Allopurinol enhances the blood pressure lowering effect of enalapril in children with hyperuricemic essential hypertension

The Role of Uric Acid in Human Health: Insights from the Uricase Gene

Uric acid is the final product of purine metabolism and is converted to allantoin in most mammals via the uricase enzyme. The accumulation of loss of function mutations in the uricase gene rendered hominoids (apes and humans) to have higher urate concentrations compared to other mammals. The loss of human uricase activity may have allowed humans to survive environmental stressors, evolution bottlenecks, and life-threatening pathogens. While high urate levels may contribute to developing gout and cardiometabolic disorders such as hypertension and insulin resistance, low urate levels may increase the risk for neurodegenerative diseases. The double-edged sword effect of uric acid has resurrected a growing interest in urate's antioxidant role and the uricase enzyme's role in modulating the risk of obesity. Characterizing both the effect of uric acid levels and the uricase enzyme in different animal models may provide new insights into the potential therapeutic benefits of uric acid and novel uricase-based therapy.

Serum Uric Acid Might Be Positively Associated With Hypertension in Chinese Adults: An Analysis of the China Health and Nutrition Survey

Background: Previous studies have clarified the relationship between serum uric acid (SUA) and hypertension; most of previous studies suggest that elevated uric acid levels are associated with an increased risk of hypertension, while in China, there are relatively few studies to explore above association. The objective of this longitudinal study is to investigate the correlation of SUA and hypertension in Chinese adults with a nationwide large-scale sample.

Methods: Data from the China Health and Nutrition Survey 2009, 2011, and 2016 were used; a total of 8,469 participants (3,973 men and 4,496 women) were involved. This study was conducted separately by gender. Clinical characteristics of the participants among different uric acid groups are compared. The binary logistic regression analysis was conducted to examine the association between SUA and hypertension. Restricted cubic spline analysis with three knots of the SUA concentration were used to characterize the dose-response relationship. Additionally, we compared the incidence of hypertension in the different baseline uric acid groups during follow-up in 2011 and 2015.

Results: After the covariates were fully adjusted, we found that elevated uric acid levels were correlated with increased risk of hypertension in both males (p < 0.01) and females (p < 0.01). With 2-year or 6-year of follow-up, we found participants with higher baseline uric acid levels had a higher incidence of hypertension (p < 0.01). In stratified analysis by obesity, above relationship remained significant in nonobesity population (males: p < 0.05, females: p < 0.01) and became nonsignificant in obesity people. In stratified analysis by age, above positively correlation remained significant in middle-aged men (p < 0.05) and elderly women (p < 0.01). Restricted cubic spline revealed the dose-response relationship between SUA and hypertension; we also found that above relationship was much stronger in females.

Conclusion: This study suggests that elevated SUA levels might be positively associated with an increased risk of hypertension in general Chinese adults.

FGF21 attenuates high uric acid‑induced endoplasmic reticulum stress, inflammation and vascular endothelial cell dysfunction by activating Sirt1

Uric acid (UA) is the final oxidation product of purine metabolism. Hyperuricemia has been previously reported to contribute to vascular endothelial dysfunction and the development of cardiovascular diseases, metabolic syndrome and chronic kidney diseases. In addition, it has been reported that fibroblast growth factor 21 (FGF21) can exert regulatory effects on UA‑induced lipid accumulation. Therefore, the present study aimed to investigate the possible role of FGF21 in HUVEC cell injury induced by UA. The study used UA to induce HUVEC cell injury, inhibited sirtuin 1 (Sirt1) expression using EX527 and overexpressed FGF21 by transfection. Subsequently, reverse transcription‑quantitative PCR was performed to measure the mRNA expression levels of FGF21, Sirt1 and inflammatory cytokines TNF‑α, IL‑1β and IL‑6, whereas western blotting was performed to measure their corresponding protein expression levels including FGF21, Sirt1, NLR family pyrin domain containing 3, pro‑caspase1, apoptosis‑associated speck‑like protein containing a CARD, activating transcription factor 4, C/EBP homologous protein and eukaryotic initiation factor 2. Furthermore, dichloro‑dihydro‑fluorescein diacetate staining was performed to measure intracellular reactive oxygen species (ROS) generation in HUVECs. The levels of ROS and nitric oxide were also quantified using commercial assay kits. The results demonstrated that overexpression of FGF21 significantly inhibited UA treatment‑induced endoplasmic reticulum (ER) stress, inflammation and oxidative stress in HUVECs. Furthermore, overexpression of FGF21 significantly activated Sirt1. The sirt1 inhibitor, EX527, significantly abrogated the suppressive effects of FGF21 overexpression on ER stress, inflammation and oxidative stress in UA‑stimulated HUVECs. To conclude, results of the present study suggested that FGF21 may attenuate UA‑induced ER stress, inflammation and vascular endothelial cell dysfunction by activating Sirt1. Therefore, FGF21 may be a potential effective target for the future treatment of vascular endothelial cell dysfunction.

