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

Effect of uric acid reduction on chronic kidney disease. Systematic review and meta-analysis

Accumulating evidence suggests that hyperuricemia is a pathological factor in the development and progression of chronic kidney disease. However, the potential benefit afforded by the control of uric acid (UA) is controversial. Individual studies show discrepant results, and most existing meta-analysis, especially those including the larger number of studies, lack a placebo or control group as they aim to compare efficacy between drugs. On these grounds, we performed a me-ta-analysis restricted to studies including the action of any anti-gout therapies referenced to a control or placebo arm. This approach allows for a clearer association between UA reduction and renal effect. Of the twenty-nine papers included, most used allopurinol and febuxostat and, therefore, solid conclusions could only be obtained for these drugs. Both were very effective in reducing UA, but only allopurinol was able to significantly improve glomerular filtration rate (GFR), although not in a dose-dependent manner. These results raised doubts as to whether it is the hypouricemic effect of anti-gout drugs, or a pleiotropic effect, what provides protection of kidney function. Accordingly, in a correlation study that we next performed between UA reduction and GFR improvement, no association was found, which suggests that additional mechanisms may be involved. Of note, most trials show large inter-individual response variability, probably because they included patients with heterogeneous phenotypes and pathological characteristics, including different stages of CKD and comorbidities. This highlights the need to sub classify the effect of UA-lowering therapies according to the pathological scenario, in order to identify those CKD patients that may benefit most from them. Systematic Review Registration: CRD42022306646 https://www.crd.york.ac.uk/prospero/.

Polydatin Ameliorates High Fructose-Induced Podocyte Oxidative Stress via Suppressing HIF-1α/NOX4 Pathway

Long-term high fructose intake drives oxidative stress, causing glomerular podocyte injury. Polydatin, isolated from Chinese herbal medicine Polygonum cuspidatum, is used as an antioxidant agent that protects kidney function. However, it remains unclear how polydatin prevents oxidative stress-driven podocyte damage. In this study, polydatin attenuated high fructose-induced high expression of HIF-1α, inhibited NOX4-mediated stromal cell-derived factor-1α/C-X-C chemokine receptor type 4 (SDF-1α/CXCR4) axis activation, reduced reactive oxygen species (ROS) production in rat glomeruli and cultured podocytes. As a result, polydatin up-regulated nephrin and podocin, down-regulated transient receptor potential cation channel 6 (TRPC6) in these animal and cell models. Moreover, the data from HIF-1α siRNA transfection showed that high fructose increased NOX4 expression and aggravated SDF-1α/CXCR4 axis activation in an HIF-1α-dependent manner, whereas polydatin down-regulated HIF-1α to inhibit NOX4 and suppressed SDF-1α/CXCR4 axis activation, ameliorating high fructose-induced podocyte oxidative stress and injury. These findings demonstrated that high fructose-driven HIF-1α/NOX4 pathway controlled podocyte oxidative stress damage. Intervention of this disturbance by polydatin could help the development of the therapeutic strategy to combat podocyte damage associated with high fructose diet.

Effectiveness of Urate-Lowering Therapy for Renal Function in Patients With Chronic Kidney Disease: A Meta-Analysis of Randomized Clinical Trials

Background and Objective: Hyperuricemia is closely related to chronic kidney disease (CKD). The effects of urate-lowering therapy (ULT) on renal outcomes are uncertain, and whether it is warranted in CKD patients is currently unclear. The aim of our meta-analysis of randomized clinical trials (RCTs) was to assess the effectiveness and safety of ULT for improving kidney function in patients with CKD.

Methods: RCTs were retrieved from the PubMed, Embase, MEDLINE and Cochrane Central Register of Controlled Trials databases. The meta-analysis was performed using Review Manager and Stata/SE software. The outcomes were changes in renal function and serum uric acid (SUA), serum creatinine, and adverse events.

Results: Twelve RCTs with 1,469 participants were included in the meta-analysis. ULT was found to effectively lower SUA (standard mean difference (SMD): -2.70; 95% confidence interval (CI): -3.71, -1.69) but the renoprotective effects were not superior to those of control therapy (placebo or usual therapy), which were stable in the subgroup analyses and sensitivity analyses. Regarding adverse events, their risks did not increase in the ULT group compared with the control group and were stable in the sensitivity analyses.

