Serum Uric Acid Exhibits Inverse Relationship with Estimated Glomerular Filtration Rate

Effect of Febuxostat versus Allopurinol on the Glomerular Filtration Rate and Hyperuricemia in Patients with Chronic Kidney Disease

Hyperuricemia is a risk factor for the progression of chronic kidney disease (CKD). We compared febuxostat versus allopurinol in the progression of CKD and hyperuricemia in 101 patients with Stage 3-4 CKD treated with febuxostat or allopurinol for at least 6 months for hyperuricemia (>7 mg/dL) between January 2012 and December 2016. Baseline characteristics, serum uric acid (SUA), serum creatinine, and estimated glomerular filtration rate (eGFR) at entry and 6 months were compared. The primary outcome was the decline in eGFR and the secondary outcomes were reductions in SUA and adverse events. Fifty-four were in the febuxostat group and 47 were in the allopurinol group. The baseline characteristics were comparable except for age. The mean dose of febuxostat and allopurinol was 43.70 ± 14.5 mg and 108.51 ± 40 mg, respectively. After 6 months, the median rate of decline in eGFR was 1.2 mL/min/1.73 m2 (IQR: 1.2, 5.5) in the febuxostat group and 3.1 mL/min/1.73 m2 (0.6, 6.2) in the allopurinol group, but this was not statistically significant (P = 0.136). The mean reduction in SUA was significantly better (P = 0.004) in the febuxostat group (3.9 ± 1.7 mg/dL) compared with the allopurinol group (2.1 ± 1.0 mg/dL). Both drugs had no serious adverse events. Febuxostat was better at reducing hyperuricemia than allopurinol, but there was no significant difference in the progression of CKD. Large randomized trials and long-term follow-up are necessary to see whether febuxostat has a favorable effect on the progression of CKD.

The Bidirectional Relationship between Chronic Kidney Disease and Hyperuricemia: Evidence from a Population-Based Prospective Cohort Study

BACKGROUND

Although several studies have examined the association between chronic kidney disease (CKD) and hyperuricemia (HUA), the direction of the association remains unclear. We aimed to investigate whether there was a bidirectional association between them.

METHODS

The present study was conducted in three analyses. Analysis I included 25,433 participants free of HUA at baseline to evaluate the associations between CKD and estimated glomerular filtration rate (eGFR) with incident HUA. Analysis II had 28,422 participants free of CKD at baseline to analyze the relationships between HUA and serum uric acid (sUA) with new-onset CKD. Cox proportional hazards regression models were applied to evaluate the association involved in Analysis I and II. Analysis III included 31,028 participants with complete data and further dissected the bidirectional association between sUA and eGFR using cross-lag models.

RESULTS

New-onset HUA and CKD were observed in the first round of the follow-up study among 1597 and 1212 participants, respectively. A significantly higher risk of HUA was observed in individuals with CKD compared to individuals without CKD (HR = 1.58, 95% CI: 1.28-1.95). The adjusted HRs (95% CIs) of HUA were 3.56 (2.50-5.05) for the participants in the group of eGFR less than 60 mL·min^-1·1.73 m^-2, 1.61 (1.42-1.83) for those in the group of eGFR between 60 and 90 mL·min^-1·1.73 m^-2, and 1.74 (1.42-2.14) for those in the group of eGFR more than 120 mL·min^-1·1.73 m^-2, compared with the group of eGFR between 90 and 120 mL·min^-1·1.73 m^-2. A higher risk of CKD was also observed in individuals with HUA compared to individuals without HUA (HR = 1.28, 95% CI: 1.12-1.47). Compared with the first quintile of sUA, the adjusted HR (95% CI) of CKD was 1.24 (1.01-1.51) for the participants in the fourth quantile. There was a bidirectional relationship between sUA and eGFR, with the path coefficients (ρ₁ = -0.024, p < 0.001) from baseline eGFR to follow-up sUA and the path coefficients (ρ₂ = -0.015, p = 0.002) from baseline sUA to follow-up eGFR.