Incident hyperuricemia in relation to antihypertensive therapy with the irbesartan/hydrochlorothiazide combination

OBJECTIVE

We investigated serum uric acid changes and incident hyperuricemia in relation to the achieved blood pressure (BP) after 12 weeks of antihypertensive therapy with the irbesartan/hydrochlorothiazide combination.

METHODS

The study participants were 449 patients who completed the study. Analysis of covariance and multiple logistic regression analyses were performed to calculate the least square mean changes (± standard error) from baseline in serum uric acid and odds ratios (ORs) for incident hyperuricemia according to the achieved levels of BP.

RESULTS

Adjusted analyses showed that serum uric acid changes differed according to the achieved SBP/DBP (P = 0.002), with a smaller mean (± standard error) increase in the range of 130-139/<90 mm Hg (n = 132, 19.8 ± 5.7 µmol/L) than that of ≥140/90 (n = 129, 32.4 ± 7.3 µmol/L) or <130/90 mm Hg (n = 188, 39.5 ± 5.1 µmol/L). Adjusted analyses showed similar results for the incident hyperuricemia (n = 95, 24.0%) in those patients with normal serum uric acid at baseline (n = 396). The risk of incident hyperuricemia was lower (OR, 0.45; 95% confidence interval 0.25-0.83; P = 0.04) in patients with an achieved SBP/DBP of 130-139/<90 mm Hg (n = 117, incidence rate, 17.1%) than those with an achieved SBP/DBP of ≥140/90 (n = 118, 31.4%) or <130/90 mm Hg (n = 161, 23.6%).

CONCLUSIONS

Thiazide-induced changes in serum uric acid or incident hyperuricemia were associated with the achieved SBP/DBP, being lower at the level of 130-139/<90 mm Hg.

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.

[Asymptomatic Hyperuricemia: Treatment Approaches According to the Risk of Cardiovascular and Renal Events]

Asymptomatic hyperuricemia (HU) is widespread in the population. Results of multiple studies have demonstrated independent associations between increased levels of uric acid and risk of arterial hypertension, cardiovascular diseases, and chronic kidney disease. HU is considered as an independent predictor of cardiovascular and all-cause mortality. Despite the extensive study of this issue, there is still no unified answer to questions regarding the necessity of urate-lowering therapy in asymptomatic HU, whereas results of studies on the effect of this therapy on outcomes of cardiovascular and kidney diseases are controversial. This review summarized the basic, currently available information on this issue.

Harnessing hyperuricemia to atherosclerosis and understanding its mechanistic dependence

Atherosclerosis is regarded as the disease of the arterial vasculature. The main characteristics of atherosclerosis are the abnormal accumulation of lipids, increased inflammatory cells, matrix deposits, and proliferation of smooth muscle cells. Diabetes mellitus, obesity, and hyperlipidemia are the most studied risk factors of atherosclerosis. One least studied risk factor is the uric acid (UA), a high UA in circulation is interlinked with many pathological processes. Several epidemiological studies suggest elevated UA levels as an essential biomarker in the forecast of several cardiovascular diseases. Available evidence claims that UA upholds the atherosclerosis process via disturbing lipid metabolism, reducing the nitric oxide synthesis in endothelial cells, promoting the proliferation of vascular smooth muscle cells, and overwhelms inflammation. In endothelial dysfunction and coronary artery lesions, UA is considered as an independent predictor. The updated studies on the involvement of hyperuricemia in atherosclerosis prove that treatment with xanthine oxidase (XO) inhibitors not just benefits the treatment of hyperuricemia but also reduces the burden of atherosclerosis to a greater extent. In this review, we highlight how the hyperuricemia affects vascular integrity, causes atherosclerosis, and the mechanism of action of XO inhibitors on atherosclerosis.

