Serum uric acid and cardiovascular events in successfully treated hypertensive patients

Relation between serum uric acid and carotid intima-media thickness in healthy postmenopausal women

OBJECTIVE

Serum uric acid (SUA) is associated with cardiovascular disease (CVD). However it is still disputed whether the relationship is mediated by other risk factors such as obesity, dyslipidaemia, hypertension and insulin resistance. We explored the association of the uric acid level with carotid intima-media thickness (IMT), a well known marker of CVD, in postmenopausal healthy women.

METHODS

We consecutively enrolled postmenopausal women undergoing a screening for health evaluation. After an accurate clinical examination, and a biochemical evaluation, the enrolled subjects underwent B mode ultrasonography to assess common carotid intima media thickness.

RESULTS

Among 234 women aged 45-70 years, the uric acid level is associated with carotid IMT independently of other prognostic factors (p=0.03). In particular, women in the highest tertiles of uric acid level have a greater IMT than women in the lowest tertile (p=0.007).

CONCLUSIONS

Independently of other cardiovascular risk factors, SUA levels are associated with carotid IMT even in subjects without the metabolic syndrome. This confirms and expands the role of uric acid in the determinism of CVD. Prospective trials would be useful to evaluate interventions aimed at lowering the uric acid level.

Association between serum uric acid level and peripheral arterial disease

BACKGROUND

Higher serum uric acid levels have been implicated in the development and progression of atherosclerotic cardiovascular disease. However, it is not clear whether serum uric acid levels are related to subclinical measures of cardiovascular disease, including peripheral arterial disease (PAD). We examined the association between increasing serum uric acid levels and PAD in the US general population.

METHODS

A cross-sectional study was conducted among 3987 National Health and Nutrition Examination Survey 1999-2002 participants aged > or =40 years, without clinical history of cardiovascular disease. Main outcome-of-interest was PAD defined as ankle-brachial index <0.9 (n=229).

RESULTS

Higher serum uric acid levels were positively associated with PAD, independent of smoking, body mass index (BMI), hypertension, diabetes, serum total cholesterol, serum creatinine, and other confounders. Multivariable odds ratio (OR) [95 percent confidence intervals (CI)] comparing serum uric acid levels > or =75th percentile (> or =380.8 micromol/L) to uric acid levels <50th percentile (<315.6 micromol/L) was 1.62 (1.08-2.44), p-trend=0.015. This association persisted in separate analysis among men and women. Further, the results were consistent in subgroup analyses by categories of age, current smoking, BMI, and diabetes mellitus.

CONCLUSIONS

Higher serum uric acid levels are associated with PAD in the US general population. These results suggest that PAD may be an important indicator of the reported association between higher serum uric acid levels and clinical cardiovascular disease. Future prospective studies are required to clarify the temporal nature of this relationship.

The role of renin–angiotensin system inhibition in the treatment of hypertension in metabolic syndrome: are all the angiotensin receptor blockers equal?

The metabolic syndrome (MetS) is a strong predictor of cardiovascular morbidity and mortality, as well as new Type 2 diabetes. MetS consists of visceral obesity, elevated blood pressure, impaired glucose metabolism, atherogenic dyslipidaemia (elevated triglycerides and low levels of high-density lipoprotein cholesterol), as well as other metabolic abnormalities. The underlying pathophysiology seems to be largely, but not uniquely, attributable to insulin resistance. Existing antihypertensive drugs were designed to lower blood pressure rather than to modify the metabolic abnormalities associated with hypertension. This review considers the role of renin-angiotensin system inhibition and especially the use of angiotensin receptor blockers (ARBs) in the treatment of hypertension in MetS. There are differences among ARBs. Among them is the uricosuric effect of losartan. Furthermore, telmisartan may function as a partial agonist of the peroxisome proliferator-activated receptor-gamma (PPAR-gamma).

Status of Uric Acid Management in Hypertensive Subjects

Hyperuricemia in hypertensive subjects has been considered one of risk factors of cardiovascular diseases. We investigated the status of uric acid management in 799 hypertensive subjects (432 females and 367 males; mean age 70.9 years) managed by 43 doctors (19 cardiologists and 24 noncardiologists; 25 private practice doctors and 18 hospital doctors). The serum uric acid level was available in 85.7% of the patients. This availability was equivalent regardless of facility size, and more cardiologists than noncardiologists monitored this information. The prevalence of hyperuricemia was 17.5% and was higher in men and in patients with high triglyceridemia, left ventricular hypertrophy, renal dysfunction, proteinuria, and smokers, but was not higher in subjects with chronic heart failure, diabetes mellitus, and those with prescriptions for diuretics and beta-blockers. The average serum uric acid level was higher in men and patients with chronic heart failure, renal dysfunction, high triglyceridemia, low high-density cholesterolemia, smokers, and subjects prescribed beta-blockers. Fifty percent of hyperuricemic patients were medicated, and 48.6% of them cleared the uric acid target level (6 mg/dL). No differences were observed in the treatment rate or the achievement rate of the target between genders, concurrent diseases, and physician specialties. Although doctors, especially cardiologists, have a high concern for the serum uric acid level, they do not intervene intensively, and specific treatment for individual patterns is not routinely given. Thus, more attention to uric acid management is necessary in hypertensive subjects to prevent cardiovascular diseases.

Serum uric acid as a risk factor for cardiovascular and renal disease: an old controversy revived

Hyperuricemia is commonly associated with traditional risk factors such as abnormalities in glucose metabolism, dyslipidemia, and hypertension. Recent studies have revived the controversy over the role of serum uric acid as an independent prognostic factor for cardiovascular mortality. The authors review clinical and experimental evidence concerning the role of serum uric acid in the development of cardiovascular and renal damage. Results of trials suggesting that serum uric acid variations over time may have a prognostic impact are also discussed.

Uric acid and xanthine oxidase: future therapeutic targets in the prevention of cardiovascular disease?

Serum uric acid may be an independent risk factor for cardiovascular disease. This review examines this association, potential mechanisms, and explores whether strategies to reduce uric acid will improve outcomes. The recent studies of xanthine oxidase inhibition are given particular focus. Epidemiological evidence supports the theory that uric acid is an independent risk factor for cardiovascular disease. Recent studies of losartan, atorvastatin and fenofibrate suggest that uric acid reduction contributes to the risk reduction offered by these therapies. Several small studies of xanthine oxidase inhibition have shown improvements in measures of cardiovascular function of a similar magnitude to that of other proven preventative treatments. These trial data and the convincing epidemiological evidence mandate that large clinical trials of uric acid-lowering strategies are performed in patients with or at high risk of cardiovascular disease. If such approaches are shown to be effective in reducing cardiovascular events, they would represent a novel and cost-effective preventative approach.

Hyperuricaemia and long-term outcome after hospital discharge in acute heart failure patients

BACKGROUND

Uric acid (UA) may be involved in chronic heart failure (HF) pathogenesis, entailing a worse outcome. The purpose of this study was to examine the role of hyperuricaemia as a prognostic marker after hospital discharge in acute HF patients.

METHODS

We studied 212 patients consecutively discharged after an episode of acute HF with LVEF<40%. Blood samples for UA measurement were extracted in the morning prior to discharge. The evaluated endpoints were death and new HF hospitalization.

