Effect of allopurinol on blood pressure and aortic compliance in hypertensive patients

Uric Acid and Hypertension: Prognostic Role and Guide for Treatment

The relationship between serum uric acid (SUA) and hypertension has been a subject of increasing interest since the 1870 discovery by Frederick Akbar Mahomed. Several epidemiological studies have shown a strong association between high SUA levels and the presence or the development of hypertension. Genetic analyses have found that xanthine oxidoreductase (XOR) genetic polymorphisms are associated with hypertension. However, genetic studies on urate transporters and Mendelian randomization studies failed to demonstrate a causal relationship between SUA and hypertension. Results from clinical trials on the role of urate-lowering therapy in the management of patients with hypertension are not uniform. Our study sought to analyze the prognostic and therapeutic role of SUA in the hypertensive disease, from uric acid (UA) biology to clinical trials on urate-lowering therapies.

Pharmacotherapy for hyperuricaemia in hypertensive patients

BACKGROUND

This is the second update of this systematic review. High blood pressure represents a major public health problem. Worldwide, approximately one-fourth of the adult population has hypertension. Epidemiological and experimental studies suggest a link between hyperuricaemia and hypertension. Hyperuricaemia affects 25% to 40% of those with untreated hypertension; a much lower prevalence has been reported in those with normotension or in the general population. However, whether lowering serum uric acid (UA) might lower blood pressure (BP), is an unanswered question.

OBJECTIVES

To determine whether UA-lowering agents reduce BP in people with primary hypertension or prehypertension, compared with placebo.

SEARCH METHODS

The Cochrane Hypertension Information Specialist searched the following databases for randomised controlled trials up to May 2020: the Cochrane Hypertension Specialised Register, CENTRAL 2018, Issue 12, MEDLINE (from 1946), Embase (from 1974), the World Health Organization International Clinical Trials Registry Platform, and ClinicalTrials.gov. We also searched LILACS (1982 to May 2020), and contacted authors of relevant papers regarding further published and unpublished work. The searches had no language or date restrictions.

SELECTION CRITERIA

To be included in this updated review, the studies had to meet the following criteria: 1) randomised or quasi-randomised, with a group assigned to receive a UA-lowering agent and another group assigned to receive placebo; 2) double-blind, single-blind, or open-label; 3) parallel or cross-over trial design; 4) cross-over trials had to have a washout period of at least two weeks; 5) minimum treatment duration of four weeks; 6) participants had to have a diagnosis of essential hypertension or prehypertension plus hyperuricaemia (serum UA greater than 6 mg/dL in women, 7 mg/dL in men, and 5.5 mg/dL in children or adolescents); 7) outcome measures included change in 24-hour ambulatory systolic or diastolic BP, or both; or clinic-measured systolic or diastolic BP, or both.

DATA COLLECTION AND ANALYSIS

The two review authors independently collected the data using a data extraction form, and resolved any disagreements via discussion. We assessed risk of bias using the Cochrane 'Risk of bias' tool. We assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

In this review update, we screened 722 records, selected 26 full-text reports for evaluation. We identified no ongoing studies and did not add any new studies. We included three randomised controlled trials (RCTs), enrolling 211 people with hypertension or prehypertension, plus hyperuricaemia. Low-certainty evidence from three RCTs found inconclusive results between those who received UA-lowering drugs and placebo, in 24-hour ambulatory systolic (MD -6.2 mmHg, 95% CI -12.8 to 0.5) or diastolic BP (-3.9 mmHg, 95% CI -9.2 to 1.4). Low-certainty evidence from two RCTs found that UA-lowering drugs reduced clinic-measured systolic BP (-8.43 mmHg, 95% CI -15.24 to -1.62) but results for clinic-measured diastolic BP were inconclusive (-6.45 mmHg, 95% CI -13.60 to 0.70). High-certainty evidence from three RCTs found that serum UA levels were reduced by 3.1 mg/dL (95% CI 2.4 to 3.8) in the participants that received UA-lowering drugs. Low-certainty evidence from three RCTs found inconclusive results regarding the occurrence of adverse events between those who received UA-lowering drugs and placebo (RR 1.86, 95% CI 0.43 to 8.10).

