Serum uric acid as a cardiovascular risk factor for heart disease

Sex differences between serum uric acid levels and cardiovascular outcomes in patients with coronary artery disease after stent implantation

Background

The relationship between elevated serum uric acid (SUA) levels and cardiovascular outcomes after stent implantation remains uncertain. This study sought to evaluate the impact of SUA on 12-month cardiovascular outcomes after stent implantation.

Methods

We performed a retrospective study of patients who successfully underwent stent implantation and enrolled 3,222 patients with coronary artery disease (CAD) from a single center. SUA levels were measured before stent implantation. The patients were divided into six groups (<4, 4-4.9, 5-5.9, 6-6.9, 7-7.9 and ≥ 8 mg/dL) at SUA intervals of 1.0 mg/dL. The incidence of cardiovascular outcomes in the six groups was monitored for 1 year after stent implantation and the hazard ratios were estimated. Hazard ratios (HRs) and 95% confidence intervals (95% CIs) for cardiovascular outcomes were estimated using a Cox proportional hazard regression analysis. The primary endpoint was all-cause death. The secondary endpoint was a composite of all-cause death, myocardial infarction, target vessel revascularization, stent thrombosis and stroke. The follow-up duration was 12 months.

Results

Over the 12-month follow-up period, there were 101 all-cause deaths and 218 MACCE. After adjustment for several parameters, the group with SUA levels of more than or equal to 8 mg/dL had significantly higher hazard ratios in the incidence of all-cause death or MACCE. The group with <4.0 mg/dL had significantly higher hazard ratios in all-cause death only in male patients. In contrast, there were no significant differences observed for cardiovascular outcomes in female patients.

Conclusions

Our study identified a U-shaped association between SUA levels and cardiovascular outcomes during 12-month follow-up for males, but not for females. Further studies are warranted to clarify the sex differences between SUA levels and clinical outcomes.

Uric acid in metabolic syndrome: Does uric acid have a definitive role?

Increased serum uric acid (SUA) levels are commonly seen in patients with metabolic syndrome and are widely accepted as risk factors for hypertension, gout, non-alcoholic fatty liver disease, chronic kidney disease (CKD), and cardiovascular diseases. Although some ambiguity for the exact role of uric acid (UA) in these diseases is still present, several pathophysiological mechanisms have been identified such as increased oxidative stress, inflammation, and apoptosis. Accumulating evidence in genomics enlightens genetic variabilities and some epigenetic changes that can contribute to hyperuricemia. Here we discuss the role of UA within metabolism and the consequences of asymptomatic hyperuricemia while providing newfound evidence for the associations between UA and gut microbiota and vitamin D. Increased SUA levels and beneficial effects of lowering SUA levels need to be elucidated more to understand its complicated function within different metabolic pathways and set optimal target levels for SUA for reducing risks for metabolic and cardiovascular diseases.

Role of asymptomatic hyperuricemia in the progression of chronic kidney disease and cardiovascular disease

Previous research has investigated whether hyperuricemia serves as an independent risk factor for cardiovascular and renal diseases. Hyperuricemia is defined as an abnormally high level of uric acid (UA; i.e., serum urate level > 6.8 mg/dL). Hyperuricemia has been considered a complication of chronic kidney disease (CKD). However, it seems to play a pathogenic role in the progression of renal diseases. There has been increasing focus on the link between hyperuricemia and CKD. The results of randomized controlled trials have implied independent associations between hyperuricemia and the progression of cardiovascular and renal morbidities. These associations may be mediated by renin-angiotensin system activation, nitric oxide synthase inhibition, and macrovascular/microvascular disease development. There remains controversy regarding the use of serum UA level as an indirect index of renal vascular disease. This literature review focuses on the role of asymptomatic hyperuricemia in the progression of CKD, as well as the association between hyperuricemia and cardiovascular disease. It also provides a general overview of the physiological metabolism of UA.

Relationship between serum uric acid levels and the incidence of cardiovascular events after percutaneous coronary intervention

BACKGROUND

The role of serum uric acid (SUA) as an independent risk factor for coronary artery disease remains unclear. The aim of this study was to investigate whether the SUA levels could affect the incidence of major adverse cardiac events (MACE) after percutaneous coronary intervention (PCI).

