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

Serum uric acid, kidney volume and progression in autosomal-dominant polycystic kidney disease

BACKGROUND

Hyperuricemia has been implicated in the development and progression of chronic kidney disease, both in animal experiments and in clinical studies. As a potentially modifiable risk factor, we examined whether serum uric acid levels correlate with early hypertension, kidney volume and progression to end-stage renal disease (ESRD) in autosomal-dominant polycystic kidney disease (ADPKD).

METHODS

Retrospective analysis of a prospective observational study of the natural history of ADPKD, conducted at the University of Colorado between 1985 and 2005. Included are 680 ADPKD adults who provided data on blood pressure, renal volume, renal function, uric acid, age at the onset of ESRD or last known age without ESRD. Serum uric acid levels were examined as a continuous variable and as gender-specific quartiles. The main outcome of interest was age at the onset of ESRD; secondary outcomes were hypertension onset before age 30 years and total kidney volume (TKV) at the study visit.

RESULTS

Subjects with early-onset hypertension had higher age-adjusted serum uric acid levels than those with no or late-onset hypertension despite similar creatinine clearance. After adjusting for age, gender and creatinine clearance, there was a 5.8% increase in TKV and 4.1% increase in TKV/body surface area for every 1 mg/dL increase in uric acid (P = 0.007). The multivariate-adjusted Cox regression demonstrated a greater hazard ratio for ESRD for subjects in the 4th and 3rd quartiles of uric acid compared with the 1st [4.8 (2.6-8.9; P < 0.001) and 2.9 (1.6-5.3; P < 0.001)].

CONCLUSIONS

Higher serum uric acid levels are associated with earlier onset of hypertension, larger kidney volume and increased hazard for ESRD in ADPKD independent of gender, body mass index and renal function at the study visit. Randomized interventional studies will be necessary to examine whether treating hyperuricemia has a protective role in ADPKD.

Reduced glomerular function and prevalence of gout: NHANES 2009-10

Background

The renal tubule is a major route of clearance of uric acid, a product of purine metabolism. The links between reduced glomerular filtration rate (GFR), hyperuricemia, and gout in the general population are not well understood. The objective of the present study was to estimate prevalence of gout and hyperuricemia among people with impaired GFR in the US general population.

Study Design

Cross-sectional, survey-weighted analyses of data on adults (age>20 years) in the 2009–10 cycle of the US National Health and Nutrition Examination Surveys (n = 5,589). Associations between self-reported physician diagnosis of gout and degrees of renal impairment were the primary focus of the present analyses.

Results

In the 2009–2010 period, there was an estimated 7.5 million people with gout in the US. There were 1.25 million men and 0.78 million women with moderate or severe renal impairment and gout. The age standardized prevalence of gout was 2.9% among those with normal GFR compared to 24% among those with GFR<60 ml/min/1.73 m².In multivariable logistic regression analyses that adjusted for age, gender, body mass index, hypertension, diabetes, hypertension medications, including diuretics, blood lead levels, and hyperlipidemia, the odds ratios of gout and hyperuricemia were 5.9 (2.2, 15.7) and 9.58 (4.3, 22.0) respectively among those with severe renal impairment compared to those with no renal impairment. Approximately 2–3 fold increase in prevalence of gout was observed for each 30 ml/min/1.73 m² decrease in GFR, after accounting for the above factors.

Conclusions

Renal glomerular function is an important risk factor for gout. The prevalence of hyperuricemia and gout increases with decreasing glomerular function independent of other factors. This association is non-linear and an eGFR of 60 ml/min/1.73 m² appears to be a threshold for the dramatic increase in the prevalence of gout.

A review investigating the effect of allopurinol on the progression of kidney disease in hyperuricemic patients with chronic kidney disease

This communication provides a brief report on the studies evaluating the use of allopurinol for delay of kidney disease progression and a discussion of the current limitations and future research needed. To date, only 5 studies have reported a delay in the progression of kidney disease with allopurinol use; a sixth study is currently underway. Allopurinol does seem to delay the progression of kidney disease as measured by using serum creatinine and glomerular filtration rates in hyperuricemic patients with chronic kidney disease. However, randomized, double-blind, placebo-controlled trials enrolling more patients and controlling for confounding variables are needed to confirm these findings.

Effects of urate-lowering therapy in hyperuricemia on slowing the progression of renal function: a meta-analysis

Uric acid (UA) is generally regarded as an independent risk factor for poor prognosis of patients with kidney disease. However, urate-lowering therapy (ULT) in asymptomatic hyperuricemia is conservative. Whether the beneficial effect on renal function can be achieved by lowering UA remains uncertain. A compound search for randomized controlled trials was conducted in databases consisting of MEDLINE, EMBASE, the Cochrane Library, the Chinese Biomedical Literature Database, and Chinese Science and Technology periodical databases. Two investigators independently screened these studies, assessed the included trials, and extracted data. Eleven articles with a total number of 753 participants met the criteria and were included in our meta-analysis. The results showed that ULT was associated with a decrease in serum creatinine and an increase in eGFR. Our study further confirms that ULT may have beneficial effects on slowing the progression of renal function.

Latest evidence on gout management: what the clinician needs to know

Until recently, the last drug approved for the treatment of gout by the United States Food and Drug Administration was allopurinol in 1966. Since 2008, two new drugs for the treatment of gout, febuxostat and pegloticase, have been approved in the US. Febuxostat has been approved in the EU and pegloticase approval is anticipated. A new single-ingredient colchicine preparation is available in the US, and the treatment recommendations for the use of colchicine in acute gout have evolved, now favoring a low-dose regimen. Several other exciting drugs are in development. Herein, we review some of basic principles in the diagnosis and staging of gout. We then examine current treatment principles, with particular attention to febuxostat and pegloticase, offering suggestions as to where they might fit into a modern therapeutic algorithm for gout treatment. We then present available data on several exciting new agents in development, including interleukin-1 inhibitors, and relate them to advances in our understanding of gout pathogenesis. We conclude with some important nonpharmacologic principles for optimal management of this ancient and eminently treatable disease. Dedicated gout research, going on quietly in the background of other breathtaking advances in rheumatology, is now paying off. This comes at a time when the number of patients affected by gout continues to rise, mainly due to an epidemic of obesity. An effort to improve lifestyle choices as a society and better management of the disease by clinicians should have a positive impact on gout incidence and outcome in our lifetimes.

