Effects of Allopurinol on the Progression of Chronic Kidney Disease

The Pattern of Allopurinol Prescription Among Chronic Kidney Disease Patients in a Tertiary Care Centre: A Single-Centre Experience

Context

Hyperuricemia is prevalent in patients with chronic kidney disease (CKD). Although it is associated with CKD incidence and progression, treating asymptomatic hyperuricemia with uric acid-lowering agents is still debatable.

Aim of Work

determine the rate of non-classical prescription of allopurinol in CKD patients.

Settings and Design

This was a retrospective study of adult patients prescribed allopurinol with CKD (stages 2–5) in Doctor Soliman Fakeeh Hospital (DSFH) Jeddah, Saudi Arabia, from 1/1/2016 to 1/1/2017.

Subjects and Methods

Eligible patients were identified from the hospital’s pharmacy system and cross-referenced with the electronic health records. Demographic data, laboratory results and indication as recorded by the prescribing physician were extracted. Prescriptions with no indication were categorized based on the uric acid levels. Hyperuricemia was documented as mild (6–10 mg/dL in females and 7–13 mg/dL in males) and severe (>13mg/dL in men and >10mg/dL in women).

Statistical Analysis Used

Descriptive statistics (frequencies, percentages).

Results

From the 594 identified patients, 464 (78.1%) were males. A third of prescriptions (209/594) had no indication, 43.5% of which (91/209) had no documented uric acid levels, and 16.3% (34/209) had normal levels. Including patients with undocumented indication, 64.2% (381/594) were prescribed allopurinol for hyperuricemia, 86.4% of which (329/381) had mild hyperuricemia, and only 13.6% (52/381) had severe hyperuricemia. Other indications included malignancy-related disorders (6.2%, 37/594), gouty arthritis (5.2%, 31/594), and stones of unknown aetiology (3.4%, 20/594).

Conclusion

The percentage of allopurinol prescription to patients with CKD without a clear indication in our centre was markedly high. This might increase the risk for side effects with no evidence-based benefits.

Different clinical impact of hyperuricemia according to etiologies of chronic kidney disease: Gonryo Study

BACKGROUND

Hyperuricemia is highly prevalent in chronic kidney disease (CKD) patients, but the evidence for a relationship between uric acid (UA) and clinical outcomes in CKD patients is limited and inconsistent. We hypothesized that UA has a different impact on clinical outcomes according to the underlying disease causing CKD.

METHODS

This study prospectively investigated the associations between UA and renal and non-renal outcomes according to the underlying disease causing CKD in 2,797 Japanese patients under the care of nephrologists. The patients were categorized into four groups: primary renal disease (n = 1306), hypertensive nephropathy (n = 467), diabetic nephropathy (n = 275), and other nephropathy (n = 749). The renal outcome was defined as end-stage renal disease (ESRD), and the non-renal outcome was defined as a composite endpoint of cardiovascular events (CVEs) and all-cause mortality.

RESULTS

During a median 4.8-year follow-up, 359 (12.8%) patients reached the renal outcome, and 260 (9.3%) reached the non-renal outcome. In the all-patient analysis, hyperuricemia was not associated with the risks for renal and non-renal outcomes, but in primary renal disease (PRD) and hypertensive renal disease (HTN) patients, hyperuricemia was significantly associated with non-renal outcomes. Per 1 mg/dl higher UA level, multivariable adjusted hazard ratio was 1.248 (95% CI: 1.003 to 1.553) for PRD, and 1.250 (1.035 to 1.510) for HTN. Allopurinol did not reduce the risks for renal and non-renal outcomes, both in all patients and in the subgroup analysis.

CONCLUSIONS

The effect of hyperuricemia on clinical outcomes in CKD patients varies according to the underlying disease causing CKD. Hyperuricemia is an independent risk factor for non-renal outcomes in primary renal disease and hypertensive renal disease patients. Allopurinol did not decrease the risks for renal and non-renal outcomes.

Association of uric acid with kidney function and albuminuria: the Uric Acid Right for heArt Health (URRAH) Project

BACKGROUND

Hyperuricemia is commonly observed in patients with chronic kidney disease (CKD). However, a better understanding of the relationship among uric acid (UA) values, glomerular filtration rate (GFR) and albuminuria may shed light on the mechanisms underlying the excess of cardiovascular mortality associated with both chronic kidney disease and hyperuricemia and lead to better risk stratification. Our main goal was to study the relationships between serum uric acid and kidney disease measures (namely estimated GFR [eGFR] and albuminuria) in a large cohort of individuals at cardiovascular risk from the URic acid Right for heArt Health (URRAH) Project database.

METHODS

Clinical data of 26,971 individuals were analyzed. Factors associated with the presence of hyperuricemia defined on the basis of previously determined URRAH cutoffs for cardiovascular and all-cause mortality were evaluated through multivariate analysis. Chronic kidney disease was defined as eGFR < 60 ml/min per 1.73 m² and/or abnormal urinary albumin excretion diagnosed as: (i) microalbuminuria if urinary albumin concentration was > 30 and ≤ 300 mg/L, or if urinary albumin-to-creatinine ratio (ACR) was > 3.4 mg/mmol and ≤ 34 mg/mmol; (ii) macroalbuminuria if urinary albumin concentration was > 300 mg/L, or if ACR was > 34 mg/mmol.

RESULTS

Mean age was 58 ± 15 years (51% males, 62% with hypertension and 12% with diabetes), mean eGFR was 81 ml/min per 1.73m2²with a prevalence of eGFR < 60 and micro- or macroalbuminuria of 16, 15 and 4%, respectively. Serum uric acid showed a trend towards higher values along with decreasing renal function. Both the prevalence of gout and the frequency of allopurinol use increased significantly with the reduction of eGFR and the increase in albuminuria. Hyperuricemia was independently related to male gender, eGFR strata, and signs of insulin resistance such as body mass index (BMI) and triglycerides.

CONCLUSIONS

The lower the eGFR the higher the prevalence of hyperuricemia and gout. In subjects with eGFR < 60 ml/min the occurrence of hyperuricemia is about 10 times higher than in those with eGFR > 90 ml/min. The percentage of individuals treated with allopurinol was below 2% when GFR was above 60 ml/min, it increased to 20% in the presence of CKD 3b and rose further to 35% in individuals with macroalbuminuria.