RESULTS

Mean UA levels were 7.4+/-2.4 mg/dl (range 1.6 to 16 mg/dl), with 127 (60%) of patients being within the range of hyperuricaemia. Hyperuricaemia was associated with a higher risk of death (n=48) (HR 2.0, 95% CI 1.1-3.9, p=0.028), new HF readmission (n=67) (HR 1.8, 95% CI 1.1-3.1, p=0.023) and the combined event (n=100) (HR 1.9, 95% CI 1.2-2.9, p=0.004). At 24 months, cumulative event-free survival was lower in the two higher UA quartiles (36.9% and 40.7% vs. 63.5% and 59.5%, log rank=0.006). After adjustment for potential confounders, hyperuricaemia remains an independent risk factor for adverse outcomes (HR 1.6, 95% CI 1.1-2.6, p=0.02).

CONCLUSIONS

In hospitalized patients with acute HF and LV systolic dysfunction, hyperuricaemia is a long-term prognostic marker for death and/or new HF readmission.

Concentration-Dependent Mode of Interaction of Angiotensin II Receptor Blockers with Uric Acid Transporter

Serum uric acid (SUA) is currently recognized as a risk factor for cardiovascular disease. It has been reported that an angiotensin II receptor blocker (ARB), losartan, decreases SUA level, whereas other ARBs, such as candesartan, have no lowering effect. Because the renal uric acid transporter (URAT1) is an important factor controlling the SUA level, we examined the involvement of URAT1 in those differential effects of various ARBs on SUA level at clinically relevant concentrations. This study was done by using URAT1-expressing Xenopus oocytes. Losartan, pratosartan, and telmisartan exhibited cis-inhibitory effects on the uptake of uric acid by URAT1, whereas at higher concentrations, only telmisartan did, and these ARBs reduced the uptake in competitive inhibition kinetics. On the other hand, candesartan, EXP3174 [2-n-butyl-4-chloro-1-[(2'-(1H-tetrazol-5-yl)biphenyl-4-yI)methyl]imidazole-5-carboxylic acid] (a major metabolite of losartan), olmesartan, and valsartan were not inhibitory. Preloading of those ARBs in the oocytes enhanced the URAT1-mediated uric acid uptake, showing a trans-stimulatory effect. The present study is a first demonstration of the differential effects of ARBs on URAT1 that some ARBs are both cis-inhibitory and trans-stimulatory, depending on concentration, whereas others exhibit either a trans-stimulatory or cis-inhibitory effect alone, which could explain the clinically observed differential effects of ARBs on SUA level. Furthermore, it was found that such differential effects of ARBs on URAT1 could be predicted from the partial chemical structures of ARBs, which will be useful information for the appropriate use and development of ARBs without an increase of SUA.

An apigenin-derived xanthine oxidase inhibitor from Palhinhaea cernua

Fractionation of the ethanol extract of Palhinhaea cernua afforded a new (1) and two known p-coumaroylated apigenin glycosides (2, 3) in addition to dillenetin, rhamnazin, alpha-onocerin, beta-sitosterol, and (E)-2-hydroxy-5-methoxycinnamic acid. The structure of compound 1 was elucidated as apigenin-4'-O-(2' '-O-p-coumaroyl)-beta-D-glucopyranoside by a combination of its spectroscopic data. The new glycoside 1 inhibits xanthine oxidase (IC(50): 23.95 +/- 0.43 microM) in a competitive-noncompetitive manner with K(i) and K(I) values of 14.35 and 93.68 microM, whereas compounds 2 and 3 were inactive. The distribution and significance of acylated flavonoid glycosides are discussed.

The relationship between uric acid and its oxidative product allantoin: a potential indicator for the evaluation of oxidative stress in birds

Uric acid is the main nitrogenous waste product in birds but it is also known to be a potent antioxidant. Hominoid primates and birds lack the enzyme urate oxidase, which oxidizes uric acid to allantoin. Consequently, the presence of allantoin in their plasma results from non-enzymatic oxidation. In humans, the allantoin to uric acid ratio in plasma increases during oxidative stress, thus this ratio has been suggested to be an in vivo marker for oxidative stress in humans. We measured the concentrations of uric acid and allantoin in the plasma and ureteral urine of white-crowned sparrows (Zonotrichia leucophrys gambelii) at rest, immediately after 30 min of exercise in a hop/hover wheel, and after 1 h of recovery. The plasma allantoin concentration and the allantoin to uric acid ratio did not increase during exercise but we found a positive relationship between the concentrations of uric acid and allantoin in the plasma and in the ureteral urine in the three activity phases. In the plasma, the slope of the regression describing the above positive relationships was significantly higher immediately after activity. We suggest that the slope indicates the rate of uric acid oxidation and that during activity this rate increases as a result of higher production of free radicals. The present study demonstrates that allantoin is present in the plasma and in the ureteral urine of white-crowned sparrows and therefore might be useful as an indicator of oxidative stress in birds.

Severity of gouty arthritis is associated with Q-wave myocardial infarction: a large-scale, cross-sectional study

To examine whether serum urate level and other aspects of gouty arthritis are independently associated with Q-wave myocardial infarction (QWMI) in gouty population, we performed a cross-sectional study. A total of 22,572 gouty cases were enrolled. QWMI was defined as a positive finding by resting electrocardiographic criteria excluding the conditions producing pseudoinfarction. The variables of gout were tested univariately and multivariately, controlling for the covariates by logistic regression analysis. The above analysis was then repeated in subgroups of young-aged (<50 years), old-aged (> or = 50 years), male, and female patients. Increased serum urate level was significantly associated with QWMI in all subjects and male subgroup [odds ratio (OR), 1.120; 95% confidence interval (CI), 1.020-1.229; OR, 1.106; 95% CI, 1.001-1.223, respectively, for each mg/dl increment]. After controlling for serum urate level and the covariates, increased affected joint count was also independently associated with QWMI finding in all subjects, male and old-aged subgroups (OR, 1.098; 95% CI, 1.014-1.189; OR, 1.094; 95% CI, 1.005-1.192; OR, 1.095; 95% CI, 1.001-1.199, respectively). Tophi formation was independently associated with QWMI in young-aged subgroup (OR, 2.494; 95% CI, 1.159-5.366). None of the variables of gout including hyperuricemia was significantly associated with QWMI in female subgroup after controlling for covariates. This study first demonstrates that gout is associated with QWMI by both the severity of gouty arthritis and serum urate level, while the association of urate to QWMI could be different between age strata and genders.

Hyperuricemia and Associated Diseases

After introduction of urate-lowering therapy, asympotomatic hyperuricemia was treated with allopurinol or uricosuric agents in the belief that hyperuricemia and/or gout caused chronic kidney disease. Epidemiologic studies in the 1970s, however, failed to confirm the view that hyperuricemia and gout were independent risk factors for chronic kidney disease. As a result, urate-lowering pharmacotherapy is generally not recommended at the present time in the management of asymptomatic hyperuricemia even though recent epidemiological, experimental, and clinical studies have prompted reexamination of a causal role for hyperuricemia (with or without gout) in chronic kidney disease as well as other important disorders including cardiovascular disease, hypertension, and metabolic syndrome. The issue of such a role remains unresolved and this article reviews the current status of the relationship between hyperuricemia and associated disorders.