Hyperuricemia and the progression of chronic kidney disease: is uric acid a marker or an independent risk factor?

Hyperuricemia is seen when kidney function declines. Whether elevated uric acid (UA) levels play a role in the initiation and progression of kidney disease is a subject of a great debate. Animal studies demonstrate that elevated UA level is a risk factor for kidney disease. In humans, the relationship between UA and kidney disease is more complicated. Cross-sectional studies show an association of hyperuricemia with the presence of CKD; however, from cross-sectional studies, one cannot determine which came first-the elevated UA level or the kidney disease. UA levels are also associated with other risk factors for kidney disease, including hypertension, metabolic syndrome, and microalbuminuria, but it is not clear whether these are mediators or confounders of a relationship. Observational studies suggest a relationship of UA level with incident CKD, but studies evaluating the relationship with decline in kidney function in established CKD are conflicting. Finally, small clinical trials using allopurinol to lower UA levels provide weak, but potentially promising, evidence that lowering UA levels may retard the progression of CKD. In this article, we will review the evidence of the association of hyperuricemia and CKD.

Educational paper: Progression in chronic kidney disease and prevention strategies

Chronic kidney disease (CKD) in children is a rare but devastating condition. Once a critical amount of nephron mass has been lost, progression of CKD is irreversible and results in end-stage renal disease (ESRD) and need of renal replacement therapy. The time course of childhood CKD is highly variable. While in children suffering from congenital anomalies of the kidneys and the urinary tract, progression of CKD in general is slow, in children with acquired glomerulopathies, disease progression can be accelerated resulting in ESRD within months. However, irrespective of the underlying kidney disease, hypertension and proteinuria are independent risk factors for progression. Thus, in order to prevent progression, the primary objective of treatment should always aim for efficient control of blood pressure and reduction of urinary protein excretion. Blockade of the renin-angiotensin-aldosterone system preserves kidney function not only by lowering blood pressure, but also by reducing proteinuria and exerting additional anti-proteinuric, anti-fibrotic, and anti-inflammatory effects. Besides, intensified blood pressure control, aiming for a target blood pressure below the 50th percentile, may exert additive renoprotective effects. Additionally, other modifiable risk factors, such as anemia, metabolic acidosis, dyslipidemia, and altered bone-mineral homeostasis may also contribute to CKD progression. In conclusion, beyond strict blood pressure control and reduction of urinary protein excretion, identification and treatment of both, renal disease-related and conventional risk factors are mandatory in children with CKD in order to prevent deterioration of kidney function.

Uric acid as a target of therapy in CKD

The prevalence of chronic kidney disease (CKD) has increased and will continue to increase in the United States and worldwide. This is alarming considering that CKD is an irreversible condition and patients who progress to chronic kidney failure have reduced quality of life and high mortality rates. As such, it is imperative to identify modifiable risk factors to develop strategies to slow CKD progression. One such factor is hyperuricemia. Recent observational studies have associated hyperuricemia with kidney disease. In addition, hyperuricemia is largely prevalent in patients with CKD. Data from experimental studies have shown several potential mechanisms by which hyperuricemia may contribute to the development and progression of CKD. In this article, we offer a critical review of the experimental evidence linking hyperuricemia to CKD, highlight gaps in our knowledge on the topic as it stands today, and review the observational and interventional studies that have examined the potential nephroprotective effect of decreasing uric acid levels in patients with CKD. Although uric acid also may be linked to cardiovascular disease and mortality in patients with CKD, this review focuses only on uric acid as a potential therapeutic target to prevent kidney disease onset and progression.

Albuminuria, proteinuria, and urinary albumin to protein ratio in chronic kidney disease

BACKGROUND

Both albuminuria and proteinuria are important disease markers of chronic kidney disease (CKD). Their relationship and the ratio between urinary albumin and protein in patients with CKD have not been investigated. Whether clinical features can affect these measurements is not clear.

METHODS

We conducted a cross-sectional study in 602 CKD patients. Demographic data, including age, gender, and co-morbidity such as diabetes, hypertension, hyperuricemia, and hyperlipidemia, were reviewed and recorded. Their urinary albumin, total protein, and creatinine were determined and urinary albumin to creatinine ratio (UACR), total protein to creatinine ratio (UPCR), and albumin to total protein ratio (UAPR) were calculated. Their estimated glomerular filtration rate (eGFR) was calculated according to serum creatinine. The correlation between UACR and UPCR was thus analyzed. We also investigated factors associated with these urinary measurements.

RESULTS

UACR and UPCR increased progressively as renal function deteriorated, while UAPR increased to a plateau in CKD stage 4. There was direct relationship between UACR and UPCR. UAPR rose exponentially with the increase of both UACR and UPCR when UACR <500 mg/g or UPCR <1,000 mg/g. Multivariate regression analysis revealed diabetes and hyperuricemia were associated with increased UACR and UPCR, while both urinary parameters were inversely related to male gender and eGFR. Diabetes and hyperuricemia were associated with increased UAPR and UAPR was negatively correlated with age and eGFR.

CONCLUSION

There was a significant association between UACR and UPCR in patients with CKD. Characteristics of patients, renal function, and co-morbidities all affected UACR, UPCR, and UAPR.

Hyperuricemia at 1 year after renal transplantation, its prevalence, associated factors, and graft survival

BACKGROUND

The present study investigated the prevalence and predictors for the development of hyperuricemia within 1 year after transplantation and their associations with genetic polymorphisms and graft outcome in patients taking tacrolimus and mycophenolate mofetil.

METHODS

One hundred twenty-one renal allograft recipients transplanted between January 2001 and March 2009 were studied. Patients with serum uric acid concentrations above 7.0 mg/dL within 1 year after transplantation were defined as having hyperuricemia, and all were treated with allopurinol. Genetic polymorphisms of nitric oxide synthase, angiotensin-converting enzyme, methylenetetrahydrofolate reductase, and 3 uric acid transporters were examined.

RESULTS

At 1 year after transplantation, 46 (38%) recipients developed hyperuricemia. Male gender, higher body mass index, long-term pretransplantation dialysis, and hypertension were associated with the development of hyperuricemia. The estimated glomerular filtration rate (eGFR) at 1 year after transplantation was lower in the patients with hyperuricemia than in those without. There were no differences in graft survival between the two groups. The pharmacokinetics of tacrolimus and mycophenolic acid and 6 polymorphisms were not associated with hyperuricemia. In the multivariate analysis, male gender, long-term pretransplantation dialysis (>36 months), and eGFR (<60 mL/min) were independently associated with the development of hyperuricemia.