AUTHORS' CONCLUSIONS

In this updated Cochrane Review, the current RCT data are insufficient to know whether UA-lowering therapy lowers BP. More studies are needed.

Cardiovascular safety risks associated with gout treatments

INTRODUCTION

Uric acid is the final byproduct of purine metabolism. The loss of the enzyme that hydrolyzes uric acid to allantoin was lost, leading to a decrease in uric acid excretion and its further accumulation. The buildup of uric acid leads to damage in different organ systems, including the cardiovascular system. With the increasing burden of cardiovascular disease worldwide, a growing body of evidence has addressed the relationship between urate, cardiovascular outcomes, and gout medication cardiovascular safety. Areas covered: We discuss the most common gout therapies used for the reduction of serum urate and management of gout flares in different observational and clinical trials and their effects on different aspects of cardiovascular disease. We selected the most representative clinical studies that evaluated cardiovascular outcomes with each gout therapy as well as recommendation given by the most representative guidelines from Rheumatology societies for the management of gout.

EXPERT OPINION

The treatment of gout reduces joint damage and it can also lessen CV morbidity. Allopurinol shows CV safety profile when compared to other ULTs. Evidence supporting CV safety with the use of colchicine and IL-1 agents is promising and research needs to be conducted to further assess this outcome.

Effects of Angiotensin-Converting Enzyme Inhibitors on Arterial Stiffness: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

To determine the effects of ACEIs on arterial stiffness, a meta-analysis of randomized controlled trials was conducted. Relevant articles that investigated the effects of ACEIs on arterial stiffness from PubMed, Embase, and the Cochrane library from inception to September 2018 were systematically retrieved. The investigated outcomes included brachial-ankle pulse wave velocity (ba-PWV) and carotid-femoral PWV (cf-PWV) by using weighted mean differences (WMDs) and 95% confidence intervals (CIs) with the random-effects model. A total of 17 RCTs including 1,458 individuals were included. The summary results indicated no significant differences between ACEIs and control for ba-PWV and cf-PWV. Also, no significant differences between ACEI and control for ba-PWV and cf-PWV were observed in hypertensive patients, while the therapeutic effects of ACEI versus placebo showed statistically significant difference. Moreover, subgroup analysis indicated that the levels of ba-PWV were significantly associated if the study was conducted in Western countries, mean age <60.0 years, percentage male ≥60.0%, compared with ARBs, baseline PWV <10.0, and high-quality study. Furthermore, the significant levels of cf-PWV in patients who received ACEIs were observed when percentage male was ≥60.0% and the studies were of high-quality. Finally, no significant differences were observed between ACEIs and other antihypertensive drugs regarding the changes of systolic blood pressure (SBP) and diastolic blood pressure (DBP). The overall analysis suggested no significant differences between ACEIs and other antihypertensive drugs for ba-PWV and cf-PWV levels, whereas ACEIs versus placebo showed lower levels of ba-PWV and cf-PWV.

Pegloticase Treatment Significantly Decreases Blood Pressure in Patients With Chronic Gout

Serum urate is correlated with blood pressure (BP), and lowering urate may decrease BP, but a consistent effect has not been observed. Here, we evaluated whether pegloticase, a recombinant uricase conjugated to polyethylene glycol, which can lead to persistently low serum urate levels (<1 mg/dL), can modulate BP in subjects with chronic refractory gout. This post hoc analysis used results from two 6-month randomized clinical trials in which subjects were treated with 8 mg pegloticase every 2 or 4 weeks (q2w or q4w) or placebo. Responders in this study were defined as those individuals in whom a persistently low urate level (<6 mg/dL and usually <1 mg/dL) was maintained. Serial sitting BP was measured in 173 subjects, and estimated glomerular filtration rate was determined at baseline and after 3 and 6 months. Significant reductions in mean arterial pressure (MAP) from baseline to 6 months were noted in q2w responders ( P=0.0028), whereas reductions in MAP in other groups were not significant. Significant decreases in both systolic and diastolic BP paralleled the change in MAP. Of the 62% of q2w responders exhibiting persistent decreases in MAP, there were no significant differences in baseline age, sex, race, weight, body mass index, history of hypertension, hyperlipidemia, history of coronary artery disease, gout duration, MAP, serum urate, estimated glomerular filtration rate or urinary uric acid/creatinine ratio compared with those who did not lower MAP. No significant changes in estimated glomerular filtration rate occurred in any of the groups during the study. Responders to biweekly pegloticase who maintained a persistently lower serum urate level throughout the trial experienced significant reductions in both systolic and diastolic BP that were independent of changes in renal function. Clinical Trial Registration- URL: http://www.clinicaltrials.gov . Unique identifier: NCT00325195.

