gamma-tocopherol traps mutagenic electrophiles such as NO(X) and complements alpha-tocopherol: physiological implications

Peroxynitrite, a powerful mutagenic oxidant and nitrating species, is formed by the near diffusion-limited reaction of .NO and O2.- during activation of phagocytes. Chronic inflammation induced by phagocytes is a major contributor to cancer and other degenerative diseases. We examined how gamma-tocopherol (gammaT), the principal form of vitamin E in the United States diet, and alpha-tocopherol (alphaT), the major form in supplements, protect against peroxynitrite-induced lipid oxidation. Lipid hydroperoxide formation in liposomes (but not isolated low-density lipoprotein) exposed to peroxynitrite or the .NO and O2.- generator SIN-1 (3-morpholinosydnonimine) was inhibited more effectively by gammaT than alphaT. More importantly, nitration of gammaT at the nucleophilic 5-position, which proceeded in both liposomes and human low density lipoprotein at yields of approximately 50% and approximately 75%, respectively, was not affected by the presence of alphaT. These results suggest that despite alphaT's action as an antioxidant gammaT is required to effectively remove the peroxynitrite-derived nitrating species. We postulate that gammaT acts in vivo as a trap for membrane-soluble electrophilic nitrogen oxides and other electrophilic mutagens, forming stable carbon-centered adducts through the nucleophilic 5-position, which is blocked in alphaT. Because large doses of dietary alphaT displace gammaT in plasma and other tissues, the current wisdom of vitamin E supplementation with primarily alphaT should be reconsidered.

Post-challenge glucose predicts coronary atherosclerotic progression in non-diabetic, post-menopausal women

AIMS: We sought to determine whether fasting or post-challenge glucose were associated with progression of coronary atherosclerosis in non-diabetic women. METHODS: We performed a post-hoc analysis of 132 non-diabetic women who underwent 75-g oral glucose tolerance testing. The primary outcome of interest was progression of atherosclerosis determined by baseline and follow-up coronary angiography, a mean of 3.1 +/- 0.9 years apart. We analysed the association of change in minimal vessel diameter (DeltaMD) by quartile of fasting and post-challenge glucose using mixed models that included adjustment for age, systolic blood pressure, total : high-density lipoprotein cholesterol ratio, current smoking, lipid-lowering and anti-hypertensive medication use and other covariates. RESULTS: At baseline, participants had a mean age of 65.7 +/- 6.7 years and a mean body mass index of 27.9 +/- 8.5 kg/m(2). Although there were no significant differences in atherosclerotic progression by fasting glucose category (P for trend across quartiles = 0.99), there was a significant inverse association between post-challenge glucose and DeltaMD (in mm) (Q1 : 0.01 +/- 0.03; Q2 : 0.08 +/- 0.03; Q3 : 0.13 +/- 0.03; Q4 : 0.11 +/- 0.03; P for trend = 0.02). CONCLUSIONS: In post-menopausal women without diabetes, post-challenge glucose predicts angiographic disease progression. These findings suggest that even modest post-challenge hyperglycaemia influences the pathogenesis of atherosclerotic progression.

Contribution of 20 single nucleotide polymorphisms of 13 genes to dyslipidemia associated with antiretroviral therapy