METHODS AND RESULTS

We retrospectively examined the clinical records of 1,949 patients who underwent successful PCI. First, they were divided into two groups based on an SUA level of 7.0mg/dl. Among the two groups, the incidence of MACE was measured for a maximum of 5 years after PCI. Next, we divided them into 6 groups at SUA intervals of 1.0mg/dl and estimated the hazard ratios of each group. The Kaplan-Meier curve demonstrated that patients with SUA levels of >7.0mg/dl had a higher incidence of MACE than those with 7.0mg/dl or less. However, according to the multivariate analysis, the SUA level was not significantly correlated with the incidence of MACE because other factors could strongly affect it. Meanwhile, the group with SUA levels between 4.1-5.0mg/dl had a lower hazard ratio compared to groups with SUA levels of more than 5.1mg/dl. However, the hazard ratio of the group with SUA levels of 4.0mg or less was not lower than that of the group with SUA levels of 4.1-5.0mg/dl. Even after adjustment for several parameters, nearly the same results before adjustment were obtained for the hazard ratios of each group.

CONCLUSION

The present study demonstrated that the SUA level was one of the most valuable predictors of cardiovascular events after PCI, with elevated SUA levels adversely affecting secondary prevention.

The IDF Definition Is Better Suited for Screening Metabolic Syndrome and Estimating Risks of Diabetes in Asian American Adults: Evidence from NHANES 2011-2016

OBJECTIVE

extensive effort has been made to better define metabolic syndrome (MetS). Whether current definitions accurately diagnose MetS and predict risk of cardiovascular disease (CVD) or diabetes in diverse ethnic groups remains largely unknown. The objective of this study was to compare the prevalence of MetS and risk of CVD and diabetes among Asian American adults using two MetS definitions, one proposed by the Third Report of the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (ATP III) and one by the International Diabetes Federation (IDF).

METHODS

we obtained a nationally representative sample of 2121 Asian American adults in the noninstitutionalized civilian population of the United States from the National Health and Nutrition Examination Survey (2011-2016). We computed age-adjusted, gender-specific MetS prevalence and each MetS component using ATP III and IDF definitions.

RESULTS

based on the IDF definition, MetS prevalence was 39.26% among Asian American men and 39.66% among Asian American women included in the study sample. Based on the ATP III definition, MetS prevalence in our sample was 39.38% among men and 36.11% among women. We found good concordance between the IDF and the ATP III definitions in identifying MetS in Asian American adults. Those with MetS defined only by the IDF definition had significantly higher body mass index (BMI) and waist circumference than those with MetS defined only by the ATP III definition. The IDF definition also better predicted elevated fasting insulin.

CONCLUSIONS

the IDF definition is more pertinent than the ATP III definition for screening and estimating risk of CVD and diabetes in Asian American adults. Future studies should examine differences in MetS prevalence across Asian ethnic groups to facilitate the development of culturally tailored strategies improve MetS prevention and detection in Asian Americans.

Precipitation of Soluble Uric Acid Is Necessary for In Vitro Activation of the NLRP3 Inflammasome in Primary Human Monocytes

OBJECTIVE

To investigate the effects of soluble uric acid (UA) on expression and activation of the NOD-like receptor (NLR) pyrin domain containing protein 3 (NLRP3) inflammasome in human monocytes to elucidate the role of hyperuricemia in the pathogenesis of gout.

METHODS

Primary human monocytes and the THP-1 human monocyte cell line were used to determine the effects of short- and longterm exposure to UA on activation of the NLRP3 inflammasome and subsequent interleukin 1β (IL-1β) secretion by ELISA and cell-based assays. Expression of key NLRP3 components in monocytes from patients with a history of gout were analyzed by quantitative PCR.

RESULTS

Precipitation of UA was required for activation of the NLRP3 inflammasome and subsequent release of IL-1β in human monocytes. Neither monosodium urate (MSU) crystals nor soluble UA had any effect on activation of the transcription factor, nuclear factor-κB. Prolonged exposure of monocytes to soluble UA did not alter these responses. However, both MSU crystals and soluble UA did result in a 2-fold increase in reactive oxygen species. Patients with gout (n = 15) had significantly elevated serum UA concentrations compared to healthy individuals (n = 16), yet secretion of IL-1β and expression of NLRP3 inflammasome components in monocytes isolated from these patients were not different from those of healthy controls.