Natural flavonol fisetin attenuated hyperuricemic nephropathy via inhibiting IL-6/JAK2/STAT3 and TGF-β/SMAD3 signaling

BACKGROUND

The naturally occurring flavonol fisetin (3,3',4',7-tetrahydroxyflavone), widely dispersed in fruits, vegetables and nuts, has been reported to exert anti-inflammatory, antioxidant and anti-angiogenic effects. Our previous study indicated fisetin ameliorated inflammation and apoptosis in septic kidneys. However, the potential nephroprotective effect of fisetin in hyperuricemic mice remains unknown.

PURPOSE

The current study was designed to investigate the effect of fisetin on hyperuricemic nephropathy (HN) and explore the underlying mechanisms.

METHODS

The HN was induced in mice by mixing of potassium oxonate (2400 mg/kg) and adenine (160 mg/kg) in male C57BL/6J mice. Fisetin (50 or 100 mg/kg) was orally administrated either simultaneously with the establishment of HN or after HN was induced. As a positive control, allopurinol of 10 mg/kg was included. Uric acid levels in the serum and urine as well as renal function parameters were measured. Renal histological changes were measured by periodic acid-Schiff (PAS) and Masson's trichrome stainings. The expression of gene/protein in relation to inflammation, fibrosis, and uric acid excretion in the kidneys of HN mice or uric acid-treated mouse tubular epithelial (TCMK-1) cells were measured by RNA-seq, RT-PCR, western blot and immunohistochemical analysis.

RESULTS

Treatment with fisetin, regardless of administration regimen, dose-dependently attenuated hyperuricemia-induced kidney injury as indicated by the improved renal function, preserved tissue architecture, and decreased urinary albumin-to-creatinine ratio. Additionally, fisetin lowered uricemia by modulating the expression of kidney urate transporters including urate transporter 1(URAT1), organic anion transporter 1 (OAT1), organic anion transporter 3 (OAT3) and ATP binding cassette subfamily G member 2 (ABCG2). Moreover, hyperuricemia-induced secretions of proinflammatory factors including tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6) and monocyte chemoattractant protein-1(MCP-1) in HN mice and uric acid-stimulated TCMK-1 cells were mitigated by fisetin treatment. Meanwhile, fisetin attenuated kidney fibrosis in HN mice with restored expressions of alpha-smooth muscle actin (α-SMA), collagen I and fibronectin. Mechanistically, fisetin regulated the aberrant activation of signal transducer and activator of transcription-3 (STAT3) signaling and transforming growth factor-β (TGF-β) signaling in the HN kidneys and uric acid-stimulated TCMK-1 cells.

CONCLUSION

Fisetin lowered uricemia, suppressed renal inflammatory response, and improved kidney fibrosis to protect against hyperuricemic nephropathy via modulation of STAT3 and TGF-β signaling pathways. The results highlighted that fisetin might represent a potential therapeutic strategy against hyperuricemic nephropathy.

A semi-mechanistic exposure-response model to assess the effects of verinurad, a potent URAT1 inhibitor, on serum and urine uric acid in patients with hyperuricemia-associated diseases

Verinurad, a uric acid transporter 1 (URAT1) inhibitor, lowers serum uric acid by promoting its urinary excretion. Co-administration with a xanthine oxidase inhibitor (XOI) to simultaneously reduce uric acid production rate reduces the potential for renal tubular precipitation of uric acid, which can lead to acute kidney injury. The combination is currently in development for chronic kidney disease and heart failure. The aim of this work was to apply and extend a previously developed semi-mechanistic exposure–response model for uric acid kinetics to include between-subject variability to verinurad and its combinations with XOIs, and to provide predictions to support future treatment strategies. The model was developed using data from 12 clinical studies from a total of 434 individuals, including healthy volunteers, patients with hyperuricemia, and renally impaired subjects. The model described the data well, taking into account the impact of various patient characteristics such as renal function, baseline fractional excretion of uric acid, and race. The potencies (EC50s) of verinurad (reducing uric acid reuptake), febuxostat (reducing uric acid production), and oxypurinol (reducing uric acid production) were: 29, 128, and 13,030 ng/mL, respectively. For verinurad, symptomatic hyperuricemic (gout) subjects showed a higher EC50 compared with healthy volunteers (37 ng/mL versus 29 ng/mL); while no significant difference was found for asymptomatic hyperuricemic patients. Simulations based on the uric acid model were performed to assess dose–response of verinurad in combination with XOI, and to investigate the impact of covariates. The simulations demonstrated application of the model to support dose selection for verinurad.

Hyperuricemia and chronic kidney disease: to treat or not to treat

Hyperuricemia is common in chronic kidney disease (CKD) and may be present in 50% of patients presenting for dialysis. Hyperuricemia can be secondary to impaired glomerular filtration rate (GFR) that occurs in CKD. However, hyperuricemia can also precede the development of kidney disease and predict incident CKD. Experimental studies of hyperuricemic models have found that both soluble and crystalline uric acid can cause significant kidney damage, characterized by ischemia, tubulointerstitial fibrosis, and inflammation. However, most Mendelian randomization studies failed to demonstrate a causal relationship between uric acid and CKD, and clinical trials have had variable results. Here we suggest potential explanations for the negative clinical and genetic findings, including the role of crystalline uric acid, intracellular uric acid, and xanthine oxidase activity in uric acid-mediated kidney injury. We propose future clinical trials as well as an algorithm for treatment of hyperuricemia in patients with CKD.

Recent evidence on the effect of urate-lowering treatment on the progression of kidney disease

PURPOSE OF REVIEW

Several observational studies have shown that hyperuricemia is associated with chronic kidney disease (CKD) progression and is a potential therapeutic target in people with CKD. This review discusses the results of three recently published placebo-controlled randomized trials evaluating the effect of urate-lowering treatment on the progression of CKD with at least 2 years of follow-up.

RECENT FINDINGS

The Febuxostat versus Placebo Randomized Controlled Trial Regarding Reduced Renal Function in Patients with Hyperuricemia Complicated by Chronic Kidney Disease Stage 3 trial evaluated the effect of febuxostat in 443 patients with stage 3 CKD (mean estimated glomerular filtration rate [eGFR] 45 mL/min/1.73 m2) and asymptomatic hyperuricemia (mean serum urate 7.8 mg/dL). The Controlled trial of slowing of Kidney Disease progression From the Inhibition of Xanthine oxidase and Preventing Early Renal Loss in Diabetes trials respectively evaluated the effect of allopurinol in 369 adults with stage 3 or 4 CKD (mean eGFR 31.7 mL/min/1.73 m2, mean serum urate 8.2 mg/dL) with high progression risk and 530 patients with type 1 diabetes and diabetic kidney disease (mean eGFR 74.7 mL/min/1.73 m2, mean serum urate 6.1 mg/dL). Despite the large and sustained reductions in serum urate levels in all 3 trials, urate-lowering treatment with febuxostat or allopurinol did not result in clinically meaningful improvement in kidney outcomes.