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.

Pharmacology of enalapril in children: a review

Enalapril is an angiotensin-converting enzyme (ACE) inhibitor that is used for the treatment of (paediatric) hypertension, heart failure and chronic kidney diseases. Because its disposition, efficacy and safety differs across the paediatric continuum, data from adults cannot be automatically extrapolated to children. This review highlights paediatric enalapril pharmacokinetic data and demonstrates that these are inadequate to support with certainty an age-related effect on enalapril/enalaprilat pharmacokinetics. In addition, our review shows that evidence to support effective and safe prescribing of enalapril in children is limited, especially in young children and heart failure patients; studies in these groups are either absent or show conflicting results. We provide explanations for observed differences between age groups and indications, and describe areas for future research.

Uric Acid and Hypertension: An Update With Recommendations

The association between increased serum urate and hypertension has been a subject of intense controversy. Extracellular uric acid drives uric acid deposition in gout, kidney stones, and possibly vascular calcification. Mendelian randomization studies, however, indicate that serum urate is likely not the causal factor in hypertension although it does increase the risk for sudden cardiac death and diabetic vascular disease. Nevertheless, experimental evidence strongly suggests that an increase in intracellular urate is a key factor in the pathogenesis of primary hypertension. Pilot clinical trials show beneficial effect of lowering serum urate in hyperuricemic individuals who are young, hypertensive, and have preserved kidney function. Some evidence suggest that activation of the renin-angiotensin system (RAS) occurs in hyperuricemia and blocking the RAS may mimic the effects of xanthine oxidase inhibitors. A reduction in intracellular urate may be achieved by lowering serum urate concentration or by suppressing intracellular urate production with dietary measures that include reducing sugar, fructose, and salt intake. We suggest that these elements in the western diet may play a major role in the pathogenesis of primary hypertension. Studies are necessary to better define the interrelation between uric acid concentrations inside and outside the cell. In addition, large-scale clinical trials are needed to determine if extracellular and intracellular urate reduction can provide benefit hypertension and cardiometabolic disease.

Uric acid and hypertension: a focused review and practical recommendations

: Uric acid levels are higher in humans than in other mammals. Best known as an extracellular antioxidant, uric acid also increases salt sensitivity, fat storage, and lipogenesis. Xanthine oxidase-related oxidative stress may also induce endothelial dysfunction and renal vasoconstriction. Renal structure abnormalities contribute to salt-sensitive and uric acid-independent hypertension. Maternal hyperuricemia during pregnancy and hyperuricemia early in life are likewise independent risk factors for hypertension. Genetic polymorphism is potentially involved in the activity of xanthine oxidoreductase, but further studies are needed. Xanthine oxidase inhibition consistently decreases blood pressure in younger hypertensive patients, albeit modestly. Hyperuricemia affects one out of five adults as a result of the Western diet, insulin resistance, and renal dysfunction. This review advocates lifestyle changes to maintain uric acid levels within the normal range in young (pre)hypertensive individuals or normotensives with a family history of hypertension, metabolic disorders, or obesity; moreover, antihypertensive medications that increase uric acid levels should be avoided.

Hyperuricemia and Hypertension: Links and Risks

Hyperuricemia has long been recognized to be associated with increased cardiovascular risk, including risk of developing hypertension. Epidemiological findings suggest that the link with hypertension is stronger in children and adolescents. Uric acid acts as a strong antioxidant compound in the extracellular environment but has pro-inflammatory effects within the intracellular setting. A chronic phase of microvascular injury is known to occur after prolonged periods of hyperuricemia. This is proposed to contribute to afferent arteriolopathy and elevation of blood pressure that may become unresponsive to uric acid-lowering therapies over time. Studies have struggled to infer direct causality of hyperuricemia due to a vast number of confounders including body mass index. The aim of this review is to present the available data and highlight the need for large scale prospective randomized controlled trials in this area. At present, there is limited evidence to support a role for uric acid-lowering therapies in helping mitigate the risk of hypertension.