CONCLUSION

Despite reports indicating that soluble UA can prime and activate the NLRP3 inflammasome in human peripheral blood mononuclear cells, precipitation of soluble UA into MSU crystals is essential for in vitro NLRP3 signaling in primary human monocytes.

Dynamic changes in purine catabolism in patients with acute coronary syndrome that underwent percutaneous coronary intervention

BACKGROUND

Cardiovascular diseases are global problems. They are causes of death in about 43% of people worldwide and may become the most widespread reason of death by 2020. The prognosis is directly dependent to immediate diagnosis and on time treatment. Introduction of new biochemical markers as the early diagnosis of complications after coronary revascularization is very important in this period. Herein, we assayed the changes of purine catabolites in patients with acute coronary syndrome (ACS) before and after percutaneous coronary intervention (PCI) in comparison with control group.

METHODS

Thirty five ACS patients (20 males and 15 females) were included (57±17 years old) in the study. The determination of intermediates of purine catabolism as guanine, hypoxanthine (GCS), adenine, xanthine (Kc) and uric acid (MK) were assayed before and 3 days after PCI. Conditionally, 35 healthy-matched persons were included in the control group. Purine catabolites were determined in plasma through the method of Oreshnikov E.V (2008).

RESULTS

In ACS patients, prior to PCI, there was a tendency to increase the concentration of guanine (P=0.001), hypoxanthine (P=0.002) adenine (P=0.0003), xanthine (P=0.000003) and uric acid (P=-0.000001) relative to the upper limits of normal ranges. And on the third day after PCI, there was the second tendency to increase the levels of guanine (P=0.000001), hypoxanthine (P=0.000001) adenine (P=0.0000001), xanthine (P=0.000001) and uric acid (P=0.0000001) relative to upper limits of normal ranges.

CONCLUSION

Increment of plasma purine catabolites can be a marker of inflammation and instability of coronary artery plaques and may be used as a restenosis marker in patients with history of PCI.

Serum Uric Acid as an Independent Risk Factor for the Presence and Severity of Early-Onset Coronary Artery Disease: A Case-Control Study

Serum uric acid (UA) is the final product of purine metabolism in humans. The present study is aimed at identifying the potential association between serum UA and early-onset coronary artery disease (EOCAD). The study population consisted of 1093 EOCAD patients aged ≤50 years, and 1117 age- and sex-matched apparently healthy people served as controls. The concentrations of UA were measured by uricase method. The severity of CAD was evaluated by Gensini score. The mean serum level of UA was 5.843 ± 1.479 mg/dl in EOCAD patients and 5.433 ± 1.529 mg/dl in controls. Serum UA levels were significantly higher in the EOCAD group than those in the control group (P < 0.001) and was an independent risk factor for EOCAD (OR = 1.100, 95% CI: 1.022–1.185). The early-onset myocardial infarction patients with 3-vessel disease had higher serum UA levels than those with 1- or 2-vessel disease. The serum UA levels of EOCAD patients with acute coronary syndrome were significantly higher than those with chronic coronary artery disease. EOCAD patients with hyperuricemia had higher Gensini scores than those without hyperuricemia. In addition, the serum UA levels were affected by drinking (P < 0.01) and were positively correlated with serum creatinine (r = 0.323) and weight (r = 0.327). Our results show that serum UA was an independent risk factor for EOCAD. The serum UA levels were associated with the presence and severity of EOCAD and suggested that UA may be involved in the progression of EOCAD.

Prevalence of peripheral artery disease (PAD) and factors associated: An epidemiological analysis from the population-based Screening PRE-diabetes and type 2 DIAbetes (SPREDIA-2) study

AIM

To describe the prevalence of Peripheral Artery Disease (PAD) in a random population sample and to evaluate its relationship with Mediterranean diet and with other potential cardiovascular risk factors such as serum uric acid and pulse pressure in individuals ranged 45 to 74 years.

METHODS

Cross-sectional analysis of 1568 subjects (mean age 6.5 years, 43% males), randomly selected from the population. A fasting blood sample was obtained to determine glucose, lipids, and HbA1C levels. An oral glucose tolerance test was performed in non-diabetic subjects. PAD was evaluated by ankle-brachial index and/or having a prior diagnosis.

