Oxidative stress-mediated arterial dysfunction in patients with metabolic syndrome: Effect of ascorbic acid

Recent insights into mechanisms of hypoxia-induced vasodilatation in the human brain

The cerebral vasculature manages oxygen delivery by adjusting arterial blood in-flow in the face of reductions in oxygen availability. Hypoxic cerebral vasodilatation, and the associated hypoxic cerebral blood flow reactivity, involve many vascular, erythrocytic and cerebral tissue mechanisms that mediate elevations in cerebral blood flow via micro- and macrovascular dilatation. This contemporary review focuses on in vivo human work - with reference to seminal preclinical work where necessary - on hypoxic cerebrovascular reactivity, particularly where recent advancements have been made. We provide updates with the following information: in humans, hypoxic cerebral vasodilatation is partially mediated via a - likely non-obligatory - combination of: (1) nitric oxide synthases, (2) deoxygenation-coupled S-nitrosothiols, (3) potassium channel-related vascular smooth muscle hyperpolarization, and (4) prostaglandin mechanisms with some contribution from an interrelationship with reactive oxygen species. And finally, we discuss the fact that, due to the engagement of deoxyhaemoglobin-related mechanisms, reductions in O2 content via haemoglobin per se seem to account for ∼50% of that seen with hypoxic cerebral vasodilatation during hypoxaemia. We further highlight the issue that methodological impediments challenge the complete elucidation of hypoxic cerebral reactivity mechanisms in vivo in healthy humans. Future research is needed to confirm recent advancements and to reconcile human and animal findings. Further investigations are also required to extend these findings to address questions of sex-, heredity-, age-, and disease-related differences. The final step is to then ultimately translate understanding of these mechanisms into actionable, targetable pathways for the prevention and treatment of cerebral vascular dysfunction and cerebral hypoxic brain injury.

Carbonylated Proteins as Key Regulators in the Progression of Metabolic Syndrome

Based on the known role of oxidative stress in the pathogenesis and progression of metabolic syndrome, we used two-dimensional gel electrophoresis with immunochemical detection of protein carbonyls (2D-Oxyblot) to characterize the carbonylated proteins induced by oxidative stress in spontaneously hypertensive rats/NDmcr-cp (CP), an animal model of metabolic syndrome. We also profiled the proteins that showed change of expression levels in their epididymal adipose tissue at the pre-symptomatic (6-week-old) and the symptomatic (25-week-old) stages of the metabolic syndrome. Two-dimensional fluorescence difference gel electrophoresis (2D-DIGE) combined with matrix-assisted laser desorption ionization time-of-flight tandem mass spectrometry (MALDI-TOF/TOF MS) was used to analyze proteins extracted from the epididymal adipose tissue. The up-regulated proteins identified at the pre-symptomatic stage were mainly associated with ATP production and redox reaction, while the down-regulated proteins found at the symptomatic stage were involved in antioxidant activity and the tricarboxylic acid (TCA) cycle. Further analysis using the 2D-Oxyblot showed significantly high carbonylation levels of gelsolin and glycerol-3-phosphate dehydrogenase [NAD+] at the symptomatic stage. These results suggest that reduced antioxidant capacity underlies the increased oxidative stress state in the metabolic syndrome. The identified carbonylated proteins, including gelsolin, are potential targets that may act as key regulators in the progression of the metabolic syndrome.

Is vitamin C a booster of the effects of dietary nitrate on endothelial function? Physiologic rationale and implications for research

Endothelial dysfunction (ED) is an early marker of vascular damage linked to the loss of integrity of the endothelial lining and represents a key step in the pathogenesis of atherosclerosis and cardiovascular diseases (CVDs). ED may be reversible, hence the development and testing of effective early interventions could be beneficial for the prevention and treatment of CVDs. Recent studies have demonstrated that the consumption of dietary nitrate (NO₃^-), an inorganic anion that serves as a substrate for the gas transmitter nitric oxide (NO), can lower blood pressure, improve endothelial function and, in observational studies, reduce the risk for CVD. We hypothesize that the co-consumption of NO₃^- with vitamin C, which is a potent antioxidant, could enhance the "yield" of NO produced from a given NO₃^- dose byThis could translate into greater NO-dependent effects on endothelial function (EF) and overall vascular health (than may be experienced with NO₃^- supplementation alone). This review presents evidence to suggest that the combination of vitamin C and dietary nitrate could represent a promising and effective approach to improve EF and reduce CVD risk, and discuss opportunities for future research.

Metabolic Spectrum of Liver Failure in Type 2 Diabetes and Obesity: From NAFLD to NASH to HCC

Liver disease is the spectrum of liver damage ranging from simple steatosis called as nonalcoholic fatty liver disease (NAFLD) to hepatocellular carcinoma (HCC). Clinically, NAFLD and type 2 diabetes coexist. Type 2 diabetes contributes to biological processes driving the severity of NAFLD, the primary cause for development of chronic liver diseases. In the last 20 years, the rate of non-viral NAFLD/NASH-derived HCC has been increasing rapidly. As there are currently no suitable drugs for treatment of NAFLD and NASH, a class of thiazolidinediones (TZDs) drugs for the treatment of type 2 diabetes is sometimes used to improve liver failure despite the risk of side effects. Therefore, diagnosis, prevention, and treatment of the development and progression of NAFLD and NASH are important issues. In this review, we will discuss the pathogenesis of NAFLD/NASH and NAFLD/NASH-derived HCC and the current promising pharmacological therapies of NAFLD/NASH. Further, we will provide insights into "adipose-derived adipokines" and "liver-derived hepatokines" as diagnostic and therapeutic targets from NAFLD to HCC.

Dehydroascorbic acid, the oxidized form of vitamin C, improves renal histology and function in old mice

Oxidative stress and inflammation are crucial factors that increase with age. In the progression of multiple age-related diseases, antioxidants and bioactive compounds have been recognized as useful antiaging agents. Oxidized or reduced vitamin C exerts different actions on tissues and has different metabolism and uptake. In this study, we analyzed the antiaging effect of vitamin C, both oxidized and reduced forms, in renal aging using laser microdissection, quantitative reverse-transcription polymerase chain reaction, and immunohistochemical analyses. In the kidneys of old SAM mice (10 months of age), a model of accelerated senescence, vitamin C, especially in the oxidized form (dehydroascorbic acid [DHA]) improves renal histology and function. Serum creatinine levels and microalbuminuria also decrease after treatment with a decline in azotemia. In addition, sodium-vitamin C cotransporter isoform 1 levels, which were increased during aging, are normalized. In contrast, the pattern of glucose transporter 1 expression is not affected by aging or vitamin C treatment. We conclude that oxidized and reduced vitamin C are potent antiaging therapies and that DHA reverses the kidney damage observed in senescence-accelerated prone mouse 8 to a greater degree.

Interventions targeted at oxidatively generated modifications of nucleic acids focused on urine and plasma markers

Oxidative stress is associated with the development and progression of numerous diseases. However, targeting oxidative stress has not been established in the clinical management of any disease. Several methods and markers are available to measure oxidative stress, including direct measurement of free radicals, antioxidants, redox balance, and oxidative modifications of cellular macromolecules. Oxidatively generated nucleic acid modifications have attracted much interest due to the pre-mutagenic oxidative modification of DNA into 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), associated with cancer development. During the last decade, the perception of RNA has changed from that of a 'silent messenger' to an 'active contributor', and, parallelly oxidatively generated RNA modifications measured as 8-oxo-7,8-dihydro-guanosine (8-oxoGuo), has been demonstrated as a prognostic factor for all-caused and cardiovascular related mortality in patients with type 2 diabetes. Several attempts have been made to modify the amount of oxidative nucleic acid modifications. Thus, this review aims to introduce researchers to the measurement of oxidatively generated nucleic acid modifications as well as critically review previous attempts and provide future directions for targeting oxidatively generated nucleic acid modifications.