BACKGROUND: HIV-1 infected individuals have an increased cardiovascular risk which is partially mediated by dyslipidemia. Single nucleotide polymorphisms in multiple genes involved in lipid transport and metabolism are presumed to modulate the risk of dyslipidemia in response to antiretroviral therapy. METHODS: The contribution to dyslipidemia of 20 selected single nucleotide polymorphisms of 13 genes reported in the literature to be associated with plasma lipid levels (ABCA1, ADRB2, APOA5, APOC3, APOE, CETP, LIPC, LIPG, LPL, MDR1, MTP, SCARB1, and TNF) was assessed by longitudinally modeling more than 4400 plasma lipid determinations in 438 antiretroviral therapy-treated participants during a median period of 4.8 years. An exploratory genetic score was tested that takes into account the cumulative contribution of multiple gene variants to plasma lipids. RESULTS: Variants of ABCA1, APOA5, APOC3, APOE, and CETP contributed to plasma triglyceride levels, particularly in the setting of ritonavir-containing antiretroviral therapy. Variants of APOA5 and CETP contributed to high-density lipoprotein-cholesterol levels. Variants of CETP and LIPG contributed to non-high-density lipoprotein-cholesterol levels, a finding not reported previously. Sustained hypertriglyceridemia and low high-density lipoprotein-cholesterol during the study period was significantly associated with the genetic score. CONCLUSIONS: Single nucleotide polymorphisms of ABCA1, APOA5, APOC3, APOE, and CETP contribute to plasma triglyceride and high-density lipoprotein-cholesterol levels during antiretroviral therapy exposure. Genetic profiling may contribute to the identification of patients at risk for antiretroviral therapy-related dyslipidemia.

Lipid profiles for antiretroviral-naive patients starting PI- and NNRTI-based therapy in the Swiss HIV cohort study

BACKGROUND: Blood lipid abnormalities in patients on highly active antiretroviral therapy (HAART) have been associated with exposure to protease inhibitors (PIs), particularly ritonavir. First therapy with a non-nucleoside reverse transcriptase inhibitor (NNRTI) leads to relatively favourable lipid profiles. We report on medium-term lipid profiles (up to 5 years) for antiretroviral-naive patients starting NNRTI- and PI-based HAART in the Swiss HIV Cohort Study. METHODS: Since April 2000, blood samples taken at visits scheduled every 6 months have been analysed for cholesterol and triglyceride concentrations. For 1065 antiretroviral-naive patients starting HAART after April 2000, we estimated changes in concentration over time using multivariate linear regression with adjustment for baseline covariates, use of lipid-lowering drugs and whether the sample was taken in a fasting state. RESULTS: Non-high density lipoprotein (HDL) cholesterol levels increase with increasing exposure to either PI- or NNRTI-based therapy, HDL cholesterol levels increase and triglyceride levels decrease with increasing exposure to NNRTI-based therapy, whereas triglyceride levels increase with increasing exposure to PI-based therapy. Between NNRTI-based therapies, there is a slight difference in triglyceride levels, which tend to increase with increasing exposure to efavirenz and to decrease with increasing exposure to nevirapine. Of the three common PI-based therapies, nelfinavir appears to have a relatively favourable lipid profile, with little change with increasing exposure. Of the other two PI therapies, lopinavir with ritonavir has a more favourable profile than indinavir with ritonavir, with smaller increases in both non-HDL cholesterol and triglycerides and an increase in HDL cholesterol. Increasing exposure to abacavir is associated with a decrease in the level of triglycerides. CONCLUSION: In general, NNRTI-based therapy is associated with a more favourable lipid profile than PI-based therapy, but different PI-based therapies are associated with very different lipid profiles. Nelfinavir appears to have a relatively favourable lipid profile. Of the two boosted PI therapies, lopinavir appears to have a more favourable lipid profile than indinavir.

Modeling the influence of APOC3, APOE, and TNF polymorphisms on the risk of antiretroviral therapy-associated lipid disorders

BACKGROUND: Single-nucleotide polymorphisms in genes involved in lipoprotein and adipocyte metabolism may explain why dyslipidemia and lipoatrophy occur in some but not all antiretroviral therapy (ART)-treated individuals. METHODS: We evaluated the contribution of APOC3 -482C-->T, -455T-->C, and 3238C-->G; epsilon 2 and epsilon 4 alleles of APOE; and TNF -238G-->A to dyslipidemia and lipoatrophy by longitudinally modeling >2600 lipid determinations and 2328 lipoatrophy assessments in 329 ART-treated patients during a median follow-up period of 3.4 years. RESULTS: In human immunodeficiency virus (HIV)-infected individuals, the effects of variant alleles of APOE on plasma cholesterol and triglyceride levels and of APOC3 on plasma triglyceride levels were comparable to those reported in the general population. However, when treated with ritonavir, individuals with unfavorable genotypes of APOC3 and [corrected] APOE were at risk of extreme hypertriglyceridemia. They had median plasma triglyceride levels of 7.33 mmol/L, compared with 3.08 mmol/L in the absence of ART. The net effect of the APOE*APOC3*ritonavir interaction was an increase in plasma triglyceride levels of 2.23 mmol/L. No association between TNF -238G-->A and lipoatrophy was observed. CONCLUSIONS: Variant alleles of APOE and APOC3 contribute to an unfavorable lipid profile in patients with HIV. Interactions between genotypes and ART can lead to severe hyperlipidemia. Genetic analysis may identify patients at high risk for severe ritonavir-associated hypertriglyceridemia.