RESULTS

PAD prevalence was 3.81% (95% CI, 2.97-4.87) for all participants. In men, PAD prevalence was significantly higher than in women [5.17% (95% CI, 3.74-7.11) vs. 2.78% (95% CI, 1.89-4.07); p = 0.014]. Serum uric acid in the upper quartile was associated with the highest odds ratio (OR) of PAD (for uric acid > 6.1 mg/dl, OR = 4.31; 95% CI, 1.49-12.44). The remaining variables more strongly associated with PAD were: Heart rate >90 bpm (OR = 4.16; 95%CI, 1.62-10.65), pulse pressure in the upper quartile (≥ 54 mmHg) (OR = 3.82; 95%CI, 1.50-9.71), adherence to Mediterranean diet (OR = 2.73; 95% CI, 1.48-5.04), and former smoker status (OR = 2.04; 95%CI, 1.00-4.16).

CONCLUSIONS

Our results show the existence of a low prevalence of peripheral artery disease in a population aged 45-74 years. Serum uric acid, pulse pressure and heart rate >90 bpm were strongly associated with peripheral artery disease. The direct association between Mediterranean diet and peripheral artery disease that we have found should be evaluated through a follow-up study under clinical practice conditions.

Hyperuricemia, Cardiovascular Disease, and Hypertension

In recent years, there has been an increase in the prevalence of hyperuricemia, and the latter has attracted attention as an adult lifestyle-associated disease, together with hypertension, diabetes, and dyslipidemia. Although hyperuricemia is known to be an independent risk factor for hypertension, whether it is an independent risk factor for cardiovascular disease remains controversial. Recently, some small-scale interventional studies on antihyperuricemic medications showed that the latter improved angina symptoms and prevented cardiovascular disease. Here, we will mainly explain the cause of hyperuricemia and the associations between hyperuricemia, hypertension, and cardiovascular disease based on the latest published evidence.

Serum uric acid plays a protective role for bone loss in peri- and postmenopausal women: a longitudinal study

OBJECTIVE

Oxidative stress has been linked to osteoporosis. Serum uric acid (UA), a strong endogenous antioxidant, has been associated with higher bone mineral density (BMD), lower bone turnover and lower prevalence of fractures in a large cross-sectional study of men. Whether this relationship is present in women and how UA relates to changes in BMD longitudinally has not been examined.

METHODS

A sample of 356 peri- and postmenopausal women, mean age 60.5 years was studied. Each individual had baseline BMD and body composition measurements by dual energy x-ray absorptiometry (DXA) and at least one repeat measure, on average 9.7 years later. Annual rate of change in BMD (A%ΔBMD) was calculated. UA was measured at each DXA visit. Calciotropic hormones and bone turnover markers were measured at the final visit only.

RESULTS

Cross-sectional data analyses revealed that women with higher UA levels had significantly higher absolute BMD measures at all skeletal sites. These women also had higher measures of body weight and its components such as lean mass (LM) and fat mass (FM). Results of multiple regression analyses showed a positive association between UA and BMD that remained significant even after accounting for possible confounders including LM and FM. Regression analyses of the longitudinal BMD data demonstrated significant associations between serum UA levels and annual rates of change in BMD at all skeletal sites. After adjustment associations remained significant for lumbar spine, forearm and whole body BMD but not for hip BMD.

CONCLUSION

Higher serum UA levels appear to be protective for bone loss in peri- and postmenopausal women and this relationship is not affected by changes in body composition measures.

Serum uric acid is an independent risk factor for cardiovascular disease and mortality in hypertensive patients