SUMMARY

The results of large and well-designed placebo-controlled trials do not support the use of urate-lowering therapy to slow the progression of CKD.

Association between serum uric acid and new onset and progression of chronic kidney disease in a Japanese general population: Iki epidemiological study of atherosclerosis and chronic kidney disease

BACKGROUND

Although several risk factors for chronic kidney disease (CKD) have been proposed, it remains unclear whether elevated serum uric acid (SUA) is negatively association with kidney function. The aim of this study was to elucidate the association between SUA and new onset and progression of CKD in a Japanese general population.

METHODS

This was a population-based retrospective cohort study using annual health checkup data of residents of Iki Island. A total of 5,507 adults (979 with CKD and 4,528 without) were included. The outcomes were new onset of CKD among participants without CKD at baseline, and progression of CKD among those with CKD. A Cox proportional hazards model was used to evaluate the association between SUA and new onset and progression of CKD.

RESULTS

During mean follow-up of 4.6 years, 757 cases of new onset of CKD and 193 with progression of CKD were observed. SUA was significantly associated with new onset of CKD (adjusted hazard ratio 1.13, [95% confidence interval 1.03-1.24] per standard deviation [SD] increase in SUA). In contrast, SUA was not significantly associated with progression of CKD (hazard ratio 1.08, [0.92-1.27] per SD increase). Similar results were obtained when classifying uric acid as categorical.

CONCLUSION

SUA was significantly associated with increased risk for new onset of CKD, but not with progression of CKD among a Japanese general population.

The Management of Gout in Renal Disease

Gout, a debilitating inflammatory arthritis, currently affects more than 9 million Americans. Hyperuricemia, the laboratory abnormality associated with the development of gout, also occurs in a significant number of patients with chronic kidney disease (CKD), a condition that affects approximately 14% of the US population. Several recent studies have attempted to provide a definitive link between the presence of hyperuricemia and progression of CKD; however, the treatment of asymptomatic hyperuricemia in CKD is not supported by recent randomized controlled trials. The pharmacology of acute gout flares and urate lowering is complicated in patients who also have evidence of CKD, primarily because of an increased risk of medication toxicity. Recipients of kidney transplants are particularly at risk of debilitating gout and medication toxicity. We review the available data linking CKD, gout, and hyperuricemia, providing practice guidelines on managing gout in CKD patients and kidney transplant recipients. We advocate for much greater involvement of nephrologists in the management of gout in renal patients.

Medications for gout and its comorbidities: mutual benefits?

PURPOSE OF REVIEW

To review recent literature with relevance to the management of multimorbid patients with gout, i.e., gout medication repurposed for comorbidities and vice versa.

RECENT FINDINGS

Adding to the previous success of interleukin-1 inhibition, two trials on low-dose colchicine's role in cardiovascular disease (CVD) demonstrated potential benefits in patients with or without gout. In Colchicine Cardiovascular Outcomes Trial, a composite CVD endpoint was reduced by 23% among patients who had experienced a recent myocardial infarction. In Low-Dose Colchicine 2, the composite CVD endpoint was reduced 31% among those with stable coronary artery disease. Use of urate-lowering therapy (ULT) for renal protection in patients without gout produced null results. Allopurinol did not benefit the glomerular filtration rate in two trials (Controlled trial of slowing of Kidney Disease progression From the Inhibition of Xanthine oxidase and Preventing Early Renal Function Loss) among patients with chronic kidney disease (with or without hyperuricemia, but not gout). SGLT-2 inhibitors, a medication recommended for patients with diabetes and CVD, diabetic kidney disease, or heart failure, demonstrated a protective effect against gout flares in a secondary trial analysis and a large observational study.

SUMMARY

The role of colchicine may expand beyond gout flare prevention to patients with existing CVD. The renal benefit of ULT among patients with gout remains unclear. SGLT-2 inhibitors may benefit diabetic patients who have gout as a comorbidity.

Managing hyperuricemia and gout in chronic kidney disease: a clinical conundrum

PURPOSE OF REVIEW

There is controversy regarding the impact of hyperuricemia on the progression of chronic kidney disease (CKD), and gout remains sub optimally managed in this population. We discuss the prescribing of drugs for the treatment of gout in patients with CKD.

RECENT FINDINGS

There is a lack of consensus from expert guidelines, and prescribers have concerns regarding the risk of adverse reactions from medicines used to treat gout. These situations appear to contribute to suboptimal management of gout in this cohort. Recent data have challenged the role of urate lowering therapy (ULT) in the management of asymptomatic hyperuricemia in CKD.

SUMMARY

ULT should be commenced in all patients with severe, recurrent disease, tophaceous gout and evidence of joint damage. Most international guidelines recommend a treat-to-target approach for the management of gout. In CKD, ULT should be started at low dose with up titration adjusted to serum urate levels, rather than being based on the creatinine clearance. If patients fail first-line therapy, alternative agents are utilized, the specific agent depending on ease of access, burden of disease and other comorbidities. This approach should be incorporated into routine practice to ensure optimal treatment of gout in CKD. More research is required to investigate whether treatment of asymptomatic hyperuricemia has clinical benefits.

Serum uric acid is associated with increased risk of posttransplantation diabetes in kidney transplant recipients: a prospective cohort study

BACKGROUND

Serum uric acid (SUA) is associated with fasting glucose in healthy subjects, and prospective epidemological studies have shown that elevated SUA is associated with increased risk of type 2 diabetes. Whether SUA is independently associated with higher risk of posttransplantation diabetes mellitus (PTDM) in kidney transplant recipients (KTR) remains unknown.

METHODS

We performed a longitudinal cohort study of 524 adult KTR with a functioning graft ≥1-year, recruited at a university setting (2008-2011). Multivariable-adjusted Cox proportional-hazards regression analyses were performed to assess the association between time-updated SUA and risk of PTDM (defined according the American Diabetes Association's diagnostic criteria).

RESULTS

Mean (SD) SUA was 0.43 (0.11) mmol/L at baseline. During 5.3 (IQR, 4.1-6.0) years of follow-up, 52 (10%) KTR developed PTDM. In univariate prospective analyses, SUA was associated with increased risk of PTDM (HR 1.75, 95% CI 1.36-2.26 per 1-SD increment; P < 0.001). This finding remained materially unchanged after adjustment for components of the metabolic syndrome, lifestyle, estimated glomerular filtration rate, immunosuppressive therapy, cytomegalovirus and hepatitis C virus infection (HR 1.89, 95% CI 1.32-2.70; P = 0.001). These findings were consistent in categorical analyses, and robust in sensitivity analyses without outliers.