The Effect of Xanthine Oxidase Inhibitors on Blood Pressure and Renal Function

Several epidemiological studies have demonstrated the existence of a correlation between high serum uric acid (SUA) levels, hypertension, and chronic kidney disease (CKD). Xantine oxidase inhibitors (XOI) are the most powerful uric acid lowering drugs, with presumed beneficial effects on cardiovascular and renal system. The multifactorial mechanism linking hyperuricemia with cardiovascular and renal diseases involves both the SUA level and the xanthine oxidase (XO) activity. In this context, the clinical research has been recently focused at assessing the efficacy of urate-lowering drugs active on XO in patients with abnormal blood pressure values and renal dysfunction. The mechanism of action responsible for the beneficial effect of XOI has not completely elucidated, and long-term studies involving large population samples are needed. In particular, XOI could play an important role in the management of hypertension and CKD, especially in patients not entirely controlled by conventional therapies. In the present review, we summarize the results of recent clinical trials that largely support a positive effect of allopurinol and febuxostat on blood pressure, glomerular filtration rate (GFR), and serum creatinine in different populations of patients. Will these drugs be considered a reliable choice or alternative to currently used drugs for the hypertension and kidney failure treatment? The debate is open, but much evidence is accumulating and supporting this role.

Pharmacotherapy for hyperuricemia in hypertensive patients

BACKGROUND

High blood pressure represents a major public health problem. Worldwide, approximately one-fourth of the adult population has hypertension. Epidemiological and experimental studies suggest a link between hyperuricemia and hypertension. Hyperuricemia affects 25% to 40 % of individuals with untreated hypertension; a much lower prevalence has been reported in normotensives or in the general population. However, whether lowering serum uric acid (UA) might lower blood pressure (BP) is an unanswered question.

OBJECTIVES

To determine whether UA-lowering agents reduce BP in patients with primary hypertension or prehypertension compared with placebo.

SEARCH METHODS

The Cochrane Hypertension Information Specialist searched the following databases for randomized controlled trials up to February 2016: the Cochrane Hypertension Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL) (2016, Issue 2), MEDLINE (from 1946), Embase (from 1974), the World Health Organization International Clinical Trials Registry Platform, and ClinicalTrials.gov. We also searched LILACS up to March 2016 and contacted authors of relevant papers regarding further published and unpublished work.

SELECTION CRITERIA

To be included in this review, the studies had to meet the following criteria: 1) randomized or quasi-randomized, with a group assigned to receive a UA-lowering agent and another group assigned to receive placebo; 2) double-blind, single-blind or open-label; 3) parallel or cross-over trial; 4) cross-over trials had to have a washout period of at least two weeks; 5) minimum treatment duration of four weeks; 6) participants had to have a diagnosis of essential hypertension or prehypertension, and hyperuricemia (serum UA greater than 6 mg/dL in women, 7 mg/dL in men and 5.5 mg/dL in children/adolescents); 7) outcome measures assessed included change in clinic systolic, diastolic or 24-hour ambulatory BP.

DATA COLLECTION AND ANALYSIS

The two review authors independently collected the data using a data extraction form, and resolved any disagreements via discussion. We assessed risk of bias using the Cochrane Collaboration' Risk of bias' tool.