The continuums of impairment in vascular reactivity across the spectrum of cardiometabolic health: A systematic review and network meta-analysis

This study aimed to assess, for the first time, the change in vascular reactivity across the full spectrum of cardiometabolic health. Systematic searches were conducted in MEDLINE and EMBASE databases from their inception to March 13, 2017, including studies that assessed basal vascular reactivity in two or more of the following health groups (aged ≥18 years old): healthy, overweight, obesity, impaired glucose tolerance, metabolic syndrome, or type 2 diabetes with or without complications. Direct and indirect comparisons of vascular reactivity were combined using a network meta-analysis. Comparing data from 193 articles (7226 healthy subjects and 19344 patients), the network meta-analyses revealed a progressive impairment in vascular reactivity (flow-mediated dilation data) from the clinical onset of an overweight status (-0.41%, 95% CI, -0.98 to 0.15) through to the development of vascular complications in those with type 2 diabetes (-4.26%, 95% CI, -4.97 to -3.54). Meta-regressions revealed that for every 1 mmol/l increase in fasting blood glucose concentration, flow-mediated dilation decreased by 0.52%. Acknowledging that the time course of disease may vary between patients, this study demonstrates multiple continuums of vascular dysfunction where the severity of impairment in vascular reactivity progressively increases throughout the pathogenesis of obesity and/or insulin resistance, providing information that is important to enhancing the timing and effectiveness of strategies that aim to improve cardiovascular outcomes.

Hazelnut and cocoa spread improves flow-mediated dilatation in smokers

Hazelnut and cocoa spread is an Italian product containing cocoa and hazelnut. Several epidemiological studies suggest that cocoa and hazelnuts cocoa exert beneficial cardiovascular effects. To investigate whether in smokers, hazelnut and cocoa spread elicits artery dilatation via down-regulation of oxidative stress. Flow-mediated dilatation (FMD), oxidative stress (as assessed by serum isoprostanes excretion, Nox2 activation and NO bioavailability) and antioxidant status [as assessed by vitamin E levels, plasma total polyphenols and H₂O₂ breaking down activity (HBA)] were studied in 20 smokers in a crossover, single-blind study. Patients were randomly allocated to 60 g of Hazelnut and cocoa spread or 60 g of milk chocolate (≤ 35% cocoa). FMD, serum isoprostanes, Nox2 activation, NOx, vitamin E, HBA and total polyphenols were assessed at baseline and 2 h after chocolate ingestion. After Hazelnut and cocoa spread intake, FMD and NOx significantly increased (from 4.3 ± 2.8 to 8.0 ± 3.2%, p < 0.001 and from 23.1 ± 5.5 to 32.0 ± 12.6 µM, p = 0.016, respectively); conversely, serum isoprostanes and Nox2 activation significantly decreased (from 302.8 ± 59.8 to 240.7 ± 90.8 pmol/l, p = 0.03 and from 25 ± 4.4 to 22.6 ± 3.2, p = 0.03, respectively). After Hazelnut and cocoa spread intake, serum total polyphenols, vitamin E and HBA significantly increased (from 133.8 ± 49.7 to 202.5 ± 69.5 mg/l GAE, p = 0.001; from 3.56 ± 1.4 to 4.5 ± 1.0 μmol/mmol cholesterol, p = 0.002 and from 63.3 ± 13.2 to 74.2 ± 12.4%, p = 0.003, respectively). No changes in the above variables were observed after milk chocolate intake. A linear correlation analysis shows that Δ (expressed by difference of values between before and after chocolate intake) of FMD correlates with Δ of total polyphenols and Δ of vitamin E. This study shows that Hazelnut and cocoa spread improves FMD with a mechanism potentially involving downregulation of oxidative stress and eventually increased NO generation in smokers.

Targeting vascular (endothelial) dysfunction

Cardiovascular diseases are major contributors to global deaths and disability-adjusted life years, with hypertension a significant risk factor for all causes of death. The endothelium that lines the inner wall of the vasculature regulates essential haemostatic functions, such as vascular tone, circulation of blood cells, inflammation and platelet activity. Endothelial dysfunction is an early predictor of atherosclerosis and future cardiovascular events. We review the prognostic value of obtaining measurements of endothelial function, the clinical techniques for its determination, the mechanisms leading to endothelial dysfunction and the therapeutic treatment of endothelial dysfunction. Since vascular oxidative stress and inflammation are major determinants of endothelial function, we have also addressed current antioxidant and anti-inflammatory therapies. In the light of recent data that dispute the prognostic value of endothelial function in healthy human cohorts, we also discuss alternative diagnostic parameters such as vascular stiffness index and intima/media thickness ratio. We also suggest that assessing vascular function, including that of smooth muscle and even perivascular adipose tissue, may be an appropriate parameter for clinical investigations.

LINKED ARTICLES

This article is part of a themed section on Redox Biology and Oxidative Stress in Health and Disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.12/issuetoc.

Cardiovascular function in male and female JCR:LA-cp rats: effect of high-fat/high-sucrose diet

Thirty percent of the world population is diagnosed with metabolic syndrome. High-fat/high-sucrose (HF/HS) diet (Western diet) correlates with metabolic syndrome prevalence. We characterized effects of the HF/HS diet on vascular (arterial stiffness, vasoreactivity, and coronary collateral development) and cardiac (echocardiography) function, oxidative stress, and inflammation in a rat model of metabolic syndrome (JCR rats). Furthermore, we determined whether male versus female animals were affected differentially by the Western diet. Cardiovascular function in JCR male rats was impaired versus normal Sprague-Dawley (SD) rats. HF/HS diet compromised cardiovascular (dys)function in JCR but not SD male rats. In contrast, cardiovascular function was minimally impaired in JCR female rats on normal chow. However, cardiovascular function in JCR female rats on the HF/HS diet deteriorated to levels comparable to JCR male rats on the HF/HS diet. Similarly, oxidative stress was markedly increased in male but not female JCR rats on normal chow but was equally exacerbated by the HF/HS diet in male and female JCR rats. These results indicate that the Western diet enhances oxidative stress and cardiovascular dysfunction in metabolic syndrome and eliminates the protective effect of female sex on cardiovascular function, implying that both males and females with metabolic syndrome are at equal risk for cardiovascular disease.NEW & NOTEWORTHY Western diet abolished protective effect of sex against cardiovascular disease (CVD) development in premenopausal animals with metabolic syndrome. Western diet accelerates progression of CVD in male and female animals with preexisting metabolic syndrome but not normal animals. Exacerbation of baseline oxidative stress correlates with accelerated progression of CVD in metabolic syndrome animals on Western diet.

