Hyperuricaemia--where nephrology meets rheumatology

The positive association between hyperuricemia and polycystic ovary syndrome and analysis of related factors

Purpose

To examine the potential association between polycystic ovary syndrome (PCOS) and hyperuricemia and to elucidate the underlying contributory factors.

Methods

Retrospective study on 603 women with PCOS and 604 women without PCOS. Anthropometric features, reproductive hormone profiles, and metabolic parameters were measured and compared between two groups of patients. Examinations of correlations between SUA levels and other parameters were conducted to discern potential correlations.

Results

Both serum uric acid levels and the incidence of hyperuricemia exhibited statistically significant elevations in women with PCOS when compared to their counterparts without PCOS. Nonetheless, this statistical difference was not found between the obese subgroup after stratifying study subjects by body mass index (BMI). Pearson's correlation analysis underscored the prominence of BMI as a robust factor influencing SUA levels in women, regardless of their PCOS status. Furthermore, multivariable linear regression model demonstrated significant positive associations between SUA levels and several variables, namely dehydroepiandrosterone sulfate (DHEA-S), free androgen index (FAI), total cholesterol (TC), triglycerides (TG), free fatty acids (FFA), fasting insulin (FINS), homeostatic model assessment of insulin resistance (HOMA-IR), area under the curve for insulin (AUC-I), alanine aminotransferase (ALT), and aspartate aminotransferase (AST). Additionally, it is noteworthy that the prevalence of hyperuricemia exhibited a positive association with fasting plasma glucose (FPG) levels, while conversely, it displayed a negative association with estradiol (E2) levels.

Conclusions

PCOS is associated with a significant elevation of SUA level and hyperuricemia prevalence. HA, IR, and dyslipidemia may be the mediators in the pathogenesis of hyperuricemia in women with PCOS.

Comorbidity in gout at the time of first diagnosis: sex differences that may have implications for dosing of urate lowering therapy

Background

The aim of this study is to examine the occurrence of comorbidities at the time of first diagnosis of gout compared with matched population controls, overall and by sex, as well as to examine the crude and age-standardized prevalence of these comorbidities in men and women with gout at first diagnosis.

Methods

A population-based study used data from Swedish national and regional registers, including 14,113 gout patients aged ≥ 20 years, with a first recorded diagnosis of gout between 1 January 2006 and 31 December 2012, and 65,782 population controls, matched by age, sex and county. Prevalence ratios (95% confidence intervals) comparing gout cases and controls were calculated, overall and by sex. Crude and age-standardized prevalence (95% confidence interval) of all comorbidities in gout patients were calculated, to show differences between sexes, taking also the higher age at diagnosis in women into account.

Results

All examined comorbidities were 1.2–2.5-fold more common in gout patients at diagnosis than in population controls in both sexes. Women with gout were on average 6 years older than men at first gout diagnosis and most comorbidities, including obesity and diuretic use, were or tended to be more frequent in women than in men. When standardizing for age, women had a higher prevalence of thromboembolism (6.6% vs 5.2%) and chronic obstructive pulmonary disease (3.1% vs 2.4%). Men, on the other hand, had a higher prevalence of coronary heart disease (9.4% vs 6.4%), atrial fibrillation (9.0% vs 6.0%), congestive heart failure (7.7% vs 6.6%) and stroke (4.1% vs 3.3%).

Conclusions

The occurrence of most comorbidities was significantly increased at first diagnosis of gout in both sexes. Women were older at diagnosis and had higher occurrence of most comorbidities, including obesity and diuretic use, factors that increase serum urate, and this needs to be taken into account when starting and optimizing urate lowering therapy. These sex differences were attenuated when standardizing for age and the occurrence of cardiovascular diseases was actually higher in men.

Electronic supplementary material

The online version of this article (10.1186/s13075-018-1596-x) contains supplementary material, which is available to authorized users.

Serum uric acid levels and multiple health outcomes: umbrella review of evidence from observational studies, randomised controlled trials, and Mendelian randomisation studies

Objective To map the diverse health outcomes associated with serum uric acid (SUA) levels.Design Umbrella review.Data sources Medline, Embase, Cochrane Database of Systematic Reviews, and screening of citations and references.Eligibility criteria Systematic reviews and meta-analyses of observational studies that examined associations between SUA level and health outcomes, meta-analyses of randomised controlled trials that investigated health outcomes related to SUA lowering treatment, and Mendelian randomisation studies that explored the causal associations of SUA level with health outcomes.Results 57 articles reporting 15 systematic reviews and144 meta-analyses of observational studies (76 unique outcomes), 8 articles reporting 31 meta-analyses of randomised controlled trials (20 unique outcomes), and 36 articles reporting 107 Mendelian randomisation studies (56 unique outcomes) met the eligibility criteria. Across all three study types, 136 unique health outcomes were reported. 16 unique outcomes in meta-analyses of observational studies had P<10-6, 8 unique outcomes in meta-analyses of randomised controlled trials had P<0.001, and 4 unique outcomes in Mendelian randomisation studies had P<0.01. Large between study heterogeneity was common (80% and 45% in meta-analyses of observational studies and of randomised controlled trials, respectively). 42 (55%) meta-analyses of observational studies and 7 (35%) meta-analyses of randomised controlled trials showed evidence of small study effects or excess significance bias. No associations from meta-analyses of observational studies were classified as convincing; five associations were classified as highly suggestive (increased risk of heart failure, hypertension, impaired fasting glucose or diabetes, chronic kidney disease, coronary heart disease mortality with high SUA levels). Only one outcome from randomised controlled trials (decreased risk of nephrolithiasis recurrence with SUA lowering treatment) had P<0.001, a 95% prediction interval excluding the null, and no large heterogeneity or bias. Only one outcome from Mendelian randomisation studies (increased risk of gout with high SUA levels) presented convincing evidence. Hypertension and chronic kidney disease showed concordant evidence in meta-analyses of observational studies, and in some (but not all) meta-analyses of randomised controlled trials with respective intermediate or surrogate outcomes, but they were not statistically significant in Mendelian randomisation studies.Conclusion Despite a few hundred systematic reviews, meta-analyses, and Mendelian randomisation studies exploring 136 unique health outcomes, convincing evidence of a clear role of SUA level only exists for gout and nephrolithiasis.

