Uric acid: role in cardiovascular disease and effects of losartan

Hyperuricemia and coronary heart disease mortality: a meta-analysis of prospective cohort studies

Background

Hyperuricemia may be associated with an increased risk of coronary heart disease (CHD) mortality; however, the results from prospective studies are conflicting. The objective of this study was to assess the association between hyperuricemia and risk of CHD mortality by performing a meta-analysis.

Methods

Pubmed and Embase were searched for relevant prospective cohort studies published until July 2015. Studies were included only if they reported data on CHD mortality related to hyperuricemia in a general population. The pooled adjusted relative risk (RR) was calculated using a random-effects model.

Results

A total of 14 studies involving 341 389 adults were identified. Hyperuricemia was associated with an increased risk of CHD mortality (RR: 1.14; 95 % CI: 1.06–1.23) and all-cause mortality (RR: 1.20; 95 % CI: 1.13–1.28). For each increase of 1 mg/dl of serum uric acid (SUA), the overall risks of CHD and all-cause mortality increased by 20 and 9 %, respectively. According to the gender subgroup analyses, hyperuricemia increased the risk of CHD mortality in women (RR: 1.47; 95 % CI: 1.21–1.73) compared to men (RR: 1.10; 95 % CI: 1.00–1.19). The risk of all-cause mortality was greater in women.

Conclusions

Hyperuricemia may modestly increase the risk of CHD and all-cause mortality. Future research is needed to determine whether urate–lowering therapy has beneficial effects for reducing CHD mortality.

Electronic supplementary material

The online version of this article (doi:10.1186/s12872-016-0379-z) contains supplementary material, which is available to authorized users.

Functional and Structural Characterization of Purine Nucleoside Phosphorylase from Kluyveromyces lactis and Its Potential Applications in Reducing Purine Content in Food

Consumption of foods and beverages with high purine content increases the risk of hyperuricemia, which causes gout and can lead to cardiovascular, renal, and other metabolic disorders. As patients often find dietary restrictions challenging, enzymatically lowering purine content in popular foods and beverages offers a safe and attractive strategy to control hyperuricemia. Here, we report structurally and functionally characterized purine nucleoside phosphorylase (PNP) from Kluyveromyces lactis (KlacPNP), a key enzyme involved in the purine degradation pathway. We report a 1.97 Å resolution crystal structure of homotrimeric KlacPNP with an intrinsically bound hypoxanthine in the active site. KlacPNP belongs to the nucleoside phosphorylase-I (NP-I) family, and it specifically utilizes 6-oxopurine substrates in the following order: inosine > guanosine > xanthosine, but is inactive towards adenosine. To engineer enzymes with broad substrate specificity, we created two point variants, KlacPNP^N256D and KlacPNP^N256E, by replacing the catalytically active Asn256 with Asp and Glu, respectively, based on structural and comparative sequence analysis. KlacPNP^N256D not only displayed broad substrate specificity by utilizing both 6-oxopurines and 6-aminopurines in the order adenosine > inosine > xanthosine > guanosine, but also displayed reversal of substrate specificity. In contrast, KlacPNP^N256E was highly specific to inosine and could not utilize other tested substrates. Beer consumption is associated with increased risk of developing gout, owing to its high purine content. Here, we demonstrate that KlacPNP and KlacPNP^N256D could be used to catalyze a key reaction involved in lowering beer purine content. Biochemical properties of these enzymes such as activity across a wide pH range, optimum activity at about 25°C, and stability for months at about 8°C, make them suitable candidates for food and beverage industries. Since KlacPNP^N256D has broad substrate specificity, a combination of engineered KlacPNP and other enzymes involved in purine degradation could effectively lower the purine content in foods and beverages.

Association of serum uric acid and cardioembolic stroke in patients with acute ischemic stroke

BACKGROUND

Although high uric acid levels have been reported to be a risk factor for cardiovascular disease and stroke, the relationship between serum uric acid (SUA) levels and cardioembolic stroke (CES) has not been fully elucidated. In this study, we sought to investigate the relationship between the risk of CES and SUA levels. We hypothesized that SUA concentrations are associated with CES.

METHODS

We retrospectively analyzed 2350 patients with acute ischemic stroke who were admitted to the Seoul National University Hospital between 2002 and 2010. The participants were stratified into five groups according to SUA levels obtained within 24h after stroke onset. The association between SUA levels and CES was evaluated using multivariable logistic regression models.

RESULTS

Of the 2350 patients, 412 (27.7%) were classified with CES, and 1077 (72.3%) were classified with non-CES, including LAA (large artery atherosclerosis) and SVO (small vessel occlusion). Among the acute stroke patients, SUA levels were higher in those with atrial fibrillation and other cardiovascular risk factors. Compared with the non-CES patients, the CES patients were more likely to fall in the highest quintile of SUA level. Multivariate analysis revealed that the patients with SUA concentrations in the highest quintile were associated with CES (OR=2.59, 95% CI: 1.35-4.97), test for trend P<0.001. Similar results were obtained for gender-based subgroups by (in men, OR=2.34, 95% CI: 1.06-5.15 and in women OR=3.41, 95% CI: 1.15-10.07), test for trend P<0.01 and P<0.001, respectively.

CONCLUSION

SUA level is associated with the risk of CES in acute ischemic stroke patients of both sexes. Further prospective clinical trials of lowering SUA to prevent CES may be worth considering.

Association of serum uric acid level with mortality and morbidity of patients with acute ST-elevation myocardial infarction

Introduction: Investigating the clinical impact of serum uric acid (UA) and its lowering agents on the complications and mortality of acute ST-elevation myocardial infarction (STEMI) can open a new era in STEMI treatment. The aim of this study was to evaluate the effect of on admission serum UA level on the mortality and morbidity of patients admitted with STEMI.

Methods: A number of 608 patients with STEMI were enrolled in this study from December 21, 2012 until February 19, 2014. Patients were followed for 20 months. Male to female ratio was 2.53, and the mean age of patients was 62.6±13.4. The relationship between the level of UA and patients’ mortality and morbidity, left ventricular ejection fraction (LVEF), atrial and ventricular arrhythmia was analyzed.

Results: Patients with high serum UA level had higher Killip class after STEMI (P=0.001). Mean LVEF was measured to be 39.5±9.6 in normal UA group and 34.6±11.6 in high UA group (P=0.001). In comparison with normal UA group, high UA group had significantly higher cTnI (2.68±0.09 vs 4.09±0.42, respectively, P=0.001), increased blood pressure (P=0.009), and higher atrial fibrillation (AF) occurrence (P=0.03), but no association was seen between ventricular tachycardia and serum UA level. Short term and midterm mortality were not different in two groups (P=0.44 and 0.31, respectively).

