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

Serum uric acid levels correlate with filling pressures in systolic heart failure

The authors studied the relationship between liver function tests and serum uric acid level with clinical and hemodynamic profiles in heart failure. Fifty patients (aged 44±15 years; 74.5% men) with an ejection fraction (EF) <35% were enrolled and clinical assessment was performed. Hemodynamic indices (including pulmonary arterial pressure [PAP], pulmonary capillary wedge pressure [PCWP], and cardiac index were studied by standard Edwards Lifesciences Swan-Ganz catheters, and liver function tests and serum uric acid level were measured simultaneously. Fifty age- and sex-matched controls with normal EF were also studied. A total of 73% of patients had ischemic cardiomyopathy. Mean uric acid level was 7.2±3.8 mg/dL and was significantly higher than in the control group (P value<.001). In multivariate analysis, uric acid correlated significantly with PAP (r=.5, P<.001) and PCWP (r=.4, P=.002) and was also associated with clinical signs of rales, edema, paroxysmal nocturnal dyspnea (r=.5, P=.01), and New York Heart Association class (r=.4, P=.005). Uric acid level was also correlated inversely with left ventricular EF (r=.27, P=.006). Elevated uric acid levels in patients with systolic heart failure is associated with impaired clinical and hemodynamic profile and might be used as a noninvasive indicator of elevated left ventricular filling pressures.

Uric acid levels and atrial fibrillation in hypertensive patients

OBJECTIVE

Uric acid (UA) is a cardiovascular risk marker associated with oxidative stress and inflammation. Recently, atrial fibrillation (AF) has been associated with inflammation and oxidative stress. The objective of this observational study was to investigate the association between UA levels and AF in hypertensive patients.

METHODS

Consecutive patients with hypertension were screened. We excluded subjects with coronary artery disease, congestive heart failure, diabetes, valvular heart disease, congenital heart disease, cardiomyopathy, renal failure, inflammatory conditions, thyroid dysfunction, respiratory diseases, and those who were taking drugs that affect UA metabolism (apart from diuretics). The final study population consisted of 451 patients. Fifty of them (11%) had AF (paroxysmal: 38; persistent: 8; permanent: 4). Demographic, clinical, laboratory, and echocardiographic characteristics were carefully recorded.

RESULTS

After univariate analysis, age, duration of hypertension, serum creatinine, serum UA, left atrial diameter (LAD), interventricular septum thickness, and left ventricular posterior wall thickness were significantly increased in patients with AF compared with non-AF patients, while the estimated glomerular filtration (eGFR) level was much lower in patients with AF than in those without AF. After multivariate logistic regression analysis, the independent predictors of AF were UA (OR: 1.008; 95% CI: 1.003-1.013, p=0.002) and LAD (OR: 1.160; 95% CI: 1.068-1.260; p<0.001).

CONCLUSION

We demonstrated an independent association between increased serum UA levels and AF in hypertensive patients. Undoubtedly, larger studies in different populations should further examine this potential association as well as the underlying pathophysiological mechanisms.

Increased plasma xanthine oxidase activity is related to nuclear factor kappa beta activation and inflammatory markers in familial combined hyperlipidemia

BACKGROUND AND AIMS

Xanthine oxidase (XO) has been described as one of the major enzymes producing free radicals in blood. Oxidative stress and inflammatory processes have been implicated in the pathogenesis of endothelial dysfunction and the progression of atherosclerosis but until now, there is little data about the influence of vascular prooxidant systems and inflammation in familial combined hyperlipidemia (FCH). Our goal was to evaluate whether XO activity was altered in FCH and if it was related to the inflammatory process represented by NFkB, IL-6 and hsCRP, and assessing the correlation between XO activity and insulin resistance (IR).