Any link of gout disease control among hypertensive patients and onset of end-stage renal disease? Results from a population-based study

AIM

To determine the impact of allopurinol non-adherence as a proxy for uncontrolled disease on primary prevention of end-stage renal disease (ESRD).

METHODS

A cohort of 2752 patients with gout diagnosis was reconstructed using the Québec Régie de l’assurance maladie du Québec and MedEcho administrative databases. Eligible patients were new users of allopurinol, aged 45-85, with a diagnosis of hypertension, and treated with an antihypertensive drug between 1997 and 2007.

RESULTS

Major risk factor for ESRD onset was chronic kidney disease at stages 1 to 3 [rate ratio (RR) = 8.00; 95% confidence interval (CI): 3.16-22.3 and the severity of hypertension (≥ 3 vs < 3 antihypertensives)] was a trending risk factor as a crude estimate (RR = 1.94; 95%CI: 0.68-5.51). Of 341 patients, cases (n = 22) and controls (n = 319), high adherence level (≥ 80%) to allopurinol therapy, compared with lower adherence level (< 80%), was associated with a lower rate of ESRD onset (RR = 0.35; 95%CI: 0.13-0.91).

CONCLUSION

Gout control seem to be associated with a significant decreased risk of ESRD onset in hypertensive populations, further research should be conducted confirming this potential associated risk.

Effect of Rhizoma Polygoni Cuspidati and Ramulus Cinnamomi compatibility on uric acid metabolism and urinary neutrophil gelatinase-associated lipocalin and kidney injury molecule-1 in rats with hyperuricemia

OBJECTIVE

To explore the effects of Rhizoma Polygoni Cuspidati and Ramulus Cinnamomi compatibility (PR) on uric acid metabolism and the expression of urinary neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) in rats with hyperuricemia.

METHODS

Seventy male Sprague Dawley (SD) rats were randomly divided into 7 groups with 10 rats per group, including the normal group, model group, allopurinol group, benzbromarone group and PR groups at 3 doses (3.5, 7, 14 g/kg). Except the normal group, rats of the other groups were intragastrically administered 100 mg/kg hypoxanthine and 250 mg/kg ethambutol, and subcutaneously injected with 200 mg/kg potassium oxonate. All rats were continuously modeled for 17 days, and gavaged with corresponding drugs. The rats of the normal and model groups were gavaged with saline, once a day, for 2 weeks. The levels of serum uric acid (SUA), blood urea nitrogen (BUN) and creatinine (Cr) were determined. In addition, the contents of NGAL and KIM-1 in urine and the mRNA and protein expressions of xanthine oxidase (XOD) in liver of hyperuricemia rats were measured by reverse transcription polymerase chain reaction (RT-PCR) and Western blot, respectively. Moreover, the pathological changes of kidney were analyzed by hematoxylin and eosin (HE) stain method.

RESULTS

Compared with the normal group, the levels of SUA, BUN, NGAL and KIM-1 and the expressions of hepatic XOD mRNA and protein in the hyperuricemia rats were increased signifificantly (P<0.01). PR signifificantly decreased the levels of SUA, BUN, NGAL and KIM-1 and down-regulated the mRNA and protein expressions of hepatic XOD (P<0.05 or P<0.01). In addition, the pathological changes of kidney were signifificantly suppressed by oral administration of PR.

CONCLUSIONS

PR ameliorated uric acid metabolism and protected renal function, the underlying mechanism was mediated by decreasing the levels of SUA, BUN, NGAL and KIM-1, inhibiting the expression of hepatic XOD and ameliorating the pathological change of kidney.

Post-streptococcal acute glomerulonephritis complicated by gouty arthritis: a case report

Gouty arthritis is uncommon in childhood and adolescence. On the other hand, there has been no report of cases with development of gouty arthritis with post-streptococcal acute glomerulonephritis (PSAGN) in pediatric patients. Here we report the case of a mildly obese 12-year-old boy with PSAGN complicated by gouty arthritis of the left first metatarsophalangeal joint. On follow-up, it was confirmed that as serum C3 level returned to normal, urinary excretion of uric acid increased and serum uric acid level decreased, thereby resolving the burning pain of the left big toe. In this case, not only did renal insufficiency associate with PSAGN but also mild obesity may have led to hyperuricemia and gouty arthritis. In conclusion, clinicians should be aware that PSAGN may be complicated by gouty arthritis in obese pediatric patients.