Conclusion: In the current study, high serum UA level in patients with acute myocardial infarction (MI) was not associated with higher in-hospital or midterm mortality, but it was associated with lower LVEF, higher Killip class, elevated cTnI, creatinine, triglyceride, and higher AF.

High serum uric acid levels increase the risk of metabolic syndrome in elderly women: The PRO.V.A study

BACKGROUND AND AIMS

Serum uric acid (SUA) is the end-product of purine metabolism in humans, and its levels often increase in subjects with metabolic syndrome (MetS). Despite several studies demonstrating a relationship between increased SUA levels and the prevalence of MetS, prospective data on SUA as a predictor of the incidence of MetS in the elderly are limited. Our aim was to conduct a prospective study on the association between SUA concentrations and the onset of MetS in an elderly Italian cohort.

METHODS AND RESULTS

This is a cohort study (Progetto Veneto Anziani; Pro.V.A.) involving community-dwelling subjects aged ≥65 years and followed up for a mean 4.4 years. We included 1128 participants (aged 74.7 ± 7.1 years) without MetS at the baseline. Gender-specific SUA groups according to the standard deviation (SD) from the mean were considered, taking the incidence of MetS as the main outcome. The mean SUA level was significantly higher in men than in women (5.4 ± 1.2 vs. 4.5 ± 1.2 mg/dl; p < 0.0001). Over the 4.4-year follow-up, 496 individuals developed MetS. After adjusting for potential confounders, Cox's regression analysis revealed no relationship between higher baseline SUA concentrations and the incidence of MetS in men or in the sample as whole, while women with SUA levels more than 1 SD above the mean (≥5.7 mg/dl) carried a 58% higher risk (95%CI: 1.03-2.40; p = 0.03) of being newly diagnosed with MetS during the follow-up.

CONCLUSION

High SUA levels significantly and independently predicted MetS in older women, but not in men, over a 4.4-year follow-up.

MicroRNAs: tools of mechanistic insights and biological therapeutics discovery for the rare neurogenetic syndrome Lesch-Nyhan disease (LND)

MicroRNAs (miRNAs) are small regulatory RNAs that modulate the translation of mRNA. They have emerged over the past few years as indispensable entities in the transcriptional regulation of genes. Their discovery has added additional layers of complexity to regulatory networks that control cellular homeostasis. Also, their dysregulated pattern of expression is now well demonstrated in myriad diseases and pathogenic processes. In the current review, we highlight the role of miRNAs in Lesch-Nyhan disease (LND), a rare neurogenetic syndrome caused by mutations in the purine metabolic gene encoding the hypoxanthine-guanine phosphoribosyltransferase (HPRT) enzyme. We describe how experimental and biocomputational approaches have helped to unravel genetic and signaling pathways that provide mechanistic understanding of some of the molecular and cellular basis of this ill-defined neurogenetic disorder. Through miRNA-based target predictions, we have identified signaling pathways that may be of significance in guiding biological therapeutic discovery for this incurable neurological disorder. We also propose a model to explain how a gene such as HPRT, mostly known for its housekeeping metabolic functions, can have pleiotropic effects on disparate genes and signal transduction pathways. Our hypothetical model suggests that HPRT mRNA transcripts may be acting as competitive endogenous RNAs (ceRNAs) intertwined in multiregulatory cross talk between key neural transcripts and miRNAs. Overall, this approach of using miRNA-based genomic approaches to elucidate the molecular and cellular basis of LND and guide biological target identification might be applicable to other ill-defined rare inborn-error metabolic diseases.

Serum uric acid and other short-term predictors of electrocardiographic alterations in the Brisighella Heart Study cohort

INTRODUCTION

Recent studies show that serum uric acid (SUA) is a predictor of atrial fibrillation, while its association with other kinds of arrhythmias is not yet established. We aimed to evaluate the incidence of the most common electrocardiographic alterations in a relatively large sample of general population and their association with SUA.

MATERIALS AND METHODS

We selected a Brisighella Heart Study cohort sample of 1557 subjects, consecutively visited in the 2004 and 2008 surveys, in a setting of primary prevention for cardiovascular disease and without a known diagnosis of arrhythmia or left ventricular hypertrophy, excluding subjects affected by gout or taking any antihyperuricemic agent or drugs able to interfere with the QT interval. A step-wise Cox regression analysis was used to determine the independent prognostic significance of age, gender, physical activity, smoking, body mass index (BMI), fasting plasma glucose, mean arterial pressure (MAP), heart rate, LDL-cholesterol, HDL-cholesterol, triglycerides, SUA and eGFR on ECG alterations during a 4-year follow-up.

RESULTS

No one of the considered variables was associated with the incident diagnosis of sinus tachycardia and sinus bradycardia. SUA predicted incident tachyarrhythmias, Q waves and ECG signs of left ventricular hypertrophy; age, female sex and active smoking predicted incident tachyarrhythmias; male sex, active smoking and LDL-cholesterol predicted incident ECG signs of previous myocardial infarction; BMI and MAP predicted incident ECG-diagnosed left ventricular hypertrophy.

CONCLUSION

In a cohort of general population, SUA seems to be a significant middle-term predictor of electrocardiographically diagnosed myocardial infarction, left ventricular hypertrophy and tachyarrhythmias.

Association of apolipoprotein E (ApoE) polymorphisms with risk of primary hyperuricemia in Uygur men, Xinjiang, China

BACKGROUND

Apolipoprotein E (ApoE) participates in lipoprotein metabolism and immune regulation. This study assessed association between ApoE polymorphisms with hyperuricemia and uric acid metabolism in Uygur men, Xinjiang, China.

METHODS

A total of 474 hyperuricemia patients and 518 healthy male controls were recruited from the Health Screening Center, Uygur region of Xinjiang, China and subjected to ApoE genotyping using a multiplex amplification refractory mutation system PCR.