CONCLUSION

The incidence of hyperuricemia in our cohort was 38%. Male gender and long-term pretransplantation dialysis were predictors for the development of hyperuricemia. The eGFR was lower in patients with hyperuricemia, but graft survival did not differ between the patients with hyperuricemia treated with alloprinol and those without hyperuricemia. We could not define the significance of the pharmacokinetics of immunosuppressants and genetic risk factors for hyperuricemia.

Can existing drugs approved for other indications retard renal function decline in patients with type 1 diabetes and nephropathy?

Mounting evidence from human, animal, and in vitro studies indicates that existing drugs, developed to treat other disorders, also might be effective in preventing or slowing the progression of diabetic nephropathy to end-stage renal disease. Examples of such drugs include the urate-lowering agent allopurinol, the anti-tumor necrosis factor agents etanercept and infliximab, and the immunomodulating drug abatacept. Because some of these medications are already on the market and have been used for a number of years for other indications, they can be tested immediately in human beings for a beneficial effect on renal function in diabetes. Special emphasis should be placed on evaluating the use of these drugs early in the course of diabetic nephropathy when renal damage is most likely to be reversible and interventions can yield the greatest delay to end-stage renal disease.

Effect of allopurinol on blood pressure: a systematic review and meta-analysis

Allopurinol is a potent xanthine oxidase inhibitor that is used in hyperuricemic patients to prevent gout. It has also been shown to decrease cardiovascular complications in a myriad of cardiovascular conditions. However, studies have reported conflicting evidence on its effects on blood pressure (BP). A systematic review was conducted using Medline, PubMed, Embase, and the Cochrane Library for all the longitudinal studies that assessed the efficacy of allopurinol on systolic and diastolic BP. A total of 10 clinical studies with 738 participants were included in the analysis. Compared with the control group, systolic BP decreased by 3.3 mm Hg (95% confidence interval [CI], 1.4-5.3 mm Hg; P=.001) and diastolic BP decreased by 1.3 mm Hg (95% CI, 0.1-2.5 mm Hg; P=.03) in patients treated with allopurinol. When analysis was restricted to the higher-quality randomized controlled trials, similar changes in systolic and diastolic BPs were found: 3.3 mm Hg (95% CI, 0.8-5.8 mm Hg; P<.001) and 1.4 mm Hg (95% CI, 0.1-2.7 mm Hg; P=.04), respectively. Allopurinol is associated with a small but significant reduction in BP. This effect can be potentially exploited to aid in controlling BP in hypertensive patients with hyperuricemia.

Oxidative stress, anti-oxidant therapies and chronic kidney disease

Chronic kidney disease (CKD) is a common and serious problem that adversely affects human health, limits longevity and increases costs to health-care systems worldwide. Its increasing incidence cannot be fully explained by traditional risk factors. Oxidative stress is prevalent in CKD patients and is considered to be an important pathogenic mechanism. Oxidative stress develops from an imbalance between free radical production often increased through dysfunctional mitochondria formed with increasing age, type 2 diabetes mellitus, inflammation, and reduced anti-oxidant defences. Perturbations in cellular oxidant handling influence downstream cellular signalling and, in the kidney, promote renal cell apoptosis and senescence, decreased regenerative ability of cells, and fibrosis. These factors have a stochastic deleterious effect on kidney function. The majority of studies investigating anti-oxidant treatments in CKD patients show a reduction in oxidative stress and many show improved renal function. Despite heterogeneity in the oxidative stress levels in the CKD population, there has been little effort to measure patient oxidative stress levels before the use of any anti-oxidants therapies to optimize outcome. This review describes the development of oxidative stress, how it can be measured, the involvement of mitochondrial dysfunction and the molecular pathways that are altered, the role of oxidative stress in CKD pathogenesis and an update on the amelioration of CKD using anti-oxidant therapies.

Coronary artery dilation among patients with paediatric-onset systemic lupus erythematosus

OBJECTIVES

This study aimed to evaluate increased coronary artery dimensions in patients with paediatric-onset systemic lupus erythematosus (SLE) in comparison with healthy controls, and to identify risk factors associated with increased coronary artery dimensions in the SLE patients.

METHODS

As part of a longitudinal cohort study of coronary artery disease (CAD) in paediatric-onset SLE, 83 children with SLE and 36 healthy controls were enrolled for a cross-sectional analysis. Their coronary artery diameters were measured by echocardiography while their body mass index (BMI), blood pressure, and other cardiovascular factors were recorded. The age at diagnosis, serum uric acid (UA) and creatinine levels, and other lupus-related factors were further evaluated in SLE patients. Data were analysed using linear regression.

RESULTS

Mean body surface area (BSA)-adjusted dimensions of the left coronary artery (LCA) and right coronary artery (RCA) were significantly larger in SLE patients than in controls (both p < 0.001). The age at diagnosis, BMI, and serum UA and creatinine levels were associated with LCA and RCA diameters. There were no correlations between the coronary artery diameters and blood pressure, SLE duration, SLE Disease Activity Index (SLEDAI), C-reactive protein (CRP), C3, C4, anti-double-stranded-DNA (anti-dsDNA), or lipid profile. In multivariate analysis, serum UA level, age at diagnosis, and BMI were consistently associated with coronary artery dimensions (p < 0.001, p = 0.008, and p = 0.006 for LCA; p = 0.020, 0.013, and 0.008 for RCA).

CONCLUSIONS

Increased coronary artery diameters were found in children with SLE and were associated with higher serum UA levels. The pathogenic mechanisms warrant further investigation.

Gout and organ transplantation

Acute and chronic gout are common complications following organ transplantation. Risk factors include those shared with the general population (eg, diuretic use) and transplant-specific risk factors (eg, cyclosporine). Clinical features of gout are similar to those seen in the general population, although tophi may be more common. A definitive diagnosis requires demonstration of monosodium urate crystals within synovial fluid or tophi. Treatment is often empiric, although a poor response should prompt joint aspiration to exclude septic arthritis. Corticosteroids are commonly used to treat acute gout due to the adverse profile and drug interactions with NSAIDs and colchicine. Sustained reduction of serum urate (≤6 mg/dL) is critical in long-term management. Allopurinol is the most commonly used agent, although vigilant monitoring is required if combined with azathioprine. Other options include febuxostat and benzbromarone. The role of newer agents such as interleukin-1 inhibitors and uricases remains to be determined. General measures should include minimizing diuretic use.

