Use of allopurinol in slowing the progression of renal disease through its ability to lower serum uric acid level

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 risk of diabetic kidney disease

Diabetic kidney disease (DKD) is the leading cause of end-stage kidney disease (ESKD) in the Western world. Better control of glycemia and blood pressure, including renin-angiotensin system blockade (RASB), appear to have slowed DKD progression rate but have been unable to substantially decrease the annual incidence of new cases of DKD related ESKD. Thus, new treatment targets are needed. Higher levels of serum uric acid (SUA) have been associated with increased risk and progression of DKD in persons with types 1 (T1D) and 2 (T2D) diabetes and of chronic kidney disease (CKD) in general. This review presents the epidemiological, clinical, and clinical trial evidence regarding the hypothesis that SUA reduction could slow progression of DKD and/or CKD in general.

Pharmacogenetic Testing for Prevention of Severe Cutaneous Adverse Drug Reactions

Severe cutaneous adverse reactions (SCAR), such as Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and drug rash with eosinophilia and systemic symptoms (DRESS), are idiosyncratic and unpredictable drug-hypersensitivity reactions with a high-mortality rate ranging from 10% to over 30%, thus causing a major burden on the healthcare system. Recent pharmacogenomic studies have revealed strong associations between SCAR and the genes encoding human-leukocyte antigens (HLAs) or drug-metabolizing enzymes. Some of pharmacogenetic markers have been successfully applied in clinical practice to protect patients from SCAR, such as HLA-B*15:02 and HLA-A*31:01 for new users of carbamazepine, HLA-B*58:01 for allopurinol, and HLA-B*57:01 for abacavir. This article aims to update the current knowledge in the field of pharmacogenomics of drug hypersensitivities or SCAR, and its implementation in the clinical practice.

Association between Nod-like receptor protein 3 inflammasome and gouty nephropathy

Crystalized deposits of monosodium urate activate the Nod-like receptor protein 3 (NLRP3) inflammasome, resulting in kidney damage. The present study investigated whether the NLRP3 inflammasome is associated with the progression of hyperuricaemia and gouty nephropathy. Adult male patients were recruited at the Affiliated Baoan Hospital of Shenzhen and divided into three groups of 15 patients each: The control group, the hyperuricaemia group and the gouty nephropathy group. General characteristics and organ function indicators were also measured for each patient. NLRP3, apoptosis-associated speck like protein (ASC) and caspase-1 mRNA and protein expressions in peripheral blood mononuclear cells were detected. The expression of certain downstream inflammatory factors, including interleukin (IL)-1β and IL-18 were also assessed in plasma. The results demonstrated that the concentration of uric acid and creatinine were increased in the hyperuricaemia and gouty nephropathy groups compared with the control group. NLRP3, ASC and caspase-1 mRNA and protein expression, and IL-1β and IL-18 expression were increased in the hyperuricaemia and gouty nephropathy groups compared with the control group. In addition, ASC and caspase-1 mRNA and protein expression, and IL-1β expression were higher in the gouty nephropathy group compared with the hyperuricaemia group. In conclusion, the present results supported the hypothesis that the NLRP3 inflammasome signalling pathway is associated with gouty nephropathy leading to initiation of the inflammatory response and causing renal damage.

Comparison of uric acid reduction and renal outcomes of febuxostat vs allopurinol in patients with chronic kidney disease

Whether the clinical trial treatment effect of urate-lowering therapy (ULT) in patient with chronic kidney disease (CKD) is generalizable to real-word settings is unclear. This study aimed to compare febuxostat with allopurinol for uric acid reduction and renal protection in patients with CKD. Adult CKD patients newly treated with ULT were identified using electronic health records from 2010 to 2015 from a large healthcare delivery system in Taiwan. Patients with renal replacement therapy or undergoing ULT for <3 months were excluded. Propensity score-matched cohort study design was conducted to compare outcomes between patients initiated with febuxostat or allopurinol therapy. Cox regression analyses were employed to compare the adjusted hazards ratio (aHR) of incident event of estimated glomerular filtration rate (eGFR) ≥ 30% decrease, and the difference in longitudinal changes in serum uric acid (SUA) and eGFR between groups was analyzed using linear mixed model. Overall, 1050 CKD patients who initiated febuxostat (n = 525) or allopurinol (n = 525) treatment were observed for 2.5 years. Compared with allopurinol, febuxostat use was associated with higher rate of patients maintaining SUA target <6 mg/dL in >80% of follow-up time with a reduction in mean SUA change. There were no significant differences in the mean eGFR changes over time between the febuxostat and allopurinol groups or in the risk of eGFR decline ≥30% of baseline. Febuxostat was associated with greater reduction in SUA level than allopurinol in patients with CKD. However, febuxostat and allopurinol showed no difference in renal function changes during study follow-up. These findings require further investigation with long-term follow up in CKD patients with hyperuricemia.

Dexamethasone increases renal free fatty acids and xanthine oxidase activity in female rats: could there be any gestational impact?

Dexamethasone (DEX) is used for various conditions in female and even during pregnancy. We tested the hypothesis that DEX exposure in female rats would lead to renal free fatty acid (FFA) accumulation with elevated xanthine oxidase (XO) activity that would be aggravated by pregnancy. Twenty-four female rats (n = 6/group) were randomly assigned to non-pregnant (NPR), DEX-exposed non-pregnant (NPR + DEX), pregnant (PRE) and DEX-exposed pregnant (PRE + DEX), respectively. NPR and PRE rats received vehicle (po) while NPR + DEX and PRE + DEX groups received DEX (0.2 mg/kg; po), between gestational days 14 and 19. Data showed that DEX exposure caused increased plasma creatinine, urea, renal FFA accumulation, lipid peroxidation, aminotranferases, depressed glutathione, increased activity of XO, and elevated uric acid in both pregnant and non-pregnant rats. The findings of this study indicate that DEX exposure would cause renal FFA accumulation and glutathione depletion that are accompanied by increased activity of XO/uric acid independently of gestation. The study also implies that DEX-induced renal damage could be worsened by gestation.

Effects of Allopurinol on the Progression of Chronic Kidney Disease

BACKGROUND

Elevated serum urate levels are associated with progression of chronic kidney disease. Whether urate-lowering treatment with allopurinol can attenuate the decline of the estimated glomerular filtration rate (eGFR) in patients with chronic kidney disease who are at risk for progression is not known.

METHODS

In this randomized, controlled trial, we randomly assigned adults with stage 3 or 4 chronic kidney disease and no history of gout who had a urinary albumin:creatinine ratio of 265 or higher (with albumin measured in milligrams and creatinine in grams) or an eGFR decrease of at least 3.0 ml per minute per 1.73 m² of body-surface area in the preceding year to receive allopurinol (100 to 300 mg daily) or placebo. The primary outcome was the change in eGFR from randomization to week 104, calculated with the Chronic Kidney Disease Epidemiology Collaboration creatinine equation.

RESULTS

Enrollment was stopped because of slow recruitment after 369 of 620 intended patients were randomly assigned to receive allopurinol (185 patients) or placebo (184 patients). Three patients per group withdrew immediately after randomization. The remaining 363 patients (mean eGFR, 31.7 ml per minute per 1.73 m²; median urine albumin:creatinine ratio, 716.9; mean serum urate level, 8.2 mg per deciliter) were included in the assessment of the primary outcome. The change in eGFR did not differ significantly between the allopurinol group and the placebo group (-3.33 ml per minute per 1.73 m² per year [95% confidence interval {CI}, -4.11 to -2.55] and -3.23 ml per minute per 1.73 m² per year [95% CI, -3.98 to -2.47], respectively; mean difference, -0.10 ml per minute per 1.73 m² per year [95% CI, -1.18 to 0.97]; P = 0.85). Serious adverse events were reported in 84 of 182 patients (46%) in the allopurinol group and in 79 of 181 patients (44%) in the placebo group.