RESULTS

Apolipoprotein E3/3 genotype was the predominant type with a frequency of 67.7%, while E2/2 was lower than E4/4 in Uygur males. The frequencies of ApoE2, E3, and E4 alleles were 8.5%, 80.1% and 11.4%, respectively. Distribution of ApoE genotypes was significantly different in hyperuricemia patients from the healthy controls (p<0.001). Particularly, the frequency of ApoE E3/3 was 71.7%, E2/3 9.3%, E3/4 9.3%, E4/4 3.2%, E2/4 2.3%, and E2/2 0.2% in patients vs. 68.1%, 4.6%, 2.9%, 12%, 0.6%, and 4.6% in controls, respectively. Moreover, frequency of ApoE E2 allele was greater in the healthy controls than in patients (p<0.001) and the highest level of uric acid occurred in those with ApoE2/4 and E3/4 genotypes, whereas the lowest uric acid level occurred in those with ApoE E2/2 genotype. In addition, the subjects with the ApoE2 allele had a lower uric acid and LDL-C level than those with the ApoE3 allele and ApoE4 allele (p<0.05). The risk of developing hyperuricemia in subjects without the ApoE2 allele was 1.7 fold higher than those subjects with the ApoE2 allele.

CONCLUSIONS

This study revealed frequencies and distributions of ApoE alleles and genotypes in Uygur males, which are different from Han Chinese. ApoE E4 was associated with a slightly higher risk of primary hyperuricemia, whereas ApoE E2 was associated with reduced risk of primary hyperuricemia and LDL-C level.

Mechanistic insights into xanthine oxidoreductase from development studies of candidate drugs to treat hyperuricemia and gout

Xanthine oxidoreductase (XOR), which is widely distributed from humans to bacteria, has a key role in purine catabolism, catalyzing two steps of sequential hydroxylation from hypoxanthine to xanthine and from xanthine to urate at its molybdenum cofactor (Moco). Human XOR is considered to be a target of drugs not only for therapy of hyperuricemia and gout, but also potentially for a wide variety of other diseases. In this review, we focus on studies of XOR inhibitors and their implications for understanding the chemical nature and reaction mechanism of the Moco active site of XOR. We also discuss further experimental or clinical studies that would be helpful to clarify remaining issues.

Predictors of Chronic Total Occlusion in Nonculprit Artery in Patients With Acute Coronary Syndrome

Chronic total occlusion (CTO) in a noninfarct-related artery (non-IRA) is an independent predictor of mortality in acute coronary syndrome (ACS). Mean platelet volume (MPV) and serum uric acid (SUA) are associated with cardiovascular events in ACS. We investigated the relationship between the presence of non-IRA-CTO with MPV and SUA levels in patients with ACS. Patients (n = 1024) who underwent urgent coronary angiography for ACS were included in this study. Blood samples were drawn on admission. Patients were categorized into 2 groups: non-IRA-CTO (−) and non-IRA-CTO (+). The MPV and SUA levels on admission were significantly higher in the non-IRA-CTO (+) group than in the non-IRA-CTO (−) group ( P < .001). At multivariate analysis, MPV (odds ratio [OR]: 4.705, P < .001) and SUA (OR: 2.535, P < .001) were independent predictors of non-IRA-CTO together with age, hemoglobin, ejection fraction, and non-ST-segment elevation ACS. The MPV and SUA levels were significant and independent predictors for the presence of non-IRA-CTO in patients with ACS.

[Effects of the combination of angiotensin receptor blockers and thiazide diuretics on laboratory values (levels of serum potassium, sodium, and uric acid)]

The combination of angiotensin receptor blockers (ARB) and a thiazide diuretic (hereafter, ARB/diuretic) is expected to improve patient adherence and increase the therapeutic effects because of the lower number of pills that require to be administered. In addition, an ARB/diuretic combination alleviates hypokalemia that frequently develops in patients receiving thiazide diuretics. In this study, we used electronic medical records to investigate the laboratory values (serum levels of potassium, sodium, and uric acid) of 194 ambulatory and hospitalized patients at the Gifu Municipal Hospital who received ARB/diuretic combination therapy for the first time between February 2010 and September 2012. According to the grade of classification of low serum potassium and sodium levels, the serum potassium level in one patient was grade 3 and the serum sodium level in two patients was grade 3 after the initiation of ARB/diuretic combination therapy. After administration of ARB/diuretic combination therapy, two patients received potassium supplements because their serum potassium levels decreased below the reference value. Similarly, one patient received a sodium supplement because of a decrease in the sodium level below the reference value. Uric acid level increased above the reference value after administration of the ARB/diuretic combination therapy in one patient; thus, this patient received antihyperuricemic agents. Therefore, pharmacists must carefully monitor the serum levels of potassium, sodium, and uric acid, particularly in the first six months after the initiation of ARB/diuretic combination therapy.

Genetic and Environmental Influences on Cardiovascular Disease Risk Factors: A Study of Chinese Twin Children and Adolescents

We evaluated the genetic and environmental contributions to metabolic cardiovascular risk factors and their mutual associations. Eight metabolic factors (body mass index, waist circumference, waist-to-hip ratio, systolic blood pressure, diastolic blood pressure, total serum cholesterol, serum triglycerides, and serum uric acid) were measured in 508 twin pairs aged 8–17 years from the Qingdao Twin Registry, China. Linear structural equation models were used to estimate the heritability of these traits, as well as the genetic and environmental correlations between them. Among boys, body mass index and uric acid showed consistently high heritability (0.49–0.81), whereas other traits showed moderate to high common environmental variance (0.37–0.73) in children (8–12 years) and adolescents (13–17 years) except total cholesterol. For girls, moderate to high heritability (0.39–0.75) were obtained for six metabolic traits in children, while only two traits showed high heritability and others mostly medium to large common environmental variance in adolescents. Genetic correlations between the traits were strong in both boys and girls in children (rg = 0.64–0.99 between body mass index and diastolic blood pressure; rg = 0.71–1.00 between body mass index and waist circumference), but decreased for adolescent girls (rg = 0.51 between body mass index and waist-to-hip ratio; rg = 0.55 between body mass index and uric acid; rg = 0.61 between body mass index and systolic blood pressure). The effect of genetic factors on most metabolic traits decreased from childhood to adolescence. Both common genetic and specific environmental factors influence the mutual associations among most of the metabolic traits.