The purpose of the study was to investigate the association of serum uric acid (UA) levels in hypertensive patients with the prognosis for cardiovascular disease (CVD) and mortality. This hospital-based cohort study included 669 patients with essential hypertension. A questionnaire was used to identify patients in whom hypertensive complications had occurred, as well as causes of death. The primary end point of this study was new onset of stroke or CVD (new onset of angina pectoris, myocardial infarction or heart failure). We evaluated the baseline characteristics of patients, including UA levels, and assessed whether UA levels could be used to predict stroke and CVD. We also classified subjects into four groups according to the serum UA levels. During a mean follow-up period of 7.1±0.1 years, 71 strokes, 58 cases of CVD and 64 deaths were recorded. Kaplan-Meier analysis revealed that subjects in the high UA group had a higher frequency of stroke and CVD (P=0.0120) and total mortality (P=0.0021). A Cox proportional hazard model determined that, after adjusting for traditional risk factors, serum UA levels were predictive of CVD (relative risk=1.30; P=0.0073), stroke and CVD (relative risk=1.19; P=0.0141), mortality (relative risk=1.23; P=0.0353) and stroke CVD and mortality (relative risk=1.19; P=0.0083), but not stroke (P=0.4268). The significant correlations were particularly marked in women. Serum UA levels may be an independent risk factor for stroke and CVD in patients with essential hypertension, particularly women.

Hyperuricemia and its related factors in an urban population, Izmir, Turkey

The aim of this study was to examine the prevalence of hyperuricemia and its associated factors in an urban area of Izmir, located in western Turkey. Our study group was selected by computerized sampling from the participants of a larger population-based study searching for the prevalence of rheumatoid arthritis in Balcova and Narlidere districts of Izmir. A total of 132 subjects (69 women and 63 men) were included in this study. Serum uric acid, glucose, creatinine and lipid levels were studied. Body composition along with body fat percentage was determined anthropometrically. A total of 16 subjects had hyperuricemia (4 women and 12 men). The overall prevalence of hyperuricemia was 12.1% and the mean uric acid level was 4.9 +/- 1.3 mg/dl. Males had significantly higher uric acid levels than females (P < 0.05; 5.5 +/- 1.3 vs. 4.3 +/- 1.1 mg/dl, respectively). The prevalence of hypertension, diabetes, obesity and metabolic syndrome was 24.4, 5.3, 28 and 26.5%, respectively. There was no gouty subject. Sum of skinfold thickness (SFT) measurements and creatinine levels were the independent predictors of hyperuricemia (beta = 0.45, 0.47, respectively). Uric acid measurement is important not only for inflammatory rheumatic disorders but also for predicting metabolic syndrome and related coronary artery disease. There is sex difference in uric acid levels in favor of women most probably explained by gonadal hormones. Hyperuricemia is significantly predicted by anthropometric measure of SFT which is a simple clinical screening method along with creatinine levels.

Distinct roles of Nox1 and Nox4 in basal and angiotensin II-stimulated superoxide and hydrogen peroxide production

NADPH oxidases are major sources of superoxide (O2*-) and hydrogen peroxide (H2O2) in vascular cells. Production of these reactive oxygen species (ROS) is essential for cell proliferation and differentiation, while ROS overproduction has been implicated in hypertension and atherosclerosis. It is known that the heme-containing catalytic subunits Nox1 and Nox4 are responsible for oxygen reduction in vascular smooth muscle cells from large arteries. However, the exact mechanism of ROS production by NADPH oxidases is not completely understood. We hypothesized that Nox1 and Nox4 play distinct roles in basal and angiotensin II (AngII)-stimulated production of O2*- and H2O2. Nox1 and Nox4 expression in rat aortic smooth muscle cells (RASMCs) was selectively reduced by treatment with siNox4 or antisense Nox1 adenovirus. Production of O2*- and H2O2 in intact RASMCs was analyzed by dihydroethidium and Amplex Red assay. Activity of NADPH oxidases was measured by NADPH-dependent O2*- and H2O2 production using electron spin resonance (ESR) and 1-hydroxy-3-carboxypyrrolidine (CPH) in the membrane fraction in the absence of cytosolic superoxide dismutase. It was found that production of O2*- by quiescent RASMC NADPH oxidases was five times less than H2O2 production. Stimulation of cells with AngII led to a 2-fold increase of O2*- production by NADPH oxidases, with a small 15 to 30% increase in H2O2 formation. Depletion of Nox4 in RASMCs led to diminished basal H2O2 production, but did not affect O2*- or H2O2 production stimulated by AngII. In contrast, depletion of Nox1 in RASMCs inhibited production of O2*- and AngII-stimulated H2O2 in the membrane fraction and intact cells. Our data suggest that Nox4 produces mainly H2O2, while Nox1 generates mostly O2*- that is later converted to H2O2. Therefore, Nox4 is responsible for basal H2O2 production, while O2*- production in nonstimulated and AngII-stimulated cells depends on Nox1. The difference in the products generated by Nox1 and Nox4 may help to explain the distinct roles of these NADPH oxidases in cell signaling. These findings also provide important insight into the origin of H2O2 in vascular cells, and may partially account for the limited pharmacological effect of antioxidant treatments with O2*- scavengers that do not affect H2O2.