Hyperuricemia as a marker for progression of immunoglobulin A nephropathy

BACKGROUND

The variable clinical and histopathological manifestations of immunoglobulin A nephropathy (IgAN) make it difficult to predict disease progression. A recent study showed that hyperuricemia, a condition common in hypertension and vascular disease, may contribute to renal dysfunction and histological changes including renal arteriosclerosis, tubular atrophy, and interstitial fibrosis. Herein, we investigated the clinical significance of uric acid level at the time of biopsy, as a marker of IgAN progression.

METHODS

We included 193 patients with biopsy-proven IgAN. Renal disease progression was defined as serum creatinine elevation above 1.2 mg/dL or over 20% elevation from baseline. Hyperuricemia was defined as a serum uric acid level ≥7.3 mg/dL in men and ≥5.3 mg/dL in women, which were 1 standard deviation above the mean value in the normal subjects.

RESULTS

The hyperuricemia group (n=50) had higher blood pressure, body mass index, and serum creatinine, and a greater amount of proteinuria and a lower glomerular filtration rate than the nonhyperuricemia group (n=143). Hyperuricemia increased the risk of IgAN progression (odds ratio, 4.53; 95% confidence interval, 1.31-15.66). The disease progression group (n=26) had a greater frequency of hyperuricemia, hypertension, and nephrotic range proteinuria than the nonprogression group (n=119). The renal survival analysis showed that the hyperuricemia group had a higher rate of IgAN disease progression.

CONCLUSION

Hyperuricemia at the time of diagnosis is an important marker for IgAN progression.

Relationship between serum uric acid and internal carotid resistive index in hypertensive women: a cross-sectional study

Background

The impact of serum uric acid (SUA) on arteries of hypertensive subjects remains to be fully established. This study investigated the relationship between SUA and carotid structural and hemodynamic parameters in hypertensive men and women.

Methods

Three hundred and thirty eight patients (207 women and 131 men) were cross-sectionally evaluated by clinical, laboratory, hemodynamic and carotid ultrasound analysis. Common carotid diameters, circumferential wall tensions, Young’s Elastic Modulus, Stiffness Index, Arterial Compliance and intima-media thickness (IMT) were determined. Internal carotid artery resistive index (ICRI), a hemodynamic measure that reflects local vascular impedance and microangiopathy, was also assessed.

Results

Univariate analysis showed no significant correlation of SUA with carotid diameters, elasticity/stiffness indexes, IMT and circumferential wall tensions in both genders. Conversely, SUA correlated with ICRI (r = 0.34; p < 0.001) in women, but not in men, and hyperuricemic women presented higher ICRI than normouricemic ones (0.684 ± 0.007 vs. 0.649 ± 0.004; p < 0.001). Stepwise and logistic regression analyses adjusted for potential confounding factors showed that ICRI was independently associated with SUA and hyperuricemia in women.

Conclusions

This study demonstrated that SUA was associated with ICRI in hypertensive women, suggesting that there might gender-related differences in the relationship between SUA and vascular damage in subjects with systemic hypertension.

Effects of hyperuricemia on renal function of renal transplant recipients: a systematic review and meta-analysis of cohort studies

Background

Hyperuricemia is an independent risk factor of nephropathy, but its role in renal transplant recipients (RTRs) is controversial.

Methods

Based on the methods of Cochrane systematic reviews, we searched MEDLINE (1948–2011.6), EMBASE (1956–2011.6), CBM (Chinese Biomedicine Database) (1978–2011.6) to identify cohort studies assessing the association between uric acid level and kidney allograft. Two authors independently screened the studies, assessed the risk of bias of included studies and extracted data. Unadjusted odds ratio(OR), mean difference (MD), adjusted hazard ratio (aHR) and their corresponding 95%CI were pooled to assess the effects of hyperuricemia on kidney allograft.

Results

Twelve cohort studies were included and the quality was moderate to high based on the NEWCASTLE-OTTAWA quality assessment scale. RTRs with hyperuricemia had lower eGFR (P<0.0001, 95%CI−16.34∼6.14) and higher SCr (P<0.00001, 95%CI 0.17∼0.31) than those with normal uric acid level. Meta-analysis showed that hyperuricemia was a risk factor of chronic allograft nephropathy (Unadjusted OR = 2.85, 95%CI 1.84∼4.38, adjusted HR = 1.65, 95%CI 1.02∼2.65) and graft loss (Unadjusted OR = 2.29, 95%CI 1.55∼3.39; adjusted HR = 2.01, 95%CI 1.39∼2.94).

Conclusions

Current evidence suggests that hyperuricemia may be an independent risk factor of allograft dysfunction. Hyperuricemia may modestly increase the risk of poor outcomes of RTRs. Future research is needed to verify whether lowering uric acid level could improve the kidney function and prognosis of RTRs with hyperuricemia.

Effects of cilnidipine on serum uric acid level and urinary nitrogen monoxide excretion in patients with hypertension

The effects of cilnidipine on the serum uric acid level and urinary NO excretion in hypertensive patients were investigated. Blood and urine samples of 16 hypertensive outpatients were collected before and 2 months after cilnidipine therapy (10 mg). The serum uric acid level decreased significantly after cilnidipine treatment, while the uric acid-creatinine clearance ratio was unaffected. The cilnidipine medication produced a significant increase in urinary NO excretion, although amlodipine did not change it significantly. Therefore, cilnidipine has a profound antihypertensive effect and may reduce the serum uric acid level and increase NO production in the kidney.