METHOD AND RESULTS

40 Non-related subjects with FCH and 30 control subjects were included, all of them non-diabetic, normotensive and non-smokers. We measured lipid profile, glucose, insulin, uric acid, XO activity, malondialdehyde (MDA), IL-6 and hsCRP in plasma and NFkB activity in circulating mononuclear cells. Patients with FCH showed significantly higher levels of uric acid, XO activity, MDA, NFkB activity, IL-6 and hsCRP than controls. XO activity was independently related to NFkB activity with an odds ratio of 4.082; to IL-6 with an odds ratio of 4.191; and to IR with an odds ratio of 3.830. Furthermore, mean NFkB activity, IL-6 levels, and IR were highest in the highest percentile of XO activity.

CONCLUSIONS

Subjects with FCH showed increased XO and NFkB activities and low grade inflammatory markers related to atherosclerosis. XO activity was correlated with higher inflammatory activity and IR. These data could explain, in part, the high cardiovascular disease risk present in these patients.

Epidemiological association between uric acid concentration in plasma, lipoprotein(a), and the traditional lipid profile

BACKGROUND

Elevated levels of uric acid in serum (SUA) or plasma (PUA) are increasingly related to cardiovascular disease. It is unclear whether they are independent risk factors or simply markers, reflecting association with other traditional risk factors.

METHODS

We retrospectively assessed results of a lipid profile, including total cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglycerides, total cholesterol to HDL-C ratio (TC/HDL-C), the atherogenic index of plasma (AIP), and lipoprotein(a) (Lp[a]), in a large cohort of unselected adult outpatients.

RESULTS

Hyperuricemic men displayed significantly increased values of triglycerides and AIP when compared with men with normal PUA levels. In hyperuricemic women, significant differences were observed for HDL-C, triglycerides, TC/HDL-C, and AIP compared with women with normal PUA levels. The percentage of patients with unfavorable values was statistically higher for triglycerides and AIP in hyperuricemic men; for HDL-C, triglycerides, TC/HDL-C, and AIP in hyperuricemic women. In multivariable linear regression analysis triglycerides, AIP, and TC/HDL-C were independently associated with PUA in women, whereas no significant association was observed in men.

CONCLUSION

PUA measurement might be advisable in patients to identify those at increased risk of cardiovascular disease (CVD) who might benefit from further triage and intervention.

The effect of allopurinol on the cerebral vasculature of patients with subcortical stroke; a randomized trial

AIMS

New preventative strategies for stroke are required. One promising strategy is uric acid reduction and xanthine oxidase inhibition with allopurinol. We sought to investigate whether allopurinol improves cerebrovascular reactivity (CVR) following subcortical stroke.

METHODS

We performed a randomized, double-blind, controlled study to investigate the effect of a 3-month course of 300 mg allopurinol once daily vs. placebo on CVR in individuals with recent (within 6 months) subcortical stroke. Participants were randomized on a 1:1 basis. CVR was defined as the percentage change in middle cerebral artery flow velocity following an intravenous injection of 15 mg kg(-1) of acetazolamide. Our primary end-point was the CVR difference between baseline and 3 months. Secondary end-points included measures of peripheral vascular reactivity and blood markers of inflammation and endothelial activation.

RESULTS

We enrolled 50 participants; 45 completed the protocol. Baseline serum urate was 0.35 mmol l(-1) (SD 0.1) and 0.34 mmol l(-1) (SD 0.1) in the allopurinol and placebo groups, respectively. There were no serious adverse events related to treatment. CVR did not change following treatment with allopurinol [median CVR change 0.89% after allopurinol (n = 20) and -0.68% after placebo (n = 25); 95% confidence interval for estimated difference in medians -13.4, 25.5, P = 0.64]. Urate was significantly lowered by allopurinol but no change in other secondary end-points was seen.

CONCLUSION

Xanthine oxidase inhibition with allopurinol has previously been shown to improve cerebrovascular function, but no benefit was seen in this study. It may therefore be that previous encouraging findings will not translate into important clinical benefits.