Ascorbic acid promotes extracellular matrix deposition while preserving valve interstitial cell quiescence within 3D hydrogel scaffolds

Current options for aortic valve replacements are non-viable and thus lack the ability to grow and remodel, which can be problematic for paediatric applications. Toward the development of living valve substitutes that can grow and remodel, porcine aortic valve interstitial cells (VICs) were isolated and encapsulated within proteolytically degradable and cell-adhesive poly(ethylene glycol) (PEG) hydrogels, in an effort to study their phenotypes and functions. The results showed that encapsulated VICs maintained high viability and proliferated within the hydrogels. The VICs actively remodelled the hydrogels via secretion of matrix metalloproteinase-2 (MMP-2) and deposition of new extracellular matrix (ECM) components, including collagens I and III. The soft hydrogels with compressive moduli of ~4.3 kPa quickly reverted VICs from an activated myofibroblastic phenotype to a quiescent, unactivated phenotype, evidenced by the loss of α-smooth muscle actin expression upon encapsulation. In an effort to promote VIC-mediated ECM production, ascorbic acid (AA) was supplemented in the medium to investigate its effects on VIC function and phenotype. AA treatment enhanced VIC spreading and proliferation, and inhibited apoptosis. AA treatment also promoted VIC-mediated ECM remodelling by increasing MMP-2 activity and depositing collagens I and III. AA treatment did not significantly influence the expression of α-smooth muscle actin (myofibroblast activation marker) and alkaline phosphatase (osteogenic differentiation marker). No calcification or nodule formation was observed within the cell-laden hydrogels, with or without AA treatment. These results suggest the potential of this system and the beneficial effect of AA in heart valve tissue engineering. Copyright © 2015 John Wiley & Sons, Ltd.

Lifestyle modifications supported by regional health nurses lowered insulin resistance, oxidative stress and central blood pressure in subjects with metabolic syndrome

BACKGROUND

This study was attempted to investigate whether lifestyle modifications supported by regional health nurses should improve cardio-metabolic factors--including adipocytokines, oxidative stress, and arterial stiffness--in subjects with metabolic syndrome.

METHODS

Thirty-six subjects with metabolic syndrome were enrolled, 28 of whom completed the 6-month lifestyle modifications (male:female=19:9). Blood and urine test results were examined in relation to metabolic factors before and after 6-month nutritional and physical activity modifications. In addition, oral glucose tolerance tests were performed and arterial stiffness was measured by brachial-ankle pulse wave velocity and radial augmentation index before and after them.

RESULTS

Six-month lifestyle modifications significantly reduced body weight, homeostasis model assessment index, and low-density lipoprotein cholesterol (LDL-C). They significantly attenuated oxidative stress measured by the urinary 8-hydroxy-2-deoxyguanosine/creatinine ratio. They also lowered brachial and central systolic blood pressure. They tended to decrease waist circumferences and the levels of C-reactive protein. However they did not significantly change the levels of adipocytokines, including tumour necrosis factor, soluble tumour necrosis factor receptors, and interleukin 6, or arterial stiffness measured by brachial-ankle pulse wave velocity and radial augmentation index.

CONCLUSIONS

Six-month lifestyle modifications supported by regional health nurses lowered body weight, insulin resistance, LDL-C, oxidative stress, and peripheral and central blood pressure in subjects with metabolic syndrome.

Relationship between HSP70-2 A+1267G Polymorphism and Cardiovascular Events of Chinese Peritoneal Dialysis Patients

BACKGROUND

Heat shock proteins (HSPs) are expressed by cells in response to various environmental stresses. A single-nucleotide polymorphism A+1267G of the HSPA1B gene affects the expression of HSP70-2, with the A allele being protective against inflammatory conditions. We investigated the relation between the HSP A+1267G polymorphism and the clinical outcomes of Chinese peritoneal dialysis (PD) patients.

METHODS

We studied 347 new PD cases (181 males, age 56.6 ± 13.7 years). Genotyping was done by standard methods. Patients were followed for 40.5 ± 20.7 months for survival analysis.

RESULTS

For the entire cohort, there was no difference in the 5-year survival between genotype groups. However, there was a significant interaction between HSP polymorphism and diabetic status on the cardiovascular event-free survival. In patients without pre-existing diabetes, 5-year cardiovascular event-free survival of the GG/AG genotype group was significantly better than that of the AA genotype group (57.2 vs. 32.1%, p = 0.011).

CONCLUSION

The G allele of the HSP70-2 A+1267G polymorphism confers survival advantages in non-diabetic PD patients. The role of HSP in the pathogenesis of cardiovascular disease in renal failure patients needs further investigation.

Cinacalcet may improve oxidative DNA damage in maintenance hemodialysis patients: an observational study

BACKGROUND

Oxidative stress is accepted as a non-classical cardiovascular risk factor in patients on maintenance hemodialysis (HD). The aim of this study was to evaluate the impact of cinacalcet on oxidative stress biomarkers, oxidative DNA damage (8-hydroxy-2'-deoxyguanosine/deoxyguanosine), endothelial function (FMD %) and carotid artery intima-media thickness (CIMT) in HD patients.

METHODS

Forty-two chronic HD patients with secondary hyperparathyroidism undergoing 60 mg/day cinacalcet treatment with a follow-up of 6 months and 38 age- and sex-matched healthy individuals were included in this prospective study. Plasma malondialdehyde (MDA) levels and 8-hydroxy-2'-deoxyguanosine/deoxyguanosine ratio (8-OHdG/dG) were determined as oxidative stress markers. Superoxide dismutase (SOD), paraoxonase (PON), catalase (CAT), carbonic anhydrase (CAN) and glutathione peroxidase (GPx) activities were measured as antioxidants. FMD % and CIMT were assessed by ultrasonography.

RESULTS

MDA levels were decreased; SOD, PON, CAT, CAN and GPx activities were increased after 6 months of cinacalcet treatment in HD patients. Although CIMT remained stabile, there was a significant improvement in FMD % as well as a notable reduction trend in 8-OHdG/dG ratio after 6 months of treatment.

CONCLUSION

Our data have demonstrated that cinacalcet improves oxidative stress, genomic damage, endothelial function and increases antioxidant protection in HD patients after 6 months of treatment.

NOX2-generated oxidative stress is associated with severity of ultrasound liver steatosis in patients with non-alcoholic fatty liver disease

Background

Chronic oxidative stress is one of the key mechanisms responsible for disease progression in non-alcoholic fatty liver disease. However, so far, few studies reported increased circulating levels of oxidative stress markers in patients with non-alcoholic fatty liver and no study has been performed with newer markers of systemic oxidative stress. The aim was to assess the relationship between urinary 8-iso-prostaglandin F2α and serum soluble NOX2-derived peptide and the severity of liver steatosis in subjects with non-alcoholic fatty liver.

Methods

The study was performed in 264 consecutive patients referred for suspected metabolic disease. Steatosis was defined according to Hamaguchi ultrasonographic criteria. Oxidative stress was assessed by urinary 8-iso- prostaglandin F2α and serum soluble NOX2-derived peptide levels.

Results

Patients with non-alcoholic fatty liver had higher (p < 0.001) mean values of urinary 8-iso-PGF2α and of serum soluble NOX2-derived peptide, alanine aminotransferase, Cytokeratin-18 and homeostasis model of insulin resistance and lower values of serum adiponectin as compared to those without. Prevalence of metabolic syndrome and of its clinical features was significantly higher in patients with non-alcoholic fatty liver. Same findings were also observed after the exclusion of obese subjects, or subjects with diabetes or with metabolic syndrome and in those not taking statin medication. In addition, the levels of urinary 8-iso-PGF2α were independent predictors of non-alcoholic fatty liver and a strong association of urinary 8-iso-PGF2α and of serum soluble NOX2-derived peptide with the severity of steatosis at ultrasound was also observed.

Conclusions

We demonstrated increased markers of oxidative stress in subjects with non-alcoholic fatty liver. Urinary 8-iso-PGF2α and serum soluble NOX2-derived peptide levels were independent from obesity, diabetes and metabolic syndrome and increased with the severity of liver steatosis at ultrasound.