MAIN RESULTS

In this review update, we examined the abstracts of 349 identified papers and selected 21 for evaluation. We also identified three ongoing studies, the results of which are not yet available. Three other randomized controlled trials (RCTs) (two new), enrolling individuals with hypertension or prehypertension, and hyperuricemia, met the inclusion criteria for the review and were included in the meta-analysis. Low quality of evidence from three RCTs indicate no reduction in systolic (MD -6.2 mmHg, 95% CI -12.8 to 0.5) or diastolic (-3.9 mmHg, 95% CI -9.2 to 1.4) 24-hour ambulatory BP with UA-lowering drugs compared with placebo. Low quality of evidence from two RCTs reveal a reduction of systolic clinic BP (-8.43 mmHg, 95% CI -15.24 to -1.62) but not diastolic clinic BP (-6.45 mmHg, 95% CI -13.60 to 0.70). High quality of evidence from three RCTs indicates that serum UA levels were reduced by 3.1 mg/dL (95% CI 2.4 to 3.8) in the participants that received UA-lowering drugs. Very low quality of evidence from three RCTs suggests that withdrawals due to adverse effects were not increased with UA-lowering therapy (RR 1.86, 95% CI 0.43 to 8.10).

AUTHORS' CONCLUSIONS

In this updated systematic review, the RCT data available at present are insufficient to know whether UA-lowering therapy also lowers BP. More studies are needed.

Effects of Allopurinol on Arterial Stiffness: A Meta-Analysis of Randomized Controlled Trials

Background

Several studies have tested the effects of allopurinol on arterial stiffness, but the results have been inconclusive. We aimed to conduct a meta-analysis to investigate the impacts of allopurinol treatment on arterial stiffness, as measured by pulse wave velocity (PWV) and augmentation index (AIx).

Material/Methods

Randomized controlled trials (RCTs) assessing the effects of allopurinol on arterial stiffness were identified through searching PubMed, Web of Science, EMBASE, the Cochrane Library for Central Register of Clinical Trials, and China National Knowledge Infrastructure up to December 2015. The primary endpoints were the change of PWV and AIx after allopurinol treatment. The weighted mean difference (WMD) or standardized mean difference (SMD) and the 95% confidence interval (CI) of each study were pooled for meta-analysis.

Results

A total of 11 RCTs met the inclusion criteria and were included in the final meta-analysis. Eight RCTs with 1,111 patients were pooled for PWV; eight RCTs with 397 patients were pooled for PWV. Allopurinol administration did not significantly change PWV (WMD=−0.19 m/s, 95% CI: −0.49 to 0.12, Z=1.21, p=0.23), but significantly reduced AIx (SMD=−0.34, 95% CI: −0.54 to −0.14, Z=3.35, p=0.0008).

Conclusions

Although our meta-analysis showed some favorable effects of allopurinol treatment on improving AIx, its impact on arterial stiffness must be tested in more large-scale RCTs.

The role of pulmonary arterial stiffness in COPD

COPD is the second most common cause of pulmonary hypertension, and is a common complication of severe COPD with significant implications for both quality of life and mortality. However, the use of a rigid diagnostic threshold of a mean pulmonary arterial pressure (mPAP) of ≥25mHg when considering the impact of the pulmonary vasculature on symptoms and disease is misleading. Even minimal exertion causes oxygen desaturation and elevations in mPAP, with right ventricular hypertrophy and dilatation present in patients with mild to moderate COPD with pressures below the threshold for diagnosis of pulmonary hypertension. This has significant implications, with right ventricular dysfunction associated with poorer exercise capability and increased mortality independent of pulmonary function tests.

The compliance of the pulmonary artery (PA) is a key component in decoupling the right ventricle from the pulmonary bed, allowing the right ventricle to work at maximum efficiency and protecting the microcirculation from large pressure gradients. PA stiffness increases with the severity of COPD, and correlates well with the presence of exercise induced pulmonary hypertension. A curvilinear relationship exists between PA distensibility and mPAP and pulmonary vascular resistance (PVR) with marked loss of distensibility before a rapid rise in mPAP and PVR occurs with resultant right ventricular failure. This combination of features suggests PA stiffness as a promising biomarker for early detection of pulmonary vascular disease, and to play a role in right ventricular failure in COPD. Early detection would open this up as a potential therapeutic target before end stage arterial remodelling occurs.