Chronic kidney disease as a risk factor for incident gout among men and women: retrospective cohort study using data from the Framingham Heart Study

OBJECTIVES

Historically, the nature of association between chronic kidney disease (CKD) and gouty arthritis has been unclear. The goal of the present study was to test the hypothesis that CKD is an independent risk factor for developing incident gout.

DESIGN

Patients were from the original Framingham Heart Study cohort. Using Cox proportional hazard models we estimated the HR of CKD to incident gout among men and women separately after adjusting for age, alcohol consumption, smoking, hypertension, diabetes and body mass index.

SETTINGS

Patients were all from Framingham, Massachusetts, USA.

PARTICIPANTS

Excluding patients who had CKD in the first visit from this study, 2159 men and 2558 women were selected covering a 54-year period (1948-2002).

RESULTS

There were 371 incident cases (231 men and 140 women) of gout over the follow-up of 140,421 person-years. Incidence rates of gout per 1000 person-years for participants with and without CKD were 6.82 (95% CI 5.10 to 9.10) and 2.43 (2.18 to 2.71), respectively. In multivariable Cox models, CKD was associated with gout, with a HR of 1.88 (1.13 to 3.13) among men and 2.31 (1.25 to 4.24) among women. Additional analyses using alternate definitions for CKD and cross-sectional study did not change the results. Sensitivity analysis suggested that the observed findings might be an underestimate of the true relative risk.

CONCLUSIONS

The present study provides epidemiological evidence to support the notion that CKD is a risk factor for gout.

Associations of the uric acid related genetic variants in SLC2A9 and ABCG2 loci with coronary heart disease risk

Background

Multiple studies investigated the associations between serum uric acid and coronary heart disease (CHD) risk. However, further investigations still remain to be carried out to determine whether there exists a causal relationship between them. We aim to explore the associations between genetic variants in uric acid related loci of SLC2A9 and ABCG2 and CHD risk in a Chinese population.

Results

A case–control study including 1,146 CHD cases and 1,146 controls was conducted. Association analysis between two uric acid related variants (SNP rs11722228 in SLC2A9 and rs4148152 in ABCG2) and CHD risk was performed by logistic regression model. Adjusted odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. Compared with subjects with A allele of rs4148152, those with G allele had a decreased CHD risk and the association remained significant in a multivariate model. However, it altered to null when BMI was added into the model. No significant association was observed between rs11722228 and CHD risk. The distribution of CHD risk factors was not significantly different among different genotypes of both SNPs. Among subjects who did not consume alcohol, the G allele of rs4148152 showed a moderate protective effect. However, no significant interactions were observed between SNP by CHD risk factors on CHD risk.

Conclusions

There might be no association between the two uric acid related SNPs with CHD risk. Further studies were warranted to validate these results.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-015-0162-7) contains supplementary material, which is available to authorized users.

Interaction of inflammation, hyperuricemia, and the prevalence of hypertension among adults free of metabolic syndrome: NHANES 2009-2010

Background

Hyperuricemia and markers of inflammation are correlated with the risk for hypertension. Whether hyperuricemia has any impact on the association between C‐reactive protein (CRP) and hypertension is not known.

Methods and Results

We analyzed cross‐sectional data from the National Health and Nutrition Examination Survey, 2009–2010, using ordinary least squares and logistic regression models. Those who met the criteria for metabolic syndrome, had self‐reported gout, or were <20 years old were excluded. For each 1‐SD increase in serum urate, the serum CRP concentration was 20% higher in unadjusted linear regression models and 13% higher in multivariable linear regression models, after accounting for the effects of age, sex, race, socioeconomic and educational strata, renal function, lipids, smoking, and body mass index. In multivariable models adjusting for the same covariates, hyperuricemia was associated with hypertension with an odds ratio of 2.21 (1.71 to 2.85). When analyzed separately, this was observed in men and women. In multivariable analyses of the overall sample, elevated CRP levels were not associated with hypertension.

Conclusions

Among adults free of metabolic syndrome, elevated uric acid, but not elevated CRP, is independently associated with prevalent hypertension.

Chronic kidney disease and the risk of incident gout among middle-aged men: a seven-year prospective observational study

OBJECTIVE

The kidney is the major organ that facilitates excretion of urate in humans. Surprisingly, few studies have assessed whether a reduced glomerular filtration rate (GFR) and/or kidney damage is associated with a higher incidence of gout, and this study was undertaken to address this question.

METHODS

Data from a 7-year followup of patients enrolled in the Multiple Risk Factor Intervention Trial, a primary prevention trial for cardiovascular disease among 12,866 men ages 35-57 years, were used for the present investigation. Presence of gout was determined by the study physicians from the original trial. Chronic kidney disease was defined using criteria similar to those proposed by the National Kidney Foundation. The Cox proportional hazards regression model was used to assess the association between gout and chronic kidney disease, after accounting for the effects of potential confounders.

RESULTS

Overall, there were 722 cases of physician- diagnosed incident gout over 76,602 person-years of followup. The standardized incidence ratio of gout among those with chronic kidney disease was 1,217 (95% confidence interval [95% CI] 1,191-1,244). The adjusted hazard ratio (HR) among those with chronic kidney disease was 1.61 (95% CI 1.60-1.61). Each standard deviation decline in the estimated GFR was associated with an HR of 1.43 (95% CI 1.35-1.51). Including the serum urate level, as well as the urate-chronic kidney disease interaction term, as variables in the second analysis did not attenuate the HR. Proteinuria and hematuria, two markers of kidney damage, were associated with an elevated risk of gout independent of the estimated GFR.