CONCLUSIONS

In KTR, higher SUA levels are strongly and independently associated with increased risk of PTDM. Our findings are in agreement with accumulating evidence supporting SUA as novel independent risk marker for type 2 diabetes, and extend the evidence, for the first time, to the clinical setting of outpatient KTR.

[Less is more… in the general practitioner's internistic surgery : Subclinical hypothyroidism, hyperuricemia, routine ECG and NT-proBNP as selected examples]

Exceeding the need for care in general practitioner (GP) practices is a known problem that affects the work of approximately 16,000 specialists for internal medicine in the family practice context every day in Germany. In order to spare patients unnecessary treatment and measures, these must be critically questioned on a regular basis. Subclinical hypothyroidism (SH) and hyperuricemia (HU) are frequent laboratory constellations. The selected articles by Stott et al., de Montmollin et al. and Mooijaart et al. could show that treatment of SH in older patients is not effective. Furthermore, according to the studies of Li et al. and Badve et al. treatment of HU is only beneficial in the treatment of gout and nephrolithiasis and has no influence on the development of chronic kidney disease. The Canadian group of Bhatia demonstrated that the ECG for low-risk patients that is often part of health check-ups in Canada, usually results in more follow-up examinations without the groups with and without ECG differing with respect to major adverse cardiac events (MACE). Laboratory chemical analysis of N‑terminal prohormone of brain natriuretic peptide (NT-proBNP) for managing the treatment of heart failure is also not more effective than traditional treatment methods according to Felker et al., therefore, it can be discarded. "Choosing wisely", "Less is more" and the "Klug entscheiden (Smart decisions)" recommendations by the German Society for Internal Medicine are initiatives that make the process of avoiding overprovision of care accessible for all practitioners in a short and concise form.

Treating Hyperuricemia: The Last Word Hasn't Been Said Yet

Gout as well as asymptomatic hyperuricemia have been associated with several traditional cardiovascular risk factors and chronic kidney disease. Both in vitro studies and animal models support a role for uric acid mediating both hemodynamic and tissue toxicity leading to glomerular and tubule-interstitial damage, respectively. Nevertheless, two recent well designed and carried out trials failed to show the benefit of allopurinol treatment on kidney outcomes, casting doubts on expectations of renal protection by the use of urate lowering treatment. With the aim of providing possible explanations for the lack of effect of urate lowering treatment on chronic kidney disease progression, we will critically review results from all available randomized controlled trials comparing a urate-lowering agent with placebo or no study medication for at least 12 months and report renal clinical outcomes.

Why Does Hyperuricemia Not Necessarily Induce Gout?

Hyperuricemia is a risk factor for gout. It has been well observed that a large proportion of individuals with hyperuricemia have never had a gout flare(s), while some patients with gout can have a normuricemia. This raises a puzzle of the real role of serum uric acid (SUA) in the occurrence of gout flares. As the molecule of uric acid has its dual effects in vivo with antioxidant properties as well as being an inflammatory promoter, it has been placed in a delicate position in balancing metabolisms. Gout seems to be a multifactorial metabolic disease and its pathogenesis should not rely solely on hyperuricemia or monosodium urate (MSU) crystals. This critical review aims to unfold the mechanisms of the SUA role participating in gout development. It also discusses some key elements which are prerequisites for the formation of gout in association with the current therapeutic regime. The compilation should be helpful in precisely fighting for a cure of gout clinically and pharmaceutically.

Kidney Allograft Fibrosis: Diagnostic and Therapeutic Strategies

Interstitial fibrosis with tubule atrophy (IF/TA) is the response to virtually any sustained kidney injury and correlates inversely with kidney function and allograft survival. IF/TA is driven by various pathways that include hypoxia, renin-angiotensin-aldosterone system, transforming growth factor (TGF)-β signaling, cellular rejection, inflammation and others. In this review we will focus on key pathways in the progress of renal fibrosis, diagnosis and therapy of allograft fibrosis. This review discusses the role and origin of myofibroblasts as matrix producing cells and therapeutic targets in renal fibrosis with a particular focus on renal allografts. We summarize current trends to use multi-omic approaches to identify new biomarkers for IF/TA detection and to predict allograft survival. Furthermore, we review current imaging strategies that might help to identify and follow-up IF/TA complementary or as alternative to invasive biopsies. We further discuss current clinical trials and therapeutic strategies to treat kidney fibrosis.Supplemental Visual Abstract; http://links.lww.com/TP/C141.

Allopurinol and Renal Outcomes in Adults With and Without Type 2 Diabetes: A Retrospective, Population-Based Cohort Study and Propensity Score Analysis

OBJECTIVES

Elevated uric acid (UA) is common in diabetes and is implicated in the pathogenesis of chronic kidney disease (CKD). Lowering UA with allopurinol may delay CKD progression. We assessed the association between allopurinol and renal outcomes in older adults both with and without diabetes, and whether this differed by diabetes status.

METHODS

We conducted a population-based, retrospective cohort study of older adults ≥66 years of age with a gout flare using administrative data from Ontario, Canada. The primary outcome was doubling of creatinine or kidney failure. Secondary outcomes were a composite of death or kidney failure, decline in estimated glomerular filtration rate by >30%, death and kidney failure. New allopurinol users were compared with nonusers using Cox proportional hazards models and inverse probability of treatment weighting (IPTW). An interaction between allopurinol use and presence or absence of diabetes was assessed.

RESULTS

Among 5,937 older adults with a gout flare (1,911 with diabetes), 1,304 (22%) were newly treated with allopurinol. Median follow-up time was 1.11 (interquartile range, 0.33 to 3.21) years for allopurinol users and 3.38 (interquartile range, 1.42 to 4.43) years for nonusers. There was no association between allopurinol use and the primary outcome (IPTW-adjusted hazard ratio, 0.97; 95% confidence interval, 0.72 to 1.31), and this did not differ by diabetes status. Allopurinol use was not associated with any of the secondary outcomes.

CONCLUSIONS

Allopurinol use was not associated with renal outcomes in older adults with or without diabetes. This supports the interpretation of UA as a biomarker of CKD risk rather than a modifiable target for prevention or treatment of CKD.