The Virtual International Stroke Trials Archive (VISTA): Results and Impact on Future Stroke Trials and Management of Stroke Patients

Background

The Virtual International Stroke Trials Archive was established to improve stroke care and trial design through the collation, categorization and potential access to data sets from clinical trials for the treatment of stroke.

Methods

Virtual International Stroke Trials Archive currently provides access to a combined data set of 29 anonymised acute stroke trials and one acute stroke registry with data on >27 500 patients aged between 18 and 103 (mean 71) years.

Results

Virtual International Stroke Trials Archive has facilitated research across a broad canvas. The prognosis was poor in patients with very high blood pressure at the time of admission or with a wide variability of systolic blood pressure during the acute phase. The late occurrence of hyperthermia following an ischaemic stroke worsens the prognosis. Stroke lateralisation is not an important predictor of cardiac adverse events or 90-day mortality. Haemorrhagic transformation is seen frequently in patients with cardio-embolic strokes and is associated with a poor prognosis when occurring after the acute phase. Virtual International Stroke Trials Archive has allowed various prognostic models for patients with ischaemic or haemorrhagic stroke to be established and validated. More direct outcomes such as lesion volume can be useful in phase II clinical trials for determining whether a phase III trial should be undertaken. New outcome measures such as ‘home time’ may also strengthen future trials. On a worldwide level, the prognosis of stroke patients differs considerably between various countries.

Conclusion

Virtual International Stroke Trials Archive provides an excellent opportunity for analysis of natural history data and prognosis. It has the potential to influence clinical trial design and implementation through exploratory data analyses.

The potential for xanthine oxidase inhibition in the prevention and treatment of cardiovascular and cerebrovascular disease

There is a now a wealth of epidemiological, animal, and clinical data to suggest the benefits of uric acid reduction and hxanthine oxidase inhibition in prevention of vascular disease. This review discusses the available epidemiological, preclinical, and clinical data and considers arguments for and against a role for serum uric acid in common cardiovascular disorders. It concludes that large scale trials with clinical endpoints are justified to address this important question and to define whether use of drugs such as allopurinol should be a routine part of preventative strategies.

Usefulness of combining serum uric acid and C-reactive protein for risk stratification of patients with coronary artery disease (Bezafibrate Infarction Prevention [BIP] study)

Combined assessment of serum uric acid (UA) and C-reactive protein (CRP) compared with single-marker evaluation in patients with coronary artery disease (CAD) was performed. CRP is an independent predictor of cardiac events in patients with or without CAD. Data regarding the prognostic value of UA in patients with CAD are conflicting. The primary end point (fatal or nonfatal myocardial infarction or sudden cardiac death) was related to levels of UA and CRP in 2,966 patients with CAD enrolled in the Bezafibrate Infarction Prevention trial who were followed for a mean period of 6.2 years. Primary end-point rates were directly related to increasing tertiles (from tertile 1 [T1] to tertile 3 [T3]) of UA (12.7%, 12.8%, and 17.6% respectively, p for trend <0.0001) and CRP (11.5%, 14.2%, and 17.3% respectively, p for trend <0.002). By multivariable analysis, T3 UA (>6.25 mg/dl) and T3 CRP (>5.37 mg/dl) were shown to be independently associated with a significant increase in risk for the primary end point (hazard ratio 1.30, 1.01 to 1.68, p = 0.04; hazard ratio 1.31, 1.02 to 1.69, p = 0.03, respectively). Primary end-point rates were similarly high in those patients with a combination of T3 UA and T1 CRP levels (hazard ratio 1.68, 1.05 to 2.66) or a combination of T3 CRP and T1 serum UA levels (hazard ratio 1.64, 1.04 to 2.58) or in patients with T3 of the 2 markers (hazard ratio 1.66, 1.07 to 2.59). In conclusion, combined assessment of UA and CRP levels provides incremental information for risk stratification of patients with CAD with low levels of a single marker.