Conclusion: The findings of our meta-analysis suggested that ULT can effectively lower SUA, but there is insufficient evidence to support the renoprotective effects of ULT in CKD patients. In addition, ULT is safe for patients with CKD.

Systematic Review Registration:https://clinicaltrials.gov/, identifier PROSPERO (CRD42020200550).

Hyperuricemia and Associated Factors in Children with Chronic Kidney Disease: A Cross-Sectional Study

Background: Hyperuricemia is increasingly recognized as a risk factor for chronic kidney disease (CKD) just in adults. The purpose of this study was to investigate the clinical characteristics of hyperuricemia and its associated factors in Chinese children with CKD at a single center. Methods: A cross-sectional study of 170 CKD children collected from the Department of Nephrology, The Zhejiang University Children’s Hospital was conducted. The clinical data, including anthropometric data, blood pressure measurements, and biochemical parameters, were recorded and analyzed retrospectively. The factors associated with hyperuricemia in CKD children were evaluated by Pearson and Spearman correlation analysis and multiple logistic regression analysis. Results: The mean age was 9.79 ± 4.10 years, and 72 (42.35%) were girls. Higher blood urea nitrogen (BUN), serum creatinine, cystatin C, D-dimer, lower hemoglobin, albumin, and estimated glomerular filtration rate (eGFR) were significantly associated with higher serum uric acid (SUA). In multiple logistic regression analysis, anemia and higher BUN were both positively associated factors, whereas eGFR ≥ 90 mL/min/1.73 m² was a negatively associated factor for subjects with SUA ≥ 390 µmol/L (6.5 mg/dL). Conclusions: SUA was significantly associated with kidney risk factors in CKD children. Monitoring and controlling SUA, Hb, BUN, and Scr levels in CKD children may help to prevent the progression of CKD.

Urate-lowering therapy for gout and asymptomatic hyperuricemia in the pediatric population: a cross-sectional study of a Japanese health insurance database

BACKGROUND

Our previous research showed that uric acid lowering therapy (ULT) for gout and hyperuricemia is being prescribed for pediatric patients even though these drugs have not been approved for use in children. However, the actual clinical situation has not been clearly elucidated. In this paper, we provide an in-depth look at the details of actual clinical practice.

METHODS

This retrospective cross-sectional study accessed health insurance data for 696,277 children from April 2016 through March 2017 to identify pediatric patients with gout or asymptomatic hyperuricemia, calculate the proportion of patients prescribed ULTs, and analyze population characteristics. Adherence and mean dose for febuxostat and allopurinol, the most commonly prescribed drugs, were also analyzed.

RESULTS

Among children with gout or asymptomatic hyperuricemia, we found that 35.1% (97/276) were prescribed ULT. This proportion increased with age, especially among males. By comorbidity, ULT was prescribed to 47.9% (46/96) of patients with kidney disease, 41.3% (26/63) for cardiovascular disease, 40.0% (6/15) for Down syndrome, and 27.1% (32/118) for metabolic syndrome. In patients with kidney disease, febuxostat was prescribed more than twice as frequently as allopurinol (28 vs. 12). Median values for the medication possession ratio (MPR) of febuxostat and allopurinol were 70.1 and 76.7%, respectively, and prescriptions were continued for a relatively long period for both drugs. Both drugs were prescribed at about half the adult dose for patients 6-11 years old and about the same as the adult dose for patients 12-18 years old.

CONCLUSIONS

This study showed that the continuous management of serum uric acid is being explored using off-label use of ULT in pediatric patients with gout or asymptomatic hyperuricemia in Japan. Drug selection is based on patient characteristics such as sex, age, and comorbidities, and pediatric dosage is based on usage experience in adults. To develop appropriate pediatric ULT, clinical trials are needed on the efficacy and safety of ULT in the pediatric population.

TRIAL REGISTRATION

UMIN000036029 .

Safety and effectiveness of lanthanum carbonate for hyperphosphatemia in chronic kidney disease (CKD) patients: a meta-analysis

Objective

The aim of this study was to determine the efficacy and safety of lanthanum carbonate (LC) versus calcium salts, non-LC phosphate binders (PBs), sevelamer, or placebo in patients with chronic kidney disease (CKD).