Concentraciones séricas de uratos y excreción urinaria de ácido úrico en individuos con síndrome metabólico

BACKGROUND AND OBJECTIVES

Hyperuricemia is considered a feature of the metabolic syndrome (MS) despite serum uric acid (SUA) is not considered a diagnostic criterion. The main physiopathological disturbance leading to the increased SUA is not completely understood.

PATIENTS AND METHOD

Descriptive study without drug intervention including 141 subjects (NCEP-ATPIII: 105 with MS and 36 without MS). Serum UA levels were compared in subjects with and without MS. The mechanism of the rise in SUA levels was assessed (overproduction or decreased renal excretion). The relation of SUA levels to the HOMA index was also evaluated.

RESULTS

Subjects with MS showed significantly higher SUA levels (5.6 [1.6] vs 4.6 [1.7] mg/dl, p = 0.002), and lower urinary UA excretion than subjects without MS (UA clearance 3.60 [2.41] vs 4.65 [3.04] ml/min/m2, p = 0.049; excreted fraction of filtered UA 7.15 [4.72] vs 9.81 [6.78%], p = 0.045). Sex (male 6.1 [1.6] vs female 4.9 [1.6] mg/dl, p < 0.001), alcohol intake (drinkers 6.1 [1.8] vs non-drinkers 5.2 [1.6] mg/dl, p < 0.01), and MS (present 5.6 [1.6] absent 4.6 [1.7] mg/dl, p < 0.002), were significantly associated with SUA. In the multiple regression analysis, sex and MS were independently associated with SUA.

CONCLUSIONS

This study demonstrates significantly higher SUA levels in subjects with MS. A decreased urinary UA excretion, instead of urate overproduction, was the leading mechanism to explain high SUA. Serum UA levels were not associated with the HOMA index.

Therapeutic effects of xanthine oxidase inhibitors: renaissance half a century after the discovery of allopurinol

The prototypical xanthine oxidase (XO) inhibitor allopurinol, has been the cornerstone of the clinical management of gout and conditions associated with hyperuricemia for several decades. More recent data indicate that XO also plays an important role in various forms of ischemic and other types of tissue and vascular injuries, inflammatory diseases, and chronic heart failure. Allopurinol and its active metabolite oxypurinol showed considerable promise in the treatment of these conditions both in experimental animals and in small-scale human clinical trials. Although some of the beneficial effects of these compounds may be unrelated to the inhibition of the XO, the encouraging findings rekindled significant interest in the development of additional, novel series of XO inhibitors for various therapeutic indications. Here we present a critical overview of the effects of XO inhibitors in various pathophysiological conditions and also review the various emerging therapeutic strategies offered by this approach.

Diagnosis and management of gout: a rational approach

Gout is one of the best understood among the rheumatological disorders and one of the most satisfying to treat. Even non-specialists should be able to diagnose and treat most patients provided some important principles are appreciated. Management of a minority of patients, including those with renal impairment is difficult and often unsatisfactory, because of restricted treatment options. In this paper, the basic principles underlying the diagnosis and management of gout are discussed first, followed by practical approaches.

Allopurinol Reduces Neointimal Hyperplasia in the Carotid Artery Ligation Model in Spontaneously Hypertensive Rats

Uric acid and oxidative stress promote cardiovascular diseases, including atherosclerosis and hypertension. Xanthine oxidase, through which uric acid is generated, is a free-radical generating enzyme. The aim of the current study was to investigate whether allopurinol, an inhibitor of xanthine oxidase activity, affects vascular remodeling and vascular smooth muscle cell (VSMC) proliferation. In the carotid artery ligation model using spontaneously hypertensive rats (SHR), treatment with allopurinol induced a reduction in the neointima/media ratio by 27% (38.5+/-34.3% in the control group and 28.1 20.8% in the allopurinol-treated group, respectively, p<0.01) without alterations in vascular circumference at 3 weeks after ligation when compared to the control. Allopurinol lowered the serum uric acid concentration (147.0+/-3.6 micromol/l in the control group and 16.1+/-3.6 micromol/l in the allopurinol-treated group, respectively p<0.01) and xanthine oxidase activity, but not the blood pressure. In an in vitro study, high concentrations of uric acid (100 and 200 micromol/l) stimulated VSMC growth, but there was no stimulation of these cells by a low concentration of uric acid (50 micromol/I) or by any of three concentrations of xanthine (50, 100 and 200 micromol/l). In addition, allopurinol (5 micromol/I) had no effect on the cell growth. In conclusion, uric acid is a potent stimulator of VSMC proliferation, and allopurinol prevented vascular remodeling in SHR at least in part by inhibiting uric acid concentration.

Gender-Related Association of Serum Uric Acid and Left Ventricular Hypertrophy in Hypertension

BACKGROUND

The aim of the present study was to determine whether sex differences contribute to the association of serum uric acid and left ventricular hypertrophy in individuals with hypertension.

METHODS AND RESULTS

Seventy participants with essential hypertension (34 men, 36 women; 54.4 +/- 1.6 years old) were enrolled to undergo echocardiography to calculate the left ventricular mass index (LVMI). Twenty-four-hour ambulatory blood pressure monitoring was done to assess blood pressure level precisely. The LVMI was significantly correlated with serum uric acid (r = 0.295, p = 0.013) in all participants. After controlling for factors such as age, sex, mean 24-h systolic blood pressure, creatinine clearance, and duration of hypertension, serum uric acid was still found to be significantly and independently associated with LVMI. Because serum uric acid was significantly higher in men than in women (6.8 +/- 0.3 and 5.1 +/- 0.2 mg/dl, respectively), subsequent analysis was performed by gender. Multiple regression analysis revealed that the LVMI was significantly and independently associated with serum uric acid in women, but not in men.

CONCLUSIONS

The potential effect of uric acid on LV hypertrophy is more pronounced in female than in males with essential hypertension.

Status of endothelial dependent vasodilation in patients with hyperuricemia

Hyperuricemia has been associated with an increased risk for cardiovascular disease and increased mortality. However, the biologic mechanisms that link elevated serum uric acid to cardiovascular disease are uncertain. This study tested the hypothesis that elevated serum uric acid is associated with impaired endothelial function in hyperuricemic patients without any overt cardiovascular disease. Seventeen male patients with hyperuricemia (mean age 42+/-4 years) and 9 control subjects (mean age 45+/-5 years) were studied. All subjects were nonsmokers. All patients had never been treated for hyperuricemia, were on no medications, and were free of any other known diseases. Endothelial function was evaluated by flow-mediated dilation measured by ultrasound. Flow-mediated dilation was significantly impaired in patients with hyperuricemia (4.0+/-0.7%) compared with control subjects (6.4+/-0.8%) (p=0.044). Flow-mediated dilation correlated inversely with uric acid levels (r=-0.4, p=0.05). Nitrate-induced dilation was 12.3+/-1.0% in patients with hyperuricemia and 11.8+/-2.3% in control subjects (p=0.82). Impaired endothelial-dependent vasodilation is present in hyperuricemic patients even in the absence of any overt cardiovascular disease. The elevated serum uric acid, per se, may constitute a novel risk factor for endothelial dysfunction.