CONCLUSIONS

In patients with chronic kidney disease and a high risk of progression, urate-lowering treatment with allopurinol did not slow the decline in eGFR as compared with placebo. (Funded by the National Health and Medical Research Council of Australia and the Health Research Council of New Zealand; CKD-FIX Australian New Zealand Clinical Trials Registry number, ACTRN12611000791932.).

Serum Urate Lowering with Allopurinol and Kidney Function in Type 1 Diabetes

BACKGROUND

Higher serum urate levels are associated with an increased risk of diabetic kidney disease. Lowering of the serum urate level with allopurinol may slow the decrease in the glomerular filtration rate (GFR) in persons with type 1 diabetes and early-to-moderate diabetic kidney disease.

METHODS

In a double-blind trial, we randomly assigned participants with type 1 diabetes, a serum urate level of at least 4.5 mg per deciliter, an estimated GFR of 40.0 to 99.9 ml per minute per 1.73 m² of body-surface area, and evidence of diabetic kidney disease to receive allopurinol or placebo. The primary outcome was the baseline-adjusted GFR, as measured with iohexol, after 3 years plus a 2-month washout period. Secondary outcomes included the decrease in the iohexol-based GFR per year and the urinary albumin excretion rate after washout. Safety was also assessed.

RESULTS

A total of 267 patients were assigned to receive allopurinol and 263 to receive placebo. The mean age was 51.1 years, the mean duration of diabetes 34.6 years, and the mean glycated hemoglobin level 8.2%. The mean baseline iohexol-based GFR was 68.7 ml per minute per 1.73 m² in the allopurinol group and 67.3 ml per minute per 1.73 m² in the placebo group. During the intervention period, the mean serum urate level decreased from 6.1 to 3.9 mg per deciliter with allopurinol and remained at 6.1 mg per deciliter with placebo. After washout, the between-group difference in the mean iohexol-based GFR was 0.001 ml per minute per 1.73 m² (95% confidence interval [CI], -1.9 to 1.9; P = 0.99). The mean decrease in the iohexol-based GFR was -3.0 ml per minute per 1.73 m² per year with allopurinol and -2.5 ml per minute per 1.73 m² per year with placebo (between-group difference, -0.6 ml per minute per 1.73 m² per year; 95% CI, -1.5 to 0.4). The mean urinary albumin excretion rate after washout was 40% (95% CI, 0 to 80) higher with allopurinol than with placebo. The frequency of serious adverse events was similar in the two groups.

CONCLUSIONS

We found no evidence of clinically meaningful benefits of serum urate reduction with allopurinol on kidney outcomes among patients with type 1 diabetes and early-to-moderate diabetic kidney disease. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases and others; PERL ClinicalTrials.gov number, NCT02017171.).

Effects of uric acid on kidney function decline differ depending on baseline kidney function in type 2 diabetic patients

BACKGROUND

Most existing data regarding effects of uric acid (UA) on diabetic kidney disease have considered patients with preserved kidney function. We examined a hypothesis that there are differences in the effects of serum UA levels on the decline in kidney function depending on baseline kidney function in diabetic patients.

METHODS

In this historical cohort study, 7033 type 2 diabetic patients were analyzed and classified into two groups as follows: nonchronic kidney disease (non-CKD), with an estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m2 (n = 4994), and CKD, with an eGFR <60 mL/min/1.73 m2 (n = 2039). The composite endpoint was a ≥30% decrease in eGFR from baseline or the initiation of renal replacement therapy. The hazard ratio (HR) of serum UA levels at baseline was estimated using multivariate Cox proportional hazards models.

RESULTS

There was a significant interaction between UA levels and baseline eGFR with respect to the endpoint (P < 0.001). The HRs of 1 mg/dL increase in UA levels were 1.13 [95% confidence interval (CI) 1.05-1.22, P = 0.002] and 0.93 (95% CI 0.88-0.99, P = 0.02) in the non-CKD and CKD groups, respectively. When patients were classified by quintile of UA levels, the HRs of those in the 5th quintile (versus 1st quintile) were 1.64 (95% CI 1.23-2.18, P < 0.001) and 0.76 (95% CI 0.58-0.99, P = 0.05) in the non-CKD and CKD groups, respectively.

CONCLUSIONS

The effects of UA on kidney function decline might differ depending on baseline kidney function in type 2 diabetic patients. High UA levels are the prognostic factor only in patients with preserved kidney function.

Comparative Renoprotective Effect of Febuxostat and Allopurinol in Predialysis Stage 5 Chronic Kidney Disease Patients: A Nationwide Database Analysis

Hyperuricemia has been associated with chronic kidney disease (CKD) progression. The antihyperuricemic febuxostat's potential renoprotective effect has been demonstrated in stage 1-3 CKD. Large-scale studies comparing the renoprotective potential of febuxostat and allopurinol in advanced CKD are lacking. We exclusively selected 6,057 eligible patients with predialysis stage 5 CKD prescribed either febuxostat or allopurinol using the National Health Insurance Research Database in Taiwan during 2012-2015. There were 69.57% of allopurinol users and 42.01% febuxostat users who required long-term dialysis (P < 0.0001). The adjusted hazard ratio (HR) of 0.65 (95% confidence interval (CI) 0.60-0.70) indicated near 35% lower hazards of long-term dialysis with febuxostat use. The renal benefit of febuxostat was consistent across most patient subgroups and/or using the propensity score-matched cohort. The adjusted HR was 0.66 (95% CI, 0.61-0.70) for long-term dialysis or death. In conclusion, lower risk of progression to dialysis was observed in predialysis stage 5 CKD febuxostat users without compromising survival.

Changes in Urinary Microalbumin Levels after Correction of Hyperuricemia in Patients with Gout: An Observational Cohort Study

Background

Gout is commonly associated with metabolic syndrome. Strong association between the serum uric acid level and microalbuminuria has also been observed in various studies.

Aim

To observe the change in urinary microalbumin after urate-lowering treatment in patients with gout and microalbuminuria. Methodology. A prospective, observational study was conducted at a tertiary-level rheumatic center (NCRD) in Kathmandu, Nepal. Adults diagnosed with gout using the 2015 ACR/EULAR criteria and microalbuminuria were enrolled in the study after obtaining informed consent. Sociodemographic profile and clinical history were recorded at baseline. Serum uric acid levels, spot urinary microalbumin (MAU) excretion, blood sugar, lipid profile, and blood pressure were measured at baseline, 3-month follow-up, and 6-month follow-up. A paired t-test was used to compare the change in mean MAU after treatment.

Results

A total of 778 patients diagnosed with gout were screened for microalbuminuria. Among them, 114 (14.6%) had urinary microalbumin levels of >30.0 mg/L during presentation. Mean MAU level among those with microalbuminuria was 132.4 ± 124.6 mg/L. Thirty-five patients had concomitant HTN and were put on ARBs (20 mg of telmisartan). All received 40 mg of febuxostat. In patients with ARBs, MAU reduced significantly after 3 months of treatment with ARBs. Reduction in MAU in those without ARBs was seen after the 6-month follow-up, and the change was statistically significant.

Conclusions

There is significant reduction in MAU after the use of urate-lowering drugs in patients with gout.

Management of hyperuricemia in asymptomatic patients: A critical appraisal

While there is consensus on starting urate-lowering therapy (ULT) in cases of symptomatic hyperuricemia, the frequent condition of asymptomatic hyperuricemia (AH) remains a challenge due to differences in the findings of studies that have addressed the issue. Uric acid has anti-oxidant properties, but high levels predispose to gout and may play a role in metabolic syndrome. We systematically evaluated randomized controlled trials (RCTs) addressing ULT in patients with AH, to assess the current evidence. We found broad heterogeneity among the studies (13 RCTs), in terms of study design and population, making findings challenging to interpret and generalize; hard end-points were not assessed. Allopurinol is often prescribed for AH despite the fact that its use is not backed by conclusive evidence from prospective RCTs, nor is it recommended by the guidelines. Its potential benefits, in terms of absolute risk reduction, must be weighed against its potential for harm since it can trigger severe adverse hypersensitivity reactions, sometimes even fatal. RCTs with hard end-points are needed to assess the risk/benefit of lowering uric acid in subjects with AH, particularly as secondary prevention for cardiovascular risk and in patients with different degrees of renal disease. To date, particularly after the result from the CARES trial, preventive treatment of asymptomatic and non-severe hyperuricemia is not recommended.