CONCLUSION

Chronic kidney disease manifesting as reduced glomerular function or as presence of blood or protein in the urine increases the risk of incident gout.

Effect of pegloticase on renal function in patients with chronic kidney disease: a post hoc subgroup analysis of 2 randomized, placebo-controlled, phase 3 clinical trials

BACKGROUND

Pegloticase is approved in the US for treatment of refractory chronic gout. Since chronic kidney disease (CKD) is common in these patients, we conducted a post-hoc analysis of 2 replicate phase 3 trials and the subsequent open-label extension study to determine the effects of pegloticase on renal function in patients with CKD stages 3 and 4, as well as the effects of renal dysfunction on pegloticase efficacy and safety.

FINDINGS

Patients with renal insufficiency were randomized to pegloticase 8 mg every 2 weeks (n = 42), pegloticase 8 mg every 4 weeks (n = 41), or placebo (n = 20) for 6 months as defined by the study protocols. Renal function was assessed by estimated glomerular filtration rate (eGFR). All patients completing the randomized trials could participate in an open-label extension study for a further 2.5 years. Uric acid response, the primary end point in the trials, was plasma uric acid <6.0 mg/dl for 80% of months 3 and 6.Mean eGFR in both pegloticase dosing cohorts remained constant over the randomized treatment phase and long-term open-label extension study. The number of patients achieving uric acid response was similar across CKD stages (32% stage 1, 23% stage 2, 35% stage 3, and 39% stage 4, respectively, P = 0.3). There was no difference in the pegloticase safety profile based on CKD stage.

CONCLUSIONS

Pegloticase treatment does not impact eGFR in CKD patients and response to pegloticase is independent of CKD stage.

TRIAL REGISTRATION

Clinical trial identifier: NCT00325195.

Adherence to antihypertensive agents improves risk reduction of end-stage renal disease

Uncontrolled hypertension is associated with an increased risk of end-stage renal disease (ESRD). Intensified blood pressure control may slow progression of chronic kidney disease; however, the impact of antihypertensive agent adherence on the prevention of ESRD has never been evaluated. Here we assessed the impact of antihypertensive agent adherence on the risk of ESRD in 185,476 patients in the RAMQ databases age 45 to 85 and newly diagnosed/treated for hypertension between 1999 and 2007. A case cohort study design was used to assess the risk of and multivariate Cox proportional models were used to estimate the adjusted hazard ratio of ESRD. Adherence level was reported as a medication possession ratio. Mean patient age was 63 years, 42.2% male, 14.0% diabetic, 30.3% dyslipidemic, and mean follow-up was 5.1 years. A high adherence level of 80% or more to antihypertensive agent(s) compared to a lower one was related to a risk reduction of ESRD (hazard ratio 0.67; 95% confidence intervals 0.54-0.83). Sensitivity analysis revealed that the effect is mainly in those without chronic kidney disease. Risk factors for ESRD were male, diabetes, peripheral artery disease, chronic heart failure, gout, previous chronic kidney disease, and use of more than one agent. Thus, our study suggests that a better adherence to antihypertensive agents is related to a risk reduction of ESRD and this adherence needs to be improved to optimize benefits.

Serum urate and incidence of kidney disease among veterans with gout

OBJECTIVE

To study the association between serum urate level (sUA) and the risk of incident kidney disease among US veterans with gouty arthritis.

METHODS

From 2002 through 2011 adult male patients with gout who were free of kidney disease were identified in the data from the Veterans Administration VISN 16 database and were followed until incidence of kidney disease, death, or the last available observation. Accumulated hazard curves for time to kidney disease were estimated for patients with average sUA levels > 7 mg/dl (high) versus ≤ 7 mg/dl (low) based on Kaplan-Meier analyses; and statistical comparison was conducted using a log-rank test. A Cox proportional hazard model with time-varying covariates was used to estimate the unadjusted and adjusted hazard ratios for kidney disease.

RESULTS

Eligible patients (n = 2116) were mostly white (53%), with average age 62.6 years, mean body mass index 31.2 kg/m(2), and high baseline prevalence of hypertension (93%), hyperlipidemia (67%), and diabetes (20%). Mean followup time was 6.5 years. The estimated rates of all incident kidney disease in the overall low versus high sUA groups were 2% versus 4% at Year 1, 3% versus 6% at Year 2, and 5% versus 9% at Year 3, respectively (p < 0.0001). After adjustment, high sUA continued to predict a significantly higher risk of kidney disease development (HR 1.43, 95% CI 1.20-1.70).

CONCLUSION

Male veterans with gout and sUA levels > 7 mg/dl had an increased incidence of kidney disease.

Polydatin ameliorates renal injury by attenuating oxidative stress-related inflammatory responses in fructose-induced urate nephropathic mice

A series of studies have recently demonstrated that the oxidative stress, nuclear factor-kappa B (NF-κB) activation and the subsequent coordinated inflammatory responses played an important role in the pathogenesis of urate nephropathy (UN). Polydatin has been suggested to have the properties of anti-oxidative, anti-inflammatory and nephroprotective effects. However, the possible protective and beneficial effects of polydatin on UN are not fully elucidated. Therefore, we investigated the potential beneficial effects and possible mechanisms of polydatin on UN. In this study, polydatin showed inhibitory activities on xanthine oxidase to repress the level of serum uric acid in vivo and in vitro. Further investigations revealed that polydatin displayed little toxic effects and significantly ameliorated the renal function in fructose-induced UN mice. The nephroprotective activities of polydatin was not only due to the effects on remarkably attenuating the oxidative stress induced by uric acid, but also on markedly suppressing the oxidative stress-related inflammatory cascade, including decreasing the expressions of NF-κB p65, COX-2 and iNOS proteins and inhibiting the productions of TNF-α, PGE(2) and IL-1β. These findings elucidated that polydatin exhibited prominent nephroprotective activities and low toxic effects.