CONCLUSIONS

The present study indicated that CKD and HUA were closely associated, and there was a bidirectional relationship between sUA and eGFR.

Mancozeb induces nephrotoxicity by impairing the oxidative phosphorylation pathway: A transcriptome study

This study analyzed the mechanism underlying mancozeb (MCZ)-induced kidney injury by detecting kidney function indicators, combined with transcriptome and metabolome sequencing. Twenty mice were randomly assigned into two groups (control and MCZ groups) to explore the MCZ-induced kidney toxicity. The control group was gavaged with 0.2 mL of deionized water, and the MCZ group with 0.2 mL of 100 mg/kg MCZ for 30 days. The kidney structure of the MCZ group was damaged, with slight hyaline degeneration in the kidney tubular epithelial envelope. The creatinine (CRE) and uric acid (UA) were significantly increased in the MCZ group than in the control group. Moreover, the reactive oxygen species (ROS) significantly accumulated in the MCZ group kidneys. Compared to the control group, superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) were significantly decreased in the MCZ group, while the MDA content was substantially increased. The differentially expressed genes (DEGs) in the MCZ group were mainly enriched in the oxidative phosphorylation pathway. Besides, in the MCZ group, ndufs1 and ndufab1 genes were significantly up-regulated, while cox5b, ndufa5, and ndufa6 genes were significantly down-regulated, consistent with the PCR verification results. The metabolomic analysis identified cGMP-PKG signaling pathway of MCZ-induced nephrotoxicity, with Guanosine monophosphate and Adenosine 5'-monophosphate as the main altered metabolites. These results indicated that MCZ impairs the mice kidneys by obstructing the oxidative phosphorylation pathway, which increases oxidative stress in the kidneys, resulting in kidney injury.

Hyperuricemia: an unrecognized risk factor for kidney-related sequelae in children with hemolytic uremic syndrome

BACKGROUND

Chronic kidney-related sequelae after STEC-HUS occur in 20-40% of patients. Hyperuricemia (HU) may cause acute and chronic toxicity involving the kidneys. We retrospectively assessed if there was an association between the presence of HU during the acute illness and that of kidney-related sequelae in children with STEC-HUS.

METHODS

Children with STEC-HUS who had clinical and laboratory data at 2 years of follow-up were included in this case-control study. Univariate and multivariate analyses were performed between patients with (cases) or without (controls) kidney-related sequelae to identify factors associated with outcomes, including different measures of serum uric acid (sUA) (baseline level, peak, and duration of HU). HU was defined as sUA > 8 mg/dL.

RESULTS

Of 86 patients included, 77.9% had HU. Patients with sequelae (n = 41) had a higher prevalence of HU (41/41 vs. 26/45, p < 0.01), higher baseline leukocyte count, serum creatinine (sCr), and sUA levels as well as lower sodium than controls. During hospitalization, cases also had higher sCr peak, sUA peak and duration of HU, requirement and duration of dialysis, extrarenal complications, and hypertension. By multivariate analysis, after adjusting for length of dialysis, only duration of HU (p = 0.0005; OR 1.7, 95% CI 1.27-2.36) remained as an independent predictor of sequelae, with a best cutoff of 5.5 days (AUC 0.95, specificity 80%, sensitivity 100%).

CONCLUSIONS

The presence of HU is a common finding in children with STEC-HUS and its duration during the acute stage was associated with kidney-related sequelae, regardless of the duration of dialysis. A higher resolution version of the Graphical abstract is available as Supplementary Information.

Relationship Between Sporadic Renal Cysts and Renal Function Detected by Isotope Renography in Type 2 Diabetes

PURPOSE

This study aimed to reveal the relationship between the volume of sporadic renal cysts and renal function in patients with type 2 diabetes (T2D).