Excess dietary fluoride affects laying performance, egg quality, tissue retention, serum biochemical indices, and reproductive hormones of laying hens

The present study aimed to evaluate the effects of excess dietary fluoride (F) on laying performance, egg quality, tissue retention, serum biochemical indices, and serum reproductive hormones of laying hens. A total of 384 Hy-Line Gray hens, 37 wk old, were treated with sodium fluoride added to a corn-soybean meal basal diet at 0, 400, 800, and 1200 mg fluorine/kg feed. The results showed that dietary F levels at 800 and 1200 mg/kg markedly decreased ADFI, laying rate, average egg weight, and increased feed conversion ratio (FCR) (P < 0.05). Dietary F levels at 800 and 1200 mg/kg dramatically decreased the egg quality of albumen height, yolk color, eggshell strength, and eggshell thickness, and on the 49th D, 400 mg/kg F group significantly decreased the eggshell strength, compared to those of control group. Fluoride residues in tissues of hens were increased significantly with the increase of dietary F supplemental levels (P < 0.05). Fluoride concentrations were generally high in feces, eggshell, tibia, kidney, and ovary, and the highest in feces, following with eggshell and tibia, lower in kidney and ovary, and the lowest in serum. Serum uric acid levels and alanine aminotransferase activity increased significantly (P < 0.05), and glucose, triglycerides, and phosphorus decreased significantly (P < 0.05) in response to dietary F concentration, compared to those of the control group, respectively. Dietary F supplementation at 1200 mg/kg significantly decreased (P < 0.05) the estrogen concentrations in serum, compared to those of the control group. Concentrations of progesterone in the fluoride-treated groups were significantly (P < 0.05) decreased relative to those of the control group. In conclusion, these results indicated that the excessive ingestion of F has had a detrimental effect on egg laying rate and quality of eggs by damaging the function of the liver, kidney, and ovary of laying hens.

Effects of uric acid dysregulation on the kidney

Recently, research has redirected its interests in uric acid (UA) from gout, an inflammatory disease in joints, to groups of closely interrelated pathologies associated with cardiovascular and kidney dysfunction. Many epidemiological, clinical, and experimental studies have shown that UA may play a role in the pathophysiology of the cardiorenal syndrome continuum; however, it is still unclear if it is a risk factor or a causal role. Hyperuricemia has been well studied in the past two decades, revealing mechanistic insights into UA homeostasis. Likewise, some epidemiological and experimental evidence suggests that hypouricemia can lead to cardiorenal pathologies. The goal of this review is to highlight why studying both hyperuricemia and hypouricemia is warranted as well as to summarize the relevance of UA to kidney function.

Uric acid and inflammation in kidney disease

Asymptomatic hyperuricemia is frequently observed in patients with kidney disease. Although a substantial number of epidemiologic studies have suggested that an elevated uric acid level plays a causative role in the development and progression of kidney disease, whether hyperuricemia is simply a result of decreased renal excretion of uric acid or is a contributor to kidney disease remains a matter of debate. Over the last two decades, multiple experimental studies have expanded the knowledge of the biological effects of uric acid beyond its role in gout. In particular, uric acid induces immune system activation and alters the characteristics of resident kidney cells, such as tubular epithelial cells, endothelial cells, and vascular smooth muscle cells, toward a proinflammatory and profibrotic state. These findings have led to an increased awareness of uric acid as a potential and modifiable risk factor in kidney disease. Here, we discuss the effects of uric acid on the immune system and subsequently review the effects of uric acid on the kidneys mainly in the context of inflammation.

The effect for hyperuricemia inpatient of uric acid overproduction type or in combination with topiroxostat on the pharmacokinetics, pharmacodynamics and safety of dotinurad, a selective urate reabsorption inhibitor

BACKGROUND

Dotinurad, a novel selective urate reabsorption inhibitor (SURI), increases urinary uric acid excretion. The aim of this study is to examine the pharmacokinetics, pharmacodynamics, and safety of dotinurad according to the type of hyperuricemia, with or without concomitant use of xanthine oxidase inhibitor, in uric acid "overproduction type" patients.

METHODS

This open-label clinical pharmacology study was conducted in a hospital. Dotinurad 1 mg was administered for 7 days to hyperuricemic patients with uric acid "overproduction type" (overproduction group, n = 6; and combination group, n = 6) and uric acid "underexcretion type" (underexcretion group, n = 6). In the combination group, topiroxostat 80 mg was used concomitantly.

RESULTS

No significant differences were observed in pharmacokinetics and safety between overproduction group and underexcretion group, and the percent change in serum uric acid level and the amount of urinary uric acid excretion after administration were comparable. In "overproduction type" patients of combination group, the percent change in serum uric acid level significantly increased and the amount of urinary uric acid excretion significantly decreased compared to those of overproduction group. No clinically meaningful differences were observed in safety between the overproduction group and the combination group.

CONCLUSION

In inpatients, differences in hyperuricemic type did not significantly influence the pharmacokinetics, pharmacodynamics, and safety of dotinurad. Moreover, in "overproduction type", the coadministration of dotinurad and topiroxostat had an add-on serum uric acid lowering effect and suppressed urinary uric acid excretion.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02837198.

Intensive uric acid-lowering therapy in CKD patients: the protocol for a randomized controlled trial

BACKGROUND

Hyperuricemia would be a risk factor for the development/progression of CKD. However, several studies showed U-shape association between serum uric acid level and renal impairment, suggesting that hypouricemia was rather associated with renal dysfunction. Perhaps, there is the optimal target level of serum UA for renal function.

METHODS

The Target-UA study is a multicenter randomized controlled trial. Eligible CKD patients (eGFR ≥ 30, < 60 mL/min/1.73 m2 and urine protein < 0.5 g/gCr or urine albumin to creatinine ratio (ACR) < 300 mg/gCr) with serum UA ≥ 8.0 mg/dL (≥ 7.0 mg/dl: under the treatment) will be enrolled and be randomly assigned to the intensive therapy group (target serum UA level ≥ 4.0 mg/dL, < 5.0 mg/dL) or the standard therapy group (serum UA level ≥ 6.0 mg/dL, < 7.0 mg/dL). Topiroxostat, a new xanthine oxidase inhibitor, will be administered to treat hyperuricemia. The primary endpoint is a change in logarithmic value of urine ACR between baseline and week 52 of treatment. The secondary endpoints include changes in serum UA, eGFR, urine protein, lipid profile, and onset of composite cardiovascular events, renal events, gouty arthritis, and attack of urolithiasis. The number of subjects has been set to be 185 in each group for a total of 370.

DISCUSSION

This is the first study, to the best of our knowledge, to determine the optimal target level of serum UA for renal protection and is expected to lead to progress in CKD treatment.

TRIAL REGISTRATION

(UMIN000026741 and jRCTs051180146).

Uric Acid Lowering and Biomarkers of Kidney Damage in CKD Stage 3: A Post Hoc Analysis of a Randomized Clinical Trial

RATIONALE & OBJECTIVE

Hyperuricemia is associated with chronic kidney disease (CKD) progression. We evaluated whether lowering serum uric acid levels improves levels of biomarkers of kidney damage.

STUDY DESIGN

Post hoc analysis of clinical trial participants.