Hyperuricemia in Children and Adolescents: Present Knowledge and Future Directions

Recent evidence suggests that hyperuricemia is an important condition in children and adolescents, particularly in association with noncommunicable diseases. This review aims to summarize our current understanding of this condition in pediatric patients. An analysis of serum uric acid reference values in a healthy population indicates that they increase gradually with age until adolescence, with differences between the sexes arising at about 12 years of age. This information should be taken into consideration when defining hyperuricemia in studies. Gout is extremely rare in children and adolescents, and most patients with gout have an underlying disease. The major causes of hyperuricemia are chronic conditions, including Down syndrome, metabolic or genetic disease, and congenital heart disease, and acute conditions, including gastroenteritis, bronchial asthma (hypoxia), malignant disorders, and drug side effects. The mechanisms underlying the associations between these diseases and hyperuricemia are discussed, together with recent genetic information. Obesity is a major cause of hyperuricemia in otherwise healthy children and adolescents. Obesity is often accompanied by metabolic syndrome; hyperuricemia in obese children and adolescents is associated with the components of metabolic syndrome and noncommunicable diseases, including hypertension, insulin resistance, dyslipidemia, and chronic kidney disease. Finally, strategies for the treatment of hyperuricemia, including lifestyle intervention and drug administration, are presented.

Uric acid induced inflammatory responses in endothelial cells via up-regulating(pro)renin receptor

Hyperuricemia is an important risk factor for vascular inflammation, yet the potential mechanisms of uric acid (UA) in endothelial cells are not well understood. UA has been found to stimulate renin-angiotensin system (RAS) activation in human umbilical vein endothelial cells (HUVECs). (Pro)renin receptor ((P)RR) is widely expressed in endothelial cells and able to induce RAS activation. Whether UA-induced endothelial cell inflammation is via up-regulating (P)RR remained unknown. Primary HUVECs were cultured and treated with UA, under the condition of (P)RR or AT1 silencing. The degree of inflammation in HUVECs was determined by Real-time PCR and monocyte adhesion assay. The protein levels of (P)RR were determined by western blotting or immunofluorescence. Probenecid was used to block UA re-absorption in this study. Adhesion of monocytes to HUVECs was elucidated by microfluidic chip. We found (P)RR is up-regulated in HUVECs following UA stimulation. UA promoted vascular inflammation, which was characterized by up-regulating of cytokines and enhanced monocyte adhesion. Silencing of (P)RR alleviated UA-induced vascular inflammation. Probenecid treatment abolished UA-induced vascular inflammation in HUVECs via suppressing (P)RR up-regulation. This finding was further verified by using microfluidic chip. Our findings indicate that (P)RR plays a critical role in endothelial inflammation in response to UA stimulation.

Effect of allopurinol on the glomerular filtration rate of children with chronic kidney disease

BACKGROUND

Hyperuricemia is a leading risk factor for the development of chronic kidney disease (CKD). We hypothesized that lowering serum uric acid (SUA) with allopurinol in hyperuricemic children with CKD may reduce the risk of CKD progression.

METHODS

A total of 70 children, aged 3-15 years, with elevated serum uric acid level (SUA) > 5.5 mg/dL and CKD stages 1-3 were prospectively randomized to receive allopurinol 5 mg/kg/day (study group, n = 38) or no treatment (control group, n = 32) for 4 months. The primary and secondary outcomes were changes in estimated glomerular filtration rate (eGFR) (> 10 mL/min/1.73m²) and the SUA (> 1.0 mg/dL) from baseline values, respectively.

RESULTS

Baseline age, gender, blood pressure (BP), body mass index (BMI), SUA, high-sensitive C-reactive protein (hsCRP), and eGFR were similar in allopurinol and control subjects. Allopurinol treatment resulted in a decrease in SUA, a decrease in systolic and diastolic BP, a decrease in hsCRP, and an increase in eGFR compared with the baseline values (p < 0.05 for all). No significant difference was observed in the control hyperuricemic subjects. In multiple regression analysis after incorporating variables (age, gender, BMI, systolic and diastolic BP, CRP, and SUA), eGFR was independently related to SUA both before and after treatments (p = 0.03 vs. p = 0.02, respectively). All patients in the study group tolerated allopurinol, and there were no adverse reactions observed by physical examination or reported by patients.

CONCLUSION

Urate-lowering therapy with allopurinol, over a 4-month period, can improve renal function in children with CKD stages 1-3.

Uric acid and cardiovascular risk: What genes can say

BACKGROUND

Although the relationship of elevated serum uric acid levels and cardiovascular disease has been established in a great number of studies, the causal relevance of this finding remains ambiguous. An approach to evaluate the causal relevance of biomarkers is to exploit the natural randomised allocation of allelic variation in genes affecting their level, also known as Mendelian randomisation.