MATERIALS AND METHODS

One hundred and seventy-one patients that underwent renal imaging and other routine examinations at the Shanghai Pudong Hospital were included in this study. The Gates' method of glomerular filtration rate (GFR) was measured by ^99mTc-DTPA renal dynamic imaging in addition to the eGFR, calculated by the Chronic Kidney Disease Epidemiology Collaboration equation (CKD-EPI).

RESULTS

Our results showed that BMI, total iGFR, and eGFR showed significant differences between patients with T2D with or without SRC (p < 0.05). Spearman correlation analysis showed that cyst volume was positively correlated with Scr and gender but not iGFR (p > 0.05). The total iGFR positively correlated with eGFR (r = 0.83, p < 0.0001) and negatively with Scr (r = -0.78, p < 0.0001), age (r = -0.43, p < 0.0001), duration of T2D (r = -0.25, p = 0.001), and BMI (r = -0.21, p = 0.006) but not gender (r = -0.03, p = 0.668). The multilinear regression model revealed that gender (β = 0.346, p < 0.001), iGFR (β = -0.705, p < 0.001), and serum uric acid (β = 0.195, p = 0.032) were independent predictors of Scr. Moreover, we observed a significant increase in Scr in males (p < 0.05). Finally, we found that the split kidney function reflected by iGFR and related parameters such as time to peak (PTT) and half time of excretion (excrete t1/2) did not mutually distinguish from each other significantly whether they are measured in patients with renal cysts or in those without renal cysts (p > 0.05).

CONCLUSION

Our preliminary results suggest that in T2D, SRCs may be a renal complication of diabetic nephropathy. Although we found that the patients with renal cysts may display reduced iGFR, the volume of simple cysts seems not to exacerbate renal insufficiency. Isotope renography is a useful tool to evaluate the split kidney functions in diabetic patients who acquire single-side cysts.

Relationship between uric acid and kidney function in adults at risk for tumor lysis syndrome

Uric acid drives acute kidney injury in tumor lysis syndrome (TLS). This study investigated the relationship between uric acid and changes in estimated glomerular filtration rate (eGFR) in adults at risk for TLS. Linear regression was used to evaluate the relationship between uric acid area under the curve (AUC) and percent change in eGFR from baseline at hospital dismissal, 1 and 3 months. In 210 included participants, each 100 mg*hour/dL increase in 24 h AUC was associated with an average decline in eGFR at hospital dismissal of 9% (95%CI 3, 15) in univariate analysis. Each 100 mg*hour/dL increase in 24 h AUC was independently associated with an average decline in eGFR of 8% (95%CI 2, 13) at 1 month after dismissal. Additional research is needed to confirm these findings and determine whether treatments that reduce overall uric acid exposure improve kidney outcomes. Preserving kidney health could favorably impact cancer treatment eligibility, tolerability, and outcomes.

Hyperuricemia in Kidney Disease: A Major Risk Factor for Cardiovascular Events, Vascular Calcification, and Renal Damage

Kidney disease, especially when it is associated with a reduction in estimated glomerular filtration rate, can be associated with an increase in serum urate (uric acid), suggesting that hyperuricemia in subjects with kidney disease may be a strictly secondary phenomenon. Mendelian randomization studies that evaluate genetic scores regulating serum urate also generally have not found evidence that serum urate is a causal risk factor in chronic kidney disease. Nevertheless, this is countered by a large number of epidemiologic, experimental, and clinical studies that have suggested a potentially important role for uric acid in kidney disease and cardiovascular disease. Here, we review the topic in detail. Overall, the studies strongly suggest that hyperuricemia does have an important pathogenic role that likely is driven by intracellular urate levels. An exception may be the role of extracellular uric acid in atherosclerosis and vascular calcification. One of the more striking findings on reviewing the literature is that the primary benefit of lowering serum urate in subjects with CKD is not by slowing the progression of renal disease, but rather by reducing the incidence of cardiovascular events and mortality. We recommend large-scale clinical trials to determine if there is a benefit in lowering serum urate in hyperuricemic subjects in acute and chronic kidney disease and in the reduction of cardiovascular morbidity and mortality in subjects with end-stage chronic kidney disease.