Serum lipoproteins during treatment with the antihypertensive agent indapamide

Considering the documented, potentially undesirable influence of various thiazide-type or loop diuretics on serum lipoproteins, we prospectively investigated in 69 men (mean age +/- SEM, 32 +/- 1 years) the metabolic effects of the new diuretic-antihypertensive compound indapamide. Compared to placebo, indapamide (2.5 mg/day) given for 6 to 8 weeks lowered (p less than 0.02 to less than 0.001) blood pressure (supine values from 148/98 +/- 3/2 to 137/93 +/- 3/2) in 29 men with mild to moderate essential hypertension, but not in 40 healthy men. In both groups, significant (p less than 0.05 to less than 0.001) decreases in body weight (-0.8 kg) and plasma potassium (-0.6 mmol/L), and increases in plasma uric acid (+20%), renin activity (+200%), and aldosterone documented good compliance. There were no significant changes in total cholesterol (in all subjects, from 208 +/- 6 to 213 +/- 6 mg/dl), low- or very low-density lipoprotein (VLDL) cholesterol (127 +/- 6 to 129 +/- 6 and 21 +/- 1 to 21 +/- 2 respectively), high-density lipoprotein cholesterol (50 +/- 1 to 51 +/- 1 mg/dl), total triglycerides (Tg) (108 +/- 5 to 112 +/- 6 mg/dl), VLDL-Tg, apoproteins A1 and A2, plasma glucose, epinephrine, norepinephrine, sodium, calcium, magnesium, and creatinine; apoprotein B (84 +/- 2 to 88 +/- 3 mg/dl) and plasma insulin after glucose loading dose tended to be increased minimally. The absence of distinct lipoprotein alterations after short-term indapamide treatment may be of clinical and epidemiological interest.

Effect of atazanavir versus other protease inhibitor-containing antiretroviral therapy on endothelial function in HIV-infected persons: randomised controlled trial

OBJECTIVE: Impaired endothelial function was demonstrated in HIV-infected persons on protease inhibitor (PI)-containing antiretroviral therapy, probably due to altered lipid metabolism. Atazanavir is a PI causing less atherogenic lipoprotein changes. This study determined whether endothelial function improves after switching from other PI to atazanavir. DESIGN: Randomised, observer-blind, treatment-controlled trial. SETTING: Three university-based outpatient clinics. PATIENTS: 39 HIV-infected persons with suppressed viral replication on PI-containing regimens and fasting low-density lipoprotein (LDL)-cholesterol greater than 3 mmol/l. INTERVENTION: Patients were randomly assigned to continue the current PI or change to unboosted atazanavir. MAIN OUTCOME MEASURES: Endpoints at week 24 were endothelial function assessed by flow-mediated dilation (FMD) of the brachial artery, lipid profiles and serum inflammation and oxidative stress parameters. RESULTS: Baseline characteristics and mean FMD values of the two treatment groups were comparable (3.9% (SD 1.8) on atazanavir versus 4.0% (SD 1.5) in controls). After 24 weeks' treatment, FMD decreased to 3.3% (SD 1.4) and 3.4% (SD 1.7), respectively (all p = ns). Total cholesterol improved in both groups (p<0.0001 and p = 0.01, respectively) but changes were more pronounced on atazanavir (p = 0.05, changes between groups). High-density lipoprotein and triglyceride levels improved on atazanavir (p = 0.03 and p = 0.003, respectively) but not in controls. Serum inflammatory and oxidative stress parameters did not change; oxidised LDL improved significantly in the atazanavir group. CONCLUSIONS: The switch from another PI to atazanavir in treatment-experienced patients did not result in improvement of endothelial function despite significantly improved serum lipids. Atherogenic lipid profiles and direct effects of antiretroviral drugs on the endothelium may affect vascular function. Trial registration number: NCT00447070.