Reduced renal function may explain the higher prevalence of hyperuricemia in older people

This study aimed to investigate the contribution of renal dysfunction to enhanced hyperuricemia prevalence in older people. A cohort of 13,288 Chinese people aged between 40 and 95 years were recruited from January to May 2019. Serum uric acid concentration and estimated glomerular filtration rate [eGFR] were measured. The associations between age or eGFR and serum uric acid or hyperuricemia were analyzed using linear or binary logistic regression adjusting for risk factors. Uric acid concentration and prevalence of hyperuricemia were greater in older participants. Adjustment for reduced renal function (eGFR < 60 mL/min/1.73 m²) eliminated the associations between older age and higher uric acid concentration and between older age and higher prevalence of hyperuricemia diagnosis, whereas adjustment for other risk factors did not change those associations. Lower eGFR was associated with higher uric acid concentration both before (β = - 0.296, P < 0.001) and after adjustment for age (β = - 0.313, P < 0.001). Reduced renal function was associated with hyperuricemia diagnosis both before (odds ratio, OR, 3.64; 95% CI 3.10-4.28; P < 0.001) and after adjustment for age (adjusted OR, 3.82; 95% CI 3.22-4.54; P < 0.001). Mean serum uric acid and prevalence of hyperuricemia were higher in people with eGFR < 60 mL/min/1.73 m² than those with eGFR ≥ 60 mL/min/1.73 m². The prevalence of reduced renal function increased with older age (P < 0.001). This study suggests that reduced renal function can explain the increased uric acid levels and hyperuricemia diagnoses in older people.

Hyperuricaemia, gout and allopurinol in the CKD Queensland registry

Introduction

There is scant data on the role of hyperuricaemia, gout and allopurinol treatment in chronic kidney disease (CKD). Therefore, our aim is to investigate the possible associations between hyperuricaemia, gout, prescription of allopurinol and renal outcomes in patients with CKD.

Methods

The retrospective cohort study involved 1123 Royal Brisbane and Women’s Hospital (RBWH) patients, enrolled in the CKD.QLD registry from May 2011 to August 2017. Patients were divided into two uric acid categories, with uric acid ≤ 0.36 mmol/L and > 0.36 mmol/L. Association of delta estimated glomerular filtration rate (eGFR) with gout, allopurinol treatment and hyperuricaemia were analysed.

Results

Patients with an entry urate > 0.36 mmol/L were older, had higher body mass index (BMI) and worse baseline kidney function. Proportion of patients with gout, hyperuricaemia and allopurinol treatment increased with advanced CKD stages. Age-adjusted analysis revealed a significant association between serum urate level and delta eGFR, with no significant association between gout, treatment with allopurinol and delta eGFR. Furthermore, neither gout nor the prescription of allopurinol had a significant effect on the time to renal death (composite end point of kidney replacement therapy or death).

Conclusion

Hyperuricaemia seemed to be independently associated with faster CKD progression or renal death. This was not observed with gout or prescription of allopurinol. Furthermore, allopurinol was not associated with decreased incidence of cardiovascular events. These data suggest that hyperuricaemia is likely the effect and not the cause of CKD or CKD progression.

Graphic abstract

Urate-lowering Therapy and Chronic Kidney Disease Development in Patients with Gout

Objectives: Chronic kidney disease (CKD) has emerged as a global health concern. Many studies have identified an association between hyperuricemia and CKD, and some studies have revealed that urate-lowering therapy (ULT) can attenuate CKD progression. However, only a few studies have explored the role of ULT in the prevention of new onset CKD. Methods: To compare the risk of incident CKD between users and nonusers of ULT in patients with gout, we conducted a 13-year population-based retrospective cohort study. Overall incidence of CKD was compared between 7126 ULT users and 7126 matched ULT nonusers. Results: The CKD incidence rate for both the users and nonusers of ULT was 1.7 per 100 person-years, after adjusting for sex, age, region of residence, comorbidities, and medications used. No significant difference in CKD risk (adjusted hazard ratio [aHR]: 0.97; 95% confidence interval [CI]: 0.88-1.07) was noted between the ULT users and nonusers. In the subgroup of patients with diabetes mellitus (DM) and without hypertension (HT), ULT tended to be associated with lower risk of incident CKD (aHR: 0.52; 0.95% CI: 0.28-0.97). Compared with the risk of new onset CKD in patients receiving xanthine oxidase inhibitors, those receiving uricosuric agents seemed to have a lower risk of developing CKD (aHR: 0.81, 95% CI: 0.67-0.99). Conclusion: This population-based cohort study indicated that ULT is not associated with lower risk of CKD development. However, in the subgroup of patients with DM and without HT, ULT is associated with significantly lower risk of incident CKD.

A biodegradable bismuth–gadolinium-based nano contrast agent for accurate identification and imaging of renal insufficiency in vivo

A biodegradable gadolinium-doped mesoporous bismuth-based nanomaterial is used to diagnose kidneys with dysfunction accurately via magnetic resonance imaging in vivo.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Uric acid and cardiovascular disease: A clinical review

Uric acid, the end-product of purine metabolism in humans, is not only a cause of gout, but also may play roles in developing cardiovascular diseases such as hypertension, atrial fibrillation, chronic kidney disease, heart failure, coronary artery disease, and cardiovascular death. Several clinical investigations have reported serum uric acid as a predictive marker for cardiovascular outcomes. Although the causal relationship of hyperuricemia to cardiovascular diseases remains controversial, there has been a growing interest in uric acid because of the increased prevalence of hyperuricemia worldwide. This review article summarizes current evidence concerning the relation between hyperuricemia and cardiovascular diseases.

Allopurinol shows no benefit in slowing decline in renal function

Review of: Badve, SV, Pascoe, EM, Tiku A, et al Effects of allopurinol on progression of chronic kidney disease. New Engl J Med 2020;382:2504-13.