Estimating Creatinine Clearance in the Nonsteady State: The Determination and Role of the True Average Creatinine Concentration

Creatinine clearance is a tenet of nephrology practice. However, with just a single creatinine concentration included in the denominator of the creatinine clearance equation, the resulting value seems to apply only in the steady state. Does the basic clearance formula work in the nonsteady state, and can it recapitulate the kinetic glomerular filtration rate (GFR) equation? In the kinetic state, a nonlinear creatinine trajectory is reducible into a “true average” value that can be found using calculus, proceeding from a differential equation based on the mass balance principle. Using the fundamental theorem of calculus, we prove definitively that the true average is the correct creatinine to divide by, even as the mathematical model accommodates clinical complexities such as volume change and other factors that affect creatinine kinetics. The true average of a creatinine versus time function between 2 measured creatinine values is found by a definite integral. To use the true average to compute kinetic GFR, 2 techniques are demonstrated, a graphical one and a numerical one. We apply this concept to a clinical case of an individual with acute kidney injury requiring dialysis; despite the effects of hemodialysis on serum creatinine concentration, kinetic GFR was able to track the underlying kidney function and provided critical information regarding kidney function recovery. Finally, a prior concept of the maximum increase in creatinine per day is made more clinically objective. Thus, the clearance paradigm applies to the nonsteady state as well when the true average creatinine is used, providing a fundamentally valid strategy to deduce kinetic GFRs from serum creatinine trends occurring in real-life acute kidney injury and kidney recovery.

Impact of early rasburicase on incidence of clinical tumor lysis syndrome in lymphoma

Early administration of rasburicase to enhance uric acid (UA) elimination has been adopted without robust evidence in support of its impact on clinical outcomes in tumor lysis syndrome (TLS), specifically, the prevention of acute kidney injury (AKI). This was a retrospective cohort study of adult lymphoma patients at intermediate or high risk for TLS. Excluded patients had AKI or were on dialysis at hospital admission. The incidence of new AKI in the setting of TLS was described along with predictors of its development, including early rasburicase use. In 383 included patients, the incidence of new-onset AKI during hospitalization was 6%. Predictors included age, history of renal or cardiovascular disease, and UA >8 mg/dL. Rasburicase use did not significantly impact the risk of developing AKI (HR 2.3; p = .11). The UA level at the time of administration did not modify the effect of rasburicase on prevention of AKI (p = .36 for the interaction term).

Update on the prevention and treatment of tumor lysis syndrome

Tumor lysis syndrome is a constellation of metabolic derangements seen when tumor cells die and release their intracellular contents into the systemic circulation. Hyperkalemia, hyperphosphatemia, hypocalcemia, and hyperuricemia may lead to severe organ dysfunction and even death. Tumor lysis syndrome is classically considered a complication of successful cancer treatment, but it can also occur in untreated malignancies characterized by rapid proliferation. In this review, we cover the types of cancers and chemo- and immunotherapies associated with tumor lysis syndrome, the mechanisms by which severe metabolic derangements can develop, and the available treatments.