SETTING & PARTICIPANTS

A double-blind randomized placebo-controlled study designed to lower serum uric acid levels. 80 patients with stage 3 CKD and asymptomatic hyperuricemia were randomly assigned to allopurinol treatment or placebo (300 mg/d) for 12 weeks.

EXPOSURE/PREDICTOR

Allopurinol treatment versus placebo.

OUTCOMES & MEASURES

We evaluated the change from baseline for the following urinary biomarkers of kidney damage: albumin-creatinine ratio (ACR), neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule 1 (KIM-1), and transforming growth factor β1 (TGF-β1). Additionally, we evaluated CKD Epidemiology Collaboration (CKD-EPI)-estimated glomerular filtration rate (eGFR) and cystatin C eGFR.

ANALYTICAL APPROACH

Generalized linear mixed modeling was used.

RESULTS

After 12 weeks, allopurinol (compared to placebo) significantly lowered serum uric acid levels with an estimate of -3.3 mg/dL (95% CI, -4.1 to -2.5 mg/dL; P < 0.001). Estimates for the change for allopurinol versus placebo over time were 1.09 (95% CI, 0.77-1.54) for ACR, 0.77 (95% CI, 0.36-1.63) for NGAL, and 2.36 (95% CI, 0.97-5.70) for TGF-β1. The model did not converge for KIM-1, but Wilcoxon signed rank test showed no significant difference in change from baseline between study groups. There was no significant change observed in CKD-EPI eGFR or cystatin C eGFR.

LIMITATIONS

Post hoc analysis and short duration of the study.

CONCLUSIONS

Uric acid-lowering with allopurinol is not associated with improvement in levels of biomarkers of kidney damage in patients with asymptomatic hyperuricemia and stage 3 CKD.

FUNDING

The study was funded by the National Institutes of Health through a career development award, K23DK088833, and the Clinical and Translational Science Award UL1TR002537.

TRIAL REGISTRATION

NCT01228903.

Effect of Uric Acid Control on Serum Creatinine

OBJECTIVE

Hyperuricemia has been epidemiologically associated with multiple comorbidities including chronic renal failure and cardiovascular disease. Cause and effect are difficult to address, given comorbidities associated with and prevalence of metabolic syndrome. One impediment to achieving serum uric acid (sUa) levels less than or equal to 6.0 mg/DL is the concept that allopurinol might be nephrotoxic. We examined the relation of sUa less than or equal to 6.0 mg/dL to renal function over time.

METHODS

This is a medical records review study of 348 hyperuricemia patients identified in 2015, as having been followed with serial uric acid measurements. After 1 year of serial urate levels, to allow for treatment, patient cohorts were defined: sUa less than or equal to 6.0 mg/dL and sUa greater than 6.0 mg/dL. A repeated measure model was used to test for an association between uric acid level and serum creatinine, while adjusting for covariates.

RESULTS

There was a significant difference in the least square means of serum creatinine comparing those who achieved an sUa less than or equal to 6.0 mg/dL versus sUa greater than 6.0 mg/dL (1.39 mg/dL [95% confidence interval, 1.30-1.48] vs 1.57 mg/dL [95% confidence interval, 1.46-1.69]; p = 0.0015). This is a between-group difference in creatinine of 0.18 mg/dL. If a change in serum creatinine of 0.2 is considered significant, this short-term between-group progression of renal failure approaches clinical significance.

CONCLUSIONS

Given that most serial measures were within the first few years of follow-up, and change in renal function occurs slowly over time, the between group difference of sUa of 0.18 mg/dL is close to a clinically significant creatinine difference of 0.2 mg/dL.

An Optical Urate Biosensor Based on Urate Oxidase and Long-Lifetime Metalloporphyrins

Gout is a condition that affects over 8 million Americans. This condition is characterized by severe pain, and in more advanced cases, bone erosion and joint destruction. This study explores the fabrication and characterization of an optical, enzymatic urate biosensor for gout management, and the optimization of the biosensor response through the tuning of hydrogel matrix properties. Sensors were fabricated through the co-immobilization of oxygen-quenched phosphorescent probes with an oxidoreductase within a biocompatible copolymer hydrogel matrix. Characterization of the spectral properties and hydrogel swelling was conducted, as well as evaluation of the response sensitivity and long-term stability of the urate biosensor. The findings indicate that increased acrylamide concentration improved the biosensor response by yielding an increased sensitivity and reduced lower limit of detection. However, the repeatability and stability tests highlighted some possible areas of improvement, with a consistent response drift observed during repeatability testing and a reduction in response seen after long-term storage tests. Overall, this study demonstrates the potential of an on-demand, patient-friendly gout management tool, while paving the way for a future multi-analyte biosensor based on this sensing platform.

A non-inferiority study of the novel selective urate reabsorption inhibitor dotinurad versus febuxostat in hyperuricemic patients with or without gout

Background

Dotinurad is a novel, selective urate reabsorption inhibitor, which reduces serum uric acid levels by selective inhibition of the urate transporter 1. We evaluated the efficacy and safety of dotinurad versus febuxostat, a widely used drug in Japan, in hyperuricemic Japanese patients with or without gout.

Methods

This was a multicenter, randomized, double-blind, active-controlled, parallel-group, forced-titration study in hyperuricemic patients. Study treatment in the dotinurad and febuxostat groups was initiated at 0.5 and 10 mg/day, followed by dose titration to 2 and 40 mg/day, respectively, over 14 weeks. The primary endpoint was the percent change in serum uric acid level from the baseline to the final visit.

Results

A total of 203 hyperuricemic patients with or without gout were enrolled in the study and randomized to receive dotinurad or febuxostat. The percent change in serum uric acid level from the baseline to the final visit was 41.82% in the dotinurad group and 44.00% in the febuxostat group. The mean difference was − 2.17% (two-sided 95% confidence interval − 5.26% to 0.92%). The lower limit of the interval was above the non-inferiority margin (− 10%), demonstrating the non-inferiority of dotinurad to febuxostat. The profiles of adverse events and adverse drug reactions raised no noteworthy safety concerns in either group.

Conclusion

The non-inferiority of dotinurad to febuxostat in terms of serum uric acid lowering effect was confirmed. No noteworthy safety concerns arose.

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.

Uric acid is not associated with diabetic nephropathy and other complications in type 1 diabetes

BACKGROUND

To examine the association between plasma uric acid (UA) and the presence of diabetic complications including diabetic nephropathy and cardiovascular risk factors in patients with type 1 diabetes.

METHODS

This study, which is cross-sectional in design, included 676 Caucasian type 1 diabetes patients from the Steno Diabetes Center Copenhagen. Participants with UA within the three lowest sex-specific quartiles were compared with participants with levels in the highest quartile. Unadjusted and adjusted linear regression analyses were applied. Adjustment included sex, age, diabetes duration, body mass index, high-density lipoprotein cholesterol, smoking, haemoglobin A1c, 24-h pulse pressure, urinary albumin excretion rate (UAER), estimated glomerular filtration rate (eGFR) and treatment with renin-angiotensin-aldosterone system blockers.

RESULTS

Of the 676 patients, 372 (55%) were male, mean ± SD age was 55 ± 13 years and eGFR was 82 ± 26 mL/min/1.73 m2. The median UA was 0.30 (interquartile range 0.23-0.37) mmol/L. UA in the upper sex-specific quartile was associated with lower eGFR, higher UAER and carotid-femoral pulse wave velocity and lower 24 h and daytime diastolic blood pressure (BP) in unadjusted analyses (P < 0.001). Moreover, UA in the upper sex-specific quartile was associated with higher nighttime systolic BP and the presence of cardiovascular disease in unadjusted analyses (P ≤ 0.01), but significance was lost after adjustment (P ≥ 0.17). UA was higher across the retinopathy groups [nil (n = 142), simplex (n = 277), proliferative (n = 229) and blind (n = 19)] in unadjusted analyses (P < 0.0001), but not after adjustment (P = 0.12). Patients with an accelerated decline in eGFR (≥3 mL/min/year) had significantly higher UA at baseline (P = 0.006) compared with slow decliners (<3 mL/min/year), but significance was lost after adjustment (P = 0.10).