Daidzein supplementation decreases serum triglyceride and uric acid concentrations in hypercholesterolemic adults with the effect on triglycerides being greater in those with the GA compared with the GG genotype of ESR-β RsaI

Daidzein (one of the major isoflavones) can be metabolized to equol in certain individuals. The effects of isoflavones alone and equol status on lipid profiles are still controversial. To evaluate the 6-mo effects of daidzein on cardiovascular risk factors in hypercholesterolemic individuals and the interactions of these effects with equol status and estrogen receptor (ESR) genotypes, we conducted a randomized, double-blind, placebo-controlled trial consisting of 210 hypercholesterolemic adults (40-65 y old). The participants were randomly assigned (177 completed) to consume placebo, 40 mg daidzein (DAI40), or 80 mg daidzein (DAI80) daily for 6 mo. Daidzein decreased serum triglycerides (TGs) by 0.15 ± 0.62 mmol/L (mean ± SD) and 0.24 ± 0.61 mmol/L and decreased serum uric acid by 23 ± 47 μmol/L and 29 ± 44 μmol/L in the DAI40 and DAI80 groups, respectively. These reductions in the DAI40 and DAI80 groups were greater than those in the placebo group (P < 0.05). Other blood lipids, glucose, insulin, or glycated hemoglobin did not significantly change after daidzein treatment. No dose-dependent effects of daidzein were found. The reduction of TGs was influenced by the ESR genotype, with a greater effect observed in participants with the GA genotype compared with those with the GG genotype of ESR-β RsaI. These effects were not influenced by equol status. Six-month supplementation of daidzein significantly decreased TGs and uric acid. ESR-β RsaI genotype, not equol status, influenced daidzein's effects on TGs. Daidzein consumption may be effective to improve cardiovascular risk factors, especially in adults with the GA genotype of ESR-β RsaI. This trial was registered at the Chinese clinical trial registry as ChiCTR-TRC-10001048.

Soluble ligand CD40 and uric acid as markers of atheromatosis in patients with obstructive sleep apnea

The aim of the study was to evaluate the risk of atheromatosis in patients with obstructive sleep apnea (OSA), as based on the concentration of the pro-atherogenic soluble CD40L ligand (sCD40L) in relation to the level of uric acid. The serum levels of sCD40L and uric acid were measured in 79 OSA patients (mean apnea/hypopnea index - AHI 34.4 ± 20.9) and in 40 healthy controls. We found that sCD40L was higher in the OSA patients with hyperuricemia than that in the patients with uric acid in the normal range (sCD40L: 9.0 ng/ml vs. 8.0 ng/ml, respectively, p < 0.05). There was a positive association of sCD40L with AHI (p = 0.01) and a negative one with the mean minimal nocturnal SaO₂(p < 0.05). Uric acid correlated negatively with the mean and minimal SaO₂and positively with the oxygen desaturation index (p < 0.05). OSA patients with hyperuricemia also had a higher prevalence of hypertension and ischemic heart disease. We conclude that OSA patients with increased uric acid concentration have increased risk of atheromatosis, as indicated by a higher level of soluble pro-atherogenic ligand CD40, and a higher prevalence of cardiovascular adverse events.

Potential role of uric acid in metabolic syndrome, hypertension, kidney injury, and cardiovascular diseases: is it time for reappraisal?

Elevated serum uric acid concentration is a common laboratory finding in subjects with metabolic syndrome/obesity, hypertension, kidney disease and cardiovascular events. Hyperuricemia has been attributed to hyperinsulinemia in metabolic syndrome and to decreased uric acid excretion in kidney dysfunction, and is not acknowledged as a main mediator of metabolic syndrome, renal disease, and cardiovascular disorder development. However, more recent investigations have altered this traditional view and shown, by providing compelling evidence, to support an independent link between hyperuricemia and increased risk of metabolic syndrome, diabetes, hypertension, kidney disease and cardiovascular disorders. However, despite these new findings, controversy regarding the exact role of uric acid in inducing these diseases remains to be unfolded. Furthermore, recent data suggest that the high-fructose diet in the United State, as a major cause of hyperuricemia, may be contributing to the metabolic syndrome/obesity epidemic, diabetes, hypertension, kidney disease and cardiovascular disorder. Our focus in this review is to discuss the available evidence supporting a role for uric acid in the development of metabolic syndrome, hypertension, renal disease, and cardiovascular disorder; and the potential pathophysiology mechanisms involved.

Echocardiographic changes and treatment goal rates after a 6-month combined treatment with amlodipine and losartan: a validation study in Andean countries (METAL study)

BACKGROUND

The extent to which treatment with amlodipine/losartan may help patients and their doctors from Andean countries to reach their treatment goals remains unknown.

METHODS

We conducted a quasi-experimental, validation study in which patients with primary, uncomplicated hypertension received open-label, fixed combination therapy with amlodipine/losartan 5/50 mg or 5/100 mg according to their baseline blood pressure (BP). The primary outcome was echocardiographic reduction of left ventricular mass (LMV) after 6 months of treatment. Secondary outcomes were changes in BP, uricemia and albuminuria from baseline. We defined patients with adequately controlled hypertension as those with decreases in at least three out of these four variables.

RESULTS

From 109 eligible patients with hypertension, 99 started the protocol (70 under the low-dose combination). Echocardiography indices had mutual correlation and contributed independently to the primary outcome (Cronbach's α index = 0.66). Intention-to-treat analysis showed that 60 patients [60.6%, 95% confidence interval (CI) 50.3-70.3] had reduced LVM. Echocardiographic changes were not associated with dose levels. Favorable changes in BP, uricemia and microabuminuria were seen in 77, 64 and 76 patients respectively. After 6 months there were 64 (95% CI 54-74%) patients with adequately controlled hypertension.

CONCLUSION

Every two of three patients of this sample of Andean countries reached adequate control after 6 months of combined antihypertensive treatment with amlodipine/losartan.

Chemical nature and reaction mechanisms of the molybdenum cofactor of xanthine oxidoreductase

Xanthine oxidoreductase (XOR), a complex flavoprotein, catalyzes the metabolic reactions leading from hypoxanthine to xanthine and from xanthine to urate, and both reactions take place at the molybdenum cofactor. The enzyme is a target of drugs for therapy of gout or hyperuricemia. We review the chemical nature and reaction mechanisms of the molybdenum cofactor of XOR, focusing on molybdenum-dependent reactions of actual or potential medical importance, including nitric oxide (NO) synthesis. It is now generally accepted that XOR transfers the water-exchangeable -OH ligand of the molybdenum atom to the substrate. The hydroxyl group at OH-Mo(IV) can be replaced by urate, oxipurinol and FYX-051 derivatives and the structures of these complexes have been determined by x-ray crystallography under anaerobic conditions. Although formation of NO from nitrite or formation of xanthine from urate by XOR is chemically feasible, it is not yet clear whether these reactions have any physiological significance since the reactions are catalyzed at a slow rate even under anaerobic conditions.

Association of plasma uric acid with ischaemic heart disease and blood pressure: mendelian randomisation analysis of two large cohorts

OBJECTIVES

To assess the associations between both uric acid levels and hyperuricaemia, with ischaemic heart disease and blood pressure, and to explore the potentially confounding role of body mass index.