Effect of vitamin C on endothelial function in health and disease: a systematic review and meta-analysis of randomised controlled trials

BACKGROUND

Observational studies indicate that higher vitamin C intake is associated with reduced risk for cardiovascular diseases. However, randomised controlled trials (RCT) examining the effect of vitamin C on endothelial function (EF) have reported inconsistent results. The aims of this systematic review and meta-analysis were to determine the effect of vitamin C supplementation on EF and to investigate whether the effect was influenced by health status, study duration, dose and route of vitamin C administration.

METHODS

We searched the Medline, Embase, Cochrane Library, and Scopus databases from inception to May 2013 for studies that met the following criteria: 1) RCT with adult participants, 2) vitamin C administered alone, 3) studies that quantified EF using commonly applied methods including ultrasound, plethysmography and pulse wave analysis.

RESULTS

Pooling the data from 44 clinical trials showed a significant positive effect of vitamin C on EF (SMD: 0.50, 95% CI: 0.34, 0.66, P < 0.001). Stratification of the analysis by health outcome revealed improved EF in atherosclerotic (SMD: 0.84, 95% CI: 0.41, 1.26, P < 0.001), diabetic (SMD: 0.52, 95% CI: 0.21, 0.82, P < 0.001) and heart failure patients (SMD: 0.48, 95% CI: 0.08, 0.88, P < 0.02) after vitamin C supplementation. The effect size appeared to be unaffected by study design, duration, baseline plasma vitamin C concentration or route of administration of vitamin C. The meta-regression showed a significant positive association between vitamin C dose and improvement in EF (β: 0.00011, 95% CI: 0.00001, 0.00021, P = 0.03).

CONCLUSIONS

Vitamin C supplementation improved EF. The effect of vitamin C supplementation appeared to be dependent on health status, with stronger effects in those at higher cardiovascular disease risk. PROSPERO Database registration: CRD42013004567, http://www.crd.york.ac.uk/prospero/

Serum Cytokeratin-18 Is Associated with NOX2-Generated Oxidative Stress in Patients with Nonalcoholic Fatty Liver

Background & Aims. Hepatocyte apoptosis may play a role in progression of nonalcoholic fatty liver and oxidative stress seems one of the key mechanisms responsible for liver damage. The aim was to determine the association of oxidative stress with cytokeratin-18 M30 fragment levels, a marker of hepatocyte apoptosis. Methods. Steatosis severity was defined according to Hamaguchi's echographic criteria in 209 patients with nonalcoholic fatty liver. Serum cytokeratin-18, urinary 8-iso-prostaglandin F2 α , soluble NOX2-derived peptide, and adiponectin were measured. Results. Serum cytokeratin-18 progressively increased with steatosis severity (from 169.5 (129.3/183.8) to 176 (140/190) and 180 (169.5/192.5) μ IU/mL in mild, moderate, and severe steatosis, respectively; P < 0.01). After stratification by cytokeratin-18 tertiles, a significant progression of body mass index, HOMA-IR, triglycerides, urinary 8-iso-PGF2 α , soluble NOX2-derived peptide, and of the prevalence of diabetes and severe steatosis was found, while HDL-cholesterol and adiponectin progressively decreased. A positive correlation between cytokeratin-18 and body mass index, HOMA-IR, Hamaguchi's score, urinary 8-iso-PGF2 α , and soluble NOX2-derived peptide and a negative correlation between cytokeratin-18 and HDL-cholesterol and adiponectin were found. Body mass index, adiponectin, and soluble NOX2-derived peptide were independent predictors of serum cytokeratin-18 levels (adjusted R (2) = 0.36). Conclusion. We support an association between oxidative stress and severity of liver damage in patients with nonalcoholic fatty liver.

Does vitamin C deficiency increase lifestyle-associated vascular disease progression? Evidence based on experimental and clinical studies

SIGNIFICANCE

Despite continuous advances in the prevention of cardiovascular disease (CVD), critical issues associated with an unhealthy lifestyle remain an increasing cause of morbidity and mortality in industrialized countries.

RECENT ADVANCES

A growing body of literature supports a specific role for vitamin C in a number of reactions that are associated with vascular function and control including, for example, nitric oxide bioavailability, lipid metabolism, and vascular integrity.

CRITICAL ISSUES

A large body of epidemiological evidence supports a relationship between poor vitamin C status and increased risk of developing CVD, and the prevalence of deficiency continues to be around 10%-20% of the general Western population although this problem could easily and cheaply be solved by supplementation. However, large intervention studies using vitamin C have not found a beneficial effect of supplementation. This review outlines the proposed mechanism by which vitamin C deficiency worsens CVD progression. In addition, it discusses problems with the currently available literature, including the discrepancies between the large intervention studies and the experimental and epidemiological literature.

FUTURE DIRECTIONS

Increased insights into vitamin C deficiency-mediated CVD progression will enable the design of future randomized controlled trials that are better suited to test the efficacy of vitamin C in disease prevention as well as the identification of high-risk individuals which could possibly benefit from supplementation.

8-hydroxy-2'-deoxyguanosine in colorectal adenocarcinoma--is it a result of oxidative stress?

BACKGROUND

8-hydroxy-2'-deoxyguanosine (8-OHdG) is one of the most abundant oxidatively modified lesions in DNA and is a marker of the oxidative stress. 8-OHdG is a mutagenic lesion and it can mispair with adenine, causing G:C→T: A transversion. Our task was to determine the 8-OHdG level in patients with colorectal adenocarcinoma directly in tumor tissues and corresponding normal mucosa.

MATERIAL/METHODS

Samples of tumor tissues and corresponding normal mucosa of 47 patients undergoing surgery for colorectal cancer were analyzed. DNA was isolated from both tumor and normal tissues. Then, DNA was hydrolyzed to nucleotides using nuclease P1 and alkaline phosphatase. The 8-OHdG and 2'-dG (2'-deoxyguanosine) were determined in hydrolysates by high-performance liquid chromatography (HPLC) with electrochemical (EC) and UV detector.

RESULTS

The levels of 8-OHdG in colorectal adenocarcinoma tissues were higher than in corresponding normal mucosa. No significant differences were shown in 8-OHdG levels in the cancerous and cancer-free tissues between age and sex and stages A/B and C/D of Duke's classification.

CONCLUSIONS

8-OHdG reflects the local oxidative stress in colon adenocarcinoma tissue together with ageing processes, but not the intensity of tumorigenesis itself. Because of many factors that could influence the oxidative modification of DNA bases, its role as a diagnostic and/or prognostic factor in colon adenocarcinoma seems to be limited.

Redox-inflammatory synergy in the metabolic syndrome

Metabolic syndrome (MetS) comprises interrelated disease states including obesity, insulin resistance and type 2 diabetes (T2DM), dyslipidemia, and hypertension. Essential to normal physiological function, and yet massively damaging in excess, oxidative stress and inflammation are pivotal common threads among the pathologies of MetS. Increasing evidence indicates that redox and inflammatory dysregulation parallels the syndrome's physiological, biochemical, and anthropometric features, leading many to consider the pro-oxidative, pro-inflammatory milieu an unofficial criterion in itself. Left unchecked, cross-promotion of oxidative stress and inflammation creates a feed-forward cycle that can initiate and advance disease progression. Such redox-inflammatory integration is evident in the pathogenesis of obesity, insulin resistance and T2DM, atherogenic dyslipidemia, and hypertension, and is thus hypothesized to be the "common soil" from which they develop. The present review highlights the synergistic contributions of redox-inflammatory processes to each of the components of the MetS.