CONCLUSIONS

In type 1 diabetes patients, higher UA was associated with lower kidney function and other diabetic complications. The association between higher UA and lower eGFR and lower diastolic BP was independent of traditional risk factors.

Clinical pharmacological study of dotinurad administered to male and female elderly or young subjects

Background

Dotinurad is a novel selective urate reabsorption inhibitor (SURI) that selectively inhibits the reabsorption of uric acid in renal tubules and promotes the excretion of uric acid into urine. In this study, the effects of age and gender on the pharmacokinetics (PK), pharmacodynamics (PD), and safety of dotinurad were evaluated in healthy subjects.

Methods

An open-label study of a single oral administration of dotinurad 1 mg was conducted in elderly (≥ 65 years) Japanese males and females, and young (20–35 years) males and females (six patients each).

Results

Following a single-dose administration of dotinurad, the change in dotinurad plasma concentration showed a similar profile across groups. Regarding the PK parameters, there was no significant difference between elderly and young subjects. On comparing males and females, significant differences were observed in some parameters in elderly subjects. However, these differences in some parameters could not be detected by adjust for body weight. When PD parameters in elderly and young subjects were compared, significant differences were observed in some parameters in male subjects. On comparing males and females, significant differences were observed in some parameters in young subjects; however, the percent change in serum uric acid concentration decreased over time was relatively close for both groups. There were no clinically relevant safety problems.

Conclusion

Age and gender had no clinically meaningful effect on the PK, PD, and safety of dotinurad.

Clinical trials

ClinicalTrials.gov identifier: NCT02344875.

The association between uric acid levels and renal function of CKD patients with hyperlipidemia: a sub-analysis of the ASUCA trial

Background

The influence of uric acid (UA) on renal function and the significance of UA-lowering therapy are unclear. The purpose of the sub-analysis of the Assessment of Clinical Usefulness in chronic kidney disease patients with Atorvastatin (ASUCA) trial was to evaluate the influence of serum UA levels on renal function in Japanese chronic kidney disease patients with hyperlipidemia.

Methods

Of 344 participants in the ASUCA trial, 279 participants whose UA levels at both baseline and 24 months were available were included. Based on UA level at baseline or mean UA level during the trial period, they were divided into four groups: < 5.0, 5.0–6.0, 6.0–7.0, or ≥ 7.0 mg/dL, irrespective of allocation. Changes in the estimated glomerular filtration rate (eGFR) after 24 months were compared among the groups in relation to baseline or mean UA levels.

Results

For baseline UA levels (< 5.0, 5.0–6.0, 6.0–7.0, or ≥ 7.0 mg/dL), the change in eGFR after 24 months was − 1.32 ± 10.3, − 1.74 ± 8.94, − 2.53 ± 7.34, and − 3.51 ± 9.10 mL/min/1.73 m², respectively. A negative correlation between changes in eGFR after 24 months and baseline UA level was observed with adjustment for confounding factors. The relationship between changes in eGFR and mean UA levels during trial period showed a similar trend.

Conclusion

In CKD patients with dyslipidemia, hyperuricemia was an independent risk factor for CKD progression. An ongoing clinical trial (TARGET-UA, UMIN-ID 000,026,741) may reveal the significance of strict UA-lowering therapy in CKD patients.

Electronic supplementary material

The online version of this article (10.1007/s10157-019-01840-4) contains supplementary material, which is available to authorized users.

Coexistence of hyper-uricaemia and low urinary uric acid excretion further increases risk of chronic kidney disease in type 2 diabetes

AIM

To investigate whether hyper-uricaemia and decreased urinary uric acid excretion (UUAE) are associated with increased risk of chronic kidney disease (CKD), and whether the coexistence of hyper-uricaemia and low UUAE further increases CKD risk in type 2 diabetes mellitus (T2DM).

METHODS

In this cross-sectional study based on serum uric acid (SUA) and UUAE levels, 2846 T2DM inpatients were divided into those with normal SUA and UUAE (group 1), normal SUA and low UUAE (group 2), hyper-uricaemia and normal UUAE (group 3), and hyper-uricaemia and low UUAE (group 4). Hyper-uricaemia was defined as SUA levels ≥ 420 μmol/L in men and ≥ 360 μmol/L in women. Low UUAE was defined as levels below the first UUAE quintiles (< 2161 μmol/24 h in men, 1977 μmol/24 h in women).

RESULTS

There were trends for significantly increased prevalences of CKD (4.3%, 12.6%, 18.3%, 47.8%; P < 0.001), albuminuria (20.2%, 26.4%, 36.9%, 54.9%; P < 0.001) and macroalbuminuria (3.3%, 10.1%, 10.7%, 31.9%; P < 0.001) from groups 1 to 4, respectively. After controlling for multiple confounding factors, prevalences of CKD (P < 0.001) and urinary albumin levels (P = 0.013) showed significantly increasing trends, whereas eGFR levels were markedly decreased from groups 1 to 4 (P < 0.001).

CONCLUSION

Hyper-uricaemia and low UUAE levels are closely associated with presence of CKD, and the concomitant presence of hyper-uricaemia and decreased UUAE levels further increased CKD risk in T2DM. Thus, the combined consideration of SUA and UUAE levels may help to identify those T2DM patients at higher CKD risk.

Association between serum uric acid and chronic kidney disease in patients with hypertension: A multicenter nationwide cross-sectional study

INTRODUCTION

Current data on the role of hyperuricemia as a risk factor for renal progression in patients with hypertension is inconclusive. This study aimed to assess the association of uric acid and chronic kidney disease (CKD) in hypertensive patients using a nationwide patient sample.

METHODS

We conducted a nationwide cross-sectional study based on the DM/HT study of the Medical Research Network of the Consortium of Thai Medical Schools. This study evaluated adult patients with hypertension from 831 Thailand public hospitals in the year 2014. Serum uric acid (SUA) was categorized into quintiles (≤4.5, 4.6 to 5.4, 5.5 to 6.2, 6.3 to 7.4, ≥7.5 mg/dL). CKD was defined as estimated glomerular filtration rate of ≤ 60 mL/min/1.73 m2 . Multivariate logistic regression was performed to assess the association between SUA and CKD using uric acid of ≤4.5 mg/dL as the reference group.

RESULTS

A total of 9776 hypertensive patients with available SUA were included in the analysis. The mean SUA was 6.1±1.8 mg/dL. The prevalence of CKD in hypertensive patients was 31.8%. SUA of 4.6 to 5.4, 5.5 to 6.2, 6.3 to 7.4, and ≥7.5 mg/dL were associated with an increased CKD with ORs of 1.57 (95% CI 1.28 to 1.92), 2.15 (95% CI 1.74 to 2.66), 3.31 (95% CI 2.72 to 4.04), and 7.11 (95% CI 5.76 to 8.78), respectively. The restricted cubic spline showed significant increased CKD prevalence when uric acid ≥4.6 mg/dL.

CONCLUSION

Higher SUA was associated with increased CKD prevalence in patients with hypertension. SUA should be monitored in hypertensive patients for CKD prevention.

Febuxostat is superior to allopurinol in delaying the progression of renal impairment in patients with chronic kidney disease and hyperuricemia

PURPOSE

This study aimed to compare efficacy of renal-protective function between febuxostat and allopurinol in patients with chronic kidney disease (CKD) and hyperuricemia (HUA).

METHODS

Totally 152 CKD stage 2-3 patients complicated with HUA were recruited. According to their uric acid-lowering therapy, there were 67 patients included in febuxostat group and 85 in allopurinol group, respectively. Estimated glomerular filtration rate (eGFR), serum creatinine (Scr), 24-h proteinuria, serum uric acid (SUA) were measured at M0, M1, M3 and M6 after the treatment. Primary outcome was proportion of patients showing ≥ 10% decline in eGFR from baseline at M6.