Relationship of serum uric acid to measures of endothelial function and atherosclerosis in healthy adults

Although uric acid (UA) is considered as an antioxidant, the relationship between serum UA levels and cardiovascular diseases is not clear yet. Higher brachial artery resting diameter (BD), impaired brachial artery flow-mediated dilatation (FMD), increased carotid intima-media thickness (IMT), decreased aortic distensibility (AoD), and increased aortic stiffness index (AoSI) and elastic modulus (AoEM) are predictors for development and/or progression of atherosclerosis. In this study, BD, FMD, carotid IMT, AoD, AoSI and AoEM were studied in healthy subjects with UA concentrations in physiological range. One hundred 24 healthy volunteers between 26 and 55 years of age were included in this study. Each subject had a serum UA levels in normal range. Carotid IMT, BD and brachial FMD were measured by means of high-resolution vascular ultrasound. AoD, AoSI, AoEM were examined by transthoracic echocardiography. Endothelium-dependent dilatation (EDD) was assessed by establishing reactive hyperemia and endothelium-independent dilatation (EID) was determined by using sublingual isosorbide dinitrate. Although carotid IMT and EDD were significantly correlated with UA concentrations (r = 0.346, p < 0.0001; r = -0.255, p < 0.05, respectively), EID measurements were not significantly correlated with serum UA concentrations (r = - 0.105, p > 0.05). In addition, AoSI and AoEM were significantly correlated with serum UA levels (r = 0.368, p < 0.0001; r = -0.366, p < 0.0001, respectively), and there was a significant inverse correlation between AoD and serum UA concentrations (r = -0.366, p < 0.0001). Furthermore, in multivariate analysis, we found that serum UA concentrations were correlated with increased carotid IMT, reduced FMD and increased aortic stiffness independent of other cardiovascular risk factor (beta = 256, p = 0.002; beta = -193, p = 0.03; beta = 0.295, p < 0.0001, respectively). In healthy subjects, increased serum UA concentrations, even in physiological range, are a risk factor for increased carotid IMT, reduced FMD and increased aortic stiffness independent of other cardiovascular risk factor, and other factors related to the metabolic syndrome.

Renal dysfunction and ischemic heart disease mortality in a hypertensive population

OBJECTIVE

While recent studies indicate that renal dysfunction may be predictive of all-cause mortality and cardiovascular disease (CVD) outcomes in hypertensive individuals, there has been little attention to the specific association of ischemic heart disease (IHD) mortality and renal function. This study examines the relationship between IHD mortality and baseline glomerular filtration rate (GFR) (estimated by the Cockcroft and Gault formula) among treated hypertensive subjects.

DESIGN

A prospective cohort study of participants in a worksite-based antihypertensive treatment program in New York City (1981-1999).

PATIENTS

We studied 9929 subjects who had at least 6 months follow-up (mean 9.6 years) with a baseline serum creatinine.

MAIN OUTCOME MEASURES

IHD death outcomes (n=343) ascertained from the National Death Index.

RESULTS

Multivariate Cox proportional hazard models were constructed adjusting for known cardiovascular risk factors. Mean GFR of the cohort was 91.6 ml/min per 1.73 m. Those with lower GFR were more likely to be older, female, White, report a history of cardiovascular disease, have higher cholesterol and blood urea nitrogen values, and lower hemoglobin and body mass index than those with highest GFR. After adjustment for known cardiovascular risk factors, the risk of IHD death increased progressively as the GFR decreased. Hazard ratio for IHD mortality for each 10-unit reduction of estimated GFR below the normal threshold of >or=90 ml/min per 1.73 m was 1.33 (95% confidence interval 1.17, 1.50; P<0.001).

CONCLUSIONS

The results of this study suggest an independent inverse association between estimated GFR and IHD mortality among treated hypertensive individuals.

Uric acid causes vascular smooth muscle cell proliferation by entering cells via a functional urate transporter

BACKGROUND

Soluble uric acid stimulates vascular smooth muscle cell (VSMC) proliferation by activating mitogen-activated protein kinases, and stimulating COX-2 and PDGF synthesis. The mechanism by which uric acid enters the VSMC is not known. We hypothesized that uric acid enters via transporters similar to that observed in the kidney.

METHODS

We studied the uptake of uric acid into rat VSMC under polarized and depolarized conditions and in the presence of organic anion transport (OAT) inhibitors (probenecid and benzbromarone) or p-aminohippurate (PAH). We also examined the ability of probenecid to inhibit uric acid-induced VSMC proliferation and monocyte chemoattractant protein-1 (MCP-1) synthesis.

RESULTS

(14)C-Urate uptake was shown in VSMC and was enhanced under depolarized conditions. (14)C-Uric acid uptake was inhibited by probenecid and benzbromarone, as well as by unlabelled urate and PAH. Probenecid blocked VSMC proliferation and MCP-1 expression in response to uric acid. VSMC did not express rOAT1-3, rOAT-5 or URAT-1 mRNA by PCR, but did express the voltage-sensitive transporter (UAT) by both PCR and RNase protection assay.

CONCLUSIONS

Urate enters VSMC by both voltage-sensitive and OAT pathways, and the uptake, cell proliferation and MCP-1 expression can be blocked by OAT inhibitors. The specific transporter(s) responsible for the urate uptake remains to be determined.

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.

Serum uric acid and cardiovascular disease: recent developments, and where do they leave us?

The relationship between serum uric acid (SUA) and cardiovascular disease has been controversial. Here we review recent literature assessing whether hyperuricemia is an independent risk factor for adverse cardiovascular outcomes. Studies from the past 6 years evaluating the association of SUA with cardiovascular disease were identified through MEDLINE, EMBASE, and Cochrane library searches, bibliography cross-referencing, and review articles. Twenty-one cohort studies in healthy and high-risk patients with cardiovascular disease were identified and reviewed. In studies of high-risk patients, in which more overall events were recorded, 10 of 11 studies were supportive of an independent association. In 10 studies of healthy patients, 6 suggested an independent association of SUA with adverse cardiovascular outcomes. Increasing SUA is likely an independent risk factor for cardiovascular disease in high-risk individuals. However, the magnitude of excess risk attributable to high SUA is likely to be small in healthy individuals. Trials of SUA-lowering therapy in hyperuricemic patients evaluating the effect on cardiovascular outcomes are justified in high-risk patients.

Frequency of gouty arthritis in patients with end-stage renal disease in Japan

OBJECTIVE

The purpose of this study was to investigate gouty arthritis in Japanese patients with end-stage renal disease (ESRD).

METHODS

Questionnaires plus patient interviews and reviews of medical records were used to investigate gouty arthritis in 493 Japanese patients with ESRD receiving maintenance dialysis.

RESULTS

The frequency of gouty arthritis was 4.1% for female patients and 15.4% for male patients greater than 2 years before the start of dialysis, and 0.6% for female patients and 7.7% for male patients less than 2 years before the start of dialysis. After the start of dialysis the frequency was 3.4% for the first 2 years and 1.2% thereafter in male patients, but no gouty arthritis appeared in female patients. Although the annual number of gouty attacks was 2.0+/-4.2 greater than 2 years before the start of dialysis, and 1.9+/-6.6 less than 2 years before the start of dialysis, the annual number of attacks decreased significantly after the start of dialysis to 0.2+/-0.7 in the first 2 years and 0.1+/-0.6 thereafter.

CONCLUSIONS

The frequency of gouty arthritis in Japanese patients with ESRD is similar to that of patients with hyperuricemia in the general population and it is decreased slightly before dialysis; however, the frequency decreases markedly after dialysis.