Development of High-specificity Antibodies against Renal Urate Transporters Using Genetic Immunization

Recently three proteins, playing central roles in the bidirectional transport of urate in renal proximal tubules, were identified: two members of the organic anion transporter (OAT) family, OAT1 and OAT3, and a protein that designated renal urate-anion exchanger (URAT1). Antibodies against these transporters are very important for investigating their expressions and functions. With the cytokine gene as a molecular adjuvant, genetic immunization-based antibody production offers several advantages including high specificity and high recognition to the native protein compared with current methods. We fused high antigenicity fragments of the three transporters to the plasmids pBQAP-TT containing T-cell epitopes and flanking regions from tetanus toxin, respectively. Gene gun immunization with these recombinant plasmids and two other adjuvant plasmids, which express granulocyte/ macrophage colony-stimulating factor and FMS-like tyrosine kinase 3 ligand, induced high level immunoglobulin G antibodies, respectively. The native corresponding proteins of URAT1, OAT1 and OAT3, in human kidney can be recognized by their specific antibodies, respectively, with Western blot analysis and immunohistochemistry. Besides, URAT1 expression in Xenopus oocytes can also be recognized by its corresponding antibody with immuno-fluorescence. The successful production of the antibodies has provided an important tool for the study of UA transporters.

Molecular-specific effects of angiotensin II antagonists: clinical relevance to treating hypertension?

Angiotensin II receptor blockers (ARBs) may produce a number of molecule-specific effects that appear to be independent of interaction with the angiotensin II type 1 (AT1)-receptor. These include antagonism of the thromboxane A2 receptor, inhibition of platelet aggregation, induction of peroxisome proliferator- activated receptor gamma (PPARgamma) activity, and reduction of serum uric acid levels. However, definitive evidence is lacking that these molecule-specific effects give rise to a therapeutic advantage of one ARB over another. Currently, the possibility of a link between a molecule-specific effect of an ARB and an improvement in clinical outcomes is best illustrated by a reduction in serum uric acid levels with losartan. Data from Losartan Intervention For Endpoint reduction in hypertension (LIFE) study suggest a treatment-induced decrease in serum uric acid may contribute to the treatment benefit of a losartan-based versus atenolol-based therapy on the composite endpoint (death, myocardial infarction, or stroke). This finding should prompt further studies to investigate the long-term cardioprotective benefits issue of reducing hyperuricaemia in hypertensive patients.

Interactions of peroxynitrite with uric acid in the presence of ascorbate and thiols: implications for uncoupling endothelial nitric oxide synthase

It has been suggested that uric acid acts as a peroxynitrite scavenger although it may also stimulate lipid peroxidation. To gain insight into how uric acid may act as an antioxidant, we used electron spin resonance to study the reaction of uric acid and plasma antioxidants with ONOO-. Peroxynitrite reacted with typical plasma concentrations of urate 16-fold faster than with ascorbate and 3-fold faster than cysteine. Xanthine but not other purine-analogs also reacted with peroxynitrite. The reaction between ONOO- and urate produced a carbon-centered free radical, which was inhibited by either ascorbate or cysteine. Moreover, scavenging of ONOO- by urate was significantly increased in the presence of ascorbate and cysteine. An important effect of ONOO- is oxidation of tetrahydrobiopterin, leading to uncoupling of nitric oxide synthase. The protection of eNOS function by urate, ascorbate and thiols in ONOO(-)-treated bovine aortic endothelial cells (BAECs) was, therefore, investigated by measuring superoxide and NO using the spin probe 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethyl-pyrrolidine (CMH) and the NO-spin trap Fe[DETC]2. Peroxynitrite increased superoxide and decreased NO production by eNOS indicating eNOS uncoupling. Urate partially prevented this effect of ONOO- while treatment of BAECs with the combination of either urate with ascorbate or urate with cysteine completely prevented eNOS uncoupling caused by ONOO-. We conclude that the reducing and acidic properties of urate are important in effective scavenging of peroxynitrite and that cysteine and ascorbate markedly augment urate's antioxidant effect by reducing urate-derived radicals.