RESULTS

The eGFR at M6 was numerically higher at M6 and eGFR change (M6-M0) was increased in febuxostat group compared with allopurinol group. Most importantly, the proportion of patients showing a ≥ 10% decline in eGFR from baseline at M6 was reduced in febuxostat group compared with allopurinol group. Multivariate logistic regression analyses further validated that febuxostat vs. allopurinol was an independent predictor for reduced risk of eGFR decline ≥ 10% from baseline. Besides, SUA change (M6-M0) was decreased, but Scr change (M6-M0) and 24-h proteinuria change (M6-M0) were similar in febuxostat group compared with allopurinol group.

CONCLUSIONS

Febuxostat presents a superior effect in delaying renal impairment progression compared with allopurinol in CKD patients complicated with HUA.

Inflammation in Renal Diseases: New and Old Players

Inflammation, a process intimately linked to renal disease, can be defined as a complex network of interactions between renal parenchymal cells and resident immune cells, such as macrophages and dendritic cells, coupled with recruitment of circulating monocytes, lymphocytes, and neutrophils. Once stimulated, these cells activate specialized structures such as Toll-like receptor and Nod-like receptor (NLR). By detecting danger-associated molecules, these receptors can set in motion major innate immunity pathways such as nuclear factor ĸB (NF-ĸB) and NLRP3 inflammasome, causing metabolic reprogramming and phenotype changes of immune and parenchymal cells and triggering the secretion of a number of inflammatory mediators that can cause irreversible tissue damage and functional loss. Growing evidence suggests that this response can be deeply impacted by the crosstalk between the kidneys and other organs, such as the gut. Changes in the composition and/or metabolite production of the gut microbiota can influence inflammation, oxidative stress, and fibrosis, thus offering opportunities to positively manipulate the composition and/or functionality of gut microbiota and, consequentially, ameliorate deleterious consequences of renal diseases. In this review, we summarize the most recent evidence that renal inflammation can be ameliorated by interfering with the gut microbiota through the administration of probiotics, prebiotics, and postbiotics. In addition to these innovative approaches, we address the recent discovery of new targets for drugs long in use in clinical practice. Angiotensin II receptor antagonists, NF-ĸB inhibitors, thiazide diuretics, and antimetabolic drugs can reduce renal macrophage infiltration and slow down the progression of renal disease by mechanisms independent of those usually attributed to these compounds. Allopurinol, an inhibitor of uric acid production, has been shown to decrease renal inflammation by limiting activation of the NLRP3 inflammasome. So far, these protective effects have been shown in experimental studies only. Clinical studies will establish whether these novel strategies can be incorporated into the arsenal of treatments intended to prevent the progression of human disease.

Xanthine Oxidase Inhibitor Febuxostat Exerts an Anti-Inflammatory Action and Protects against Diabetic Nephropathy Development in KK-Ay Obese Diabetic Mice

Hyperuricemia has been recognized as a risk factor for insulin resistance as well as one of the factors leading to diabetic kidney disease (DKD). Since DKD is the most common cause of end-stage renal disease, we investigated whether febuxostat, a xanthine oxidase (XO) inhibitor, exerts a protective effect against the development of DKD. We used KK-Ay mice, an established obese diabetic rodent model. Eight-week-old KK-Ay mice were provided drinking water with or without febuxostat (15 μg/mL) for 12 weeks and then subjected to experimentation. Urine albumin secretion and degrees of glomerular injury judged by microscopic observations were markedly higher in KK-Ay than in control lean mice. These elevations were significantly normalized by febuxostat treatment. On the other hand, body weights and high serum glucose concentrations and glycated albumin levels of KK-Ay mice were not affected by febuxostat treatment, despite glucose tolerance and insulin tolerance tests having revealed febuxostat significantly improved insulin sensitivity and glucose tolerance. Interestingly, the IL-1β, IL-6, MCP-1, and ICAM-1 mRNA levels, which were increased in KK-Ay mouse kidneys as compared with normal controls, were suppressed by febuxostat administration. These data indicate a protective effect of XO inhibitors against the development of DKD, and the underlying mechanism likely involves inflammation suppression which is independent of hyperglycemia amelioration.

Impact of urate-lowering drugs on the progression and recovery from chronic kidney disease among gout patients

Background

This study investigates the association between exposure to urate-lowering drugs (ULDs) and progression and recovery from chronic kidney disease (CKD).

Methods

We identified 5860 incident gout patients at Chang Gung Memorial Hospital from 2012 to 2015. Propensity score (PS)-weighted Cox proportional hazards model was used to estimate hazard ratios (HRs) for CKD progression and improvement. A separate analysis was conducted to assess the HR for CKD progression and CKD recovery among those with worsening CKD.

Results

The incidence of CKD progression among allopurinol, febuxostat and uricosuric agent users were 1.98, 1.88 and 1.64 per 1000 person-days. Compared with allopurinol users, the PS-weighted HR (95% confidence intervals [CIs]) was 1.77 (0.85–1.76) for febuxostat users and 1.37 (0.71–1.37) for uricosuric agent users for CKD progression and 1.43 (1.26–1.62) for febuxostat users and 1.00 (0.88–1.14) for uricosuric agent users for CKD improvement. Compared to allopurinol users, the HRs for CKD progression were 1.14 (0.80–1.66) for febuxostat users and 0.92 (0.67–1.31) for uricosuric agent users. Among 741 patients who had CKD progression, the incidence of CKD recovery was 1.33, 6.21 and 3.53 per 1000 person-days for allopurinol, febuxostat and uricosuric agent users. The HRs (95% CIs) for recovery in febuxostat and uricosuric agent users were 2.17 (1.40–3.47) and 1.80 (1.20–2.83) compared to allopurinol users.

Conclusions

CKD progression and recovery are common in gout patients using ULDs. Febuxostat and benzbromarone were associated with a similar risk of CKD progression with allopurinol, which has a poorer recovery compared with other ULDs.

Uric acid induced epithelial-mesenchymal transition of renal tubular cells through PI3K/p-Akt signaling pathway

The phenotypic changes of tubular epithelial cell are hallmark features of renal diseases caused by abnormal uric acid levels. We hereby intend to investigate whether PI3K/p-Akt signaling plays a role in uric-acid induced epithelial-mesenchymal transition process. The normal rat kidney cell line (NRK-52E) was used as a proximal tubular cell model in this study. NRK-52E cells were exposed to different concentrations of uric acid, or PI3K inhibitor LY294002, or both, respectively. The effects of uric acid on cell morphology were examined by phase contrast microscopy, while molecular alternations were assessed by western blot analysis and immunofluorescence staining. We found that uric acid induced visible morphological alterations in NRK-52E cells accompanied by increased expression of α-smooth muscle actin and reduced expression of E-cadherin. Moreover, phosphorylation of Akt protein was obviously increased, whereas Akt level remained stable. Furthermore, the above effects were abolished when PI3K/p-Akt pathway was blocked by the PI3K inhibitor. These findings demonstrated that high uric acid could induce phenotypic transition of cultured renal tubular cells, which was probably via activating PI3K/p-Akt signaling pathway.

Treatment of asymptomatic hyperuricemia complicated by renal damage: a controversial issue

The prevalence of asymptomatic HUA is increasing year after year. HUA is a risk factor for the occurrence and development of renal diseases. However, the role of urate-lowering therapy in asymptomatic HUA complicated by renal damage is still controversial. In some experiments, the treatment of asymptomatic HUA complicated by renal damage may delay the progression of kidney damage. In addition, there is increasing evidence, suggesting that elevated serum uric acid is an independent risk factor for kidney disease. However, in other studies, uric acid-lowering therapy did not improve renal function, and uric acid levels could not be used as an independent predictor for CKD development. Further experimental studies are needed to determine the starting threshold and target value of asymptomatic HUA complicated by renal damage. At the same time, confirmation of the benefits of urate-lowering therapy for kidneys requires studies with larger samples and high-quality RCTs.