Cardiovascular risk factors and the metabolic syndrome in pediatric nonalcoholic fatty liver disease

BACKGROUND: Nonalcoholic fatty liver disease (NAFLD), the most common cause of liver disease in children, is associated with obesity and insulin resistance. However, the relationship between NAFLD and cardiovascular risk factors in children is not fully understood. The objective of this study was to determine the association between NAFLD and the presence of metabolic syndrome in overweight and obese children. METHODS AND RESULTS: This case-control study of 150 overweight children with biopsy-proven NAFLD and 150 overweight children without NAFLD compared rates of metabolic syndrome using Adult Treatment Panel III criteria. Cases and controls were well matched in age, sex, and severity of obesity. Children with NAFLD had significantly higher fasting glucose, insulin, total cholesterol, low-density lipoprotein cholesterol, triglycerides, systolic blood pressure, and diastolic blood pressure than overweight and obese children without NAFLD. Subjects with NAFLD also had significantly lower high-density lipoprotein cholesterol than controls. After adjustment for age, sex, race, ethnicity, body mass index, and hyperinsulinemia, children with metabolic syndrome had 5.0 (95% confidence interval, 2.6 to 9.7) times the odds of having NAFLD as overweight and obese children without metabolic syndrome. CONCLUSIONS: NAFLD in overweight and obese children is strongly associated with multiple cardiovascular risk factors. The identification of NAFLD in a child should prompt global counseling to address nutrition, physical activity, and avoidance of smoking to prevent the development of cardiovascular disease and type 2 diabetes.

Prior statin use, intracranial hemorrhage, and outcome after intra-arterial thrombolysis for acute ischemic stroke

BACKGROUND AND PURPOSE: There are only limited data on whether prior statin use and/or cholesterol levels are associated with intracranial hemorrhage (ICH) and outcome after intra-arterial thrombolysis. The purpose of this study was to evaluate the association of statin pretreatment and cholesterol levels with the overall frequency of ICH, the frequency of symptomatic ICH, and clinical outcome at 3 months. METHODS: We analyzed 311 consecutive patients (mean age, 63 years; 43% women) who received intra-arterial thrombolysis. RESULTS: Statin pretreatment was present in 18%. The frequency of any ICH was 20.6% and of symptomatic ICH 4.8%. Patients with any ICH were more often taking statins (30% versus 15%, P=0.005), more often had atrial fibrillation (45% versus 30%, P=0.016), had more severe strokes (mean National Institute of Health Stroke Scale score 16.5 versus 14.7, P=0.022), and less often good collaterals (16% versus 24%, P=0.001). Patients with symptomatic ICH were more often taking statins (40% versus 15%, P=0.009) and had less often good collaterals (0% versus 24%, P<0.001). Any ICH or symptomatic ICH were not associated with cholesterol levels. After multivariate analysis, the frequency of any ICH remained independently associated with previous statin use (OR, 3.1; 95% CI, 1.53 to 6.39; P=0.004), atrial fibrillation (OR, 2.5; CI, 1.35 to 4.75; P=0.004), National Institutes of Health Stroke Scale score (OR, 1.1; CI, 1.00 to 1.10; P=0.037), and worse collaterals (OR, 1.7; CI, 1.19 to 2.42; P=0.004). There was no association of outcome with prior statin use, total cholesterol level, or low-density lipoprotein cholesterol level. CONCLUSIONS: Prior statin use, but not cholesterol levels on admission, is associated with a higher frequency of any ICH after intra-arterial thrombolysis without impact on outcome.