SGLT2 inhibition requires reconsideration of fundamental paradigms in chronic kidney disease, 'diabetic nephropathy', IgA nephropathy and podocytopathies with FSGS lesions

In 2020, the Dapagliflozin and Prevention of Adverse Outcomes in Chronic Kidney Disease (DAPA-CKD) trial first demonstrated that inhibition of the sodium-glucose transporter-2 (SGLT2) with dapagliflozin attenuates the progression of chronic kidney disease (CKD) with proteinuria in patients with or without diabetes at an unprecedented effect size. These results have far-reaching implications for a series of traditional concepts in Nephrology. It now became obvious that CKD with and without diabetes involves a predominant SGLT2-driven pathophysiology compared with the other pathogenic pathways currently under consideration. As SGLT2 inhibition is similarly efficacious in diabetic and non-diabetic CKD with proteinuria, treating CKD rather than 'diabetic nephropathy' becomes the central paradigm. Indeed, in older adults with type 2 diabetes, CKD is rather of multifactorial origin. As the DAPA-CKD trial included more patients with immunoglobulin A nephropathy (IgAN) than any of the previous IgAN trials, dual renin-angiotensin/SGLT2 inhibition may become the new standard. The same applies for patients with podocytopathy-related focal segmental glomerulosclerosis lesions. From now on, IgAN and podocytopathy trials without SGLT2 inhibition as background therapy and without glomerular filtration rate decline as primary outcome criterion will be of limited value. These and other potential implications will trigger broad discussions and secondary research activities with conclusions difficult to predict today. However, one is for sure: Nephrology after the DAPA-CKD trial will be not the same as it was before. Finally!

Molecular Mechanisms in Early Diabetic Kidney Disease: Glomerular Endothelial Cell Dysfunction

Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease (ESRD), with prevalence increasing at an alarming rate worldwide and today, there are no known cures. The pathogenesis of DKD is complex, influenced by genetics and the environment. However, the underlying molecular mechanisms that contribute to DKD risk in about one-third of diabetics are still poorly understood. The early stage of DKD is characterized by glomerular hyperfiltration, hypertrophy, podocyte injury and depletion. Recent evidence of glomerular endothelial cell injury at the early stage of DKD has been suggested to be critical in the pathological process and has highlighted the importance of glomerular intercellular crosstalk. A potential mechanism may include reactive oxygen species (ROS), which play a direct role in diabetes and its complications. In this review, we discuss different cellular sources of ROS in diabetes and a new emerging paradigm of endothelial cell dysfunction as a key event in the pathogenesis of DKD.

A Randomized, Controlled Trial of the Effect of Allopurinol on Left Ventricular Mass Index in Hemodialysis Patients

Introduction

Increased left ventricular mass index (LVMI) is associated with mortality in end-stage renal disease. LVMI regression may improve outcomes. Allopurinol has reduced LVMI in randomized controlled trials in chronic kidney disease, diabetes, and ischemic heart disease. This study investigated whether allopurinol would regress LVMI in hemodialysis patients.

Methods

This was a randomized placebo-controlled double-blind multicenter trial funded by the British Heart Foundation (PG/12/72/29743). A total of 80 patients undergoing regular maintenance hemodialysis were recruited from NHS Tayside, NHS Greater Glasgow and Clyde and NHS Ayrshire and Arran in Scotland, UK. Participants were randomly assigned on a 1:1 ratio to 12 months of therapy with allopurinol 300 mg or placebo after each dialysis session. The primary outcome was change in LVMI, as assessed by cardiac magnetic resonance imaging (CMRI) at baseline and 12 months. Secondary outcomes were change in BP, flow-mediated dilation (FMD), augmentation indices (AIx), and pulse wave velocity (PWV).

Results

A total of 53 patients, with a mean age of 58 years, completed the study and had CMRI follow-up data for analysis. Allopurinol did not regress LVMI (change in LVMI: placebo +3.6 ± 10.4 g/m²; allopurinol: +1.6 ± 11 g/m²; P = 0.49). Allopurinol had no demonstrable effect on BP, FMD, AIx, or PWV.

Conclusion

Compared with placebo, treatment with allopurinol did not regress LVMI in this trial.

The nephrological perspective on SGLT-2 inhibitors in type 1 diabetes

Prevalence of type 1 diabetes mellitus (T1DM) is globally continuously increasing. T1DM is accompanied by a high risk of developing cardiovascular and renal comorbidities and is one of the leading causes of end-stage renal disease (ESRD). However, current therapeutic approaches for chronic and/or diabetic kidney disease (CKD/DKD) existed for a long time, and offer room for improvement, particularly in T1DM. In 2019, the European Medicines Agency (EMA) approved a first sodium/glucose co-transporter 2 inhibitor (SGLT-2i) and a first dual SGLT-1/-2i to improve glycaemic control, as an adjunctive treatment to insulin in persons with T1DM and a body mass index ≥27 kg/m². Of note, SGLT-1/2is and SGLT-2is are not approved by the Food and Drug Administration (FDA) as an adjunct treatment in T1DM, nor approved for the treatment of CKD or DKD by EMA and FDA. SGLT is have shown to mediate different renoprotective effects in type 2 diabetes mellitus in corresponding cardiovascular and renal outcome trials. First efficacy trials offer insights into potential positive effects on renal function and kidney disease of SGLTis in T1DM. This review summarizes and discusses latest available data on SGLT inhibition and provides an update on the nephrological perspective on SGLTis, specifically in T1DM.

Sex Differences in Time-Series Changes in Pseudo-R2 Values Regarding Hyperuricemia in Relation to the Kidney Prognosis

Studies on sex differences in time-series changes in pseudo-R² values regarding hyperuricemia (HU) in relation to the kidney prognosis among patients with chronic kidney disease (CKD) are scant. The kidney prognosis was evaluated in 200 patients with CKD (median follow-up, 12.3 years). Survival analyses and logistic regression analyses were conducted, generating time-series pseudo-R² values. We used four definitions of HU according to serum uric acid (SUA) levels (HU6, SUA ≥ 6.0 mg/dL; HU7, SUA ≥ 7.0 mg/dL; HU8, SUA ≥ 8.0 mg/dL) and antihyperuricemic agent use to calculate the mean and percentage of the change in pseudo-R² values from the 6th year until the end of the study (6Y–End Mean and 6Y–End Change, respectively). The multivariable Cox regression analysis showed that HU7 was significantly associated with kidney outcomes. When stratified by sex, the 6Y–End Mean was clearly higher in women than in men for all HU definitions, with the highest value (0.1755) obtained for HU7 in women. The pseudo-R² values for HU6 in women showed an increasing pattern, with a 6Y–End Change of 11.4%/year. Thus, it may be clinically meaningful to consider sex differences in the time-series pseudo-R² values regarding HU and kidney 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.

Elevated Serum Uric Acid is Associated with Rapid Decline in Kidney Function: A 10-Year Follow-Up Study

Purpose

The long-term impact of changes in serum uric acid (SUA) concentration on the estimated glomerular filtration rate (eGFR) among the general population remains unclear. We investigated the longitudinal associations between changes in SUA and eGFR over 10 years in 1222 participants with baseline eGFR ≥60 mL/min/1.73 m².