DESIGN

Mendelian randomisation analysis, using variation at specific genes (SLC2A9 (rs7442295) as an instrument for uric acid; and FTO (rs9939609), MC4R (rs17782313), and TMEM18 (rs6548238) for body mass index).

SETTING

Two large, prospective cohort studies in Denmark.

PARTICIPANTS

We measured levels of uric acid and related covariables in 58,072 participants from the Copenhagen General Population Study and 10,602 from the Copenhagen City Heart Study, comprising 4890 and 2282 cases of ischaemic heart disease, respectively.

MAIN OUTCOME

Blood pressure and prospectively assessed ischaemic heart disease.

RESULTS

Estimates confirmed known observational associations between plasma uric acid and hyperuricaemia with risk of ischaemic heart disease and diastolic and systolic blood pressure. However, when using genotypic instruments for uric acid and hyperuricaemia, we saw no evidence for causal associations between uric acid, ischaemic heart disease, and blood pressure. We used genetic instruments to investigate body mass index as a potentially confounding factor in observational associations, and saw a causal effect on uric acid levels. Every four unit increase of body mass index saw a rise in uric acid of 0.03 mmol/L (95% confidence interval 0.02 to 0.04), and an increase in risk of hyperuricaemia of 7.5% (3.9% to 11.1%).

CONCLUSION

By contrast with observational findings, there is no strong evidence for causal associations between uric acid and ischaemic heart disease or blood pressure. However, evidence supports a causal effect between body mass index and uric acid level and hyperuricaemia. This finding strongly suggests body mass index as a confounder in observational associations, and suggests a role for elevated body mass index or obesity in the development of uric acid related conditions.

Beyond gout: uric acid and cardiovascular diseases

OBJECTIVES

This article discusses the results of clinical and experimental studies that examine the association of hyperuricemia and gout with cardiovascular (CV) disease.

METHODS

Key papers for inclusion were identified by a PubMed search, and articles were selected for their relevance to the topic, according to the authors' judgment.

RESULTS AND CONCLUSIONS

Significant progress has been made in confirming an association, possibly causal, between hyperuricemia and CV outcomes. Xantine-oxidase (XO) inhibitors appear to be the most promising agents for prevention and treatment of CV consequences associated with hyperuricemia. Several small and medium sized studies have examined the effect of these agents on CV function in a variety of patient populations. Improvements in measures of endothelial function, oxidative stress, cardiac function, hemodynamics, and certain inflammatory indices have been demonstrated. Compounds for XO inhibition with more specific clinical effects and fewer side effects than allopurinol may be promising options to further explore the therapeutic potential in patients with CV disease. It is too early to make clinical recommendations with regard to the benefits of using XO inhibitor allopurinol or the novel febuxostat in patients with asymptomatic increased UA levels and high CV risk because only a small number of studies have shown that they may be beneficial in terms of CV outcomes. More studies are therefore needed to determine the potential of these drugs for reducing the risk of developing CV disease.

Which is a better treatment for hypertensive patients with diabetes: a combination of losartan and hydrochlorothiazide or a maximum dose of losartan?

BACKGROUND

This 12-month study compared the effects of a combination of losartan 50 mg and hydrochlorothiazide 12.5 mg with a maximum dose of losartan (100 mg) in hypertensive patients with diabetes.

METHODS

This was a multicenter randomized open-label study.

RESULTS

A similar reduction in systolic/diastolic blood pressure from baseline to month 3 was observed in both groups. There was also a similar decrease in UACR in both groups. A significant decrease in uric acid was observed in the maximum-dose group only. eGFR decreased in the combination group after 1 year.

CONCLUSIONS

The combination of losartan and a diuretic may be a useful option in such hypertensive patients with diabetes, provided that metabolic parameters are closely monitored. In patients with hyperuricemia and impaired renal function, a maximum dose of losartan may be more beneficial.

Vascular aging: chronic oxidative stress and impairment of redox signaling-consequences for vascular homeostasis and disease

Characteristic morphological and molecular alterations such as vessel wall thickening and reduction of nitric oxide occur in the aging vasculature leading to the gradual loss of vascular homeostasis. Consequently, the risk of developing acute and chronic cardiovascular diseases increases with age. Current research of the underlying molecular mechanisms of endothelial function demonstrates a duality of reactive oxygen and nitrogen species in contributing to vascular homeostasis or leading to detrimental effects when formed in excess. Furthermore, changes in function and redox status of vascular smooth muscle cells contribute to age-related vascular remodeling. The age-dependent increase in free radical formation causes deterioration of the nitric oxide signaling cascade, alters and activates prostaglandin metabolism, and promotes novel oxidative posttranslational protein modifications that interfere with vascular and cell signaling pathways. As a result, vascular dysfunction manifests. Compensatory mechanisms are initially activated to cope with age-induced oxidative stress, but become futile, which results in irreversible oxidative modifications of biological macromolecules. These findings support the 'free radical theory of aging' but also show that reactive oxygen and nitrogen species are essential signaling molecules, regulating vascular homeostasis.

Association of uric acid with mortality in patients with stable coronary artery disease

OBJECTIVE

The association between uric acid and cardiovascular disease is poorly studied. We undertook this study to assess whether uric acid level predicts clinical outcome in patients with stable coronary artery disease (CAD) treated with percutaneous coronary intervention (PCI).

MATERIALS/METHODS

This study included 8149 patients with stable CAD who underwent PCI. Uric acid was measured before angiography. The primary end point was 1-year mortality. Quartiles of quartiles of uric acid were: 1.49 to <5.49 mg/dl (1st quartile; n=2032 patients), 5.49 to <6.40 mg/dl (2nd quartile; n=1981 patients), 6.40 to <7.50 mg/dl (3rd quartile; n=2093 patients) and 7.50 to 21.90 mg/dl (4th quartile; n=2043 patients).

RESULTS

There were 196 deaths during the 1-year follow-up. The numbers of deaths (Kaplan-Meier estimates) according to uric acid quartiles were: 35 deaths (1.8%) in the 1st quartile, 30 deaths (1.6%) in the 2nd quartile, 45 deaths (2.2%) in the 3rd quartile and 86 deaths (4.3%) in the 4th quartile (unadjusted hazard ratio [HR]=1.60, 95% confidence interval [CI] 1.38-1.86, P<0.001 for each standard deviation [SD] increase in the logarithmic scale). After adjustment for traditional cardiovascular risk factors, renal function and inflammatory status, the association between uric acid and 1-year mortality remained significant (adjusted HR=1.26, 95% CI 1.07-1.48; P=0.005 for each standard deviation increase in the logarithmic scale). Uric acid improved predictivity of the multivariable model regarding mortality (P=0.040).