Probiotic supplements prevented oxonic acid-induced hyperuricemia and renal damage

Hyperuricemia is highly prevalent and especially common in subjects with metabolic, cardiovascular and renal diseases. In chronic kidney disease, hyperuricemia is extremely common, and uric acid (UA) excretion relies on gut uricolysis by gut microbiota. Current therapy for lowering serum UA includes drugs that may produce undesired secondary effects. Therefore, this pilot study was designed to evaluate the potential of two probiotic supplements to reduce systemic uric acid concentrations. Secondary objectives were to assess whether the hypouricemic effect related to a therapeutic benefit on the hyperuricemia-induced renal damage and hypertension. Analysis of fecal microbiota was also performed. Groups of 6 rats each were followed for 5 weeks and allocated in the following treatment groups: C = Control; HU-ND = Oxonic acid-induced hyperuricemia (HU) +regular diet; HU-P = HU+placebo; HU-F1 = HU+ probiotics formula 1 and HU-F2 = HU+ probiotics formula 2. We confirmed that oxonic acid-induced hyperuricemia produced hypertension and renal functional and structural changes, along with modest changes in the overall composition of fecal microbiota. Both probiotic-containing diets prevented HU, elevated UA urinary excretion and intrarenal UA accumulation induced by oxonic acid. The hypouricemic effect conferred by probiotic supplementation also prevented the renal changes and hypertension caused by hyperuricemia. However, probiotic treatment did not restore the fecal microbiota. In conclusion, we demonstrated for the first time the ability of probiotics containing uricolytic bacteria to lower serum uric acid in hyperuricemic animals with beneficial consequences on blood pressure and renal disease. As probiotics supplements are innocuous for human health, we recommend clinical studies to test if probiotic supplements could benefit hyperuricemic individuals.

Efficacy of febuxostat in hyperuricemic patients with mild-to-moderate chronic kidney disease: a meta-analysis of randomized clinical trials: A PRISMA-compliant article

BACKGROUND

To investigate the efficacy of febuxostat in hyperuricemic patients with chronic kidney disease (CKD), relevant randomized clinical trials (RCTs) were analyzed.

METHODS

We used PubMed, Medline, ISI Web of Science, CBMdisc, and Cochrane Library databases to conduct a systematic literature research. A fixed-effects model was used to evaluate the standardized mean differences (SMDs) with 95% confidence intervals (CIs). We conducted subgroup analysis, sensitivity analysis, and analyzed publication bias, to comprehensively estimate the renoprotective effects of febuxostat in hyperuricemic patients with CKD.

RESULTS

Among 296 retrieved studies, 5 relevant RCTs were included in the meta-analysis. The result showed that serum estimated glomerular filtration rate (eGFR) was improved after febuxostat treatment in hyperuricemic patients with CKD, with an SMD (95% CI) of 0.24 [-0.17 to 0.43] and P = .67 (fixed-effects model). No heterogeneity was observed across studies (I  = 0% and P = .67). Subgroup analysis suggested that treatment-related reductions in serum eGFR levels were not related to drug doses, intervention times, or region.

CONCLUSIONS

The present meta-analysis suggests that febuxostat may slow the progression of mild-to-moderate CKD. Given the limited number of included studies, additional large sample-size RCTs are required to determine the long-term renoprotective effects of febuxostat in hyperuricemic patients with CKD.

Tumor lysis syndrome with massive hyperphosphatemia and hyperuricemia

Tumor lysis syndrome (TLS) occurs when tumor cells release their contents into the bloodstream, typically in response to chemotherapy, leading to the characteristic findings of hyperuricemia, hyperkalemia, hyperphosphatemia, hypocalcemia, and acute kidney injury. Twinkle artifacts on renal ultrasound may indicate calcium phosphate deposits in such patients.

Weight loss for overweight and obese individuals with gout: a systematic review of longitudinal studies

OBJECTIVES

Weight loss is commonly recommended for gout, but the magnitude of the effect has not been evaluated in a systematic review. The aim of this systematic review was to determine benefits and harms associated with weight loss in overweight and obese patients with gout.

METHODS

We searched six databases for longitudinal studies, reporting the effect of weight loss in overweight/obese gout patients. Risk of bias was assessed using the tool Risk of Bias in Non-Randomised Studies of Interventions. The quality of evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation.