TLR expression on neutrophils at the pulmonary site of infection: TLR1/TLR2-mediated up-regulation of TLR5 expression in cystic fibrosis lung disease

Cystic fibrosis (CF) lung disease is characterized by infection with Pseudomonas aeruginosa and a sustained accumulation of neutrophils. In this study, we analyzed 1) the expression of MyD88-dependent TLRs on circulating and airway neutrophils in P. aeruginosa-infected CF patients, P. aeruginosa-infected non-CF bronchiectasis patients, and noninfected healthy control subjects and 2) studied the regulation of TLR expression and functionality on neutrophils in vitro. TLR2, TLR4, TLR5, and TLR9 expression was increased on airway neutrophils compared with circulating neutrophils in CF and bronchiectasis patients. On airway neutrophils, TLR5 was the only TLR that was significantly higher expressed in CF patients compared with bronchiectasis patients and healthy controls. Studies using confocal microscopy and flow cytometry revealed that TLR5 was stored intracellularly in neutrophils and was mobilized to the cell surface in a protein synthesis-independent manner through protein kinase C activation or after stimulation with TLR ligands and cytokines characteristic of the CF airway microenvironment. The most potent stimulator of TLR5 expression was the bacterial lipoprotein Pam(3)CSK(4). Ab-blocking experiments revealed that the effect of Pam(3)CSK(4) was mediated through cooperation of TLR1 and TLR2 signaling. TLR5 activation enhanced the phagocytic capacity and the respiratory burst activity of neutrophils, which was mediated, at least partially, via a stimulation of IL-8 production and CXCR1 signaling. This study demonstrates a novel mechanism of TLR regulation in neutrophils and suggests a critical role for TLR5 in neutrophil-P. aeruginosa interactions in CF lung disease.

Efficient coupling of transducin to monomeric rhodopsin in a phospholipid bilayer

G protein-coupled receptors (GPCRs) are seven transmembrane domain proteins that transduce extracellular signals across the plasma membrane and couple to the heterotrimeric family of G proteins. Like most intrinsic membrane proteins, GPCRs are capable of oligomerization, the function of which has only been established for a few different receptor systems. One challenge in understanding the function of oligomers relates to the inability to separate monomeric and oligomeric receptor complexes in membrane environments. Here we report the reconstitution of bovine rhodopsin, a GPCR expressed in the retina, into an apolipoprotein A-I phospholipid particle, derived from high density lipoprotein (HDL). We demonstrate that rhodopsin, when incorporated into these 10 nm reconstituted HDL (rHDL) particles, is monomeric and functional. Rhodopsin.rHDL maintains the appropriate spectral properties with respect to photoactivation and formation of the active form, metarhodopsin II. Additionally, the kinetics of metarhodopsin II decay is similar between rhodopsin in native membranes and rhodopsin in rHDL particles. Photoactivation of monomeric rhodopsin.rHDL also results in the rapid activation of transducin, at a rate that is comparable with that found in native rod outer segments and 20-fold faster than rhodopsin in detergent micelles. These data suggest that monomeric rhodopsin is the minimal functional unit in G protein activation and that oligomerization is not absolutely required for this process.

TRPC1 is regulated by caveolin-1 and is involved in oxidized LDL-induced apoptosis of vascular smooth muscle cells

Oxidized low-density lipoprotein (oxLDL) induced-apoptosis of vascular cells may participate in plaque instability and rupture. We have previously shown that vascular smooth muscle cells (VSMC) stably expressing caveolin-1 were more susceptible to oxLDL-induced apoptosis than VSMC expressing lower level of caveolin-1, and this was correlated with enhanced Ca(2+) entry and pro-apoptotic events. In this study we aimed to identify the molecular events involved in oxLDL-induced Ca(2+) influx and their regulation by the structural protein caveolin-1. In VSMC, transient receptor potential canonical-1 (TRPC1) silencing by ARN interference, prevents the Ca(2+) influx and reduces the toxicity induced by oxLDL. Moreover, caveolin-1 silencing induces concomitant decrease of TRPC1 expression and reduces oxLDL-induced-apoptosis of VSMC. OxLDL enhanced the cell surface expression of TRPC1, as shown by biotinylation of cell surface proteins, and induced TRPC1 translocation into caveolar compartment, as assessed by subcellular fractionation. OxLDL-induced TRPC1 translocation was dependent on actin cytoskeleton and associated with a dramatic rise of 7-ketocholesterol (a major oxysterol in oxLDL) into caveolar membranes, whereas the caveolar content of cholesterol was unchanged. Altogether, the reported results show that TRPC1 channels play a role in Ca(2+) influx and Ca(2+) homeostasis deregulation that mediate apoptosis induced by oxLDL. These data also shed new light on the role of caveolin-1 and caveolar compartment as important regulators of TRPC1 trafficking to the plasma membrane and apoptotic processes that play a major role in atherosclerosis.