Impact of serum uric acid on renal function and cardiovascular events in hypertensive patients treated with losartan

High serum uric acid level (SUA) and chronic kidney disease (CKD) are risk factors for cardiovascular events (CVEs). However, their interactions as cardiovascular risk factors remain unknown. This subanalysis of the Japan Hypertension Evaluation with Angiotensin II Antagonist Losartan Therapy (J-HEALTH) study included 7629 patients, in whom the serum creatinine level was measured at least twice. The study examined the impact of hyperuricemia (SUA ≥7 mg dl(-1)) on CVE according to the level of renal dysfunction and whether early changes in SUA predicted future glomerular filtration rates (GFRs). The mean follow-up period was 3.1 years. The patients were divided into three groups according to the baseline estimated GFR (eGFR): groups A, B and C with eGFR <45, 45-59 and ≥60 ml min(-1) per 1.73 m(2), respectively. eGFR increased from 38.1 to 57.6, from 52.8 to 67.5 and from 74.7 to 80.7 ml min(-1) per 1.73 m(2) in groups A, B and C, respectively. In non-hyperuricemic patients, the CVE rate was 10.83, 4.98 and 4.21/1000 person-years in groups A, B and C, respectively, while in hyperuricemic patients, the corresponding values were 14.18, 17.02 and 5.93. Thus, hyperuricemia increased the risk of CVE only in group B (relative risk (RR) 3.43 (95% confidence interval (CI) 1.55 to 7.60); P<0.002). The final change in the eGFR was negatively correlated with the change in SUA from baseline to year 1 (P<0.001). CVEs were more frequent in those with a decrease in eGFR. Hyperuricemia may be a major determinant of increased cardiovascular risk in CKD stage 3A, and SUA may be involved in the progression of CKD. Changes in the GFR influence the rate of CVE.

Recent advances in management of gout

Incidence and prevalence of gout have markedly increased over the last few decades in keeping with the rise in prevalence of obesity and metabolic syndrome. Until recently, management of gout in patients with associated metabolic syndrome and comorbid illnesses such as renal impairment was difficult because of limited treatment options. However, significant progress has been made in the last few years, with introduction of new treatments such as interleukin-1 antagonists for management of acute gout, and febuxostat and pegloticase for chronic gout. The association of gout with alcohol, dietary purines and fructose ingestion has been confirmed in large prospective studies, thus enabling the clinician to now provide evidence-based advice to patients. Recent efficacy and safety data favour lower over higher doses of colchicine, and oral corticosteroids over non-steroidal anti-inflammatory drugs for patients with acute gout. Local ice therapy might help to differentiate gout from other forms of inflammatory arthritis, and supplementation with vitamin C help to reduce risk of gout. Several other drugs with rational mechanisms of action are in the pipeline, and likely to be introduced over the next few years. A new era has thus begun in the field of gout.

Risk of end-stage renal disease associated with gout: a nationwide population study

Introduction

We explored the risk of end-stage renal disease (ESRD) among gout patients in a representative cohort in Taiwan.

Methods

The primary database used was the Taiwan National Health Insurance Research Database. Subjects older than 20 years without ESRD, coronary heart disease, or stroke were included in the study. The case definition of gout in the present study was gout diagnosis and medical treatment for gout. An ESRD case was defined by the presence of chronic renal failure necessitating long-term renal replacement therapy. Multivariate Cox proportional hazards models were used to evaluate the risk of ESRD among gout patients.

Results

The analysis included data of 656,108 patients who were followed up for a mean of 8.0 years. Among them, 19,963 (3.0%) patients had gout. At the end of 2008, 2,377 individuals (gout, n = 276; non-gout, n = 2,101) had ESRD, and 861 individuals (gout, n = 77, 27.9%; non-gout, n = 521, 24.8%) died due to ESRD. The rates of incidence of ESRD were 1.73 and 0.41 cases per 1,000 patient-years in the gout and non-gout groups. After adjustment for age, sex, and history of diabetes mellitus and/or hypertension, gout was associated with a hazard ratio (HR) of 1.57 for ESRD (95% confidence interval [CI], 1.38-1.79; P < 0.001). In patients with ESRD, the adjusted HR for death in patients with gout was 0.95 (0.74-1.23, P = 0.71), which was similar to the HR obtained in patients without gout.

Conclusions

Gout is associated with an increased hazard for development of ESRD.

Japanese guideline for the management of hyperuricemia and gout: second edition

Gout is a urate deposition disease caused by persistent hyperuricemia. Because gout patients present with a variety of clinical symptoms, it is necessary to have a guideline for the standard management and care of gout and hyperuricemia. The Japanese Society of Gout and Nucleic Acid Metabolism, a scientific society committed to study nucleic acid metabolism and related diseases, established the first edition of the "Guideline for the Management of Hyperuricemia and Gout" in 2002, and published the revised version in January 2010. This second edition is not only evidence based on a search of systemic literature, but also includes consensus levels by a Delphi exercise to determine the strength of the recommendations. A draft version of this guideline was reviewed by internal and external reviewers as well as a patient. In this guideline, key messages from each chapter are listed as statements together with the evidence level, consensus level, and strength of the recommendation. In this proceeding, several selected chapters on the clinical management of gout and hyperuricemia are described. We hope this guideline is appropriately used for the standard management and care of patients with hyperuricemia and gout in daily practice.

Relationship between hyperuricemia and chronic kidney disease

Because approximately 70% of uric acid is excreted from the kidney, hyperuricemia occurs when renal function deteriorates. Until now, it has not been clear if the hyperuricemia seen in such renal diseases plays a role in the progression of renal disease. However, recent clinical studies show that the serum uric acid value is closely associated with hypertension in hyperuricemic patients (cross-sectional study), and also with the onset of hypertension (longitudinal study). Furthermore, one interesting report shows that treatment of hyperuricemia with allopurinol lowers blood pressure in juvenile essential hypertension patients with hyperuricemia. In addition, it is well known that hyperuricemia is closely associated with chronic kidney disease (CKD), is a risk factor for renal insufficiency in general populations, and is a poor prognostic factor of renal function in patients who also have IgA nephropathy. On the other hand, in intervention studies on hyperuricemia, the treatment of hyperuricemia with allopurinol in CKD has resulted in a fall in blood pressure and inhibition of the progression of renal damage. Conversely, the cessation of allopurinol treatment in CKD was followed by a rise in blood pressure and the development of renal damage. Furthermore, the rise of blood pressure and development of renal damage following cessation of allopurinol treatment are only seen in patients not receiving angiotensin converting enzyme inhibitor (ACEI) or angiotensin receptor blocker (ARB). This suggests that the renin angiotensin (RA) system plays an important role in the development of hypertension and renal damage from hyperuricemia.