Effects of 5 % weight loss through diet or diet plus exercise on cardiovascular parameters of obese: a randomized clinical trial

OBJECTIVE

To evaluate the effects of 5 % weight loss, through diet only or diet plus exercise, on lipid profile, inflammation and endothelial function in obese individuals.

METHODS

In this randomized clinical trial, 48 obese individuals were randomized to either a diet only group (DI) or a diet and exercise group (DI + EXE). Treatment was maintained until 5 % of the initial body weight was lost. At baseline and upon completion, the following parameters were analyzed: total cholesterol and fractions, triglycerides, fibrinogen, von Willebrand factor, high-sensitive C-reactive protein (hs-CRP) and endothelial function (brachial artery flow-mediated vasodilation-FMD).

RESULTS

Thirteen individuals dropped out before completing the weight loss intervention. The median time required for reduction of 5 % of initial body weight was 79.7 days for the DI group and 65.9 days for the DI + EXE group (P = 0.16). In both DI (n = 18) and DI + EXE (n = 17), total cholesterol (-15.8 ± 4.8 and -10.5 ± 4.9 mg/dL, respectively), triglycerides (-33.8 ± 10.0 and -39.4 ± 10.3 mg/dL, respectively) and hs-CRP (-1.35 ± 0.41 and -0.45 ± 0.43 mg/L, respectively) decreased significantly, and in a similar response (repeated measures ANOVA). Weight loss did not change significantly the fibrinogen and FMD in both groups.

CONCLUSION

A 5 % weight loss improves lipid profile and reduces inflammation in obese individuals. Endothelial function did not change significantly. Weight loss has a significant impact on these cardiovascular risk factors, and this is independent of physical training.

The metabolic syndrome, oxidative stress, environment, and cardiovascular disease: the great exploration

The metabolic syndrome affects 30% of the US population with increasing prevalence. In this paper, we explore the relationship between the metabolic syndrome and the incidence and severity of cardiovascular disease in general and coronary artery disease (CAD) in particular. Furthermore, we look at the impact of metabolic syndrome on outcomes of coronary revascularization therapies including CABG, PTCA, and coronary collateral development. We also examine the association between the metabolic syndrome and its individual component pathologies and oxidative stress. Related, we explore the interaction between the main external sources of oxidative stress, cigarette smoke and air pollution, and metabolic syndrome and the effect of this interaction on CAD. We discuss the apparent lack of positive effect of antioxidants on cardiovascular outcomes in large clinical trials with emphasis on some of the limitations of these trials. Finally, we present evidence for successful use of antioxidant properties of pharmacological agents, including metformin, statins, angiotensin II type I receptor blockers (ARBs), and angiotensin II converting enzyme (ACE) inhibitors, for prevention and treatment of the cardiovascular complications of the metabolic syndrome.

Relationship between 8-hydroxydeoxyguanosine levels in placental/umbilical cord blood and maternal/neonatal obstetric factors

Oxidative stress is associated with the development of various diseases including cancer, arteriosclerosis, diabetes mellitus, hypertension and metabolic syndrome. However, little is known about the involvement of 8-hydroxydeoxyguanosine (8-OHdG) during the perinatal period. At present, few studies have investigated the precise correlations between 8-OHdG levels in cord blood (CB) and the physical conditions of the mother and neonate. To clarify the involvement of 8-OHdG during the perinatal period, the relationships between CB 8-OHdG levels and maternal/neonatal characteristics in vaginal deliveries were determined. The 8-OHdG levels of CB units collected from singleton gestation vaginal deliveries were analyzed. The relationships between 8-OHdG levels and perinatal characteristics were analyzed. The 8-OHdG levels in CB ranged from 0.1 to 1.39 ng/ml (median, 0.37 ng/ml). The relationships between 8-OHdG levels and the perinatal data were analyzed. The 8-OHdG levels detected in the non-smoking group were significantly lower compared to those in the smoking group. However, no significant correlation was observed between 8-OHdG levels and other maternal/ neonatal factors, including umbilical artery acid/base and gas values. Maternal smoking increases the level of the oxidative DNA damage biomarker 8-OHdG in CB. Since oxidative stress may influence the long-term health outcomes of infants after birth, understanding maternal and fetus/neonate stress conditions at delivery may help improve the health of fetuses and infants.

Weight loss is associated with improved endothelial dysfunction via NOX2-generated oxidative stress down-regulation in patients with the metabolic syndrome

The aim of this study was to assess whether adherence to a restricted-calorie, Mediterranean-type diet improves endothelial dysfunction and markers of oxidative stress in patients with metabolic syndrome. A moderately low-calorie (600 calories/day negative energy balance), low-fat, high-carbohydrate diet (<30% energy from fat, <10% from saturated fat and 55% from carbohydrate) was prescribed to 53 outpatients with the metabolic syndrome. Participants were divided into two groups according to body weight loss > or < 5% after 6 months. Group A (n = 23) showed a remarkable decrease in body weight (-6.8%), body-mass-index (-4.6%), waist circumference (-4.8%), HOMA-IR (-27.2%), plasma glucose, glycosylated haemoglobin, total and LDL-cholesterol, blood pressure, serum NOX2 (the catalytic core of NADPH oxidase) (-22.2%) and urinary8-isoprostanes (-39.0%) and an increase of serum NOx (Nitrite/Nitrate) (+116.8%) and adiponectine (+125.5%) as compared with those in group B (n = 30). A statistically significant increase in brachial artery flow-mediated dilatation was observed in group A (+24.7%; p < 0.001), while no changes were present in group B. Variations of flow-mediated dilatation were statistically and negatively correlated with changes of serum NOX2 levels (p = 0.04), body-mass-index (p < 0.01), waist circumference (0.01), glycosylated haemoglobin (p < 0.01), LDL-cholesterol (p < 0.01) and triglycerides (p < 0.05) and positively correlated with changes of serum NOx (p < 0.001) and adiponectin (p = 0.01). The results show that moderate weight loss is able to improve endothelial dysfunction in patients with the metabolic syndrome. The coexistent decrease of NOX2 activation suggests a role for oxidative stress in eliciting artery dysfunction.

Relationship between CRP polymorphism and cardiovascular events in Chinese peritoneal dialysis patients

BACKGROUND AND OBJECTIVES

The single-nucleotide polymorphism (SNP) -717A→G substitution, rs2794521, was found in the promoter of the C-reactive protein (CRP) gene. Functional studies showed that A allele promoter has higher transcriptional activity than the G allele. This study investigated the association between this SNP and the outcome of Chinese patients undergoing peritoneal dialysis (PD).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The study included 441 new PD patients (232 men; mean age ± SD, 56.7±13.5 years). CRP genotyping was determined; patients were followed for 41.3±18.3 months for cardiovascular events.

RESULTS

For the entire cohort, 5-year event-free survival rates did not differ between the AA and AG/GG groups (35.7% and 31.9%, respectively; P=0.64). However, there was significant interaction between plasma cholesterol levels and CRP genotype groups on event-free survival (P=0.04 for interaction). For patients with cholesterol levels of 200 mg/dl or greater, the 5-year event-free survival rate in the AG/GG group was significantly better than that in the AA group (54.7% versus 40.0%; P=0.04), whereas there was no difference in event-free survival between genotype groups for patients with cholesterol levels less than 200 mg/dl.