Tissue, urine and blood metabolite signatures of chronic kidney disease in the 5/6 nephrectomy rat model

INTRODUCTION

Progressive chronic kidney disease (CKD) is an important cause of morbidity and mortality. It has a long asymptomatic phase, where routine blood tests cannot identify early functional losses, and therefore identifying common mechanisms across the many etiologies is an important goal.

OBJECTIVES

Our aim was to characterize serum, urine and tissue (kidney, lung, heart, spleen and liver) metabolomics changes in a rat model of CKD.

METHODS

A total of 17 male Wistar rats underwent 5/6 nephrectomy, whilst 13 rats underwent sham operation. Urine samples were collected weekly, for 6 weeks; blood was collected at weeks 0, 3 and 6; and tissue samples were collected at week 6. Samples were analyzed on a nuclear magnetic resonance spectroscopy platform with multivariate and univariate data analysis.

RESULTS

Changes in several metabolites were statistically significant. Allantoin was affected in all compartments. Renal asparagine, creatine, hippurate and trimethylamine were significantly different; in other tissues creatine, dimethylamine, dimethylglycine, trigonelline and trimethylamine were significant. Benzoate, citrate, dimethylglycine, fumarate, guanidinoacetate, malate, myo-inositol and oxoglutarate were altered in urine or serum.

CONCLUSION

Although the metabolic picture is complex, we suggest oxidative stress, the gut-kidney axis, acid-base balance, and energy metabolism as promising areas for future investigation.

In silico design and synthesis of hesperitin derivatives as new xanthine oxidase inhibitors

Background

Hesperitin, a naturally occurring flavonoid was hybridized with phenolic acids to evaluate its potential to inhibit the activity of xanthine oxidase (XO), a key enzyme which catalyses xanthine to uric acid which is found to be associated with gout and many life style related disorders.

Objective

To develop new xanthine oxidase inhibitors from natural constituents along with antioxidant potential.

Method

In this report, we designed and synthesized hesperitin derivatives hybridized with natural phenolic acids to form ester linkage with the help of molecular docking. The synthesized compounds were evaluated for their antioxidant and xanthine oxidase inhibitory potential.

Results

The in vitro xanthine oxidase inhibitory activity and enzyme kinetics studies showed that hesperitin derivatives displayed a potential inhibition against XO in competitive manner with IC₅₀ value ranging from 9.0 to 23.15 µM and HET4 was revealed as most active derivative. Molecular simulation revealed that new hesperitin derivatives interacted with the amino acid residues SER1080, PHE798, GLN1194, ARG912, THR1083, ALA1078 and MET1038 located within the active cavity of XO. Results of antioxidant activity revealed that all the derivatives showed very good antioxidant potential.

Conclusion

Taking advantage of molecular docking, this hybridization of two natural constituent could lead to desirable xanthine oxidase inhibitors with improved activity.

The Role of a “Treat-to-Target” Approach in the Long-Term Renal Outcomes of Patients with Gout

Background: Although gout is accompanied by the substantial burden of kidney disease, there are limited data to assess renal function as a therapeutic target. This study evaluated the importance of implementing a “treat-to-target” approach in relation to renal outcomes. Methods: Patients with gout who underwent continuous urate-lowering therapy (ULT) for at least 12 months were included. The effect of ULT on renal function was investigated by means of a sequential comparison of the estimated glomerular filtration rate (eGFR). Results: Improvement in renal function was only demonstrated in subjects in whom the serum urate target of <6 mg/dL was achieved (76.40 ± 18.81 mL/min/1.73 m2 vs. 80.30 ± 20.41 mL/min/1.73 m2, p < 0.001). A significant difference in the mean change in eGFR with respect to serum urate target achievement was shown in individuals with chronic kidney disease stage 3 (−0.35 ± 3.87 mL/min/1.73 m2 vs. 5.33 ± 11.64 mL/min/1.73 m2, p = 0.019). Multivariable analysis predicted that patients ≥65 years old had a decreased likelihood of improvement (OR 0.31, 95% CI 0.13–0.75, p = 0.009). Conclusions: The “treat-to-target” approach in the long-term management of gout is associated with better renal outcomes, with a greater impact on those with impaired renal function.

The case for uric acid-lowering treatment in patients with hyperuricaemia and CKD

Hyperuricaemia is common among patients with chronic kidney disease (CKD), and increases in severity with the deterioration of kidney function. Although existing guidelines for CKD management do not recommend testing for or treatment of hyperuricaemia in the absence of a diagnosis of gout or urate nephrolithiasis, an emerging body of evidence supports a direct causal relationship between serum urate levels and the development of CKD. Here, we review randomized clinical trials that have evaluated the effect of urate-lowering therapy (ULT) on the rate of CKD progression. Among trials in which individuals in the control arm experienced progressive deterioration of kidney function (which we define as ≥4 ml/min/1.73 m² over the course of the study - typically 6 months to 2 years), treatment with ULT conferred consistent clinical benefits. In contrast, among trials where clinical progression was not observed in the control arm, treatment with ULT was ineffective, but this finding should not be used as an argument against the use of uric acid-lowering therapy. Although additional studies are needed to identify threshold values of serum urate for treatment initiation and to confirm optimal target levels, we believe that sufficient evidence exists to recommend routine measurement of serum urate levels in patients with CKD and consider initiation of ULT among those who are hyperuricaemic with evidence of deteriorating renal function, unless specific contraindications exist.

Effects of febuxostat on renal function in patients with chronic kidney disease: A systematic review and meta-analysis

BACKGROUND/OBJECTIVE

Hyperuricemia has been proven to be an independent risk factor for chronic kidney disease (CKD). However, the role of hyperuricemia in the progression of CKD remains unclear. Thus, we performed a systematic review and meta-analysis to evaluate the efficacy and safety of febuxostat, a first line urate-lowering agent, in CKD patients with hyperuricemia.

METHODS

We have systematically searched for randomized controlled trials assessing the efficacy and safety of febuxostat versus control in CKD patients with hyperuricemia through MEDLINE, PubMed, EMBASE, and Cochrane databases. All statistical analyses were conducted by using the statistical package Review Manager, version 5.3.5. Heterogeneity was assessed using the Cochrane Q and I tests and summary statistics were reported with 95% confidence interval. Two-tailed test was used for analysis and a P value of <.05 is considered statistically significant.

RESULTS

Eleven eligible trials with 1317 participants were included in the meta-analysis. A significant reduction in serum uric acid was found in the febuxostat treated group. Also, a significant higher eGFR was found in the febuxostat treated group among CKD stage 3 and 4 patients. No significant difference of major complication or death was identified between treatment and control groups.

CONCLUSIONS

The meta-analysis showed that other than its urate-lowering effect, febuxostat presented a reno-protective effect in CKD patients. More studies with larger sample sizes and higher quality are required to clarify the role of febuxostat use in the progression of CKD.

Effect of hyperuricemia and treatment for hyperuricemia in Japanese hemodialysis patients: A cohort study

Whether higher serum uric acid (UA) values comprise a risk factor for death and whether treatment for high UA is effective in patients undergoing hemodialysis (HD) are essentially unknown. To determine associations between UA and all-cause or cardiovascular (CV) mortality, interactions between UA or medication and effects on mortality, and significance of treatment for hyperuricemia in patients undergoing hemodialysis (HD). We collected the baseline data of 222,434 patients undergoing three HD sessions per week, extracted from a nationwide dialysis registry at the end of 2011 in Japan. Then we evaluated the interaction between serum uric acid level and all-cause and cardiovascular (CV) mortality by the end of 2012. Univariate and multivariate logistic regression and Cox regression analyses found higher all-cause and CV mortality rates among patients with lower, than higher UA values. Hazard ratios (HR) for all-cause and CV mortality were significantly lower in a group with, than without medication for hyperuricemia (HR, 0.837; 95% confidence interval (CI), 0.789–0.889 and HR, 0.830; 95%CI 0.758–0.909, respectively). Lower UA values remained associated with all-cause and CV mortality rates even when in patients taking medication for hyperuricemia. The chief interacting factors for higher mortality rates due to lower UA were higher BMI and diabetes mellitus. In conclusion, lower UA levels were independently associated with higher all-cause and CV mortality among Japanese patients undergoing HD. Intervention for hyperuricemia is considered to improve patient outcomes.