Genetics of variation in serum uric acid and cardiovascular risk factors in Mexican Americans

BACKGROUND

Elevated serum uric acid is associated with several cardiovascular disease (CVD) risk factors such as hypertension, inflammation, endothelial dysfunction, insulin resistance, dyslipidemia, and obesity. However, the role of uric acid as an independent risk factor for CVD is not yet clear.

OBJECTIVE

The aim of the study was to localize quantitative trait loci regulating variation in serum uric acid and also establish the relationship between serum uric acid and other CVD risk factors in Mexican Americans (n = 848; men = 310, women = 538) participating in the San Antonio Family Heart Study.

METHODS

Quantitative genetic analysis was conducted using variance components decomposition method, implemented in the software program SOLAR.

RESULTS

Mean +/- SD of serum uric acid was 5.35 +/- 1.38 mg/dl. Univariate genetic analysis showed serum uric acid and other CVD risk markers to be significantly heritable (P < 0.005). Bivariate analysis showed significant correlation of serum uric acid with body mass index, waist circumference, waist/hip ratio, total body fat, plasma insulin, serum triglycerides, high-density lipoprotein cholesterol, C-reactive protein, and granulocyte macrophage-colony stimulating factor (P < 0.05). A genome-wide scan for detecting quantitative trait loci regulating serum uric acid variation showed a significant logarithm of odds (LOD) score of 4.72 (empirical LOD score = 4.62; P < 0.00001) on chromosome 3p26. One LOD support interval contains 25 genes, of which an interesting candidate gene is chemokine receptor 2.

SUMMARY

There is a significant genetic component in the variation in serum uric acid and evidence of pleiotropy between serum uric acid and other cardiovascular risk factors.

Allopurinol and nitric oxide activity in the cerebral circulation of those with diabetes: a randomized trial

OBJECTIVE

Type 2 diabetes increases risk of stroke, perhaps because of impaired cerebrovascular basal nitric oxide (NO) activity. We investigated whether this activity is improved by a 2-week course of the xanthine oxidase inhibitor allopurinol.

RESEARCH DESIGN AND METHODS

We performed a randomized, double-blind, placebo-controlled crossover study. We measured the response to infusion of NG-monomethyl-L-arginine (l-NMMA) in males with type 2 diabetes before and after allopurinol or placebo. The primary end point was the change in internal carotid artery flow following L-NMMA infusion, expressed as the area under the flow-per-time curve.

RESULTS

We enrolled 14 participants. Allopurinol improved responses to L-NMMA when compared with responses associated with placebo (P = 0.032; median reduction in internal carotid artery flow following L-NMMA of 3,144 ml [95% CI 375-7,143]).

CONCLUSIONS

Xanthine oxidase inhibition with allopurinol appears to improve cerebral NO bioavailability, as evidenced by a greater response to infusion of L-NMMA.

Hyperuricemia in acute heart failure. More than a simple spectator?

BACKGROUND

Hyperuricemia is a prevalent condition in chronic heart failure (CHF), describing increased oxidative stress and inflammation. Although there is evidence that serum uric acid (UA) predicts mortality in CHF, its role as a prognostic biomarker in acute heart failure (AHF) has not yet been well assessed. The aim of this study was to determine if UA levels predict all-cause mortality. Additionally, as a secondary endpoint we sought the clinical predictors of UA serum level in this population.

METHODS

We analyzed 560 consecutive patients with AHF admitted in a single university center. UA (mg/dl) was measured during early hospitalization. Patient survival status was followed up after discharge (median follow-up: 330 days). The independent association of UA level with all-cause mortality was analyzed using Cox regression analysis.

RESULTS

During follow-up 165 (29.5%) deaths were identified. Patients with UA levels above the median value (>or=7.7 mg/dl) exhibited higher mortality rates (21.1 vs. 37.9%; p<0.001). In multivariable analysis, after adjusting for recognized prognostic factors and potential confounders, UA>or=7.7 mg/dl and per change in 1 mg/dl of UA was associated with an increased risk of mortality (HR 1.45, CI 95%=1.03-2.44; p=0.03 and HR 1.08, CI 95%=1.01-1.15; p=0.03, respectively).