CONCLUSIONS

CRP gene -717AG or GG genotypes is associated with cardiovascular benefit to Chinese PD patients with cholesterol levels of 200 mg/dl or greater. These findings suggest a complex interaction among cholesterol, CRP, and cardiovascular disease in PD patients.

Accelerated atherosclerosis in haemodialysis patients; correlation of endothelial function with oxidative DNA damage

BACKGROUND

Accelerated atherosclerosis is the major cause of mortality in patients on chronic haemodialysis (HD). The aim of this study was to evaluate the relationship between oxidative DNA damage [8-hydroxy-2'-deoxyguanosine/deoxyguanosine ratio (8-OHdG/dG ratio)], oxidative stress biomarkers and endothelial function in HD patients as an indicator of atherosclerosis.

METHODS

Forty-four chronic HD patients without known atherosclerotic disease and 55 age- and sex-matched healthy individuals were included in the study. Plasma malondialdehyde (MDA) levels and 8-OHdG/dG ratio were determined as oxidative stress markers. Superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities were measured as antioxidants. Endothelial function was assessed by ultrasonography.

RESULTS

8-OHdG/dG ratio and MDA levels were higher in HD patients than controls while SOD and GPx activities were lower in HD patients compared to controls. Flow-mediated dilatation FMD% in HD patients were lower than the control group (7.28 ± 0.79 versus 11.18 ± 0.82, P < 0.001). There was a significant negative correlation between FMD% and 8-OHdG/dG ratio (r = -0.678, P < 0.01) and MDA levels (r = -0.517, P < 0.01), while there was a significant positive correlation between FMD% and SOD (r = 0.538, P < 0.01) and GPx levels (r = 0.720, P < 0.01).

CONCLUSIONS

Our data have demonstrated that HD patients exhibit increased oxidative DNA damage and decreased antioxidant activity. We propose that endothelial function is negatively correlated with 8-OHdG/dG ratio and positively correlated with antioxidant enzymes. To our knowledge, this is the first study to demonstrate the inverse relationship between endothelial function and plasma oxidative DNA damage in HD patients.

Intravenous ascorbic acid infusion improves myocardial perfusion grade during elective percutaneous coronary intervention: relationship with oxidative stress markers

OBJECTIVES

Our goal was to explore whether antioxidant vitamin C infusion is able to affect the microcirculation perfusion in patients undergoing elective percutaneous coronary intervention for stable angina.

BACKGROUND

Periprocedural myocardial injury in the setting of elective percutaneous coronary intervention is associated with increased risk of death, recurrent infarction, and revascularization at follow-up. Despite excellent epicardial blood flow, impaired microcirculatory reperfusion may persist and increases the risk of vascular recurrences. Post-percutaneous coronary intervention induced-oxidative stress is one of the potential mechanisms accounting for impaired perfusion.

METHODS

Fifty-six patients were enrolled in a prospective, single-center, randomized study comparing 1 g vitamin C infusion (16.6 mg/min, over 1 h before percutaneous coronary intervention) versus placebo.

RESULTS

At the baseline, Thrombolysis In Myocardial Infarction (TIMI) myocardial perfusion grade <2 was observed in 89% and in 86% of patients randomized to the placebo or vitamin C infusion group, respectively (p > 0.05). After percutaneous coronary intervention, these percentages decreased in the placebo group (32%) and in greater measure in the vitamin C group (4%, p < 0.01). Complete microcirculatory reperfusion (TIMI myocardial perfusion grade = 3) was achieved in 79% of the vitamin C-treated group compared with 39% of the placebo group (p < 0.01); 8-hydroxy-2-deoxyguanosine (p < 0.002) and 8-iso-prostaglandin F(2alpha) (p < 0.02) plasma levels significantly increased in the placebo group while they were significantly reduced in the vitamin C-treated group (p < 0.0001). TIMI myocardial perfusion grade changes from the baseline showed significant correlation with 8-hydroxy-2-deoxyguanosine (p < 0.006) or 8-iso-prostaglandin F(2alpha) (p < 0.01) plasma levels changes.

CONCLUSIONS

In patients undergoing elective percutaneous coronary intervention, impaired microcirculatory reperfusion is improved by vitamin C infusion suggesting that oxidative stress is implicated in such a phenomenon.

Oxidative stress and endothelial dysfunction: therapeutic implications

In a previous issue of Annals of Medicine, we presented evidence in support of the concept that an abnormally increased production of reactive oxygen species plays a central role in the genesis and progression of cardiovascular disease. While a number of preclinical lines of evidence support this concept, and despite the results of many studies suggesting a beneficial impact of antioxidant drugs on endothelial function, large clinical trials have failed to demonstrate a benefit of antioxidants on cardiovascular outcomes. Studies exploring the possibility that classical antioxidants such as vitamin C, vitamin E, selenium, or folic acid may improve the prognosis of patients with cardiac disease have substantially reported neutral-and occasionally negative-results. In contrast, medications such as statins, ACE inhibitors, certain β-blockers, or angiotensin I receptor blockers, which possess indirect 'ancillary' antioxidant properties, have been associated with beneficial effects in both preclinical studies and large clinical trials. The reasons for the failure of the 'direct' approach to antioxidant therapy, and for the success of the therapy with these drugs, are discussed in the present review.

Metabolic profiling of vitamin C deficiency in Gulo-/- mice using proton NMR spectroscopy

Nutrient deficiencies are an ongoing problem in many populations and ascorbic acid is a key vitamin whose mild or acute absence leads to a number of conditions including the famously debilitating scurvy. As such, the biochemical effects of ascorbate deficiency merit ongoing scrutiny, and the Gulo knockout mouse provides a useful model for the metabolomic examination of vitamin C deficiency. Like humans, these animals are incapable of synthesizing ascorbic acid but with dietary supplements are otherwise healthy and grow normally. In this study, all vitamin C sources were removed after weaning from the diet of Gulo-/- mice (n = 7) and wild type controls (n = 7) for 12 weeks before collection of serum. A replicate study was performed with similar parameters but animals were harvested pre-symptomatically after 2-3 weeks. The serum concentration of 50 metabolites was determined by quantitative profiling of 1D proton NMR spectra. Multivariate statistical models were used to describe metabolic changes as compared to control animals; replicate study animals were used for external validation of the resulting models. The results of the study highlight the metabolites and pathways known to require ascorbate for proper flux.

Roles of adiponectin and oxidative stress in the regulation of membrane microviscosity of red blood cells in hypertensive men-an electron spin resonance study

This study was undertaken to investigate possible relationships among plasma adiponectin, 8-iso-prostaglandin F2α (8-iso-PG F2α: an index of oxidative stress), and membrane fluidity (a reciprocal value of microviscosity) in hypertensive and normotensive men using an electron spin resonance-method. The order parameter (S) for the spin-label agent (5-nitroxide stearate) in red blood cell (RBC) membranes was higher in hypertensive men than in normotensive men, indicating that membrane fluidity was decreased in hypertension. Plasma adiponectin and NO metabolites levels were lower in hypertensive men than in normotensive men. In contrast, plasma 8-iso-PG F2α levels were increased in hypertensive men compared with normotensive men. Plasma adiponectin concentration was correlated with plasma NO-metabolites, and inversely correlated with plasma 8-iso-PG F2α. The order parameter (S) of RBCs was inversely correlated with plasma adiponectin and plasma NO metabolite levels, and positively correlated with plasma 8-iso-PG F2α, suggesting that the reduced membrane fluidity of RBCs might be associated with hypoadiponectinemia, endothelial dysfunction, and increased oxidative stress. In a multivariate regression analysis, adiponectin and 8-iso-PG F2α were significant determinants of membrane fluidity of RBCs after adjustment for general risk factors. These results suggest that adiponectin and oxidative stress might have a close correlation with rheologic behavior and microcirculation in hypertension.