Simultaneous treatment with citrate prevents nephropathy induced by FYX-051, a xanthine oxidoreductase inhibitor, in rats

The possible mechanism of the underlying nephropathy found in the rat toxicity study of FYX-051, a xanthine oxidoreductase inhibitor, was investigated. Rats received oral treatment of either 1 or 3 mg/kg of FYX-051, with and without citrate for four weeks to elucidate whether nephropathy could be caused by materials deposited in the kidney. Furthermore, analysis of the renal deposits in rats was also performed. Consequently, interstitial nephritis comprising interstitial inflammatory cell infiltration, dilatation, basophilia and epithelial necrosis of renal tubules and collecting ducts, deposits in renal tubules and collecting ducts, and so forth was seen in six of the eight rats and in all eight rats in the 1 and 3 mg/kg FYX-051 alone groups, respectively, with the intensity in the 3 mg/kg group being moderate to severe. In the simultaneous treatment with citrate group, however, no alterations were observed in the kidney, except for minimal interstitial nephritis in one instance in the 3 mg/kg FYX-051 + citrate group along with an increased urinary pH, leading to an increase in xanthine solubility. Analysis of intrarenal deposits showed that the entity would be composed of xanthine crystals. The present study, therefore, showed that nephropathy in rats occurring after the administration of FYX-051 was a secondary change caused by xanthine crystals being deposited in the kidney, and no other causes could be implicated in this kidney lesion.

Clinic blood pressure responses to two amlodipine salt formulations, adipate and besylate, in adult Korean patients with mild to moderate hypertension: A multicenter, randomized, double-blind, parallel-group, 8-week comparison

BACKGROUND

The commercially available formulation of amlodipine is conjugated with besylate salt to increase water solubility. Recently, a new amlodipine salt formulation has been developed in which the free base of amlodipine is conjugated with a chemically different salt, adipate.

OBJECTIVE

The goal of this study was to compare the antihypertensive effect and tolerability of amlodipine adipate with those of amlodipine besylate in patients with mild to moderate hypertension.

METHODS

This was a multicenter, randomized, doubleblind, parallel-group study in which patients received 8 weeks of treatment with either amlodipine adipate or amlodipine besylate. The primary efficacy variable was noninferiority of the difference in mean changes from baseline in trough diastolic blood pressure (DBP) after 8 weeks of treatment. Secondary efficacy variables included mean changes in DBP, systolic blood pressure (SBP), and response rate (defined as the proportion of patients whose DBP was <90 mm Hg or whose DBP had decreased from baseline by > or =10 mm Hg). The incidence of adverse events (AEs) was also assessed.

RESULTS

Two hundred eleven patients were randomly assigned to receive amlodipine adipate (n = 106) or amlodipine besylate (n = 105). Study patients were primarily female (54.5%), with a mean (SD) age of 52.2 (9.6) years and a mean body weight of 67.1 (10.2) kg; there were no between-group differences in demographic profiles. After 4 weeks of randomized treatment, 58 (27.5%) patients (29 [27.4%] amlodipine adipate, 29 [27.6%] amlodipine besylate) had not achieved a mean DBP <90 mm Hg, and their dose was doubled. Mean DBP changes at 8 weeks were -15.2 (7.3) mm Hg in the amlodipine adipate group and -14.2 (7.4) mm Hg in the amlodipine besylate group (P = NS). Because the 95% CI for the difference in mean DBP changes between groups (-0.53 to 2.55) was within the prespecified lower limit (-4 mm Hg), amlodipine adipate was considered noninferior to amlodipine besylate. Mean SBP changes were -24.9 (12.1) mm Hg in the amlodipine adipate group and -22.0 (14.7) mm Hg in the amlodipine besylate group (P = NS). The response rates were 92.0% for amlodipine adipate and 95.4% for amlodipine besylate (P = NS). The overall incidence of clinical AEs was 20.8% in the amlodipine adipate group and 25.7% in the amlodipine besylate group (P = NS). Drug-related clinical AEs occurred in 5.7% and 12.4% of patients in the respective treatment groups (P = NS). Serum uric acid levels decreased significantly from base-line in both groups (P < 0.001).

CONCLUSIONS

Eight weeks of treatment with amlodipine adipate produced significant reductions from baseline in blood pressure in these patients with mild to moderate hypertension. The efficacy of amlodipine adipate was not inferior to that of amlodipine besylate. Tolerability was comparable between the 2 treatment groups.

The controversial role of serum uric acid in essential hypertension: relationships with indices of target organ damage

The role of serum uric acid (SUA) in the context of adverse cardiovascular events in hypertensive subjects is controversial. Additionally, the relationship between SUA and indices of target organ damage is not well defined in this setting. Towards this end, we studied 842 consecutive nondiabetic patients with stage I-II essential hypertension (office blood pressure=148/95 mmHg, aged 53.4 years), referred to our outpatient hypertensive unit within a period of 4 years. According to the urinary albumin excretion (UAE), the study population was classified into those with microalbuminuria [MA(+), UAE=20-200 mg/24 h, n=222] and those without MA [MA (-), UAE< 20 mg/24 h, n=620]. Moreover, according to the presence of left ventricular hypertrophy (LVH) the participants were subdivided into two additional groups: [LVH (+), n=305 and LVH (-), n=537]. SUA levels were higher by 0.4 mg/dl, (P=0.04) in group MA (+) compared with the group MA (-), while no difference was observed between groups LVH (+) and LVH (-) (P=NS). In the entire population, SUA was correlated with body mass index (BMI) (r=0.17, P<0.001), waist/hip ratio (r=0.3, P<0.001), office systolic blood pressure (SBP) (r=0.14, P<0.05), triglycerides levels (r=0.25, P<0.001), UAE (r=0.35, P<0.001) and HDL (r=-0.26, P<0.001). Multiple regression analysis demonstrated that SUA was significantly related with BMI, office SBP and UAE (P<0.05). In conclusion, increased SUA levels are associated with MA but not with LVH in essential hypertensive subjects. Whether these inter-relationships may elucidate the clinical positioning of augmented SUA in this setting remains to be clarified in future studies.

The increase in serum uric acid concentration caused by diuretics might be beneficial in heart failure

Patients with mild-moderate chronic heart failure (CHF) often have raised levels of serum uric acid (UA). This is due, amongst other factors, to reduced UA excretion by the kidneys, which is partly explained by restriction of sodium intake and treatment with diuretics. The decline in renal function that parallels worsening cardiac function also contributes to elevated serum UA in patients with advanced CHF. However, UA production also appears to be augmented in CHF. Because UA scavenges various reactive oxygen species, diuretic-induced elevations in serum UA could be beneficial in patients with CHF. This concept is supported by the superior performance of antihypertensive therapy with diuretics in preventing heart failure. The present hypothesis may be tested by examining the effects of add-on treatment with a thiazide-type diuretic on morbidity and mortality, or surrogate variables, in asymptomatic patients with left ventricular dysfunction but without fluid retention.

Do angiotensin II antagonists provide benefits beyond blood pressure reduction?