CONCLUSIONS

Elevated level of uric acid is an independent predictor of 1-year mortality in patients with stable CAD treated with PCI.

The uric acid metabolism pathway as a therapeutic target in hyperuricemia related to metabolic syndrome

INTRODUCTION

Uric acid (UA) increase is considered an important risk factor for the development of cardiovascular disease (CVD) favoring oxidative stress and endothelial dysfunction and is also involved in metabolic syndrome (MS) pathophysiology.

AREAS COVERED

Insulin has a physiological action on renal tubules, causing a reduction in UA clearance, what could explain the hyperuricemia found in MS. On the other hand, it was also hypothesized a causal role of UA in fructose-induced MS. Moreover, it has been suggested that higher UA levels predict the development of MS. MS subjects present a redox imbalance and UA participates in this process. UA can contribute to oxidative stress present in MS; however, it has also an important role in the antioxidant defense system. Although UA may have a protective effect due to its antioxidant properties, it is clear that the dominant effect of UA in MS is deleterious. All-cause mortality and CVD have been shown to be increased with higher UA levels.

EXPERT OPINION

It is extremely important to prescribe drugs which concomitantly decrease hyperuricemia and improve co-morbidities associated with hyperuricemia. Long-term studies to verify the consequences of decreasing UA concentration below current recommendations in asymptomatic patients are needed.

Cross-sectional and longitudinal associations between serum uric acid and metabolic syndrome

Research on the importance of serum uric acid (SUA) as a contributing metabolic factor to cardiovascular diseases has conducted to conflicting results, with most studies assuming a cross-sectional design. The aim of this study was to evaluate the association of SUA and metabolic syndrome (MetS) and its features. A representative sample of 2,485 individuals aged ≥18 years was randomly selected from the non-institutionalized resident population of Porto, Portugal. A total of 1,054 eligible subjects were included for the longitudinal analyses. Hyperuricemia was defined as SUA ≥70 mg/L in men and ≥60 mg/L in women. MetS was defined according the Joint Interim (2009) criteria. Associations were estimated using Poison regression and binomial models. In the cross-sectional analysis, subjects with hyperuricemia had a 2.10-fold increased risk of MetS as compared with normouricemic subjects (PR = 2.10, 95% CI: 1.68-2.63). Among MetS features, high triglycerides presented the strongest association with hyperuricemia (PR = 2.32, 95% CI: 1.84-2.91). The MetS crude incidence rate was 4.5/100 person-year (95% CI: 3.9-5.2) in normal uricemic and 13.0/100 person-year (95% CI: 8.5-20.0) in hyperuricemic participants. Using a multivariate longitudinal approach, hyperuricemia was positively associated with MetS incidence rate ratios (IRR = 1.73, 95% CI: 1.08-2.76). One standard deviation increase of SUA concentration was associated with a 1.22-fold increase in MetS risk (IRR = 1.22, 95% CI: 1.05-1.42). Elevated SUA presented the strongest association with high-triglycerides concentration (IRR = 1.44, 95%: 1.22-1.71) and waist circumference (IRR = 1.25, 95%: 1.05-1.49). The independent positive association between SUA and MetS suggested by this longitudinal study supports that SUA might be a risk factor for MetS.

Prognostic value of uric acid in patients with acute coronary syndromes

The association between uric acid and cardiovascular disease is incompletely understood. In particular, the prognostic value of uric acid in patients with acute coronary syndromes who undergo percutaneous coronary intervention has not been studied. This study included 5,124 patients with acute coronary syndromes who underwent percutaneous coronary intervention: 1,629 with acute ST-segment elevation myocardial infarction, 1,332 with acute non-ST-segment elevation myocardial infarction, and 2,163 with unstable angina. The primary end point was 1-year mortality. Patients were divided into quartiles according to uric acid level as follows: quartile 1, 1.3 to <5.3 mg/dl; quartile 2, 5.3 to <6.3 mg/dl; quartile 3, 6.3 to <7.5 mg/dl; and quartile 4, 7.5 to 18.4 mg/dl. There were 450 deaths during follow-up: 80 deaths in quartile 1, 77deaths in quartile 2, 72 deaths in quartile 3, and 221 deaths in quartile 4 of uric acid (Kaplan-Meier estimates of 1-year mortality 6.4%, 6.2%, 5.6%, and 17.4%, respectively; unadjusted hazard ratio 3.05, 95% confidence interval 2.54 to 3.67, p <0.001 for fourth vs first quartile of uric acid). After adjustment for traditional cardiovascular risk factors, renal function, and inflammatory status, the association between uric acid and mortality remained significant, with a 12% increase in the adjusted risk for 1-year mortality for every 1 mg/dl increase in the uric acid level. Uric acid improved the discriminatory power of the predictive model regarding 1-year mortality (absolute integrated discrimination improvement 0.008, p = 0.005). In conclusion, elevated levels of uric acid are an independent predictor of 1-year mortality across the whole spectrum of patients with acute coronary syndromes treated with percutaneous coronary intervention.

Mendelian randomization: application to cardiovascular disease

In the absence of an ethical, practical, and economical randomized trial, the epidemiologist is left to explore other methods in efforts to assert causality. An approach based on genotypic variation has the potential to mitigate against some of the problems found within conventional observational studies. Genetic variations associated with risk factors of interest at the population level can be used as proxy measures for these risk factors and to generate estimates of causal effect. The potential and the possible limitations of this approach within the cardiovascular field are presented in this review.

A potentiometric indirect uric acid sensor based on ZnO nanoflakes and immobilized uricase

In the present work zinc oxide nanoflakes (ZnO-NF) structures with a wall thickness around 50 to 100 nm were synthesized on a gold coated glass substrate using a low temperature hydrothermal method. The enzyme uricase was electrostatically immobilized in conjunction with Nafion membrane on the surface of well oriented ZnO-NFs, resulting in a sensitive, selective, stable and reproducible uric acid sensor. The electrochemical response of the ZnO-NF-based sensor vs. a Ag/AgCl reference electrode was found to be linear over a relatively wide logarithmic concentration range (500 nM to 1.5 mM). In addition, the ZnO-NF structures demonstrate vast surface area that allow high enzyme loading which results provided a higher sensitivity. The proposed ZnO-NF array-based sensor exhibited a high sensitivity of ∼66 mV/ decade in test electrolyte solutions of uric acid, with fast response time. The sensor response was unaffected by normal concentrations of common interferents such as ascorbic acid, glucose, and urea.