Uric acid as a mediator of diabetic nephropathy

Despite advances in the management of patients with diabetes, diabetic nephropathy (DN) remains the most common cause of end-stage renal disease in the United States and worldwide. Inflammation and endothelial dysfunction appear to play a central role in the onset and the progression of DN. Recent evidence has emerged in the past decade to suggest uric acid is an inflammatory factor and may play a role in endothelial dysfunction. This has lead our group and others to explore the role of uric acid in the onset and progression of DN. In this review, we highlight some of the animal and human studies that implicate uric acid in DN. Based on the evidence we review, we conclude the need for properly planned randomized controlled studies to decrease uric acid levels and assess the impact of such therapy on diabetic kidney disease.

Uric acid and chronic kidney disease: new understanding of an old problem

Although an elevation of serum uric acid level is often associated with chronic kidney disease (CKD), it remains controversial whether hyperuricemia per se is a true risk factor for the development or aggravation of CKD. Recent epidemiologic studies in healthy populations or in subjects with established kidney disease have reported the independent role of uric acid in lowering glomerular filtration rate and increasing the risk for new-onset kidney disease. Furthermore, lowering uric acid in patients with established renal disease has been reported to stabilize renal function independent of other confounders, suggesting a causative role of elevated uric acid in progression of CKD, rather than as an incidental finding related to CKD severity. In this manuscript we will discuss the potential role of uric acid in the development and aggravation of CKD based on epidemiologic, clinical and experimental studies. Given the worldwide epidemic of CKD, the importance of identifying modifiable risk factors of CKD, and the clinical implication of hyperuricemia in CKD, we propose large randomized clinical trials to investigate whether uric acid-lowering therapy can slow the progression of CKD.

Uric acid level and elevated blood pressure in US adolescents: National Health and Nutrition Examination Survey, 1999-2006

Uric acid is associated with cardiovascular disease and cardiovascular disease risk factors in adults, including chronic kidney disease, coronary artery disease, stroke, diabetes mellitus, preeclampsia, and hypertension. We examined the association between uric acid and elevated blood pressure in a large, nationally representative cohort of US adolescents, a population with a relatively low prevalence of cardiovascular disease and cardiovascular disease risk factors. Among 6036 adolescents 12 to 17 years of age examined in the 1999-2006 National Health and Nutrition Examination Survey, the mean age was 14.5 years, 17% were obese (body mass index: ≥95th percentile), and 3.3% had elevated blood pressure. Mean serum uric acid level was 5.0 mg/dL, and 34% had a uric acid level ≥5.5 mg/dL. In analyses adjusted for age, sex, race/ethnicity, and body mass index percentile, the odds ratio of elevated blood pressure, defined as a systolic or diastolic blood pressure ≥95th percentile for age, sex, and height, for each 0.1-mg/dL increase in uric acid level was 1.38 (95% CI: 1.16-1.65). Compared with <5.5 mg/dL, participants with a uric acid level ≥5.5 mg/dL had a 2.03 times higher odds of having elevated blood pressure (95% CI: 1.38-3.00). In conclusion, increasing levels of serum uric acid are associated with elevated blood pressure in healthy US adolescents. Additional prospective studies and clinical trials are needed to determine whether uric acid is merely a marker in a complex metabolic pathway or causal of hypertension and, thus, a potential screening and therapeutic target.

African American patients with gout: efficacy and safety of febuxostat vs allopurinol

BACKGROUND

African Americans are twice as likely as Caucasians to develop gout, but they are less likely to be treated with urate-lowering therapy (ULT). Furthermore, African Americans typically present with more comorbidities associated with gout, such as hypertension, obesity, and renal impairment. We determined the efficacy and safety of ULT with febuxostat or allopurinol in African American subjects with gout and associated comorbidities and in comparison to Caucasian gout subjects.

METHODS

This is a secondary analysis of the 6-month Phase 3 CONFIRMS trial. Eligible gouty subjects with baseline serum urate (sUA) ≥ 8.0 mg/dL were randomized 1:1:1 to receive febuxostat 40 mg, febuxostat 80 mg, or allopurinol (300 mg or 200 mg depending on renal function) daily. All subjects received gout flare prophylaxis. Primary efficacy endpoint was the proportion of subjects in each treatment group with sUA < 6.0 mg/dL at the final visit. Additional endpoints included the proportion of subjects with mild or with moderate renal impairment who achieved a target sUA < 6.0 mg/dL at final visit. Adverse events (AEs) were recorded throughout the study.

RESULTS

Of the 2,269 subjects enrolled, 10.0% were African American and 82.1% were Caucasian. African American subjects were mostly male (89.5%), obese (BMI ≥ 30 kg/m2; 67.1%), with mean baseline sUA of 9.8 mg/dL and mean duration of gout of 10.4 years. The proportions of African American subjects with a baseline history of diabetes, renal impairment, or cardiovascular disease were significantly higher compared to Caucasians (p < 0.001). ULT with febuxostat 80 mg was superior to both febuxostat 40 mg (p < 0.001) and allopurinol (p = 0.004). Febuxostat 40 mg was comparable in efficacy to allopurinol. Significantly more African American subjects with mild or moderate renal impairment achieved sUA < 6.0 mg/dL in the febuxostat 80 group than in either the febuxostat 40 mg or allopurinol group (p < 0.05). Efficacy rates in all treatment groups regardless of renal function were comparable between African American and Caucasian subjects, as were AE rates.

CONCLUSIONS

In African American subjects with significant comorbidities, febuxostat 80 mg is significantly more efficacious than either febuxostat 40 mg or allopurinol 200/300 mg. Febuxostat was well tolerated in this African American population.Please see related article: http://www.biomedcentral.com/1741-7015/10/15.

New insights into uric acid effects on the progression and prognosis of chronic kidney disease

Hyperuricemia is particularly common in patients with arterial hypertension, metabolic syndrome, or kidney disease. Its role, however, as a risk factor for both renal and cardiovascular outcomes and in the context of the well-established interrelationship between cardiovascular disease and chronic kidney disease (CKD) is debated. For decades high serum uric acid levels were mainly considered the result of renal dysfunction and not a true mediator of renal disease development and progression. However, recent epidemiological studies suggest an independent association between asymptomatic hyperuricemia and increased risk of arterial hypertension, CKD, cardiovascular events, and mortality. Furthermore, data from experimental models of hyperuricemia have provided robust evidence in this direction. Hyperuricemia causes increased arterial pressure, proteinuria, renal dysfunction, and progressive renal and vascular disease in rats. The main pathophysiological mechanisms of these deleterious effects caused by uric acid are endothelial dysfunction, activation of local renin-angiotensin system, increased oxidative stress, and proinflammatory and proliferative actions. A small number of short-term, single-center clinical studies support the beneficial influence of pharmaceutical reduction of serum uric acid on total cardiovascular risk, as well as on renal disease development and progression. Hyperuricemia is probably related to the incidence of primary hypertension in children and adolescents, as serum uric acid lowering by allopurinol has an antihypertensive action in this group of patients. Finally, it is clear that adequately powered randomized controlled trials are urgently required to elucidate the role of uric acid in cardiovascular events and outcomes, as well as in the development and progression of CKD.