Genetic disorders resulting in hyper- or hypouricemia

Serum uric acid concentrations are governed by the balance of urate production and excretion. Besides well-known secondary causes of hyperuricemia, such as myeloproliferative diseases, decreased renal function, and excessive dietary purine intake, there are a number of genetic disorders that result in hyper- or hypouricemia. Renal impairment in these disorders may be associated with the development of chronic kidney disease, acute kidney injury, or urate nephrolithiasis. These conditions are frequently misdiagnosed, not because the diagnosis is complicated and difficult to ascertain, but rather because of a lack of awareness of the particular condition. The first important step in the diagnosis is obtaining a detailed family history, with evaluation of serum and urinary urate concentrations. This review will aid physicians in identifying these inherited kidney disorders associated with hyperuricemia and hypouricemia. Identification of these conditions will help to explain the pathogenesis of different types of gout, and may extend insights into the urate transport and chronic kidney disease.

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.

Increased prevalence of simple renal cysts in patients with gout

The aim of this study was to determine the prevalence of simple renal cysts in gout patients and evaluate associated risk factors for its development. Hundred and forty-six patients followed at our outpatient Gout Unit and 47 sex- and age-matched healthy kidney donors who had undergone routine renal ultrasonography, using a static gray scale and real-time B-mode units with a 3.5- or 5.0-MHz transducer, were evaluated for the presence of renal cysts. Demographic and clinical characteristics of gout patients were evaluated considering possible risk factors for the occurrence of simple renal cysts such as age, male gender, hypertension, and renal impairment. The prevalence of simple renal cyst was 26.0 % in gout patients and 10.6 % in control group (P = 0.045). Gout patients with simple renal cysts presented less renal lithiasis than those without this complication (5.2 vs 25.9 %; P = 0.003) in spite of an overall higher frequency of renal stones in gout patients compared to control group (20.5 vs. 6.3 %, P = 0.025). The presence of simple renal cyst in gout was not associated with previously reported factors such as age (P = 0.296), male predominance (P = 0.688), hypertension (P = 0.314), and renal impairment (P = 254). Moreover, no association with disease duration (P = 0.843) or tophi (P = 0.616) was observed. In conclusion, gout patients have an increased prevalence of simple renal cysts associated with a lower occurrence of nephrolithiasis. Whether renal cysts have any protective effect in the development of nephrolithiasis in gout remains to be determined.

Chronic kidney disease in gout in a managed care setting

Background

To study the prevalence of chronic kidney disease (CKD) and its impact on allopurinol dosing and uric acid control among patients with gout.

Methods

This was a retrospective study using data from a large US health plan. Claims and laboratory data were analyzed for enrollees from the health plan database from January 2002 through December 2005. Patients with gout were identified from pharmacy and medical claims data based on the presence of codes for gout medication or gout diagnosis. Severity of CKD was determined using the estimated glomerular filtration rate (eGFR). Allopurinol titration was defined as a change in average daily dose from first prescription to last prescription of ≥ 50 mg.

Results

A total of 3,929 patients were identified for inclusion in this study, 39% of whom had CKD (based on having an eGFR < 90 mL/min/1.73 m²). Subjects with CKD were older (p < 0.01) and more likely to be women (p < 0.01), had a greater number of comorbid conditions (p < 0.01), and were more likely to be prescribed allopurinol (p < 0.01) compared to those with no CKD. The average starting dose of allopurinol was lower among those with CKD, and it decreased with worsening kidney function. Among the 3,122 gout patients who used allopurinol, only 25.6% without CKD and 22.2% with CKD achieved a serum uric acid concentration of < 6.0 mg/dL (p = 0.0409). Also, only 15% of allopurinol users had an upward dose titration (by ≥50 mg), but the average increase in dose did not differ significantly between those with and without CKD.

Conclusions

About two out of every five patients with gout in this population had CKD. Allopurinol doses were not adjusted in the majority of CKD patients. Serum uric acid control in gout was poor among patients without CKD and even worse among those with CKD.

A genome-wide association study of serum uric acid in African Americans

Background

Uric acid is the primary byproduct of purine metabolism. Hyperuricemia is associated with body mass index (BMI), sex, and multiple complex diseases including gout, hypertension (HTN), renal disease, and type 2 diabetes (T2D). Multiple genome-wide association studies (GWAS) in individuals of European ancestry (EA) have reported associations between serum uric acid levels (SUAL) and specific genomic loci. The purposes of this study were: 1) to replicate major signals reported in EA populations; and 2) to use the weak LD pattern in African ancestry population to better localize (fine-map) reported loci and 3) to explore the identification of novel findings cognizant of the moderate sample size.

