase activity and expression of the antiapoptotic mediator Bcl-x(L). Treatment of cells with native LDL together with the lipid hydroperoxide 13(S)-hydroperoxyoctadeca-9Z,11E-dienoic acid (HPODE, 200 micromol/L, 6 to 24 hours) also induced apoptotic cell death. Pretreatment of smooth muscle cells with vitamin C (0 to 100 micromol/L, 24 hours) attenuated the cytotoxicity and apoptosis induced by both moderately oxidized LDL and HPODE. Our findings suggest that moderately oxidized LDL, with its high lipid hydroperoxide content, rather than mildly or highly oxidized LDL, causes apoptosis of human smooth muscle cells and that vitamin C supplementation may provide protection against plaque instability in advanced atherosclerosis.     

LDL oxidized with iron in the presence of homocysteine/cystine at acidic pH has low cytotoxicity despite high lipid peroxidation

Fe(III) can have a strong oxidizing effect in the presence of reductants at acidic pH, which may occur under anaerobic conditions or in regions of inflammation. Low density lipoprotein (LDL) oxidation with Fe(III) and homocysteine/cystine at acidic pH provoked mainly formation of lipid hydroperoxides and thiobarbituric acid reactive substances (TBARS) in the absence of significant protein modification. Even when oxidized to a high TBARS content, LDL oxidized at acidic pH was not cytotoxic when added to THP-1 monocytes in a concentration causing cell death when LDL was oxidized to a similar TBARS content at plasma pH with Fe(III) or Cu(II) in the presence or absence of homocysteine/cystine. Inducible nitric oxide production by RAW264.7 mouse macrophages was only weakly inhibited by LDL oxidized at acidic pH, even if acetylated before oxidation to increase uptake, as compared to LDL oxidized with Cu(II) at plasma pH to a similar TBARS content or anodic electrophoretic mobility. LDL oxidized at acidic pH may mainly induce protective mechanisms against oxidative stress while causing little acute damage of cells.     

Moderate consumption of red wine, but not gin, decreases erythrocyte superoxide dismutase activity: A randomised cross-over trial

Background and Aims

Several studies have shown that moderate alcohol consumption reduces the risk of coronary heart disease, a disease related to oxidative stress. However, the effects of different alcoholic beverages on antioxidant status are not fully known. Our aim was therefore to compare the effects of a moderate intake of an alcoholic beverage with high polyphenol content (red wine) and another without polyphenol content (gin) on plasma antioxidant vitamins, lipid profile and oxidability of low-density lipoprotein (LDL) particles.

Methods and results

Forty healthy men (mean age, 38 years) were included in a randomised cross-over trial. After a 15-day washout period, subjects received 30 g/ethanol/d as either wine or gin for 28 days. Diet and exercise were monitored. Before and after each intervention, we measured serum vitamins, malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase activities, lipid profile, oxidized LDL and LDL resistance to ex-vivo oxidative stress. Compared to gin intervention, wine intake reduced plasma SOD activity [−8.1 U/gHb (95% confidence interval, CI, −138 to −25; P = 0.009)] and MDA levels [−11.9 nmol/L (CI, −21.4 to−2.5; P = 0.020)]. Lag phase time of LDL oxidation analysis also increased 11.0 min (CI, 1.2-20.8; P = 0.032) after wine, compared to gin, whereas no differences were observed between the two interventions in oxidation rate of LDL particles. Peroxide concentration in LDL particles also decreased after wine [−0.18 nmol/mL (CI, −0.3 to−0.08;P = 0.020)], as did plasma oxidized LDL concentrations [−11.0 U/L (CI,−17.3 to −6.1; P = 0.009)].

Conclusion

Compared to gin, red wine intake has greater antioxidant effects, probably due to its high polyphenolic content.     

Effects of zinc supplementation on antioxidant enzyme activities in healthy old subjects

A large body of experimental research indicates that oxidative stress contributes to the processes related to aging and age-related diseases. Trace elements, particularly zinc (Zn), are essential components of the endogenous enzymatic antioxidant defenses. The aim of this study was to determine the activity of three main antioxidant enzymes in plasma [i.e. superoxide dismutase (pSOD), catalase (CAT), glutathione peroxidase (GPx)] and of SOD in erythrocyte (eSOD) in a group of 1108 healthy elderly subjects from different European countries. The same enzymatic activities were evaluated in a subgroup of 108 subjects before and after Zn supplementation. We observed that eSOD activity increased with age, whereas plasma Zn decreased. Moreover, we found that women showed higher eSOD activity and lower plasma Zn compared to men. There were no age and gender-related differences in the activities of pSOD, CAT and GPx. After Zn supplementation, the activities of Zn-dependent enzymes (pSOD and eSOD), as well as plasma Zn concentration, were significantly higher than before supplementation. These results were not influenced by age, gender, plasma Zn variations (Δ Zn) and geographic area. These data suggest the potential beneficial effects of Zn supplementation on Zn-dependent antioxidant enzymes in healthy elderly subjects.     

Impact of statin therapy on LDL and non-HDL cholesterol levels in subjects with heterozygous familial hypercholesterolaemia

Background and aimsCardiovascular risk in heterozygous familial hypercholesterolaemia (HeFH) is driven by LDL cholesterol levels. Since lipid response to statin therapy presents individual variation, this study aimed to compare mean LDL and non-HDL cholesterol reductions and their variability achieved with different types and doses of the most frequently prescribed statins.Methods and resultsAmong primary hypercholesterolaemia cases on the Spanish Arteriosclerosis Society registry, 2894 with probable/definite HeFH and complete information on drug therapy and lipid profile were included.LDL cholesterol reduction ranged from 30.2 ± 17.0% with simvastatin 10 mg to 48.2 ± 14.7% with rosuvastatin 40 mg. After the addition of ezetimibe, an additional 26, 24, 21 and 24% reduction in LDL cholesterol levels was obtained for rosuvastatin, 5, 10, 20 and 40 mg, respectively. Subjects with definite HeFH and a confirmed genetic mutation had a more discrete LDL cholesterol reduction compared to definite HeFH subjects with no genetic mutation. A suboptimal response (<15% or <30% reduction in LDL cholesterol levels, respectively with low-/moderate-intensity and high-intensity statin therapy) was observed in 13.5% and, respectively, 20.3% of the subjects.ConclusionAccording to the LDL cholesterol reduction in HeFH patients, the ranking for more to less potent statins was rosuvastatin, atorvastatin and simvastatin; however, at maximum dosage, atorvastatin and rosuvastatin were nearly equivalent. HeFH subjects with positive genetic diagnosis had a lower lipid-lowering response. Approximately 1 in 5 patients on high-intensity statin therapy presented a suboptimal response.