Hypertension is a powerful risk factor for cardiovascular (CV) morbidity and mortality; therefore, blood pressure (BP) lowering plays a central role in reducing the cardiovascular complications of hypertension, including stroke. Recent outcomes studies--Losartan Intervention For Endpoint reduction in hypertension, Reduction of Endpoints in Non-insulin-dependent Diabetes Mellitus with the Angiotensin II Antagonist Losartan, and the Irbesartan Type 2 Diabetic Nephropathy Trial--suggest that some angiotensin II antagonists are associated with CV and renal effects beyond their ability to lower BP in patients with hypertension or diabetic nephropathy and may play a role in the prevention of new-onset type 2 diabetes. Angiotensin II antagonists are associated with a wide variety of vascular, cardiac, and renal effects, as well as molecule-specific effects independent of those induced by the angiotensin-I receptor. These actions may offer a mechanistic explanation for the outcome benefits observed in patients with hypertension or diabetic nephropathy. Angiotensin-converting enzyme inhibitors and calcium-channel blockers may also have effects that are not completely explained by differences in the antihypertensive response to these agents, but the evidence is less robust. Collectively, these findings suggest that management of patients with hypertension, with or without diabetes or renal disease, should no longer be viewed as simply a matter of correcting elevated BP. Antihypertensive agents that possess CV benefits beyond their BP-reducing effects should be used to prevent the development of end-organ damage.

Losartan for the treatment of hypertension and left ventricular hypertrophy: the Losartan Intervention For Endpoint reduction in hypertension (LIFE) study

Losartan is an orally active, selective, nonpeptide, angiotensin-II Type I-receptor antagonist, and was the first drug marketed in this class. It has been approved for the treatment of hypertension, and may be used alone or in combination with other antihypertensive agents. Based on the Losartan Intervention For Endpoint reduction in hypertension (LIFE) study, losartan has been approved for the reduction of cardiovascular events in patients with hypertension and left ventricular hypertrophy, but there is evidence that this benefit does not apply to black patients. Based on the Reduction of Endpoints in NIDDM with the Angiotensin II Antagonist Losartan (RENAAL) study, losartan is also indicated for the treatment of diabetic nephropathy with an elevated serum creatinine and proteinuria, in patients with Type 2 diabetes. The focus of this review is the LIFE study.

Renal xanthine oxidoreductase activity during development of hypertension in spontaneously hypertensive rats

BACKGROUND

Hyperuricaemia and reactive oxygen species have recently been associated with essential hypertension. Xanthine oxidoreductase (XOR) produces urate and, in its oxidase isoform, reactive oxygen species also. Our previous studies indicated that hypertension-prone rat strains have greater renal XOR activity than their normotensive counterparts, and that dietary sodium modifies renal XOR activity.

OBJECTIVE

To clarify whether renal XOR induction precedes or follows the development of hypertension.

METHODS

Five-week-old spontaneously hypertensive rats (SHRs) and Wistar-Kyoto (WKY) rats were kept for 3-8 weeks on low sodium (0.3% salt w/w) or high sodium (6.0% salt w/w) intakes, with or without allopurinol, an inhibitor of XOR, to study the possible pathogenetic role of XOR in hypertension. Systolic blood pressure (SBP), renal XOR activity and mRNA expression were measured.

RESULTS

Regardless of sodium intake, renal XOR activity increased twofold during growth in SHRs, but not in WKY rats. SBP increased from 122 +/- 4 to 241 +/- 13 mmHg in SHRs kept on the high-sodium diet and to 204 +/- 11 mmHg in those on the low-sodium diet. At the end of the experiment, renal XOR activity correlated with SBP in SHRs. Allopurinol prevented hypertension-induced left ventricular and renal hypertrophy in SHRs, but had negligible effect on blood pressure.

CONCLUSION

Renal XOR induction in SHRs does not precede the development of hypertension, but progress concomitantly with an increase in SBP. The results indicate a role for locally synthesized XOR in the development of hypertension-associated end-organ damage, but no major role in the development of hypertension.

Uric acid and chronic renal disease: Possible implication of hyperuricemia on progression of renal disease

Although hyperuricemia has long been associated with renal disease, uric acid has not been considered as a true mediator of progression of renal disease. The observation that hyperuricemia commonly is associated with other risk factors of cardiovascular and renal disease, especially hypertension, has made it difficult to dissect the effect of uric acid itself. However, recent epidemiologic evidence suggests a significant and independent association between the level of serum uric acid and renal disease progression with beneficial effect of decreasing uric acid levels. Furthermore, our experimental data using hyperuricemic animals and cultured cells have provided robust evidence regarding the role of uric acid on progression of renal disease. Hyperuricemia increased systemic blood pressure, proteinuria, renal dysfunction, vascular disease, and progressive renal scarring in rats. Recent data also suggest hyperuricemia may be one of the key and previously unknown mechanisms for the activation of the renin-angiotensin and cyclooxygenase-2 (COX-2) systems in progressive renal disease. Although we must be cautious in the interpretation of animal models to human disease, these studies provide a mechanism to explain epidemiologic data that show uric acid is an independent risk factor for renal progression. Although there is no concrete evidence yet that uric acid bears a causal or reversible relationship to progressive renal disease in humans, it is time to reevaluate the implication of hyperuricemia as an important player for progression of renal disease and to try to find safe and reasonable therapeutic modalities in individual patients based on their clinical data, medication history, and the presence of cardiovascular complications.

Clinical evidence for the influence of uric acid on hypertension, cardiovascular disease, and kidney disease: A statistical modeling perspective

This article critically evaluates the clinical evidence regarding the influence of uric acid on hypertension, cardiovascular disease, and kidney disease. Data on these relationships are largely observational and exceedingly complex. The complexity is owing to indirect and direct relations, and bidirectional influences, simultaneously operating on multiple outcomes. Limitations of previous analyses include inadequate statistical methods using only bivariate correlations or poorly specified multiple regression models. As a result, great controversy developed as to whether uric acid is an independent predictor of important outcomes. An example of such analytic limitations is including hypertension as an independent variable, together with uric acid, in a multivariate model for predicting cardiovascular disease. Hypertension may predict significant variance in cardiovascular disease, but the contribution of uric acid may not be recognized if uric acid exerts its influence indirectly through hypertension. Path analysis, which can model direct and indirect influences on outcomes simultaneously, would address this substantive question. Studies of uric acid in relation to hypertension, cardiovascular disease, and kidney disease using a path-analytic approach would help specify such conditions as well as optimize design of clinical trials to determine if decreasing uric acid levels improves outcomes.

Emergence of Talanin protein associated with human uric acid nephrolithiasis in the Hominidae lineage

Recently, we identified a susceptibility locus for human uric acid nephrolithiasis (UAN) on 10q21-q22 and demonstrated that a novel gene (ZNF365) included in this region produces through alternative splicing several transcripts coding for four protein isoforms. Mutation analysis showed that one of them (Talanin) is associated with UAN. We examined the evolutionary conservation of ZNF365 gene through a comparative genomic approach. Searching for mouse homologs of ZNF365 transcripts, we identified a highly conserved mouse ortholog of ZNF365A transcript, expressed specifically in brain. We did not found a mouse homolog for ZNF365D transcript encoding the Talanin protein, even if we were able to identify the corresponding genomic region in mouse and rat not yet organized in canonical gene structure suggesting that ZNF365D was originated after the branching of hominoid from rodent lineage. In mouse and in most mammals, a functional uricase degrades the uric acid to allantoin, but uricase activity was lost during the Miocene epoch in hominoids. Searching for the presence of Talanin in Primates, we found a canonical intron-exon structure with several stop codons preventing protein production in Old World and New World monkeys. In humans, we observe expression and we have evidence that ZNF365D transcript produces a functional protein. It seems therefore that ZNF365D transcript emerged during primate evolution from a noncoding genomic sequence that evolved in a standard gene structure and assumed its role in parallel with the disappearance of uricase, probably against a disadvantageous excessive hyperuricemia.