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Pulmonary hypertension is common in COPD.

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Right ventricular remodeling occurs at pressures below the diagnostic threshold of PH.

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Pulmonary arterial stiffening occurs early in the development of PH.

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Non-invasive measurement of pulmonary stiffness may serve as an early biomarker of PH.

Improving cardiovascular and renal outcomes in gout: what should we target?

Epidemiological and experimental studies have shown that hyperuricaemia and gout are intricately linked with hypertension, metabolic syndrome, chronic kidney disease and cardiovascular disease. A number of studies suggest that hyperuricaemia and gout are independent risk factors for the development of these conditions and that these conditions account, in part, for the increased mortality rate of patients with gout. In this Review, we first discuss the links between hyperuricaemia, gout and these comorbidities, and present the mechanisms by which uric acid production and gout might favour the development of cardiovascular and renal diseases. We then emphasize the potential benefit of urate-lowering therapies on cardiovascular and renal outcomes in patients with hyperuricaemia. The mechanisms that link elevated serum uric acid levels and gout with these comorbidities seem to be multifactorial, implicating low-grade systemic inflammation and xanthine oxidase (XO) activity, as well as the deleterious effects of hyperuricaemia itself. Patients with asymptomatic hyperuricaemia should be treated by nonpharmacological means to lower their SUA levels. In patients with gout, long-term pharmacological inhibition of XO is a treatment strategy that might also reduce cardiovascular and renal comorbidities, because of its dual effect of lowering SUA levels as well as reducing free-radical production during uric acid formation.

Allopurinol as a kidney-protective, cardioprotective, and antihypertensive agent: hype or reality?

Numerous experimental and clinical studies suggest that uric acid might have pathobiologic implications in the development and progression of hypertension, kidney disease, and coronary heart disease, among others, resulting in renewed interest in uric acid as a potential pathogenic mediator in these clinical conditions. Despite encouraging animal studies showing beneficial roles of allopurinol, clinical studies and randomized controlled trials remain scarce, and, despite available clinical evidence supporting a therapeutic role for allopurinol, multiple issues remain before routine use of allopurinol can be recommended for use in patients with hyperuricemia and hypertension, kidney disease, or coronary heart disease. These include a need for more robust clinical trial data that evaluate efficacy on hard clinical outcomes, optimal dose, duration of treatment, and the potential for serious allergic reactions. In this article we review the current available evidence describing the effects of allopurinol in hypertension, kidney disease, and coronary heart disease, highlighting unresolved issues surrounding allopurinol use for uric acid lowering in individuals without gout.

Relationship between serum uric acid levels and hypertension among Japanese individuals not treated for hyperuricemia and hypertension

The cause and effect relationship between serum uric acid levels and hypertension can be difficult to evaluate because antihypertensive drugs sometimes affect uric acid levels. This cross-sectional study investigated the relationship between serum uric acid levels and hypertension in a general, healthy Japanese population who were not receiving medication for hyperuricemia or hypertension. We retrospectively analyzed the medical records of 90 143 Japanese people (men, 49.1%; age, 46.3±12.0 years) undergoing an annual medical examination at St Luke's International Hospital Center for Preventive Medicine, Tokyo, between January 2004 and June 2010. Of these individuals, 82 722 (91.8%) who had never taken medications for gout, hyperuricemia or hypertension were enrolled. We compared the participant characteristics and prevalence of diastolic hypertension (⩾90 mm Hg) and/or systolic hypertension (⩾140 mm Hg) by serum uric acid quartile. The odds ratio (OR) of hypertension was 1.20 for each 1 mg dl(-1) increase in serum uric acid level after adjustment for age, sex, body mass index (BMI), dyslipidemia, diabetes, smoking and estimated glomerular filtration rate (eGFR). Compared with the lowest serum uric acid quartile, participants in the highest quartile had a 3.7-fold higher OR for hypertension. After adjustment for age, BMI, dyslipidemia, diabetes, smoking and eGFR, these ORs were 1.79 (1.62-1.98) in the total study population, 1.58 (1.44-1.75) in men and 1.60 (1.39-1.84) in women. The results were similar for both systolic and diastolic hypertension. Elevated serum uric acid levels may be as important as obesity, dyslipidemia, diabetes, smoking and reduced kidney function for the development of hypertension and should be considered in hypertension prevention programs.