RESULTS

From 3991 potentially eligible studies, 10 were included (including one randomised trial). Interventions included diet with/without physical activity, bariatric surgery, diuretics, metformin or no intervention. Mean weight losses ranged from 3 kg to 34 kg. Clinical heterogeneity in study characteristics precluded meta-analysis. The effect on serum uric acid (sUA) ranged from -168 to 30 μmol/L, and 0%-60% patients achieving sUA target (<360 μmol/L). Six out of eight studies (75%) showed beneficial effects on gout attacks. Two studies indicated dose-response relationship for sUA, achieving sUA target and gout attacks. At short term, temporary increased sUA and gout attacks tended to occur after bariatric surgery.

CONCLUSIONS

The available evidence is in favour of weight loss for overweight/obese gout patients, with low, moderate and low quality of evidence for effects on sUA, achieving sUA target and gout attacks, respectively. At short term, unfavourable effects may occur. Since the current evidence consists of a few studies (mostly observational) of low methodological quality, there is an urgent need to initiate rigorous prospective studies (preferably randomised controlled trials).

SYSTEMATIC REVIEW REGISTRATION

PROSPERO, CRD42016037937.

Identification of chronic kidney disease patient characteristics influencing the renoprotective effects of febuxostat therapy: a retrospective follow-up study

Background

The ability of antihyperuricemic therapy to exert renoprotective effects in patients with chronic kidney disease (CKD) is controversial. In the present study, we studied patient characteristics that may mask favorable impact of antihyperuricemic therapy on the progression of CKD.

Methods

This was a single-center, retrospective, follow-up study. One-hundred and seventy-eight CKD patients with hyperuricemia who received febuxostat therapy were included in this study. Mean serum uric acid (mUA) level after treatment and changes in estimated glomerular filtration rate (ΔeGFR) over 6 months were measured and their correlation was examined. Patients were divided into two groups based on mUA, and their ΔeGFR were compared. These analyses were evaluated in various subgroups.

Results

Febuxostat therapy markedly decreased UA level in any CKD stage patients without resulting in serious adverse events. eGFRs of CKD patients in the mUA < 6.0 mg/dl group were maintained, whereas those in the mUA ≥ 6.0 mg/dl group decreased. A significant inverse correlation was observed between mUA and ΔeGFR (r = −0.16, p = 0.019). The renoprotective effects of febuxostat were significant in the following subgroups: male patients, age < 70 years, systolic blood pressure < 130 mmHg, normal cholesterol levels, and absence of diabetes. Coexisting vascular risk factors appear to exert additive masking effects against febuxostat renoprotection.

Conclusions

The results of this study suggest that various vascular risk factors markedly attenuate the renoprotective effects of febuxostat.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-017-0572-z) contains supplementary material, which is available to authorized users.

Serum uric acid and acute kidney injury: A mini review

Acute kidney injury causes great morbidity and mortality in both the community and hospital settings. Understanding the etiological factors and the pathophysiological principles resulting in acute kidney injury is essential in prompting appropriate therapies. Recently hyperuricemia has been recognized as a potentially modifiable risk factor for acute kidney injury, including that associated with cardiovascular surgery, radiocontrast administration, rhabdomyolysis, and associated with heat stress. This review discussed the evidence that repeated episodes of acute kidney injury from heat stress and dehydration may also underlie the pathogenesis of the chronic kidney disease epidemic that is occurring in Central America (Mesoamerican nephropathy). Potential mechanisms for how uric acid might contribute to acute kidney injury are also discussed, including systemic effects on renal microvasculature and hemodynamics, and local crystalline and noncrystalline effects on the renal tubules. Pilot clinical trials also show potential benefits of lowering uric acid on acute kidney injury associated with a variety of insults. In summary, there is mounting evidence that hyperuricemia may have a significant role in the development of acute kidney injury. Prospective, placebo controlled, randomized trials are needed to determine the potential benefit of uric acid lowering therapy on kidney and cardio-metabolic diseases.