Galectin 9 is the sugar-regulated urate transporter/channel UAT

UAT, also designated galectin 9, is a multifunctional protein that can function as a urate channel/transporter, a regulator of thymocyte-epithelial cell interactions, a tumor antigen, an eosinophil chemotactic factor, and a mediator of apoptosis. We review the evidence that UAT is a transmembrane protein that transports urate, describe our molecular model for this protein, and discuss the evidence from epitope tag and lipid bilayer studies that support this model of the transporter. The properties of recombinant UAT are compared with those of urate transport into membrane vesicles derived from proximal tubule cells in rat kidney cortex. In addition, we review channel functions predicted by our molecular model that resulted in the novel finding that the urate channel activity is regulated by sugars and adenosine. Finally, the presence and possible functions of at least 4 isoforms of UAT and a closely related gene hUAT2 are discussed.

Consumption of high-pressurized vegetable soup increases plasma vitamin C and decreases oxidative stress and inflammatory biomarkers in healthy humans

Current evidence supports a significant association between fruit and vegetable intake and health. In this study, we assessed the effect of consuming a vegetable-soup "gazpacho" on vitamin C and biomarkers of oxidative stress and inflammation in a healthy human population. We also examined the association between vitamin C and F(2)-isoprostanes (8-epiPGF(2alpha)), uric acid (UA), prostaglandin E(2) (PGE(2)), monocyte chemotactic protein-1 (MCP-1), and the cytokines, tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and IL-6. Gazpacho is a Mediterranean dish defined as a ready-to-use vegetable soup, containing approximately 80% crude vegetables rich in vitamin C. Subjects (6 men, 6 women) enrolled in this study consumed 500 mL/d of gazpacho corresponding to an intake of 72 mg of vitamin C. On d 1, subjects consumed the gazpacho in one dose; from d 2 until the end of the study, d 14, 250 mL was consumed in the morning and 250 mL in the afternoon. Blood was collected before drinking the soup (baseline) and on d 7 and 14. Baseline plasma vitamin C concentrations did not differ between men and women (P = 0.060). Compared with baseline, the vitamin C concentration was significantly higher on d 7 and 14 of the intervention in both men and women (P < 0.05). Baseline plasma levels of UA and F(2)-isoprostanes were higher (P < or = 0.002) in men than in women. The F(2)-isoprostanes decreased on d 14 in men and women (P < or = 0.041), and UA decreased in men (P = 0.028). The concentrations of vitamin C and 8-epiPGF(2alpha) were inversely correlated (r = -0.585, P = 0.0002). Plasma PGE(2) and MCP-1 concentrations decreased in men and women (P < or = 0.05) on d 14, but those of TNF-alpha, IL-1beta, and IL-6 did not change. Consumption of the vegetable soup decreases oxidative stress and biomarkers of inflammation, which indicates that the protective effect of vegetables may extend beyond their antioxidant capacity.

The impact of serum uric acid on cardiovascular outcomes in the LIFE study

BACKGROUND

The Losartan Intervention For Endpoint reduction in hypertension (LIFE) study demonstrated the superiority of a losartan-based regimen over atenolol-based regimen for reduction of cardiovascular (CV) morbidity and mortality. It has been suggested that the LIFE study results may be related to the effects of losartan on serum uric acid (SUA). SUA has been proposed as an independent risk factor for CV morbidity and death.

METHODS

Cox regression analysis was used to assess relationship of SUA and treatment regimens with the LIFE primary composite outcome (CV death, fatal or nonfatal myocardial infarction, fatal or nonfatal stroke).

RESULTS

Baseline SUA was significantly associated with increased CV events [hazard ratio (HR) 1.024 (95% CI 1.017-1.032) per 10 micromol/L, P < 0.0001] in the entire study population. The association was significant in women [HR = 1.025 (1.013-1.037), P < 0.0001], but not in men [HR = 1.009 (0.998-1.019), P= 0.108]. After adjustment for Framingham risk score (FRS), SUA was no longer significant in the entire study population [HR = 1.006 (0.998-1.014), P= 0.122] or in men [HR = 1.006 (0.995-1.017), P= 0.291], but was significant in women [HR = 1.013 (1-1.025), P= 0.0457]. The baseline-to-end-of-study increase in SUA (standard deviation, SD) was greater (P < 0.0001) in atenolol-treated subjects (44.4 +/- 72.5 micromol/L) than in losartan-treated subjects (17.0 +/- 69.8 micromol/L). SUA as a time-varying covariate was strongly associated with events (P < 0.0001) in the entire population. The contribution of SUA to the treatment effect of losartan on the primary composite end point was 29% (14%-107%), P= 0.004. The association between time-varying SUA and increased CV risk tended to be stronger in women (P < 0.0001) than in men (P= 0.0658), although the gender-outcome interaction was not significant (P= 0.079).

CONCLUSION

The increase in SUA over 4.8 years in the LIFE study was attenuated by losartan compared with atenolol treatment, appearing to explain 29% of the treatment effect on the primary composite end point. The association between SUA and events was stronger in women than in men with or without adjustment of FRS.

Effect of statins versus untreated dyslipidemia on serum uric acid levels in patients with coronary heart disease: a subgroup analysis of the GREek Atorvastatin and Coronary-heart-disease Evaluation (GREACE) study

BACKGROUND

Little is known about the effect of dyslipidemia on serum uric acid (SUA) levels, and less is known about the effect of statin treatment on them. The GREek Atorvastatin and Coronary-heart-disease Evaluation study suggested that a mean atorvastatin dose of 24 mg/d achieves the National Cholesterol Educational Program treatment goals and significantly reduces morbidity and mortality in patients with coronary heart disease (CHD) in comparison to the usual care. Here, we report the time course of SUA levels in usual-care patients undertreated for their dyslipidemia (12% were administered statins) in comparison to structured-care patients treated with atorvastatin in the vast majority (98%).

METHODS

Mean on-study SUA levels (up to 48 months) were compared with those at baseline by using analyses of variance to assess differences over time within and between treatment groups. Cox multivariate analysis was used to investigate whether changes in SUA levels during the study were clinically relevant.

RESULTS

All patients had normal renal function at baseline; serum creatinine (SCr) levels less than 1.3 mg/dL (<115 micromol/L) and moderately elevated SUA levels (mean, 7.1 +/- 0.9 [SD] mg/dL [425 +/- 52 micromol/L]; upper normal limit, 7.0 mg/dL [415 micromol/L]). Usual-care patients (n = 800) showed an increase in SUA levels by 3.3% ( P < 0.0001). Structured-care patients (n = 800) had an 8.2% reduction in SUA levels ( P < 0.0001). In all patients not administered diuretics (n = 1,407), SUA level changes showed a positive correlation with changes in SCr levels ( r = 0.82; P < 0.0001) and an inverse correlation with estimated glomerular filtration rate ( r = -0.77; P < 0.0001). After adjustment for 19 predictors of all CHD-related events, Cox multivariate analysis involving backward stepwise logistic regression showed a hazard ratio (HR) of 0.89 (95% confidence interval [CI], 0.78 to 0.96; P = 0.03) with every 0.5-mg (30-micromol/L) reduction in SUA level, an HR of 0.76 (95% CI, 0.62 to 0.89; P = 0.001) with every 1-mg (60-micromol/L) reduction, an HR of 1.14 (95% CI, 1.03 to 1.27; P = 0.02) with every 0.5-mg increase, and an HR of 1.29 (95% CI, 1.17 to 1.43; P = 0.001) with every 1-mg increase in SUA levels.