AIM

The aim of this paper is to review the current literature regarding serum uric acid levels and cardiovascular and renal disease risk in Mendelian randomisation studies.

METHODS

PubMed and Scopus databases were searched to retrieve Mendelian studies regarding uric acid, hyperuricaemia and cardiovascular risk.

CONCLUSIONS

Genetic evidence based on conventional and novel Mendelian randomisation approaches suggest a modest, if any, causal effect of serum uric acid concentration on the development of cardiovascular disease, suggesting that further study of uric acid genes is needed in order to elucidate the relationship of serum uric acid levels and cardiovascular disease.

Clinical Practice Guideline for Screening and Management of High Blood Pressure in Children and Adolescents

These pediatric hypertension guidelines are an update to the 2004 "Fourth Report on the Diagnosis, Evaluation, and Treatment of High Blood Pressure in Children and Adolescents." Significant changes in these guidelines include (1) the replacement of the term "prehypertension" with the term "elevated blood pressure," (2) new normative pediatric blood pressure (BP) tables based on normal-weight children, (3) a simplified screening table for identifying BPs needing further evaluation, (4) a simplified BP classification in adolescents ≥13 years of age that aligns with the forthcoming American Heart Association and American College of Cardiology adult BP guidelines, (5) a more limited recommendation to perform screening BP measurements only at preventive care visits, (6) streamlined recommendations on the initial evaluation and management of abnormal BPs, (7) an expanded role for ambulatory BP monitoring in the diagnosis and management of pediatric hypertension, and (8) revised recommendations on when to perform echocardiography in the evaluation of newly diagnosed hypertensive pediatric patients (generally only before medication initiation), along with a revised definition of left ventricular hypertrophy. These guidelines include 30 Key Action Statements and 27 additional recommendations derived from a comprehensive review of almost 15 000 published articles between January 2004 and July 2016. Each Key Action Statement includes level of evidence, benefit-harm relationship, and strength of recommendation. This clinical practice guideline, endorsed by the American Heart Association, is intended to foster a patient- and family-centered approach to care, reduce unnecessary and costly medical interventions, improve patient diagnoses and outcomes, support implementation, and provide direction for future research.

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.

Effect of uric acid-lowering therapy on blood pressure: systematic review and meta-analysis

BACKGROUND

The purpose of this meta-analysis was to determine if uric acid-lowering therapy is associated with a decrease in blood pressure (BP) and serum creatinine levels.

MATERIALS AND METHODS

Medline, Cochrane, EMBASE, and Google Scholar databases were searched until 29 June 2016, with keywords: uric-acid-lowering therapy, allopurinol, febuxostat, uricosuric, and BP. Only randomized controlled trials were included. The primary outcomes were reduction in systolic BP (SBP) and diastolic BP (DBP), and secondary was reduction in serum creatinine level.

RESULTS

Patients treated with allopurinol had greater reduction in SBP (standardized difference in means [SDM] = 0.321, 95% confidence interval [CI]: 0.145-0.497, p < 0.001), DBP (SDM = 0.260, 95% CI: 0.102 to 0.417, p = 0.001), and creatinine level (SDM = 0.312, 95% CI: 0.008 to 0.615, p = 0.044) than control patients. Subgroup analysis showed that allopurinol significantly decreased SBP whether or not antihypertensive drugs were being administered; a decrease in DBP was only seen in patients receiving antihypertensive drugs. Low-dose allopurinol (≤300 mg/day) was more effective at reducing SBP than high-dose (>300 mg/day) in patients receiving antihypertensive drugs.

CONCLUSIONS

These results support that allopurinol decreases BP and creatinine levels in patients with hyperuricemia. KEY MESSAGES Allopurinol decreases SBP and DPB, and creatinine levels in patients with hyperuricemia. Allopurinol resulted in a significant decrease in SBP in patients with or without treatment of antihypertensive drugs. A dose of allopurinol of ≤300 mg per day might be more effective than a higher dose.