Methods

This was a 10-year retrospective cohort study conducted from 2007 to 2017. Rapid eGFR decline (defined as the highest quartile of change in eGFR between 2007 and 2017) and new-onset kidney disease (defined as an eGFR <60 mL/min/1.73 m² at a 10-year follow-up) were examined using multiple logistic regression analysis, adjusted for sex, age, body mass index, systolic blood pressure, SUA, fasting plasma glucose, serum total cholesterol, and triglyceride at baseline.

Results

SUA was inversely correlated with eGFR, and the slopes of the SUA-eGFR regression lines were consistently steeper in females than males. A significant inverse correlation was also observed between 10-year changes in SUA and eGFR in both sexes. Multivariate analysis showed that every 1 mg/dL increase in SUA from baseline was associated with higher risk of rapid eGFR decline and new-onset kidney disease (OR 1.25; 95% CI 1.14–1.33 and OR 1.40; 95% CI 1.26–1.49, respectively). Furthermore, the subjects in the highest SUA quartile (>6.0 mg/dL) had a 2.45 times higher risk of rapid eGFR decline (95% CI 1.51–3.42) compared to those in the lowest SUA quartile (<3.9 mg/dL).

Conclusion

Elevated baseline SUA is an independent risk factor for rapid eGFR decline and new-onset kidney disease in the general population.

Management of Hyperuricemia in Patients with Chronic Kidney Disease: a Focus on Renal Protection

PURPOSE OF REVIEW

In chronic kidney disease (CKD), plasma uric acid levels are increased because of the decrease in glomerular filtration rate. However, in addition to CKD, hyperuricemia is frequently associated with a number of other conditions such as hypertension, type 2 diabetes, obesity, and heart failure, overweight, and cardiovascular disease.

RECENT FINDINGS

It is now becoming increasingly clear that, in many clinical conditions, elevated levels of uric acid have a much greater role beyond just causing gout. The present review will summarize current knowledge on the relation between hyperuricemia, CKD, and existing comorbidities, as well as the mechanisms of uric acid-related renal damage. In addition, the role and evidence for urate-lowering therapy in prevention and cardiovascular protection in CKD patients is discussed with a focus on allopurinol and febuxostat. To date, several clinical studies have provided evidence that urate-lowering therapy may help to prevent and delay the decline of renal function in patients with CKD. Use of a xanthine oxidase inhibitor should be considered in patients who are at high renal risk and/or with declining renal function in the presence of hyperuricemia with and without deposition, although additional studies are warranted to define treatment targets. Notwithstanding, the possibility to delay deterioration of renal function in patients with CKD merits consideration.

Effect of Urate-Lowering Therapy on Cardiovascular and Kidney Outcomes: A Systematic Review and Meta-Analysis

BACKGROUND AND OBJECTIVES

Several clinical practice guidelines noted the potential benefits of urate-lowering therapy on cardiovascular disease and CKD progression; however, the effect of this regimen remains uncertain. In this systematic review, we aimed to evaluate the efficacy of urate-lowering therapy on major adverse cardiovascular events, all-cause mortality, kidney failure events, BP, and GFR.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We systematically searched MEDLINE, Embase, and the Cochrane databases for trials published through July 2020. We included prospective, randomized, controlled trials assessing the effects of urate-lowering therapy for at least 6 months on cardiovascular or kidney outcomes. Relevant information was extracted into a spreadsheet by two authors independently. Treatment effects were summarized using random effects meta-analysis.

RESULTS

We identified 28 trials including a total of 6458 participants with 506 major adverse cardiovascular events and 266 kidney failure events. Overall urate-lowering therapy did not show benefits on major adverse cardiovascular events (risk ratio, 0.93; 95% confidence interval, 0.74 to 1.18) and all-cause mortality (risk ratio, 1.04; 95% confidence interval, 0.78 to 1.39) or kidney failure (risk ratio, 0.97; 95% confidence interval, 0.61 to 1.54). Nevertheless, urate-lowering therapy attenuated the decline in the slope of GFR (weighted mean difference, 1.18 ml/min per 1.73 m² per year; 95% confidence interval, 0.44 to 1.91) and lowered the mean BP (systolic BP: weighted mean difference, -3.45 mm Hg; 95% confidence interval, -6.10 to -0.80; diastolic BP: weighted mean difference, -2.02 mm Hg; 95% confidence interval, -3.25 to -0.78). There was no significant difference (risk ratio, 1.01; 95% confidence interval, 0.94 to 1.08) in the risk of adverse events between the participants receiving urate-lowering therapy and the control group.

CONCLUSIONS

Urate-lowering therapy did not produce benefits on the clinical outcomes, including major adverse cardiovascular events, all-cause mortality, and kidney failure. Thus, there is insufficient evidence to support urate lowering in patients to improve kidney and cardiovascular outcomes.

The Crucial Role of Xanthine Oxidase in CKD Progression Associated with Hypercholesterolemia

In the present study, we investigated the effects of xanthine oxidase (XO) inhibition on cholesterol-induced renal dysfunction in chronic kidney disease (CKD) mice, and in low-density lipoprotein (LDL)-treated human kidney proximal tubule epithelial (HK-2) cells. ApoE knockout (KO) mice underwent uninephrectomy to induce CKD, and were fed a normal diet or high-cholesterol (HC) diet along with the XO inhibitor topiroxostat (1 mg/kg/day). HK-2 cells were treated with LDL (200 µg/mL) and topiroxostat (5 µM) or small interfering RNA against xanthine dehydrogenase (siXDH; 20 nM). In uninephrectomized ApoE KO mice, the HC diet increased cholesterol accumulation, oxidative stress, XO activity, and kidney damage, while topiroxostat attenuated the hypercholesterolemia-associated renal dysfunction. The HC diet induced cholesterol accumulation by regulating the expressions of genes involved in cholesterol efflux (Nr1h3 and Abca1) and synthesis (Srebf2 and Hmgcr), which was reversed by topiroxostat. Topiroxostat suppressed the expressions of genes related to hypercholesterolemia-associated inflammation and fibrosis in the unilateral kidney. LDL stimulation evoked changes in the cholesterol metabolism, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, and NF-κB pathways in HK-2 cells, which were mitigated by XO inhibition with topiroxostat or siXDH. These findings suggest that XO inhibition exerts renoprotective effects against hypercholesterolemia-associated kidney injury. XO could be a novel therapeutic target for hypercholesterolemia-associated kidney injury in uninephrectomized patients.