CONCLUSION

Data suggest that SUA level is an independent predictor of CHD recurrent events. Atorvastatin treatment significantly reduces SUA levels in patients with CHD, thus offsetting an additional factor associated with CHD risk.

Primary prevention in rheumatology: the importance of hyperuricemia

Hyperuricemia (HU) is present in 5-30% of the general population, although the prevalence is higher among some ethnic groups and seems to be increasing worldwide. Classically, chronic HU has been considered a risk factor for gout or lithiasis and is associated with alcoholism, obesity, hypertension, dyslipidemia, hyperglycemia/diabetes mellitus, renal failure and intake of certain drugs. HU is also associated with cardiovascular diseases such as hypertension, vascular disease, pre-eclampsia, pulmonary arterial hypertension, stroke, heart failure, ischemic heart disease and also metabolic syndrome, renal disease and increased mortality. It is uncertain if these associations are dependent or not, especially cardiovascular and renal diseases. Patients with chronic HU and also those with gout require both medical investigation for associated diseases or drugs as well as nutritional counseling and life-style changes. HU should alert physicians to possible complications.

Uric acid: role in cardiovascular disease and effects of losartan

A substantial body of epidemiological and experimental evidence suggests that serum uric acid is an important, independent risk factor for cardiovascular and renal disease especially in patients with hypertension, heart failure, or diabetes. Elevated serum uric acid is highly predictive of mortality in patients with heart failure or coronary artery disease and of cardiovascular events in patients with diabetes. Further, patients with hypertension and hyperuricemia have a 3- to 5-fold increased risk of experiencing coronary artery disease or cerebrovascular disease compared with patients with normal uric acid levels. Although the mechanisms by which uric acid may play a pathogenetic role in cardiovascular disease is unclear, hyperuricemia is associated with deleterious effects on endothelial dysfunction, oxidative metabolism, platelet adhesiveness, hemorheology, and aggregation. Xanthine oxidase inhibitors (e.g., allopurinol) or a variety of uricosuric agents (e.g., probenecid, sulfinpyrazone, benzbromarone, and benziodarone) can lower elevated uric acid levels but it is unknown whether these agents reversibly impact cardiovascular outcomes. However, the findings of the recent LIFE study in patients with hypertension and left ventricular hypertrophy suggest the possibility that a treatment-induced decrease in serum uric acid may indeed attenuate cardiovascular risk. LIFE showed that approximately 29% (14% to 107%, p = 0.004) of the treatment benefit of a losartan-based versus atenolol-based therapy on the primary composite endpoint (death, myocardial infarction, or stroke) may be ascribed to differences in achieved serum uric acid levels. Overall, serum uric acid may be a powerful tool to help stratify risk for cardiovascular disease. At the very least, it should be carefully considered when evaluating overall cardiovascular risk.

Hyperuricaemia does not impair cardiovascular function in healthy adults

OBJECTIVE

To investigate the possibility that uric acid (UA) can impair endothelial function, an important surrogate for atherosclerosis.

DESIGN

UA was administered locally or systemically to healthy adult men and women in a series of randomised placebo controlled studies. This temporarily raised serum UA concentrations, so that the potential effects of hyperuricaemia on mechanisms of cardiovascular disease could be studied.

MAIN OUTCOME MEASURES

The effects of UA administration on basal blood flow and responses to locally administered acetylcholine, sodium nitroprusside, and L-N(G)-monomethylarginine were studied in the forearm vascular bed with venous occlusion plethysmography. The effects of hyperuricaemia on systemic vascular resistance, large artery compliance, and baroreflex sensitivity were examined by validated non-invasive techniques.

RESULTS

UA administration caused a twofold increase in serum concentrations. However, there were no acute effects on haemodynamic variables, basal forearm blood flow, or nitric oxide dependent endothelial function.

CONCLUSION

Unlike other risk factors associated with endothelial dysfunction, acute exposure to high concentrations of UA does not impair cardiovascular function in healthy men. These findings do not support a causal link between hyperuricaemia and atherosclerosis.

Uric acid administration for neuroprotection in patients with acute brain ischemia

Uric acid is the end product of purine metabolism and a powerful water-soluble antioxidant and radical scavenger in humans whose generation is increased in situations of oxidative stress, such as brain ischemia. Although hyperuricemia has been related to an increased risk of cardiovascular events, the association was not found significant in many studies after adjustment for the effect of confounders. In the ischemic rat brain, the administration of uric acid results in neuroprotection and improved behavioral outcome. The severity of neurological impairment and the volume of infarction in patients with stroke have been found inversely related to the concentration of uric acid. In healthy volunteers, uric acid has been administered without untoward effects to show a conspicuous reduction of oxidative stress. We hypothesize that the administration of uric acid could be beneficial and cost effective in patients sustaining acute oxidative stress, such as those with acute ischemic stroke. Uric acid could also extend to more than 3 h the therapeutic window of rt-PA after stroke and it could limit the appearance of neurobehavioral changes after cardiopulmonary bypass. Prospective double blind randomized controlled trials are needed to test the value of uric acid in these clinical settings in which oxyradical formation is prominent.

Xanthine oxidoreductase and cardiovascular disease: molecular mechanisms and pathophysiological implications

There is substantial evidence that oxidative stress participates in the pathophysiology of cardiovascular disease. Biochemical, molecular and pharmacological studies further implicate xanthine oxidoreductase (XOR) as a source of reactive oxygen species in the cardiovascular system. XOR is a member of the molybdoenzyme family and is best known for its catalytic role in purine degradation, metabolizing hypoxanthine and xanthine to uric acid with concomitant generation of superoxide. Gene expression of XOR is regulated by oxygen tension, cytokines and glucocorticoids. XOR requires molybdopterin, iron-sulphur centres, and FAD as cofactors and has two interconvertible forms, xanthine oxidase and xanthine dehydrogenase, which transfer electrons from xanthine to oxygen and NAD(+), respectively, yielding superoxide, hydrogen peroxide and NADH. Additionally, XOR can generate superoxide via NADH oxidase activity and can produce nitric oxide via nitrate and nitrite reductase activities. While a role for XOR beyond purine metabolism was first suggested in ischaemia-reperfusion injury, there is growing awareness that it also participates in endothelial dysfunction, hypertension and heart failure. Importantly, the XOR inhibitors allopurinol and oxypurinol attenuate dysfunction caused by XOR in these disease states. Attention to the broader range of XOR bioactivity in the cardiovascular system has prompted initiation of several randomised clinical outcome trials, particularly for congestive heart failure. Here we review XOR gene structure and regulation, protein structure, enzymology, tissue distribution and pathophysiological role in cardiovascular disease with an emphasis on heart failure.