Antihypertensive drugs and risk of incident gout among patients with hypertension: population based case-control study

OBJECTIVE

To determine the independent associations of antihypertensive drugs with the risk of incident gout among people with hypertension.

DESIGN

Nested case-control study.

SETTING

UK general practice database, 2000-7.

PARTICIPANTS

All incident cases of gout (n = 24,768) among adults aged 20-79 and a random sample of 50,000 matched controls.

MAIN OUTCOME MEASURE

Relative risk of incident gout associated with use of antihypertensive drugs.

RESULTS

After adjusting for age, sex, body mass index, visits to the general practitioner, alcohol intake, and pertinent drugs and comorbidities, the multivariate relative risks of incident gout associated with current use of antihypertensive drugs among those with hypertension (n = 29,138) were 0.87 (95% confidence interval 0.82 to 0.93) for calcium channel blockers, 0.81 (0.70 to 0.94) for losartan, 2.36 (2.21 to 2.52) for diuretics, 1.48 (1.40 to 1.57) for β blockers, 1.24 (1.17 to 1.32) for angiotensin converting enzyme inhibitors, and 1.29 (1.16 to 1.43) for non-losartan angiotensin II receptor blockers. Similar results were obtained among those without hypertension. The multivariate relative risks for the duration of use of calcium channel blockers among those with hypertension were 1.02 for less than one year, 0.88 for 1-1.9 years, and 0.75 for two or more years and for use of losartan they were 0.98, 0.87, and 0.71, respectively (both P<0.05 for trend).

CONCLUSIONS

Compatible with their urate lowering properties, calcium channel blockers and losartan are associated with a lower risk of incident gout among people with hypertension. By contrast, diuretics, β blockers, angiotensin converting enzyme inhibitors, and non-losartan angiotensin II receptor blockers are associated with an increased risk of gout.

Losartan therapy and hyperuricemia correction in patients with metabolic syndrome and arterial hypertension

Aim. To assess the potential of the angiotensin II receptor antagonist losartan for the correction of hyperuricemia (HU) in patients with arterial hypertension (AH) and metabolic syndrome (MS). Material and methods. This open, randomised, controlled comparative study in parallel groups included 60 AH patients with MS and HU. The patients received losartan or standard therapy for 12 weeks. Results. Throughout the follow-up period, no significant difference in antihypertensive effect was observed between the losartan and standard therapy groups. Losartan group patients demonstrated a more pronounced decrease in uric acid levels (-34,7 % vs. -7,8 % in the standard therapy group; p<0,05). In addition, losartan therapy, compared to the standard treatment, was associated with improved vascular elasticity, as manifested by the pulse wave velocity decrease (-27,8 % vs. -8,1 % for carotid-femoral index, and -30,2 % vs. -12,6 % for carotidradial index, respectively; both p<0,05).

Factor analysis of modifiable cardiovascular risk factors and prevalence of metabolic syndrome in adult Taiwanese

To assess the clustering of modifiable cardiovascular risk factors among Taiwanese adults, we evaluated 579 healthy participants who underwent health examinations between May and December 2007. Exploratory factor analysis was used to examine risk factor clustering. Smoking, alcohol intake, exercise habits, body mass index, waist circumference, total cholesterol, triglycerides, high- and low-density lipoprotein cholesterol, fasting glucose, uric acid, serum hepatic enzymes, and mean arterial pressure were assessed. Separate factor analyses assessed total and low-density lipoprotein cholesterol. Principal components analysis identified five factors for a model without low-density lipoprotein cholesterol and four factors for a model without total cholesterol. Four common factors in both models explained between 51.1 and 51.8% of variance in the original 14 factors. Metabolic factors, hematological factors (white blood cells and platelets), lifestyle factors (smoking and alcohol consumption), and exercise habits and fasting blood glucose explained about 20, 11, 10, 10% of total variance, respectively. In the model without low-density lipoprotein cholesterol, total cholesterol factor explained 8.83% of variance. This study confirmed clustering of established metabolic syndrome components and revealed additional associated cardiovascular disease risk factors, including lifestyle factors, exercise and total cholesterol, which should be targeted in prevention efforts.

Indications for and utilization of angiotensin receptor II blockers in patients at high cardiovascular risk

The worldwide burden of cardiovascular disease is growing. In addition to lifestyle changes, pharmacologic agents that can modify cardiovascular disease processes have the potential to reduce cardiovascular events. Antihypertensive agents are widely used to reduce the risk of cardiovascular events partly beyond that of blood pressure-lowering. In particular, the angiotensin II receptor blockers (ARBs), which antagonize the vasoconstrictive and proinflammatory/pro-proliferative effects of angiotensin II, have been shown to be cardio vascularly protective and well tolerated. Although the eight currently available ARBs are all indicated for the treatment of hypertension, they have partly different pharmacology, and their pharmacokinetic and pharmacodynamic properties differ. ARB trials for reduction of cardiovascular risk can be broadly categorized into those in patients with/without hypertension and additional risk factors, in patients with evidence of cardiovascular disease, and in patients with severe cardiovascular disease, such as heart failure. These differences have led to their indications in different populations. For hypertensive patients with left ventricular hypertrophy, losartan was approved to have an indication for stroke prevention, while for most patients at high-risk for cardiovascular events, telmisartan is an appropriate therapy because it has a cardiovascular preventive indication. Other ARBs are indicated for narrowly defined high-risk patients, such as those with hypertension or heart failure. Although in one analysis a possible link between ARBs and increased risks of cancer has surfaced, several meta-analyses, using the most comprehensive data available, have found no link between any ARB, or the class as a whole, and cancer. Most recently, the US Food and Drug Administration completed a review of the potential risk of cancer and concluded that treatment with an ARB medication does not increase the risk of developing cancer. This review discusses the clinical evidence supporting the different indications for each of the ARBs and the outstanding safety of this drug class.

Electrochemical selective detection of uric acid using a copper-modified carbon electrode

The uric acid (UA) level in (human) serum is an important indicator of several diseases; however, its electrochemical detection is difficult because the oxidation potentials of UA and ascorbic acid (AA) are very close. In this study, we have developed a simple and efficient UA detection method using a copper-modified carbon electrode. The detection principle is based on the selective oxidation of AA by Cu(II), wherein Cu(II) reacts selectively with AA but not with UA. By performing this specific reaction on an electrode surface, we have successfully distinguished the oxidation potential of UA without AA interference.