ACE2-angiotensin-(1-7)-Mas axis and oxidative stress in cardiovascular disease

The renin-angiotensin-aldosterone system (RAAS) is a pivotal regulator of physiological homeostasis and diseases of the cardiovascular system. Recently, new factors have been discovered, such as angiotensin-converting enzyme 2 (ACE2), angiotensin-(1-7) and Mas. This newly defined ACE2-angiotensin-(1-7)-Mas axis was shown to have a critical role in the vasculature and in the heart, exerting mainly protective effects. One important mechanism of the classic and the new RAAS regulate vascular function is through the regulation of redox signaling. Angiotensin II is a classic prooxidant peptide that increases superoxide production through the activation of NAD(P)H oxidases. This review summarizes the current knowledge about the ACE2-angiotensin-(1-7)-Mas axis and redox signaling in the context of cardiovascular regulation and disease. By interacting with its receptor Mas, angiotensin-(1-7) induces the release of nitric oxide from endothelial cells and thereby counteracts the effects of angiotensin II. ACE2 converts angiotensin II to angiotensin-(1-7) and, thus, is a pivotal regulator of the local effects of the RAAS on the vessel wall. Taken together, the ACE2-angiotensin-(1-7)-Mas axis emerges as a novel therapeutic target in the context of cardiovascular and metabolic diseases.

Effect of diet-induced weight loss on endothelial dysfunction: early improvement after the first week of dieting

Obesity is associated with impaired endothelial function, and this may lead to increased cardiovascular risk. To gain insight into the beneficial effects of diet-induced weight loss on endothelial function, endothelium-dependent, flow-mediated dilation (FMD) of the brachial artery and several metabolic and inflammatory markers were assessed in 40 obese women (BMI 34.9 ± 4.88 kg/m(2)) at baseline, after the 1st week and after 5 months on a low-calorie diet of 5.0 MJ/day. Twenty lean women served as controls. At entry, the obese women had a lower FMD than the lean women (7.7 ± 1.8 vs. 11.5 ± 4.2%, p < 0.001). After 1 week of the intervention and 4% reduction of BMI, FMD improved by 22% (p = 0.005), and a decrease in circulating triglycerides, insulin, leptin, tissue type plasminogen activator and its inhibitor, von Willebrand factor, C-reactive protein and tumor necrosis factor receptor 1 was observed. Improvement of FMD was associated only with a decrease in BMI (r = 0.39, p = 0.03). Twenty-two women completed the weight reduction program and reduced their BMI by 16%. FMD was further improved by 64% (to 12.4 ± 5.3%, p = 0.001) and became comparable to that of lean women. None of the significant changes in the observed parameters was associated with improvement of FMD at the end of the program. Improvements in obesity-related endothelial dysfunction began in the 1st week of dieting and continued during the following months of this simple non-pharmacological lifestyle modification to reach normalisation of endothelial function. The favourable effect of dieting on endothelial function is independent of the accompanying improvement of classical risk factors.

Oxidative stress and membrane fluidity of red blood cells in hypertensive and normotensive men: an electron spin resonance investigation

Recent evidence indicates that oxidative stress might actively participate in the pathophysiology of hypertension, atherosclerosis, and other cardiovascular diseases. The purpose of the present study was to assess the possible link between oxidative stress and membrane fluidity in hypertensive and normotensive men. We measured the membrane fluidity (a reciprocal value of membrane microviscosity) of red blood cells (RBCs) in hypertensive and normotensive men using an electron spin resonance (ESR) and spin-labeling method. Membrane fluidity of RBCs was decreased in hypertensive men compared with normotensive men. The levels of plasma 8-Iso-prostaglandin F2alpha (8-Iso-PG F2alpha : an index of oxidative stress) were significantly higher in hypertensive men than in normotensive men. In contrast, plasma nitric oxide (NO)-metabolite levels were significantly lower in hypertensive men than in normotensive men. In the overall analysis of hypertensive and normotensive men, plasma 8-Iso-PG F2alpha levels were inversely correlated with plasma NO-metabolites. Furthermore, the reduced membrane fluidity of RBCs was associated with increased plasma 8-Iso-PG F2alpha and decreased plasma NO-metabolite levels. In a multivariate regression analysis, plasma 8-Iso-PG F2alpha was found to be an independent determinant of membrane fluidity of RBCs. The results of the present study suggest that oxidative stress might have a close correlation with the rheologic behavior of RBCs and the microcirculation in hypertensive men.

Increased plasma levels of 8-hydroxydeoxyguanosine are associated with development of colorectal tumors

Increased oxidative stress is generally thought to be associated with tumorigenesis. In this cross-sectional study, we evaluated plasma 8-hydroxydeoxyguanosine (8-OHdG) levels in patients with colorectal adenoma and cancer, as a surrogate marker of oxidative damage to deoxyribonucleic acid (DNA). We collected blood samples from 58 patients with adenoma, 32 with early cancer, 25 with advanced cancer, and 36 without polyps or cancer (as controls), and measured plasma levels of 8-OHdG by enzyme-linked immunosorbent assay. Univariate analysis by logistic regression showed that an increased level of 8-OHdG was a significant risk for adenoma [odds ratio (OR) 1.393, 95% confidence interval (CI) 1.008-1.926, p = 0.045]. In patients with early cancer, univariate analysis revealed significant differences for age, body mass index (BMI), systolic blood pressure, and 8-OHdG level. Subsequent multivariate analysis revealed that 8-OHdG [OR 1.627, 95% CI 1.079-2.453, p = 0.020] and BMI [OR 1.283, 95% CI 1.038-1.585, p = 0.021] were significant risk factors for early cancer. However, 8-OHdG was not a significant risk factor for advanced cancer. Our results suggest that an increased plasma level of 8-OHdG is associated with development of colorectal adenoma and cancer.

Hereditary deficiency of gp91(phox) is associated with enhanced arterial dilatation: results of a multicenter study

BACKGROUND

NADPH oxidase is believed to modulate arterial tone, but its role in humans is still unclear. The objective of this study was to evaluate whether NADPH oxidase is involved in flow-mediated arterial dilation (FMD).

METHODS AND RESULTS

Twenty-five patients with hereditary deficiency of gp91(phox), the catalytic core of NADPH oxidase, (X-CGD), 25 healthy subjects, and 25 obese patients matched for sex and age were recruited. FMD, platelet gp91(phox), serum levels of nitrite and nitrate as markers of nitric oxide generation, oxidized low-density lipoprotein, and urinary excretion of isoprostanes as markers of oxidative stress were determined. Platelet gp91(phox) expression was downregulated in X-CGD patients (1.0+/-0.8 mean fluorescence; P<0.001) and upregulated in obese patients (4.1+/-2.2 mean fluorescence; P=0.01) compared with healthy subjects (2.9+/-1.7 mean fluorescence). Urinary excretion of isoprostanes was reduced in X-CGD patients (41.7+/-33.3 pg/mg creatinine; P=0.04) and increased in obese patients (154.4+/-91 pg/mg creatinine; P<0.001) compared with healthy subjects (69.5+/-52.4 pg/mg creatinine). Obese patients had higher serum oxidized low-density lipoprotein than healthy subjects (35.3+/-6.7 versus 24.8+/-9.8 U/L; P<0.001) and X-CGD patients (28.5+/-7.2 U/L; P<0.001). X-CGD patients had significantly higher FMD (14.7+/-5.9%) compared with healthy subjects (7.9+/-2.5%; P<0.001); obese patients had lower FMD (5.3+/-3.0%; P=0.028) compared with healthy subjects. Serum nitrite and nitrate levels were significantly higher in patients with X-CGD (36.0+/-10.8 micromol/L; P=0.016) and lower in obese patients (9.3+/-11.0 micromol/L; P=0.001) compared with healthy subjects (27.1+/-19.1 micromol/L). Serum nitrite and nitrate levels significantly correlated with FMD (R(s)=0.403, P<0.001) and platelet gp91(phox) (R(s)=-0.515, P<0.001). FMD inversely correlated with platelet gp91(phox) (R(s)=-0.502, P<0.001) and isoprostanes (R(s)=-0.513, P<0.001).