Impact of uric acid on incident hypertension: Sex-specific analysis in different age groups

The aim of the present study is to evaluate the association of serum uric acid (UA) levels with the risk of incident hypertension among different age groups in men and women using a single large Japanese general cohort. The present study is based on annual health check-up program in Gunma, Japan. We studied 12,029 participants (mean age, 48 ​± ​9 years old; 31% women) free of prevalent cardiovascular disease and hypertension at baseline (2009). Hypertension was defined by self-report, hypertensive medication use, or measured BP ​> ​140/90 ​mmHg ​at each visit. Discrete proportional hazards regression model was used to evaluate the association of UA level at baseline with incident hypertension through 2012 adjusted for age, gender, baseline blood pressure, and other CVD risk factors among different age decade groups in men and women. During follow-up of 3 years, 12% of the cohort (n ​= ​1457) developed hypertension. UA was strongly associated with incident hypertension in the multivariable model in all participants. In age-stratified analysis, participants below 50 years of age in men had the significant association of UA with incident hypertension, whereas participants above 50 years did not. In women, participants above 40 years had the significant association, whereas participants below 40 years did not. The present data suggest that UA level is an independent predictor for incident hypertension among middle aged men below 50 years old and middle aged and the elderly women above 40 years.

Uric acid and progression of chronic kidney disease

The association between serum uric acid levels and human disease has garnered intense interest over the last decade including chronic kidney disease. Animal studies have provided evidence for a potential mechanistic role of uric acid in promoting progression of chronic kidney disease. Epidemiologic studies have also suggested an association between elevated serum uric acid levels and worsening renal function in the general population as well as in patients with chronic kidney disease. However, there is currently insufficient evidence to recommend the use of uric acid-lowering therapy to delay progression of chronic kidney disease in this patient population. Adequately powered, randomized, placebo-controlled trials are required to more precisely evaluate the risk and benefits of uric acid-lowering therapy in pediatric patients.

Rising Serum Uric Acid Level Is Negatively Associated with Survival in Renal Cell Carcinoma

Aim and Background: To investigate the association of serum uric acid (SUA) levels along with statin use in Renal Cell Carcinoma (RCC), as statins may be associated with improved outcomes in RCC and SUA elevation is associated with increased risk of chronic kidney disease (CKD). Methods: Retrospective study of patients undergoing surgery for RCC with preoperative/postoperative SUA levels between 8/2005–8/2018. Analysis was carried out between patients with increased postoperative SUA vs. patients with decreased/stable postoperative SUA. Kaplan-Meier analysis (KMA) calculated overall survival (OS) and recurrence free survival (RFS). Multivariable analysis (MVA) was performed to identify factors associated with increased SUA levels and all-cause mortality. The prognostic significance of variables for OS and RFS was analyzed by cox regression analysis. Results: Decreased/stable SUA levels were noted in 675 (74.6%) and increased SUA levels were noted in 230 (25.4%). A higher proportion of patients with decreased/stable SUA levels took statins (27.9% vs. 18.3%, p = 0.0039). KMA demonstrated improved 5- and 10-year OS (89% vs. 47% and 65% vs. 9%, p < 0.001) and RFS (94% vs. 45% and 93% vs. 34%, p < 0.001), favoring patients with decreased/stable SUA levels. MVA revealed that statin use (Odds ratio (OR) 0.106, p < 0.001), dyslipidemia (OR 2.661, p = 0.004), stage III and IV disease compared to stage I (OR 1.887, p = 0.015 and 10.779, p < 0.001, respectively), and postoperative de novo CKD stage III (OR 5.952, p < 0.001) were predictors for increased postoperative SUA levels. MVA for all-cause mortality showed that increasing BMI (OR 1.085, p = 0.002), increasing ASA score (OR 1.578, p = 0.014), increased SUA levels (OR 4.698, p < 0.001), stage IV disease compared to stage I (OR 7.702, p < 0.001), radical nephrectomy (RN) compared to partial nephrectomy (PN) (OR 1.620, p = 0.019), and de novo CKD stage III (OR 7.068, p < 0.001) were significant factors. Cox proportional hazard analysis for OS revealed that increasing age (HR 1.017, p = 0.004), increasing BMI (Hazard Ratio (HR) 1.099, p < 0.001), increasing SUA (HR 4.708, p < 0.001), stage III and IV compared to stage I (HR 1.537, p = 0.013 and 3.299, p < 0.001), RN vs. PN (HR 1.497, p = 0.029), and de novo CKD stage III (HR 1.684, p < 0.001) were significant factors. Cox proportional hazard analysis for RFS demonstrated that increasing ASA score (HR 1.239, p < 0.001, increasing SUA (HR 9.782, p < 0.001), and stage II, III, and IV disease compared to stage I (HR 2.497, p < 0.001 and 3.195, p < 0.001 and 6.911, p < 0.001) were significant factors. Conclusions: Increasing SUA was associated with poorer outcomes. Decreased SUA levels were associated with statin intake and lower stage disease as well as lack of progression to CKD and anemia. Further investigation is requisite.

Diagnosis and Long-term Management of Uromodulin Kidney Disease

Uromodulin kidney disease (UKD) is a subtype of autosomal dominant tubulointerstitial kidney disease (ADTKD), and is a rare cause of renal failure and gout in young people. Although it is inherited in an autosomal dominant fashion, the gene mutation exhibits variable expressivity so the phenotype varies dramatically among affected individuals. While it is rare, it is important for physicians in the primary care setting to be able to recognize the disorder, initiate proper workup, and refer patients to nephrology teams that are equipped to manage the long-term needs of these patients. Eventually, most will progress to renal failure with necessary renal dialysis or kidney transplant. Kidney transplant is curative as the new kidney does not have the defective tubule cell gene. The case series that follows highlights the variable presentations of the disorder among members of the same family and the necessary long-term follow-up that will often be handled by the primary care provider in conjunction with the specialist team.

Association Between Serum Uric Acid Levels and Benign Paroxysmal Positional Vertigo: A Systematic Review and Meta-Analysis of Observational Studies

Objective: The objective of the present study was to meta-analyze relevant literature to gain a comprehensive understanding of the potential relationship between serum uric acid levels and risk of benign paroxysmal positional vertigo (BPPV).

Methods: The databases of PubMed, Web of Science, Embase, Chinese National Knowledge Infrastructure, Wanfang, and SinoMed were systematically searched for observational case-control studies of the association between BPPV and serum uric acid levels published up to October 2018. Data from eligible studies were meta-analyzed using Stata 12.0.

Results: A total of 12 studies were included in the analysis. There was a strong tendency for serum uric acid levels to be associated with risk of BPPV among studies conducted in China (OR 0.69, 95%CI 0.01–1.40, p = 0.053), but not among studies outside China (OR 1.07, 95%CI 1.08–3.22, p = 0.33). Across all studies, serum uric acid level was significantly higher among individuals with BPPV than among controls (OR 0.78, 95%CI 0.15–1.41, p = 0.015), yet it did not independently predict risk of the disorder (OR 1.003, 95%CI 0.995–1.012, p = 0.471).

Conclusion: The available evidence suggests that BPPV is associated with elevated levels of serum uric acid, but these levels may not be an independent risk factor of BPPV.