Uric acid, hypertension, and chronic kidney disease among Alaska Eskimos: the Genetics of Coronary Artery Disease in Alaska Natives (GOCADAN) study

It is unknown what role uric acid (UA) may play in the increasing rates of cardiovascular disease (CVD) among Alaska Eskimos. UA is associated with both hypertension (HTN) and chronic kidney disease (CKD). The authors analyzed 1078 Genetics of Coronary Artery Disease in Alaska Natives (GOCADAN) participants. Estimated glomerular filtration rate (eGFR) was calculated from serum creatinine measures using the Modification of Diet in Renal Disease equation. CKD was defined by an eGFR of <60 mL/min/1.73 m(2) . The authors adjusted for age, sex, education, diabetes, hypertension (or eGFR), obesity, lipids, and smoking status; 7% (n=75) had prevalent CKD. eGFR decreased with increasing tertiles of serum UA (P<.001). UA was independently associated with prevalent CKD (adjusted odds ratio [OR] and 95% confidence interval [CI] of 2.04 (1.62-2.56), respectively). Twenty-one percent (n=230) had prevalent HTN and UA was independently associated with prevalent HTN (adjusted OR, 1.2; 95% CI, 1.1-1.5). UA is independently associated with prevalent CKD and HTN in this population.

Serum uric acid levels and incident chronic kidney disease in patients with type 2 diabetes and preserved kidney function

OBJECTIVE

Recent studies have suggested an association between hyperuricemia and adverse renal outcomes in nondiabetic populations. Data on the relationship between hyperuricemia and the risk of incident chronic kidney disease (CKD) in type 2 diabetic patients with normal or near-normal kidney function are lacking. We determined whether baseline serum uric acid levels predict the subsequent development of CKD in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

We followed 1,449 type 2 diabetic patients with normal kidney function and without overt proteinuria for 5 years for the occurrence of incident CKD (defined as overt proteinuria or estimated glomerular filtration rate [eGFR] <60 mL/min/1.73 m(2)).

RESULTS

During a 5-year follow-up period, 194 (13.4%) patients developed incident CKD. The cumulative incidence of CKD was significantly greater in patients with hyperuricemia than in those without hyperuricemia (29.5 vs. 11.4%, P < 0.001). In univariate logistic regression analysis, the presence of hyperuricemia roughly doubled the risk of developing CKD (odds ratio [OR] 2.55 [95% CI 1.71-3.85], P < 0.001). After adjusting for age, sex, BMI, smoking status, diabetes duration, systolic blood pressure, antihypertensive treatment, insulin therapy, HbA(1c), eGFR, and albuminuria, hyperuricemia was associated with an increased risk of incident CKD (adjusted OR 2.10 [1.16-3.76], P < 0.01). In continuous analyses, a 1-SD increment in the serum uric acid level was significantly associated with a 21% increased risk of CKD.

CONCLUSIONS

In type 2 diabetic individuals with preserved kidney function, hyperuricemia seems to be an independent risk factor for the development of incident CKD.

Treatment of chronic kidney disease

Treatment of chronic kidney disease (CKD) can slow its progression to end-stage renal disease (ESRD). However, the therapies remain limited. Blood pressure control using angiotensin-converting enzyme (ACE) inhibitors or angiotensin II receptor blockers (ARBs) has the greatest weight of evidence. Glycemic control in diabetes seems likely to retard progression. Several metabolic disturbances of CKD may prove to be useful therapeutic targets but have been insufficiently tested. These include acidosis, hyperphosphatemia, and vitamin D deficiency. Drugs aimed at other potentially damaging systems and processes, including endothelin, fibrosis, oxidation, and advanced glycation end products, are at various stages of development. In addition to the paucity of proven effective therapies, the incomplete application of existing treatments, the education of patients about their disease, and the transition to ESRD care remain major practical barriers to better outcomes.

Is there anything good in uric acid?

High uric acid (UA) levels can cause gout, urolithiasis and acute and chronic nephropathy, all of which are due to the deposit of urate crystals. There is also increasing evidence of relationships of hyperuricemia with other important disorders, including hypertension, chronic renal disease, metabolic syndrome and cardiovascular disease, as well as an increased mortality, although a causal relationship between these conditions has not been clearly established. On the other hand, low UA levels are not known to cause any disorder or disease. However, in the last few years a higher prevalence and progression of some neurological diseases have been associated with a low UA, and it is possible that they may predispose to some other disorders, mainly due to the decrease in its antioxidant activity. In this article, the known negative effects of UA are reviewed, as well as the much less-known possible positive actions, and their therapeutic implications.

The role of serum uric acid in cardiovascular disease in type 2 diabetic and non-diabetic subjects: a narrative review

The role of serum uric acid (UA) as a marker or risk factor of cardiovascular disease (CVD) is still controversial. The strong association of serum UA with established risk factors such as hypertension, Type 2 diabetes, dyslipidemia, and chronic kidney disease makes it difficult to establish a direct causal role of serum UA in the development and progression of CVD. The main aims of this review are: 1) to briefly summarize the most relevant studies concerning the association of serum UA with hypertension, chronic kidney disease, CVD events, and death both in patients without diabetes and in those with Type 2 diabetes; and 2) to briefly discuss the putative underlying mechanisms that link serum UA to adverse CVD outcomes. A search was conducted to identify relevant studies in the major electronic databases (MEDLINE and EMBASE, from January 1990 to December 2010) using Medical Subjects Headings and keywords. Collectively, by reviewing the published data in the literature, it emerges that serum UA may exert a number of potentially adverse cardiovascular effects. Nevertheless, the prognostic role of elevated serum UA level as a causal risk factor of adverse CVD outcomes remains still controversial, especially in patients with Type 2 diabetes. At this time, the treatment of asymptomatic hyperuricemia for the primary prevention of CVD is not recommended.