CONCLUSIONS

This study provides the first evidence that, in humans, gp91(phox) is implicated in the modulation of arterial tone.

Role of marginal vitamin C deficiency in atherogenesis: in vivo models and clinical studies

Vitamin C is a pivotal redox modulater in many biological reactions of which several remain poorly understood. Naturally, vitamin C has been the subject of many investigations over the past decades in relation to its possible beneficial effects on cardiovascular disease primarily based on its powerful yet general antioxidant properties. However, growing epidemiological, clinical and experimental evidence now suggests a more specific role of ascorbate in vasomotion and in the prevention of atherosclerosis. For example, in contrast to most other biological antioxidants, administration of vitamin C can apparently induce vasodilation. Millions of people worldwide can be diagnosed with vitamin C deficiency according to accepted definitions. In this perspective, the present review examines the evidence for a specific link between vitamin C deficiency and increased risk of atherosclerosis as well as the possible mechanisms by which vitamin C may exert its protective function.

Protection of vascular cells from oxidative stress by proteasome inhibition depends on Nrf2

AIMS

Increased levels of reactive oxygen species cause oxidative stress and severely damage lipids, proteins, and DNA. We have previously shown that partial proteasome inhibition induces an antioxidative gene pattern in endothelial cells. Here, we elucidate the mechanisms of proteasome inhibitor-mediated upregulation of antioxidative enzymes and cytoprotection.

METHODS AND RESULTS

Non-toxic proteasome inhibition upregulated mRNA and protein expression of superoxide dismutase 1 (SOD1) and haem oxygenase 1 (HO1) in several human endothelial and vascular smooth muscle cell types. Transcriptional activation of these enzymes was shown by inhibition of RNA polymerase II and nuclear run-on assays. Transfection of endothelial cells with luciferase reporter constructs revealed that upregulation can be largely confined to an antioxidant response element (ARE), which proved to be sufficient for transcriptional activation of SOD1 and HO1. Co-transfection studies and bandshift analyses confirmed binding of the antioxidative transcription factor NF-E2-related factor 2 (Nrf2)-which was stabilized by proteasome inhibition as shown by immunoblots-to the ARE site of HO1. Experiments with aortic endothelial and smooth muscle cells from Nrf2 wild-type and knockout mice revealed an essential role of Nrf2: in wild-type cells, proteasome inhibitor-mediated induction of SOD1 and HO1 was accompanied by protection of vascular cells against oxidative stress as determined by lactate dehydrogenase release assays. In contrast, proteasome inhibitor-mediated induction of antioxidative enzymes and cytoprotection were completely lost in cells from Nrf2 knockout mice.

CONCLUSION

Nrf2-dependent transcriptional activation of antioxidative enzymes is crucial for proteasome inhibitor-mediated protection of vascular cells against oxidative stress.

Oxidative stress is associated with arterial dysfunction and enhanced intima-media thickness in children with hypercholesterolemia: the potential role of nicotinamide-adenine dinucleotide phosphate oxidase

BACKGROUND

Endothelial dysfunction and intima-media thickness are precocious manifestations of hypercholesterolemia, but the mechanism is unclear.

OBJECTIVE

The aim of the study was to analyze the interplay among endothelial dysfunction, intima-media thickness, and oxidative stress in children with hypercholesterolemia.

METHODS

We performed a cross-sectional study comparing flow-mediated dilation, intima-media thickness, lipid profile, urinary isoprostanes as markers of oxidative stress, and platelet expression of gp91(phox), the catalytic unit of nicotinamide-adenine dinucleotide phosphate oxidase, in a population of 50 children with hypercholesterolemia (mean age +/- SD: 10.0 +/- 3.7 years) and 50 children without hypercholesterolemia (mean age: 9.2 +/- 3.5 years). Four children with hereditary deficiency of gp91(phox) were studied also.

RESULTS

Children with hypercholesterolemia had reduced flow-mediated dilation (mean +/- SD: 6.2 +/- 2.4 vs 9.2 +/- 2.5%) and enhanced intima-media thickness (0.45 +/- 0.07 vs 0.40 +/- 0.06 mm), urinary isoprostanes (86.9 +/- 51.6 vs 45.9 +/- 25.6 pg/mg creatinine), and gp91(phox) platelet expression (4.4 +/- 3.8 vs 2.0 +/- 1.7 mean fluorescence) compared with control subjects. At bivariate analysis, flow-mediated dilation was correlated with low-density lipoprotein cholesterol, intima-media thickness, urinary isoprostanes, and platelet gp91(phox). Stepwise multiple linear regression analysis showed that, in children with hypercholesterolemia, flow-mediated dilation and intima-media thickness were significantly associated with low-density lipoprotein cholesterol and urinary isoprostanes; also, gp91(phox) platelet expression was an independent predictor of urinary isoprostanes. Children with gp91(phox) hereditary deficiency showed downregulation of platelet gp91(phox) and reduced urinary excretion of isoprostanes.

CONCLUSIONS

The study suggests that gp91(phox)-mediated oxidative stress may have a pathogenic role in the anatomic and functional changes of the arterial wall occurring in children with premature atherosclerosis.

C242T Polymorphism of NADPH Oxidase p22phox and Recurrence of Cardiovascular Events in Coronary Artery Disease

Objectives— The common C242T polymorphism in the gene for the p22phox subunit of NADPH oxidase has been reported to be negatively associated with oxidative stress, but whether it confers prognostic information is not yet clear.

Methods and Results— The incidence of major adverse cardiovascular events (MACE) were determined in 237 patients with coronary stenosis during a median follow-up of 7.8 years. The p22phox genotypes were evaluated in 213 patients (89.9%) by polymerase chain reaction and Rsa I. digestion. Plasma levels of 8-hydroxy-2′-deoxyguanosine (8-OHdG), a marker of oxidative stress, were also measured. In the univariate analysis, patients with CT/TT genotypes showed reduced recurrence of cardiovascular deaths, nonfatal MI, and revascularization procedures compared with homozygous carriers of the C allele. After controlling for confounders, a significantly lower risk of new revascularization procedures (HR=0.31, 95% CI 0.12 to 0.70; P =0.014) remained associated with the T allele. The Kaplan–Meier analysis showed a longer survival free from fatal and nonfatal MI in carriers of T allele ( P <0.001). The presence of the 242T allele was associated with significantly reduced plasma concentrations of 8-OHdG.

Conclusions— The 242T allele was a predictor of lower risk of recurrence of cardiovascular events in high-risk patients and was associated with reduced systemic oxidative stress.