Methods

African American (AA) participants (n = 1,017) from the Howard University Family Study were included in this study. Genotyping was performed using the Affymetrix^® Genome-wide Human SNP Array 6.0. Imputation was performed using MACH and the HapMap reference panels for CEU and YRI. A total of 2,400,542 single nucleotide polymorphisms (SNPs) were assessed for association with serum uric acid under the additive genetic model with adjustment for age, sex, BMI, glomerular filtration rate, HTN, T2D, and the top two principal components identified in the assessment of admixture and population stratification.

Results

Four variants in the gene SLC2A9 achieved genome-wide significance for association with SUAL (p-values ranging from 8.88 × 10^-9 to 1.38 × 10^-9). Fine-mapping of the SLC2A9 signals identified a 263 kb interval of linkage disequilibrium in the HapMap CEU sample. This interval was reduced to 37 kb in our AA and the HapMap YRI samples.

Conclusions

The most strongly associated locus for SUAL in EA populations was also the most strongly associated locus in this AA sample. This finding provides evidence for the role of SLC2A9 in uric acid metabolism across human populations. Additionally, our findings demonstrate the utility of following-up EA populations GWAS signals in African-ancestry populations with weaker linkage disequilibrium.

The effect of a one-year weight reduction program on serum uric acid in overweight/obese children and adolescents

BACKGROUND

Hyperuricemia may underlie obesity and related disorders, but the impact of weight reduction and metformin on serum uric acid (sUA) in Caucasian children/adolescents is unknown.

METHODS

One hundred and thirteen children/adolescents were enrolled (83 completed) into 1-year weight reduction program (diet+exercise) without or with metformin. Anthropometric and biochemical measurements were conducted at baseline and at the end of follow-up (13 ± 3 months).

RESULTS

sUA decreased in 86% females and 67% males. Significantly more patients substantially (≥ 10%) reduced their sUA than body mass index (BMI)%. In females, sUA decreased regardless of type of intervention, but more markedly in the metformin group, and ΔsUA correlated positively with ΔBMI%, ΔWHtR (waist-to-height ratio), Δinsulin, ΔHOMA (homeostasis model of assessment), and Δtriglycerides/high density lipoprotein (HDL), but correlated negatively with baseline sUA, HOMA, insulin, and triglycerides/HDL. Of these, metformin treatment, baseline sUA, and ΔBMI% were independent predictors of sUA reduction, explaining 77% of data variability. In males, sUA reduction was significant in the metformin group only, and negatively correlated with ΔWHR (waist-to-hip ratio), ΔWHtR, Δleptin, baseline sUA, and waist circumference. Of these, baseline sUA and ΔBMI% were independent predictors of sUA reduction, explaining 69% of data variability. Except for sUA, females reduced their BMI%, waist circumference, triglycerides, triglycerides/HDL and increased HDL, while males reduced total cholesterol.

CONCLUSIONS

A longitudinal weight reduction program encompassing diet/exercise with or without metformin was more efficient in reducing sUA than weight and its effect on sUA and other metabolic parameters differed between genders. Weight loss did not condition sUA reduction, which was strongly dependent on baseline levels. The sUA reducing effects of metformin may contribute to its effects on blood pressure-lowering and endothelial function-improving properties in females.

New and improved strategies for the treatment of gout

The Western world appears to be in the midst of the third great gout epidemic of all time. In this century, gout is increasing in prevalence despite an increased understanding of its risk factors and pathophysiology, and the availability of reasonably effective treatment. The main cultural factors responsible for this appear to be diet, obesity, ethanol use and medications. Excess fructose consumption is a newly recognized modifiable risk factor. The debate has been renewed concerning hyperuricemia as an independent risk factor for renal insufficiency and cardiovascular disease. Prevention is still rooted in lifestyle choices. Existing treatments have proven to be unsatisfactory in many patients with comorbidities. New treatments are available today and on the horizon for tomorrow, which offer a better quality of life for gout sufferers. These include febuxostat, a nonpurine inhibitor of xanthine oxidase with a potentially better combination of efficacy and safety than allopurinol, and investigational inhibitors of URAT-1, an anion exchanger in the proximal tubule that is critical for uric acid homeostasis. New abortive treatments include interleukin-1 antagonists that can cut short the acute attack in 1 to 2 days in persons who cannot take nonsteroidal anti-inflammatory drugs, colchicine or corticosteroids. Lastly, newer formulations of uricase have the ability to dissolve destructive tophi over weeks or months in patients who cannot use currently available hypouricemic agents. Diagnostically, ultrasound and magnetic resonance imaging offer advanced ways to diagnose gout noninvasively, and just as importantly, a way to follow the progress of tophus dissolution. The close association of hyperuricemia with metabolic syndrome, hypertension and renal insufficiency ensures that nephrologists will see increasing numbers of gout-afflicted patients.