Materials and methods

A literature search on PubMed, Embase, and Cochrane Library databases was conducted up to 18 June 2021. Data acquisition and quality assessment were performed by two reviewers. Meta-analysis was performed to evaluate the serum biochemical parameters, adverse events, and patient-level outcomes of LC, non-LC PBs, and sevelamer for hyperphosphatemia in patients with CKD. Heterogeneity across studies was assessed utilizing the I² statistic and Q-test, and a random effect model was selected to calculate the pooled effect size.

Results

A total of 26 randomized, controlled trials and 3 observational studies were included. Compared to the other groups, better control effect of serum phosphorus (RR = 2.68, p < 0.001), reduction in serum phosphorus (95%CI = −1.93, −0.99; p < 0.001), Ca × P (95%CI = −13.89, −2.99; p = 0.002), serum intact parathyroid hormone levels (95%CI = −181.17, −3.96, p = 0.041) were found in LC group. Besides, reduced risk of various adverse effects, such as hypotension, abdominal pain, diarrhea, dyspepsia, and a score of coronary artery calcification were identified with LC in comparison to calcium salt, non-LC PBs, or placebo group. Significantly lower risk in mortality with LC treatment vs. non-LC PBs was observed, while no significant difference was identified between LC and calcium salt groups.

Conclusion

LC might be an alternative treatment for hyperphosphatemia in patients with CKD considering its comprehensive curative effect.

Hyperuricemia, Elevated Body Mass Index, Female Sex, and Albuminuria Increase the Probability of Elevated High-Sensitivity C-Reactive Protein: Results From the National Health and Nutrition Examination Survey 2015-2018

Importance: High uric acid (UA) is hypothesized to worsen kidney and cardiovascular disease morbidity via activation of systemic inflammation. Clinical trials of UA modification report reduction of the inflammatory marker high sensitivity C-reactive protein (hs-CRP) as an outcome measure, but studies have not demonstrated that hyperuricemia independently increases hs-CRP when adjusted for important confounders such as body mass index (BMI), sex, and age. Objective: To identify clinical risk factors for elevated hs-CRP, including but not limited to hyperuricemia, through a cross-sectional analysis of the National Health and Nutrition Examination Survey (NHANES) 2015-2018. Results: In the final multivariate logistic regression model, the exposure with the strongest effect on the odds of elevated hs-CRP was BMI in the fourth quartile, OR = 13.1 (95% CI 6.25-27.42), followed by female sex (OR = 4.9, 95% CI 2.92-8.34), hyperuricemia (OR = 2.2, 95% CI 1.36-3.45), urine albumin creatinine ratio (ACR; OR = 1.5, 95% CI 1.09-2.18), poor overall health (OR = 1.4, 95% CI 1.18-1.58), and interactions between hyperuricemia and sex (OR = 1.4, 95% CI 1.05-1.83), and between BMI and sex (OR = 1.2, 95% CI 1.03-1.47). Notably, chronic kidney disease (CKD) and CKD surrogates were not associated with hs-CRP despite urine ACR maintaining a significant independent effect. Conclusions: In this national population-based study, we demonstrated that hyperuricemia significantly increases the odds of elevated hs-CRP, independent from BMI, female sex, urine ACR, and overall health status. Further study is recommended to better understand the sex difference in this association and the role of albuminuria, but not CKD, in systemic inflammation.

Effects of losartan and enalapril on serum uric acid and GFR in children with proteinuria

BACKGROUND

Studies have shown that losartan reduces serum uric acid in adults, unlike angiotensin-converting enzyme inhibitors. A previous study demonstrated that losartan and enalapril had comparable effects on proteinuria in children.

METHODS

We conducted a post hoc analysis of results from a prospective trial in which the proteinuria-reducing effects of losartan and enalapril were compared. We have now evaluated (a) the effects of these medications on SUA in 248 children with proteinuria and (b) the correlation between changes in SUA and eGFR.

RESULTS

SUA levels after 36 months were found to be increased when compared to baseline in both losartan and enalapril groups. The mean change in SUA from baseline was significantly different at 12 months between 23 hypertensive patients randomised to losartan (3.69% decrease [95% CI 11.31%, 3.93%]) and 24 randomised to enalapril (12.57% increase [95% CI 3.72%, 21.41%]), p = 0.007. This significant difference remained after 24, 30 and 36 months but was observed in the entire group of 248 patients only at 12 months. There was a statistically significant negative correlation between changes in SUA and changes in eGFR at each time point over 36 months.