Allopurinol is an independent determinant of improved arterial stiffness in chronic kidney disease: a cross-sectional study

Background

Arterial stiffness is increased in patients with CKD and is a powerful predictor of cardiovascular morbidity and mortality. Use of the xanthine oxidase inhibitor allopurinol has been shown to improve endothelial function, reduce left ventricular hypertrophy and possibly improve cardiovascular outcome. We explored the relationship between use of allopurinol and arterial stiffness in patients with chronic kidney disease (CKD).

Methods

Cross-sectional observational study of 422 patients with CKD with evidence of, or at high risk of, renal disease progression. Arterial stiffness was determined by carotid-femoral pulse wave velocity (PWV).

Results

The mean age was 63±16 years, median estimated glomerular filtration rate was 25 (interquartile range: 19–31) ml/min/1.73 m² and mean PWV was 10.2±2.4 m/s. Seventy-seven patients (18%) were receiving regular allopurinol, 61% at a dose of 100 mg/day (range: 50–400 mg/day). Patients receiving allopurinol had significantly lower peripheral pulse pressure, central pulse pressure, central systolic blood pressure, serum uric acid level tissue advanced glycation end product levels but comparable high-sensitivity C-reactive protein levels. Use of allopurinol was associated with lower PWV. After adjusting for age, gender, ethnicity, tissue advanced glycation end product level, peripheral pulse pressure, smoking pack years, presence of diabetes mellitus and use of angiotensin converting enzyme inhibitor or angiotensin II receptor blocker, the use of allopurinol remained a significant independent determinant of PWV (mean difference: −0.63 m/s; 95% CI, −0.09 to −1.17 m/s, p = 0.02).

Conclusion

In patients with CKD, use of allopurinol is independently associated with lower arterial stiffness. This study provides further justification for a large definitive randomised controlled trial examining the therapeutic potential of allopurinol to reduce cardiovascular risk in people with CKD.

Effects of Various Antihypertensive Drugs on Arterial Stiffness and Wave Reflections

We reviewed trials that tested the efficacy of antihypertensive drugs in reducing arterial stiffness and wave reflections as assessed by pulse wave velocity and augmentation index, respectively. Regardless of cross-over or parallel-group comparison design, placebo-controlled trials demonstrated that antihypertensive drugs were effective in reducing pulse wave velocity. In actively-controlled parallel-group comparison studies, this effect on arterial stiffness was more evident for angiotensin-converting enzyme inhibitors or angiotensin receptor blockers than other classes of antihypertensive drugs, particularly when brachial-ankle pulse wave velocity was measured. Regardless of cross-over or parallel-group comparison or placebo- or actively-controlled design, the reviewed trials showed that β-blockers were inferior to all the other classes of antihypertensive drugs in reducing augmentation index. However, these studies had a small sample size and a short follow-up time and did not link the changes in measurements of arterial function with cardiovascular events. Whether the superiority or inferiority is clinically relevant for cardiovascular protection and prevention remains to be investigated.

Pharmacotherapy for hyperuricemia in hypertensive patients

BACKGROUND

High blood pressure represents a major public health problem. Worldwide, approximately one fourth of the adult population has hypertension. Epidemiological and experimental studies suggest a linkage between hyperuricemia and hypertension. Hyperuricemia affects 25-40 % of patients with untreated hypertension. A much lower prevalence has been reported in normotensives or in the general population. However, whether lowering serum uric acid (SUA) might lower blood pressure (BP) is an unanswered question.