Relative efficacy of casein or soya protein combined with palm or safflower-seed oil on hyperuricaemia in rats

Diets that ameliorate the adverse effects of uric acid (UA) on renal damage deserve attention. The effects of casein or soya protein combined with palm or safflower-seed oil on various serum parameters and renal histology were investigated on hyperuricaemic rats. Male Wistar rats administered with oxonic acid and UA to induce hyperuricaemia were fed with casein or soya protein plus palm- or safflower-seed oil-supplemented diets. Normal rats and hyperuricaemic rats with or without allopurinol treatment (150 mg/l in drinking water) were fed with casein plus maize oil-supplemented diets. After 8 weeks, allopurinol treatment and soya protein plus safflower-seed oil-supplemented diet significantly decreased serum UA in hyperuricaemic rats (one-way ANOVA; P < 0.05). In addition, soya protein and casein attenuated hyperuricaemia-induced decreases in serum albumin and insulin, respectively (two-way ANOVA; P < 0.05). Safflower-seed oil significantly decreased serum TAG and UA, whereas palm oil significantly increased serum cholesterol, TAG, blood urea N and creatinine. However, soya protein significantly decreased renal NO and nitrotyrosine and palm oil significantly decreased renal nitrotyrosine, TNF-alpha and interferon-gamma and increased renal transforming growth factor-beta. Casein with safflower-seed oil significantly attenuated renal tubulointerstitial nephritis, crystals and fibrosis. Comparing casein v. soya protein combined with palm or safflower-seed oil, the results support that casein with safflower-seed oil may be effective in attenuating hyperuricaemia-associated renal damage, while soya protein with safflower-seed oil may be beneficial in lowering serum UA and TAG.

Clustering of other metabolic risk factors in subjects with metabolic syndrome

Various anthropometric indices have been proposed for metabolic syndrome. We investigated the clustering of metabolic risk factors other than components of metabolic syndrome and physical activity in subjects with and without metabolic syndrome as defined by different anthropometric indices. The subjects comprised 6141 men and 2137 women who underwent routine health examinations in Tokyo. We compared metabolic risk factors (high low-density lipoprotein cholesterol, hyperuricemia, high gamma-glutamyltransferase, fatty liver) and sedentary history in subjects with and without metabolic syndrome as defined by the American Heart Association by substituting various proposed anthropometric indices of abdominal obesity (waist circumference >or=85, >or=90, or >or=102 cm for men and >or=90, >or=80, or >or=88 cm for women; waist-to-height ratio >or=0.5 for both men and women). Irrespective of the anthropometric index or sex, the age-adjusted odds ratios for risk factors and sedentary history were all significantly greater in subjects with metabolic syndrome (men and women: 1.26 approximately 1.35 and 2.06 approximately 2.63 for high low-density lipoprotein cholesterol, 2.36 approximately 2.60 and 3.88 approximately 7.20 for hyperuricemia, 2.54 approximately 3.02 and 2.92 approximately 4.05 for high gamma-glutamyltransferase, 4.42 approximately 4.87 and 9.43 approximately 12.27 for fatty liver, and 1.37 approximately 1.50 and 1.43 approximately 1.72 for sedentary history). Findings still persisted in those not receiving medication for diabetes mellitus or coronary heart disease. Therefore, attention should be paid to other metabolic risk factors in subjects with metabolic syndrome, irrespective of the anthropometric index or sex. Further study is also needed to clarify the most appropriate definition of metabolic syndrome so as to include the spectrum of risk factors that best represents the future risk of cardiovascular and other diseases.

Inflammation, oxidative stress and lipids: the risk triad for atherosclerosis in gout

For many years, the relationship between cardiovascular disease risk and gout, though strong and consistent, was suspected of being coincidental rather than causative. In recent years, compelling epidemiological and clinical data have increasingly favoured an aetiological connection. However, that connection is notably complex, involving a multifaceted model that includes interactions between inflammatory processes, oxidative stress and potential genetic influences, as well as cardiovascular and renal components that remain only partly explained. Urate appears to be able to activate the immune response, and in that context has a mediating role in the inflammatory process via the inflammasome. This interaction of urate and inflammation is central to the inflammatory cascade associated with gout flares. In the arena of oxidative stress, urate has both antioxidant and pro-oxidant properties, and while potentially beneficial in scavenging free radicals, it can also impair endothelial function and thereby give rise to atherosclerotic risk. Human and animal studies have revealed associations between hyperuricaemia and a host of atherosclerotic risk factors, whereas a reduction in urate levels is frequently associated with improvement or even resolution of such risk factors. The degree to which reduction of serum urate can reliably improve cardiovascular risk remains uncertain. It is hoped that the introduction of newer urate-lowering agents may help to clarify this picture and improve treatment options for both gout and atherosclerosis.

Update on gout and hyperuricemia

There have been recent advances in the understanding of underlying mechanisms and treatment of gout and chronic hyperuricemia, making this an important time to review the current state of the disease. The goal of this article is to provide a practical review of the current standard of care as well as discuss some new developments in the management. There is an increasing prevalence of gout and hyperuricemia worldwide. Gout confers a significant individual and societal burden and is often under-treated. Appropriate diagnosis and treatment of acute gout should be followed by aggressive and goal-oriented treatment of hyperuricemia and other risk factors. Allopurinol remains as a first-line treatment for chronic hyperuricemia, but uricosuric agents may also be considered in some patients. Febuxostat, a non-purine xanthine-oxidase inhibitor, is a new agent approved for the treatment of hyperuricemia in patients with gout, which may be used when allopurinol is contraindicated. Gout and hyperuricemia appear to be independent risk factors for incident hypertension, renal disease and cardiovascular disease. Physicians should consider cardiovascular risk factors in patients with gout and treat them appropriately and aggressively.