Clinical outcome of hyperuricemia in IgA nephropathy: a retrospective cohort study and randomized controlled trial

BACKGROUND

Hyperuricemia is an independent risk factor for renal progression in IgA nephropathy (IgAN). However, no study has evaluated the effect of allopurinol on the clinical outcome in hyperuricemic IgAN.

METHODS

First,a retrospective cohort study of 353 IgAN patients was conducted to explore the relationship between uric acid (UA) and the progression of renal disease over a mean period of 5 years. Then, 40 hyperuricemic IgAN patients were randomized to receive allopurinol (100-300 mg/day) or usual therapy for 6 months. The study outcomes were renal disease progression and/or blood pressure.

RESULTS

Hyperuricemia independently predicted renal survival at 1, 3, and 5 years after adjustment for different baseline estimated glomerular filtration rates. In the randomized controlled trial, allopurinol did not significantly alter renal progression or proteinuria. The antihypertensive drug dosage was reduced in 7 of 9 cases with hypertension in the allopurinol group compared to 0 of 9 cases in the control group (p < 0.01). UA levels correlated with mean arterial pressure in normotensive patients (r = 0.388, p < 0.001).

CONCLUSION

Hyperuricemia predicts the progression of IgAN independently of baseline estimated glomerular filtration rate. Allopurinol may improve the control of blood pressure. Further studies are required to explore the effects of lowering UA on renal protection in IgAN.

2011 recommendations for the diagnosis and management of gout and hyperuricemia

Gout is a major health problem in the United States; it affects 8.3 million people, which is approximately 4% of the adult population. Gout is most often diagnosed and managed in primary care practices; thus, primary care physicians have a significant opportunity to improve patient outcomes. Following publication of the 2006 European League Against Rheumatism (EULAR) gout guidelines, significant new evidence has accumulated, and new treatments for patients with gout have become available. It is the objective of these 2011 recommendations to update the 2006 EULAR guidelines, paying special attention to the needs of primary care physicians. The revised 2011 recommendations are based on the Grading of Recommendations Assessment, Development, and Evaluation approach as an evidence-based strategy for rating quality of evidence and grading the strength of recommendation formulated for use in clinical practice. A total of 26 key recommendations, 10 for diagnosis and 16 for management, of patients with gout were evaluated, resulting in important updates for patient care. The presence of monosodium urate crystals and/or tophus and response to colchicine have the highest clinical diagnostic value. The key aspect of effective management of an acute gout attack is initiation of treatment within hours of symptom onset. Low-dose colchicine is better tolerated and is as effective as a high dose. When urate-lowering therapy (ULT) is indicated, the xanthine oxidase inhibitors allopurinol and febuxostat are the options of choice. Febuxostat can be prescribed at unchanged doses for patients with mild-to-moderate renal or hepatic impairment. The target of ULT should be a serum uric acid level that is ≤ 6 mg/dL. For patients with refractory and tophaceous gout, intravenous pegloticase is a new treatment option. This article is a summary of the 2011 clinical guidelines published in Postgraduate Medicine. This article provides a streamlined, accessible overview intended for quick review by primary care physicians, with the full guidelines being a resource for those seeking additional background information and expanded discussion.

Management of asymptomatic hyperuricaemia in patients with chronic kidney disease by Japanese nephrologists: a questionnaire survey

AIM

Hyperuricaemia is associated with chronic kidney disease (CKD) progression and cardiovascular events (CVE). In a US study, only 4% of rheumatologists initiated urate-lowering therapy in patients with asymptomatic hyperuricaemia (AHU). The present study aimed to clarify how Japanese board-certified nephrologists manage AHU in CKD patients.

METHODS

Questionnaires on management of AHU in CKD stage 3 or more were mailed to 1500 Japanese board-certified nephrologists, excluding paediatricians and urologists, randomly selected from the directory of the Japanese Society of Nephrology (n = 2976).

RESULTS

Five hundred and ninety-five nephrologists (40%) responded. Most nephrologists (84-89%) recommended that AHU in patients in CKD stages 3-5 should be treated, but fewer nephrologists (63%) recommended that AHU in patients of CKD stage 5D should be treated. The serum urate level to start urate-lowering therapy and the target serum urate level to be achieved (mg/dL) were 8.2 ± 0.9 and 6.9 ± 0.9, 8.4 ± 0.9 and 7.0 ± 1.0, 8.6 ± 1.0 and 7.3 ± 1.1, and 9.1 ± 1.2 and 7.8 ± 1.3 at stages 3, 4, 5 and 5D, respectively. The most frequently used maximal dosage of allopurinol was 100 mg/day at each stage. Benzbromarone was used in 52% of patients at stage 3, but only in 29%, 13% and 5% of patients at stages 4, 5 and 5D, respectively. The most important reasons to treat AHU at CKD stages 3-5 were prevention of CKD progression (45%), CVE (33%), gout (18%) and urolithiasis (3%).

CONCLUSION

Most Japanese nephrologists treat AHU in pre-dialysis CKD with an aim to prevent CKD progression or CVE mainly by allopurinol.

The association between plasma uric acid and renal function decline in a Chinese population-based cohort

BACKGROUND

Uric acid may be associated with kidney damage through multiple pathways. Previous cohort studies revealed inconsistent results, and research among the non-hypertensive and non-diabetic population are extremely limited.

METHODS

This prospective cohort study included 1410 residents aged 59.1 ± 9.4 years from an urban district of Beijing, China. All participants had an estimated glomerular filtration rate >60 mL/min/1.73m(2). Plasma uric acid was assessed at baseline; and its relation with renal function decline after 4 years' follow-up was analyzed.

RESULTS

During 4 years (5630 person-years) of follow-up, 168 patients (11.9%) developed renal function decline. After adjusting for potential confounders including baseline renal function, plasma uric acid levels were independently associated with an increased risk of renal function decline, with a fully adjusted odds ratio (OR) of 1.19 [per 1 mg/dL increase; 95% confidence interval (CI) 1.04-1.38]. Analysis among 615 hypertension-free and diabetes-free participants yielded similar results, with an adjusted OR of 1.50 (per 1 mg/dL increase; 95% CI 1.13-1.98).

CONCLUSION

Our prospective cohort study revealed that plasma uric acid level is independently associated with an increasing likelihood of renal function decline.