Allopurinol and global left myocardial function in heart failure patients

Background and Aim:

Increased xanthine oxidase (XO) activity may contribute to heart failure pathophysiology. This study evaluated whether a XO inhibitor, allopurinol produces clinical and functional benefits in patients with New York Heart Association functional class III to IV heart failure due to systolic dysfunction receiving optimal medical therapy as estimated by global left myocardial function.

Patients and Methods:

Fifty-nine patients with a diagnosis of chronic heart failure due to coronary heart disease or idiopathic dilated cardiomyopathy and 20 healthy controls who attended the outpatient clinic of cardiology were subjected to full echocardiographic study including left ventricular diastolic and systolic function, and the combined index of myocardial performance [Tei index: isovolumetric relaxation time (IRT) + isovolumetric contraction time (ICT)/ejection time (ET)]. Patients were randomized to allopurinol (300 mg/day) or placebo. Improvement at 36 weeks was assessed using a composite end point comprising global left cardiac function as well as heart failure morbidity and mortality.

Results:

The percentage of patients characterized as improved, unchanged, or worsened did not differ between those receiving allopurinol or placebo. Allopurinol reduced serum uric acid (SUA) by 1.5 mg/dL (P = 0.001). In a subgroup analysis, patients with elevated SUA (more than 7mg/ dL) responded favorably to allopurinol whereas those with SUA less than 7mg/dL exhibited a trend toward no change. In addition, SUA reduction to allopurinol correlated with favorable clinical and functional response. Within the entire allopurinol patient cohort, those characterized as either improved or unchanged had significantly greater reductions in SUA compared with patients who did not change (P = 0.0007). In placebo patients, lower baseline SUA, but not change in SUA, correlated with improved clinical outcome.

Conclusions:

Allopurinol did not produce significant clinical and functional improvement in unselected patients with moderate-to-severe heart failure. However, it is suggested that it is useful in patients with elevated SUA in a manner according to degree of SUA reduction. SUA may serve as a valuable biomarker to target heart failure therapy.

The effects of poststroke captopril and losartan treatment on cerebral blood flow autoregulation in SHRsp with hemorrhagic stroke

The ability of captopril and losartan treatment to restore cerebral blood flow (CBF) autoregulation after intracerebral hemorrhagic stroke (HS) was assessed in Kyoto-Wistar stroke-prone hypertensive rats (SHRsp). Laser Doppler techniques assessed CBF autoregulation in the middle cerebral artery (MCA) perfusion domain and a pressure myograph was used to measure pressure-dependent constriction (PDC) in isolated MCAs before and after stroke and after 13, 33, and 63 days of poststroke captopril or losartan treatment. The treatments did not lower blood pressure (BP) and equally suppressed plasma aldosterone after HS. The HS development was associated with the loss of CBF autoregulation, high CBF, increased CBF conductance to elevations in BP, and the loss of PDC in the MCAs. Both treatments restored these functions to prestroke levels within 13 days. The PDC and CBF autoregulation subsequently deteriorated after 63 days of captopril treatment while being maintained at prestroke levels over all durations of losartan treatment. The SHRsp subjected to 35 days of poststroke losartan treatment exhibited less blood-brain barrier (BBB) disruption and brain herniation than captopril-treated SHRsp. The superior ability of losartan to restore CBF autoregulation and myogenic function may have contributed to the more effective attenuation of cerebral damage after HS.

Is elevated SUA associated with a worse outcome in young Chinese patients with acute cerebral ischemic stroke?

Background

Elevated serum uric acid (SUA) levels can enhance its antioxidant prosperities and reduce the occurrence of cerebral infarction. Significantly elevated SUA levels have been associated with a better prognosis in patients with cerebral infarction; however, the results from some studies on the relationship between SUA and the prognosis of patients with cerebral infarction remain controversial.

Methods

We analyzed the relationship between SUA and clinical prognosis of 585 young Chinese adults with acute ischemic stroke as determined by the modified Rankin Scale at discharge. Using multivariate logistic regression modeling, we explore the relationship between SUA levels and patient's clinical prognosis.

Results

Lower SUA levels at time of admission were observed more frequently in the lowest quintile for patients with severe stroke (P = 0.02). Patients with cerebral infarction patients caused by small-vessel blockage had higher SUA concentrations (P = 0.01) and the lower mRS scores (P < 0.01) were observed in, while the lowest SUA concentrations and the highest mRS scores were seen in patients with cardiogenic cerebral infarction patients. Logistic regression analysis adjusted for confounders confirmed the following independent predictors for young cerebral infarction: uric acid (-0.003: 95%CI 0.994 to 0.999) and platelet (0.004, 95%CI 0.993 to 0.996).

Conclusion

Elevated SUA is an independent predictor for good clinical outcome of acute cerebral infarction among young adults.

Association of a common nonsynonymous variant in GLUT9 with serum uric acid levels in old order amish

OBJECTIVE

Uric acid is the primary end product of purine metabolism. Increased serum uric acid levels have been associated with gouty arthritis as well as with a variety of cardiovascular-related phenotypes. This study was undertaken to investigate associations between uric acid levels and single-nucleotide polymorphisms (SNPs).

METHODS

A 500,000-SNP genome-wide association study of serum uric acid levels was performed in a cohort of Old Order Amish from Lancaster County, Pennsylvania.

RESULTS

The scan confirmed a previously identified region on chromosome 4 to be strongly associated with uric acid levels (P = 4.2 x 10(-11) for rs10489070). Followup genotyping revealed that a nonsynonymous coding SNP (Val253Ile; rs16890979) in GLUT9 was most strongly associated with uric acid levels, with each copy of the minor allele associated with a decrease of 0.47 mg/dl in the uric acid level (95% confidence interval 0.31-0.63 [P = 1.43 x 10(-11)]). The effect of this variant tended to be stronger in women than in men (P = 0.16 for sex-genotype interaction). The genotype effect was not modified by the inclusion of several cardiovascular risk factors, suggesting that GLUT9 is directly related to uric acid homeostasis. The SNP identified in the genome-wide scan in the Amish population (rs10489070) was also significantly associated with gout in the Framingham Heart Study (P = 0.004).

CONCLUSION

Our findings indicate that GLUT9, which is expressed in the kidney, may be a novel regulator of uric acid elimination and that a common nonsynonymous variant in this gene contributes to abnormalities in uric acid homeostasis and gout.