Caveolin-1 sensitizes vascular smooth muscle cells to mildly oxidized LDL-induced apoptosis

Oxidized low-density lipoprotein (oxLDL)-induced apoptosis of vascular cells may participate to plaque instability and rupture. Caveolin-1 has emerged as an important regulator of several signal transduction pathways and processes that play a role in atherosclerosis. In this study we examined the potential role of caveolin-1 in the regulation of oxLDL-induced Ca(2+) signaling and apoptosis in vascular smooth muscle cells (VSMC). Cells expressing caveolin-1 were more susceptible to oxLDL-induced apoptosis, and this was correlated with enhanced Ca(2+) entry and pro-apoptotic events. Moreover, caveolin-1 silencing by small interfering RNA decreased the level of apoptotic cells after oxLDL treatment. These findings provide new insights about the potential role of caveolin-1 in the regulation of oxLDL-induced apoptosis in vascular cells and its contribution to the instability of the plaque.

Microsomal triglyceride transfer protein polymorphism (-493G/T) is associated with hepatic steatosis in patients with chronic hepatitis C

BACKGROUND: Hepatic steatosis may promote progression of chronic hepatitis C (CHC). Microsomal triglyceride transfer protein (MTP) is required for assembly and secretion of ApoB lipoprotein and is implicated in hepatitis C virus (HCV)-related steatosis. The MTP -493G/T polymorphism may promote liver fat accumulation, but its role in HCV-related steatosis is still unclear. METHODS: Two hundred ninety-eight CHC patients were studied and genotyped for MTP -493G/T variants. Hepatic MTP mRNA expression and activity were determined in a subgroup. RESULTS: Patients with grades 2/3 steatosis were older, had a higher body mass index (BMI), more advanced fibrosis and lower MTP mRNA expression and carried more often HCV genotype 3 and the MTP T allele. Age, BMI, HCV-3 and MTP T allele [odds ratio (OR) 2.05; 95% confidence interval (CI) 1.2-3.53; P=0.009] were independent risk factors for steatosis grades 2/3, and in HCV genotype non-3 patients, the MTP T allele was the strongest predictor for steatosis grade 2/3 (OR 2.17; 95% CI 1.22-3.86; P=0.008). Moreover, TT carriers had higher high-density lipoprotein (65.6+/-14.6 vs 56.1+/-16.2 mg/dl; P=0.003) and apolipoprotein AI (1.80+/-0.3 vs 1.60+/-0.3 g/L; P=0.005) levels than G allele carriers. CONCLUSIONS: Chronic hepatitis C patients with the MTP -493T allele reveal higher grades of steatosis, indicating a relevant contribution to liver fat accumulation, particularly in HCV non-3 patients.

The differential effects of thiazolidindiones on atherogenic dyslipidemia in type 2 diabetes: what is the clinical significance?

Diabetic dyslipidemia is typically characterized by an increase in plasma triglycerides, a decrease in high-density lipoprotein cholesterol and a concomitant increase in atherogenic small dense low-density lipoproteins. Thiazolidindiones are able to lower the levels of fasting glucose and glycated hemoglobin significantly by improving insulin sensitivity, as well as improving some aspects of diabetic dyslipidemia: total cholesterol, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol tend to increase while triglycerides are generally decreased.