OBJECTIVES

To determine whether uric acid lowering agents reduce BP in patients with primary hypertension.

SEARCH METHODS

Electronic searches of the following sources were performed without language restriction: Cochrane Hypertension Group Specialised Register (1946 to May 2012), Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, 2012 Issue 4), MEDLINE (1946 to May 2012), EMBASE (1974 to May 2012), LILACS (1982 to July 2012), Scirus and ClinicalTrials.gov. Authors of relevant papers were also contacted regarding further published and unpublished work.

SELECTION CRITERIA

To be included in this review, the studies had to meet the following criteria: 1) Randomised or quasi-randomised with a group assigned to receive a uric acid lowering agent and another group assigned to receive placebo; 2) Double-blind, single-blind or open label; 3) Parallel or crossover trial; 4) For crossover trial, a washout period of at least two weeks; 5) Minimum treatment duration of four weeks; 6) Participants with diagnosis of essential hypertension and hyperuricemia, serum uric acid greater than 6 in women, 7 in men and 5.5 in children/adolescents; 7) Outcome measures includes change in casual or ambulatory, systolic or diastolic blood pressure.

DATA COLLECTION AND ANALYSIS

Two independent reviewers collected the data using a data extraction form. Disagreements were resolved by discussion. Risk of bias was accessed by the Cochrane Collaboration Risk of Bias Tool.

MAIN RESULTS

Three hundred and thirty-six abstracts were examined. One study (enrolling hypertensive and hyperuricemic patients) met the inclusion criteria for the review and was independently rated by both authors. No other studies were identified by the supplementary searches. The study identified as eligible for this review was a randomised controlled trial conducted in the USA (FEIG 2008 ) . This well designed double-blind, placebo-controlled, crossover trial randomised 30 adolescents (11-17 years), newly diagnosed stage 1 primary hypertension and with SUA ≥ 6mg/dl, to receive allopurinol 200 mg twice daily for 4 weeks, and placebo for 4 weeks, with a 2 week washout period between treatments. Casual BP during the allopurinol phase decreased - 6.9 mmHg (95 % CI, - 4.5 to - 9.3), systolic, and - 5.1 mmHg (95 % CI, - 2.5 to - 7.8), diastolic, versus during the placebo phase, - 2.0 mmHg (95 % CI, 0.3 to - 4.3) systolic and - 2.4 mmHg (95 % CI, 0.2 to - 4.1) diastolic. For the secondary outcome (change in 24 ambulatory BP), change in systolic BP with allopurinol was - 6.3 mmHg (95 % CI, - 3.8 to - 8.9), systolic, and - 4.6 mmHg (95% CI, - 2.4 to - 6.8), diastolic, and with placebo, 0.8 mmHg (95 % CI, 3.4 to - 2.9) systolic and - 0.3 mmHg (95 % CI, 2.3 to - 2.1) diastolic. P-value results ranged from 0.004 to 0.05. No participant dropout occurred and no adverse effects were seen in patients treated with allopurinol.

AUTHORS' CONCLUSIONS

Meta-analysis was not possible in this systematic review. In the one study that matched the inclusion criteria allopurinol decreased "in office" and ambulatory systolic and diastolic BP. Because there was only one included RCT, the number of patients providing data on pharmacotherapy for hyperuricemia in hypertension is small and restricted to adolescents with recently diagnosed mild essential hypertension. Hence, there is insufficient evidence to recommend the use of allopurinol or other hypouricemic drugs as an initial or adjuvant treatment of hypertension and more RCTs are needed.