Gout

Gout is a common arthritis caused by deposition of monosodium urate crystals within joints after chronic hyperuricaemia. It affects 1-2% of adults in developed countries, where it is the most common inflammatory arthritis in men. Epidemiological data are consistent with a rise in prevalence of gout. Diet and genetic polymorphisms of renal transporters of urate seem to be the main causal factors of primary gout. Gout and hyperuricaemia are associated with hypertension, diabetes mellitus, metabolic syndrome, and renal and cardiovascular diseases. Non-steroidal anti-inflammatory drugs and colchicine remain the most widely recommended drugs to treat acute attacks. Oral corticosteroids could be an alternative to these drugs. Interleukin 1beta is a pivotal mediator of acute gout and could become a therapeutic target. When serum uric acid concentrations are lowered below monosodium urate saturation point, the crystals dissolve and gout can be cured. Patient education, appropriate lifestyle advice, and treatment of comorbidities are an important part of management of patients with gout.

Hyperuricemia and incident heart failure

BACKGROUND

Hyperuricemia, a known correlate of oxidative stress, is a marker for adverse prognosis among individuals with heart failure. However, the relationship between hyperuricemia and the risk for incidence of heart failure in a community-based population has not been studied.

METHODS AND RESULTS

We prospectively analyzed the relationship between serum uric acid concentration at baseline and subsequent heart failure among the participants of the Framingham Offspring cohort (n=4912; mean baseline age, 36 years; 52% women). By using Cox regressions, we calculated the risk of heart failure with increasing serum uric acid after adjusting for sex, age, smoking, body mass index, renal dysfunction, diuretics, systolic blood pressure, valvular heart disease, diabetes, alcohol, and use of antihypertensive medications. The incidence rates of heart failure were approximately 6-fold higher among those at the highest quartile of serum uric acid (>6.3 mg/dL) compared with those at the lowest quartile (<3.4 mg/dL). The adjusted hazard ratio for the highest quartile of serum uric acid compared with the lowest was 2.1 (1.04 to 4.22). The relationship between hyperuricemia and heart failure was found in participants without metabolic syndrome and other subgroups as well.

CONCLUSIONS

Hyperuricemia is a novel, independent risk factor for heart failure in a group of young general community dwellers. This has implications for development of preventive strategies for heart failure.

Uric acid is a strong independent predictor of renal dysfunction in patients with rheumatoid arthritis

Introduction

Recent evidence suggests that uric acid (UA), regardless of crystal deposition, may play a direct pathogenic role in renal disease. We have shown that UA is an independent predictor of hypertension and cardiovascular disease (CVD), and that CVD risk factors associate with renal dysfunction, in patients with rheumatoid arthritis (RA). In this study we investigated whether UA associates with renal dysfunction in patients with RA and whether such an association is independent or mediated through other comorbidities or risk factors for renal impairment.

Methods

Renal function was assessed in 350 consecutive RA patients by estimated glomerular filtration rate (GFR) using the six-variable Modification of Diet in Renal Disease equation. Risk factors for renal dysfunction were recorded or measured in all participants. Linear regression was used to test the independence of the association between GFR and UA.

Results

Univariable analysis revealed significant associations between GFR and age, systolic blood pressure, total cholesterol, triglycerides, RA duration and UA. UA had the most powerful association with renal dysfunction (r = -0.45, P < 0.001). A basic model was created, incorporating all of the above parameters along with body mass index and gender. UA ranked as the first correlate of GFR (P < 0.001) followed by age. Adjustments for the use of medications (diuretics, low-dose aspirin, cyclooxygenase II inhibitors and nonsteroidal anti-inflammatory drugs) and further adjustment for markers of inflammation and insulin resistance did not change the results.

Conclusions

UA is a strong correlate of renal dysfunction in RA patients. Further studies are needed to address the exact causes and clinical implications of this new finding. RA patients with elevated UA may require screening for renal dysfunction and appropriate management.

Serum uric acid level as an independent risk factor for all-cause, cardiovascular, and ischemic stroke mortality: a Chinese cohort study

OBJECTIVE

The association between hyperuricemia and cardiovascular events has been documented in high-risk groups, but is still undetermined in general populations, especially Chinese. This study assessed the temporal association between serum uric acid level, hyperuricemia, and cardiovascular mortality.

METHODS

A prospective cohort study of 41,879 men and 48,514 women ages > or = 35 years was conducted using data from the MJ Health Screening Centers in Taiwan. Mortality from all causes, total cardiovascular disease (CVD), ischemic stroke, congestive heart failure, hypertensive disease, and coronary heart disease were compared according to increasing serum uric acid levels.

RESULTS

A total of 1,151 (21.2%) events of 5,427 total deaths were ascribed to CVD (mean followup 8.2 years). Hazard ratios (HRs) for hyperuricemia (serum uric acid level >7 mg/dl) were estimated with Cox regression model after adjusting for age, sex, body mass index, cholesterol, triglycerides, diabetes, hypertension, heavy cigarette smoking, and frequent alcohol consumption. In all patients, HRs were 1.16 (P < 0.001) for all-cause mortality, 1.39 (P < 0.001) for total CVD, and 1.35 (P = 0.02) for ischemic stroke. In subgroup analysis, the HRs for cardiovascular risk remained significant in patients with hypertension (1.44, P < 0.001) and in patients with diabetes (1.64, P < 0.001). In addition, in a low metabolic risk subgroup, the HRs for all-cause mortality and total cardiovascular morbidity were 1.24 (P = 0.02) and 1.48 (P = 0.16), respectively.

CONCLUSION

Hyperuricemia was an independent risk factor of mortality from all causes, total CVD, and ischemic stroke in the Taiwanese general population, in high-risk groups, and potentially in low-risk groups.