CONCLUSIONS

Losartan may have long-term beneficial effects on SUA and eGFR in children with proteinuria.

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.

Hyperuricemia is associated with a lower glomerular filtration rate in pediatric sickle cell disease patients

BACKGROUND

Sickle cell nephropathy (SCN) is a progressive disease that contributes significant morbidity and mortality in sickle cell disease (SCD), yet it remains poorly understood. Hyperuricemia negatively impacts renal function in the non-sickle cell population but is understudied in SCD.

METHODS

We performed a cross-sectional analysis of the first 78 pediatric SCD patients enrolled in a cohort study. The mechanism of development of hyperuricemia (defined, serum uric acid (UA) ≥ 5.5 mg/dL) was characterized as a result of either UA overproduction or inefficient renal excretion by the Simkin index and fractional clearance of urate (FCU) equations. Associations between hyperuricemia and albuminuria or estimated glomerular filtration rate (eGFR) were determined by linear regression.

RESULTS

The prevalence of hyperuricemia in this young population (mean age 11.6 ± 3.77 years) was 34.2%. Only 1 hyperuricemic participant overproduced UA by Simkin index, while 62.5% were inefficient renal excretors of UA (FCU < 4%). Hyperuricemia was associated with a significant decrease in average eGFR, -27 ml/min/1.73m² below normouricemia (mean eGFR 151.6 ± 40.32), p = 0.0122. Notably, the previously accepted association between decline of eGFR with age is significantly modified by hyperuricemia stratification, where hyperuricemia explains 44% of the variance in eGFR by age (R² = 0.44, p = 0.0004) and is nonsignificant in normouricemia (R² = 0.07, p = 0.0775).

CONCLUSION

These findings indicate that hyperuricemia may be associated with early eGFR decline in SCN. This association must be further characterized in prospective cohort studies in SCN, and hyperuricemia must be investigated as a potential therapeutic target for SCN.

Allopurinol Effects on Residual Renal Function in End-Stage Renal Disease Patients Undergoing Peritoneal Dialysis: Randomized Controlled Trial

Objective

There is increasing evidence to show that hyperuricemia may have a pathogenic role in the progression of renal diseases. We performed a prospective, randomized, controlled trial to investigate the renal effects of allopurinol treatment in hyperuricemic patients with end-stage renal disease (ESRD) who undergo peritoneal dialysis.

Methods

This was a unicenter, randomized, controlled clinical trial conducted in "Alzahra Hospital, Isfahan, Iran." Patients were randomly assigned into treatment or control group. Treatment-group patients were administered a starting allopurinol dose of 100 mg/day. The dose was adjusted according to serum uric acid level, aiming to maintain uric acid levels within the normal range. Participants were followed up for 6 months after receiving the medicine. Residual renal function (RRF) was assessed by measuring the renal component of Kt/V urea and estimating the patient's glomerular filtration rate (GFR) by calculating the mean of urea and creatinine clearance. In addition, systolic and diastolic blood pressure and serum level of creatinine were measured every 3 months during the follow-up period.

Findings

Eighty patients were enrolled in the study and divided into two groups, including 40 ESRD patients receiving allopurinol and 40 ESRD did not receive allopurinol and considered as the control group. GFR measurements showed that there was not a significant difference between patients' RRF of two groups. However, allopurinol group had higher RRF than the control group during the follow-up period. Evaluating RRF by Kt/V showed the same results.

Conclusion

Our study demonstrated significant effects of allopurinol on decreasing serum levels of uric acid in ESRD patients undergoing peritoneal dialysis. On the other hand, renal residual function of patients under treatment with allopurinol was better than the control group. We recommend that further studies should be conducted on the effects of allopurinol with greater sample size and longer time of follow-up.

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.

The Growing Epidemic of Chronic Kidney Disease: Preventive Strategies to Delay the Risk for Progression to ESRD

Hypertension, obesity and metabolic syndromes are leading risk factors for the development of chronic kidney disease (CKD). Considering the high prevalence of hypertension and obesity in children and adolescents and it's risk of progression to cardiovascular disease, CKD should be considered a serious long-term health issue in children with metabolic syndrome. Prevention of CKD requires a professional teamwork consisting of primary care physicians, nephrologists, nutritionist, pharmacist, and social work to identify and manage children at risk of developing CKD in order to provide a highly valuable management strategies. This review focuses on the principles underlying the importance of a team approach for CKD prevention.