CONCLUSION

UA serum levels is an independent predictor of all-cause mortality in an unselected patients admitted with AHF.

Allopurinol use yields potentially beneficial effects on inflammatory indices in those with recent ischemic stroke: a randomized, double-blind, placebo-controlled trial

BACKGROUND AND PURPOSE

Elevated serum uric acid level is associated with poor outcome and increased risk of recurrent events after stroke. The xanthine oxidase inhibitor allopurinol lowers uric acid but also attenuates expression of inflammatory adhesion molecules in murine models, reduces oxidative stress in the vasculature, and improves endothelial function. We sought to investigate whether allopurinol alters expression of inflammatory markers after acute ischemic stroke.

METHODS

We performed a randomized, double-blind, placebo-controlled trial to investigate the safety, tolerability, and effect of 6 weeks' treatment with high- (300 mg once a day) or low- (100 mg once a day) dose allopurinol on levels of uric acid and circulating inflammatory markers after ischemic stroke.

RESULTS

We enrolled 50 patients with acute ischemic stroke (17, 17, and 16 in the high, low, and placebo groups, respectively). Mean (+/-SD) age was 70 (+/-13) years. Groups had similar characteristics at baseline. There were no serious adverse events. Uric acid levels were significantly reduced at both 7 days and 6 weeks in the high-dose group (by 0.14 mmol/L at 6 weeks, P=0.002). Intercellular adhesion molecule-1 concentration (ng/mL) rose by 51.2 in the placebo group, rose slightly (by 10.6) in the low-dose allopurinol group, but fell in the high-dose group (by 2.6; difference between groups P=0.012, Kruskal-Wallis test).

CONCLUSIONS

Allopurinol treatment is well tolerated and attenuates the rise in intercellular adhesion molecule-1 levels seen after stroke. Uric acid levels were lowered with high doses. These findings support further evaluation of allopurinol as a preventive measure after stroke.

Associations between serum uric acid and adipokines, markers of inflammation, and endothelial dysfunction

AIM

Serum uric acid is associated with the metabolic syndrome and its components, while its relationship with cardiovascular disease is controversial. The aim of the study was to evaluate the association between uric acid and adipokines, markers of inflammation, oxidative stress, and endothelial dysfunction, which are all linked to cardiovascular disease.

METHODS

The associations between uric acid and adiponectin, resistin, leptin, high-sensitivity-C-reactive protein (hs-CRP), interleukin-6, tumor necrosis factor-alpha, nitrotyrosine, Total Antioxidant Status (TAS), E-selectin, vascular adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1) were cross-sectionally evaluated in a randomly collected sample of 100 men from a population-based cohort.

RESULTS

Subjects within the highest uric acid quartile showed a worse metabolic pattern and a higher prevalence of the metabolic syndrome [odds ratio (OR)=3.6; 95% confidence interval (CI) 1.6-8.2; p<0.001 for each 50 micromol/l uric acid increment in a logistic regression model after multiple adjustments]. Nitrotyrosine and adiponectin were significantly lower, while TAS, hs-CRP, E-selectin, ICAM-1, and VCAM-1 were higher in the groups with increased uric acid levels. In a multiple regression model, after adjustments for multiple confounders, uric acid levels were inversely associated with nitrotyrosine (p<0.001) and adiponectin (p=0.02), and directly with TAS (p<0.001), and E-selectin (p=0.006).

CONCLUSION

Serum uric acid showed opposite relationships, being associated with both beneficial (inverse association with nitrotyrosine, direct association with TAS) and detrimental (inverse association with adiponectin, direct association with E-selectin) markers, thus providing a possible explanation for the previously reported controversial and not linear association between uric acid and cardiovascular disease.