Mediterranean vegetable soup consumption increases plasma vitamin C and decreases F2-isoprostanes, prostaglandin E2 and monocyte chemotactic protein-1 in healthy humans

Consumption of fruits and vegetables is associated with a reduced risk of death from all causes including heart disease and stroke. In this work, the bioavailability of vitamin C from a Mediterranean vegetable soup (gazpacho) constituted mainly of tomato, pepper and cucumber, and its influence on plasma vitamin C, 8-epi-prostaglandin F(2alpha) (8-epi-PGF2alpha), prostaglandin E2 (PGE2), monocyte chemotactic protein-1 (MCP-1), and the cytokines/tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and IL-6 concentrations in a healthy human population were assessed. Six men and six women consumed 500 ml of commercial gazpacho per day for 14 days, corresponding to an intake of 78 mg of ascorbic acid per day. There were no differences (P = .22) in baseline plasma vitamin C concentrations between the men and women. The maximum increase (P < .05) in plasma vitamin C occurred 4 h postdose in both men and women. Vitamin C concentrations were significantly higher (P < .03) on Days 7 and 14 of the intervention. Baseline concentrations of uric acid and 8-epi-PGF2alpha were significantly higher (P < or = .032) in men than in women. Baseline concentrations of 8-epi-PGF2alpha decreased significantly (P < or = .05) by Day 14 of the intervention. A significant inverse correlation was observed between vitamin C and 8-epi-PGF2alpha (r = -.415, P = .049). Baseline concentrations of PGF2 and MCP-1 were significantly higher (P< or = .025) in men than in women but decreased significantly (P< or = .05) by Day 14 of the intervention. No effect on TNF-alpha, IL-1beta and IL-6 was observed at Day 14 of the intervention. Drinking gazpacho (500 ml/day) significantly increases plasma concentrations of vitamin C and significantly decreases 8-epi-PGF2alpha, PGE2 and MCP-1 concentrations in healthy humans.

Does asymptomatic hyperuricaemia contribute to the development of renal and cardiovascular disease? An old controversy renewed

Recent studies in both humans and experimental animals have led to renewed interest in uric acid and its association with hypertension, cardiovascular events and renal disease progression. This has also refuelled a longstanding debate regarding the precise role of this ubiquitous breakdown product of purine metabolism in these disease processes. Various lines of evidence suggest that uric acid may have a direct role in the pathogenesis of hypertension and vascular disease. Regardless of this possibility, it is apparent that serum uric acid levels serve as a powerful 'biomarker' or independent predictor of prognosis and outcome in certain renal, cardiovascular and cerebrovascular diseases. Whether these outcomes can be improved by specifically treating asymptomatic hyperuricaemia remains inadequately resolved at this stage. Data from various animal studies suggests that lowering uric acid levels may be of benefit, but the crucial human studies are still lacking. This review will examine some of the recent evidence supporting a causal and contributory role for uric acid in cardiovascular and renal disease. How clarification of the role of uric acid may guide future treatment strategies will also be discussed.

Effect of orange juice intake on vitamin C concentrations and biomarkers of antioxidant status in humans

BACKGROUND

Consumption of fruit and vegetables is associated with improved health and a decreased prevalence of chronic degenerative processes.

OBJECTIVES

The objectives were to assess the bioavailability of vitamin C from orange juice and its influence on plasma vitamin C and 8-epi-prostaglandin F(2 alpha) (8-epi-PGF(2 alpha)) concentrations in a healthy human population.

DESIGN

Six men and 6 women consumed 500 mL commercial fresh-squeezed orange juice/d for 14 d, corresponding to an intake of 250 mg ascorbic acid/d. On the first day of the study, the subjects drank the juice in one dose (dose-response study), and on days 2-14 they consumed 250 mL in the morning and 250 mL in the afternoon. Blood was collected every hour for 6 h on the first day and again on days 7 and 14.