Pharmacological inhibition of fatty acid-binding protein 4 alleviated kidney inflammation and fibrosis in hyperuricemic nephropathy

Hyperuricemia is an independent risk factor for chronic kidney disease (CKD). Excessive uric acid (UA) level in the blood leads to hyperuricemic nephropathy (HN), which is characterized by glomerular hypertension, arteriolosclerosis and tubulointerstitial fibrosis. Fatty acid binding protein 4 (FABP4) is a potential mediator of inflammatory responses which contributes to renal interstitial fibrosis. However, the roles of FABP4 in HN remains unknown. In the study, a mouse model of HN induced by feeding a mixture of adenine and potassium oxonate, severe kidney injury and interstitial fibrosis, as well as the increased kidney-expressed FABP4 protein level were evident, accompanied by the activation of inflammatory responses. Oral administration of BMS309403, a highly selective FABP4 inhibitor, improved renal dysfunction, inhibited the mRNA level of KIM-1 and NGAL, as well as reduced the expression of proinflammatory cytokines and fibrotic proteins in the injured kidneys. BMS309403 treatment also inhibited the FABP4 activity and further suppressed the activation of JAK2-STAT3 and NF-kB P65 signaling pathways in the hyperuricemia-injured kidneys and UA-stimulated human tubular epithelial (HK-2) cells, respectively. In summary, our study for the first time demonstrated that FABP4 played a crucial role in kidney inflammation and fibrosis via the regulation of JAK2-STAT3 and NF-kB P65 pathways in HN mice. The results suggested that FABP4 inhibition might be a promising therapeutic strategy for HN.

Only Hyperuricemia with Crystalluria, but not Asymptomatic Hyperuricemia, Drives Progression of Chronic Kidney Disease

BACKGROUND

The roles of asymptomatic hyperuricemia or uric acid (UA) crystals in CKD progression are unknown. Hypotheses to explain links between UA deposition and progression of CKD include that (1) asymptomatic hyperuricemia does not promote CKD progression unless UA crystallizes in the kidney; (2) UA crystal granulomas may form due to pre-existing CKD; and (3) proinflammatory granuloma-related M1-like macrophages may drive UA crystal-induced CKD progression.

METHODS

MALDI-FTICR mass spectrometry, immunohistochemistry, 3D confocal microscopy, and flow cytometry were used to characterize a novel mouse model of hyperuricemia and chronic UA crystal nephropathy with granulomatous nephritis. Interventional studies probed the role of crystal-induced inflammation and macrophages in the pathology of progressive CKD.

RESULTS

Asymptomatic hyperuricemia alone did not cause CKD or drive the progression of aristolochic acid I-induced CKD. Only hyperuricemia with UA crystalluria due to urinary acidification caused tubular obstruction, inflammation, and interstitial fibrosis. UA crystal granulomas surrounded by proinflammatory M1-like macrophages developed late in this process of chronic UA crystal nephropathy and contributed to the progression of pre-existing CKD. Suppressing M1-like macrophages with adenosine attenuated granulomatous nephritis and the progressive decline in GFR. In contrast, inhibiting the JAK/STAT inflammatory pathway with tofacitinib was not renoprotective.

CONCLUSIONS

Asymptomatic hyperuricemia does not affect CKD progression unless UA crystallizes in the kidney. UA crystal granulomas develop late in chronic UA crystal nephropathy and contribute to CKD progression because UA crystals trigger M1-like macrophage-related interstitial inflammation and fibrosis. Targeting proinflammatory macrophages, but not JAK/STAT signaling, can attenuate granulomatous interstitial nephritis.

The dirty little secret of urate-lowering therapy: useless to stop chronic kidney disease progression and may increase mortality

Hyperuricaemia is frequent in chronic kidney disease (CKD). Observational studies have shown an association with adverse outcomes and acquired hyperuricaemia (meaning serum urate levels as low as 1.0 mg/dL) in animal models induces kidney injury. This evidence does not justify the widespread use of urate-lowering drugs for asymptomatic hyperuricaemia in CKD. However, promising results from small, open-label studies led some physicians to prescribe urate-lowering drugs to slow CKD progression. Two recent, large, placebo-controlled trials (CKD-FIX and PERL) showed no benefit from urate lowering with allopurinol on the primary endpoint of CKD progression, confirming prior negative results. Despite these negative findings, it was still argued that the study population could be optimized by enrolling younger non-proteinuric CKD patients with better preserved glomerular filtration rate (GFR). However, in these low-risk patients, GFR may be stable under placebo conditions. Additionally, the increased mortality trends already identified in gout trials of urate-lowering therapy were also observed in CKD-FIX and PERL, sending a strong safety signal: 21/449 (4.7%) and 10/444 (2.2%) patients died in the combined allopurinol and placebo groups, respectively [chi-squared P-value 0.048; relative risk 2.07 (95% CI 0.98–4.34); P = 0.06]. Given the absent evidence of benefit in multiple clinical trials and the potentially serious safety issues, the clear message should be that urate-lowering therapy should not be prescribed for the indication of slowing CKD progression. Additionally, regulatory agencies should urgently reassess the safety of chronic prescription of urate-lowering drugs for any indication.

Novel therapeutic agents for the treatment of diabetic kidney disease

INTRODUCTION

Diabetic kidney disease (DKD) involves multifaceted pathophysiology which increases the risk of cardiorenal events and mortality. Conventional therapy is limited to renin-angiotensin aldosterone system inhibition and management of hyperglycemia and hypertension. Recent clinical trials have demonstrated promising nephroprotective effects of antihyperglycemic agents thus modifying guideline treatment recommendations for type 2 diabetic patients with chronic kidney disease.

AREAS OF COVERED

Relevant studies and clinical trials were searched via PubMed and clinicaltrials.gov through August 2020. Authors offer an update on clinical evidence regarding nephroprotective effects and side effects of sodium-glucose-cotransporter-2 (SGLT2) inhibitors, glucagon-like-peptide-1 (GLP1) agonists and dipeptidylpeptidase-4 (DPP4) inhibitors. They discuss the potential benefits of novel therapy targeting DKD pathogenic processes including inflammation, oxidative stress, fibrosis, and vasoconstriction shown in early phases of clinical trials and offer an opinion on key challenges and directions for future progress.

EXPERT OPINION

SGLT2 inhibitors are the most promising agents for DKD and improving cardiorenal outcomes. Mineralocorticoid-receptor antagonists and janus kinase inhibitors are also promising investigational therapies that target oxidative stress, nitric oxide synthesis, and inflammation. Novel therapeutic targets and the identification of clinically useful biomarkers may provide future therapies that detect early stages of DKD enabling a slower kidney function decline.