Uric acid in metabolic syndrome: From an innocent bystander to a central player

Uric acid, once viewed as an inert metabolic end-product of purine metabolism, has been recently incriminated in a number of chronic disease states, including hypertension, metabolic syndrome, diabetes, non-alcoholic fatty liver disease, and chronic kidney disease. Several experimental and clinical studies support a role for uric acid as a contributory causal factor in these conditions. Here we discuss some of the major mechanisms linking uric acid to metabolic and cardiovascular diseases. At this time the key to understanding the importance of uric acid in these diseases will be the conduct of large clinical trials in which the effect of lowering uric acid on hard clinical outcomes is assessed. Elevated uric acid may turn out to be one of the more important remediable risk factors for metabolic and cardiovascular diseases.

Hyperuricemia and Progression of CKD in Children and Adolescents: The Chronic Kidney Disease in Children (CKiD) Cohort Study

BACKGROUND

Hyperuricemia is associated with essential hypertension in children. No previous studies have evaluated the effect of hyperuricemia on progression of chronic kidney disease (CKD) in children.

STUDY DESIGN

Prospective observational cohort study.

SETTING & PARTICIPANTS

Children and adolescents (n=678 cross-sectional; n=627 longitudinal) with a median age of 12.3 (IQR, 8.6-15.6) years enrolled at 52 North American sites of the CKiD (CKD in Children) Study.

PREDICTOR

Serum uric acid level (<5.5, 5.5-7.5, and >7.5mg/dL).

OUTCOMES

Composite end point of either >30% decline in glomerular filtration rate (GFR) or initiation of renal replacement therapy.

MEASUREMENTS

Age, sex, race, blood pressure status, GFR, CKD cause, urine protein-creatinine ratio (<0.5, 0.5-<2.0, and ≥2.0mg/mg), age- and sex-specific body mass index > 95th percentile, use of diuretics, and serum uric acid level.

RESULTS

Older age, male sex, lower GFR, and body mass index > 95th percentile were associated with higher uric acid levels. 162, 294, and 171 participants had initial uric acid levels < 5.5, 5.5 to 7.5, or >7.5 mg/dL, respectively. We observed 225 instances of the composite end point over 5 years. In a multivariable parametric time-to-event analysis, compared with participants with initial uric acid levels < 5.5mg/dL, those with uric acid levels of 5.5 to 7.5 or >7.5mg/dL had 17% shorter (relative time, 0.83; 95% CI, 0.62-1.11) or 38% shorter (relative time, 0.62; 95% CI, 0.45-0.85) times to event, respectively. Hypertension, lower GFR, glomerular CKD cause, and elevated urine protein-creatinine ratio were also associated with faster times to the composite end point.

LIMITATIONS

The study lacked sufficient data to examine how use of specific medications might influence serum uric acid levels and CKD progression.

CONCLUSIONS

Hyperuricemia is a previously undescribed independent risk factor for faster progression of CKD in children and adolescents. It is possible that treatment of children and adolescents with CKD with urate-lowering therapy could slow disease progression.

Relationship between uric acid and blood pressure in different age groups

INTRODUCTION

Serum uric acid (UA) has been known to have a positive association with blood pressure (BP). However, the relationship between serum UA and BP in different age groups is unclear.

METHODS

A total of 45,098 Koreans who underwent health examinations at Korea Association of Health Promotion with no history of taking drugs related with UA and/or BP were analyzed for determining the relationship between serum UA and BP.

RESULTS

In men <40, serum UA was significantly associated with systolic (β = 0.25, p = 0.002) and diastolic BP (β = 0.41, p < 0.001) after adjustment for age, diabetes, dyslipidemia, body mass index, and estimated glomerular filtration rate. Men between ages 40 and 59 showed similar results regarding diastolic BP. The association between serum UA and BP was stronger in women <40 (β = 0.54, p < 0.001 for systolic BP; β = 0.65, p < 0.001 for diastolic BP) and in between 40 and 59 (β = 0.51, p < 0.001 for diastolic BP). The association was not significant in men and women ≥60. The odds ratios (ORs) of hyperuricemia for hypertension were 1.25 (95% confidence interval [CI], 1.08 to 1.45; p = 0.003) and 1.33 (95% CI, 1.11 to 1.60; p = 0.002) in men <40 and in between 40 and 59, respectively, in the multivariate analysis. The OR was 2.60 (95% CI, 1.37 to 4.94; p = 0.0034) in women <40. The relationship between hyperuricemia and hypertension was not significant in other age/gender groups.

DISCUSSION

In contrast to the elderly of 60 and over, the non-elderly showed significant associations between serum UA and BP.