RESULTS

Baseline plasma vitamin C concentrations were significantly higher (P = 0.03) among the women than among the men (56.4 +/- 4.4 compared with 44.3 +/- 3.5 micromol/L). In the dose-response study, the maximum increase in plasma vitamin C occurred 3 h postdose in both the men and the women. Vitamin C concentrations remained significantly higher on days 7 and 14 than at baseline. Baseline concentrations of 8-epi-PGF(2 alpha) were significantly higher (P = 0.03) among the men than among the women (249.6 +/- 25.4 compared with 177.7 +/- 6.2 pg/mL) but decreased significantly (P = 0.04) by day 14 of the intervention. A significant inverse correlation was observed between vitamin C and 8-epi-PGF(2 alpha) (r = -0.791, P = 0.0022). Among smokers, baseline vitamin C was lower and 8-epi-PGF(2 alpha) higher than among nonsmokers.

CONCLUSIONS

Drinking orange juice (500 mL/d) increases plasma concentrations of vitamin C and reduces concentrations of 8-epi-PGF(2 alpha) in humans. These effects were significantly more pronounced in smokers.

Serum uric acid in hypertensive patients with and without peripheral arterial disease

BACKGROUND

Uric acid is frequently elevated in hypertension. In addition to renal and metabolic disturbances, lower limb ischemia might contribute to hyperuricemia among hypertensives complicated by peripheral arterial disease (PAD).

OBJECTIVE

To test the hypothesis that uric acid status is related to lower limb function in hypertensives with PAD.

METHODS

Serum and 24-h urine uric acid levels and other risk factors were examined in 145 hypertensives free of PAD and 166 hypertensives with PAD. Ankle/brachial index (ABI) and absolute claudication distance (in PAD) on a treadmill test (ACD) were assessed.

RESULTS

In multiple regression analysis for serum uric acid in the total group, PAD emerged as an independent determinant (P=0.03) next to age (P=0.005), triglycerides (P=0.04), and insulin (P=0.02). Serum uric acid concentrations were higher in hypertensives with PAD (404+/-101 vs. 347+/-80 micromol/l, P<0.001) independent of components of the metabolic syndrome (body mass index, triglycerides, insulin) and of age, gender, diabetes mellitus, pulse pressure, cholesterol, C-reactive protein, and treatment. After adjustment for kidney function by uric acid/creatinine ratio, values remained higher in hypertensives with PAD (P=0.01). Uric acid excretion was higher in the PAD group (P<0.001), whereas uric acid clearance was comparable between both groups. In multiple regression analysis for ACD (357+/-183 m) in the PAD group, serum uric acid (P=0.02), C-reactive protein (P<0.0001), age (P=0.02), and smoking (P=0.004) were independently associated. ABI (0.62+/-0.17) was not related to uric acid in PAD patients.

CONCLUSION

Hyperuricemia is more pronounced in hypertensives complicated by PAD and is associated with worse functional status of the peripheral circulation.

Part 1. Uric acid and losartan

PURPOSE OF REVIEW

To characterize the mechanism and clinical impact of the angiotensin-receptor blocker losartan on both renal uric acid handling and thereby serum uric acid.

RECENT FINDINGS

Losartan effect on serum uric acid has been demonstrated at various stages of renal failure including most recently observations obtained in end-stage renal disease patients. Other angiotensin-receptor blockers do not alter renal handling of uric acid. The uricosuria, which accompanies losartan administration, has not been associated with adverse renal consequences, in part, because of the increase in urinary pH that follows its administration.

SUMMARY

Hyperuricemia is closely linked to both hypertension and cardiovascular disease. The development of hyperuricemia and its persistence are clearly renal processes. Likewise, the correction of hyperuricemia is often accomplished by increasing its renal excretion. A number of medications, by way of varying mechanisms, can alter renal urate handling and thereby influence serum uric acid values. Most recently, the angiotensin-receptor blocker losartan has been shown to reduce serum uric acid. The mechanism of this process relates to losartan alone and does not involve the E-3174 metabolite of this compound. This probenecid-like effect of losartan occurs shortly after drug administration, and is both transient and dose-dependent. This property of losartan, touted by some as a meaningful pharmacological distinction among the angiotensin-receptor blockers, remains to be proved, since, to date, the hypothesis that a reduction in serum uric acid alters the natural history of cardiovascular disease has not been formally tested.