Uric acid as one of the important factors in multifactorial disorders--facts and controversies

With considering serum concentration of the uric acid in humans we are observing hyperuricemia and possible gout development. Many epidemiological studies have shown the relationship between the uric acid and different disorders such are obesity, metabolic syndrome, hypertension and coronary artery disease. Clinicians and investigators recognized serum uric acid concentration as very important diagnostic and prognostic factor of many multifactorial disorders. This review presented few clinical conditions which are not directly related to uric acid, but the concentrations of uric acid might have a great impact in observing, monitoring, prognosis and therapy of such disorders. Uric acid is recognized as a marker of oxidative stress. Production of the uric acid includes enzyme xanthine oxidase which is involved in producing of radical-oxigen species (ROS). As by-products ROS have a significant role in the increased vascular oxidative stress and might be involved in atherogenesis. Uric acid may inhibit endothelial function by inhibition of nitric oxide-function under conditions of oxidative stress. Down regulation of nitric oxide and induction of endothelial dysfunction might also be involved in pathogenesis of hypertension. The most important and well evidenced is possible predictive role of uric acid in predicting short-term outcome (mortality) in acute myocardial infarction (AMI) patients and stroke. Nephrolithiasis of uric acid origin is significantly more common among patients with the metabolic syndrome and obesity. On contrary to this, uric acid also acts is an “antioxidant”, a free radical scavenger and a chelator of transitional metal ions which are converted to poorly reactive forms.

Angiotensin converting enzyme inhibitors effect on arterial stiffness and wave reflections: a meta-analysis and meta-regression of randomised controlled trials

OBJECTIVE

Several studies have assessed the effect of angiotensin converting enzyme inhibitors (ACEIs) on arterial stiffness and wave reflections as measured by pulse wave velocity (PWV) and augmentation index (AIx), respectively. We conducted a meta-analysis to investigate this effect in comparison to placebo and to other antihypertensive agents. Additionally, we investigated this effect when ACEIs are combined with other antihypertensive agents and in comparison to a combination of antihypertensive agents.

METHODS

MEDLINE, EMBASE and Cochrane Central Register of Controlled Trials (CENTRAL) were searched from inception to May 2011 on randomised controlled trials (RCTs) which assessed the effect of ACEIs on arterial stiffness vs. placebo or no treatment and ACEIs vs. angiotensin receptor blockers (ARBs), calcium channel blockers (CCBs), β-blockers and diuretics. RCTs which assessed the effect of ACEIs combined with other antihypertensives or compared ACEIs with a combination of antihypertensives were also sought. Data from included RCTs were pooled with use of fixed and random effects meta-analysis of the weighted mean change differences between the comparator groups. Heterogeneity across studies was assessed with the I(2) statistic.

RESULTS

In 5 trials including 469 patients, treatment with ACEIs (n=227) vs. placebo (n=216) significantly reduced PWV (pooled mean change difference -1.69, 95% C.I. -2.05, -1.33, p<0.00001 with insignificant heterogeneity). In 9 trials which included 378 patients, treatment with ACEIs (n=178) insignificantly reduced PWV when compared with other antihypertensives (ARBs, CCBs, β-blockers, diuretics and a combination of ACEI and ARB) (n=220) (pooled mean change difference -0.19, 95% C.I. -0.59, 0.21, p=0.36, I(2)=0%). ACEI effect on AIx in comparison to placebo was assessed in 7 trials. Treatment with ACEIs significantly reduced AIx (pooled mean change difference -3.79, 95% C.I. -5.96, -1.63, p=0.0006) with significant heterogeneity. In 7 trials, treatment with ACEIs significantly reduced AIx when compared with other antihypertensives (pooled mean change difference -1.84, 95% C.I. -3, -0.68, p=0.002, I(2)=32%, p for heterogeneity=0.11). However, this effect was only significant when compared with β-blockers (pooled mean change difference -1.6, 95% C.I. -2.84, -0.36, p=0.01). Mean BP differences between baseline and end of treatment did not predict the treatment (ACEI) induced changes in PWV.

CONCLUSIONS

ACEIs reduce PWV and AIx which are markers of arterial stiffness and wave reflections in patients with different pathological conditions. However, due to the lack of high quality and properly powered RCTs, it is not clear whether ACEIs are superior to other antihypertensive agents in their effect on arterial stiffness. The ability of ACEIs to reduce arterial stiffness (PWV) seems to be independent of its ability to reduce BP.