Fifty-nine patients with primary gout were treated with either a combination of colchicine and allopurinol or colchicine alone. Assessments of renal function over 2 years revealed a statistically significant fall of glomerular filtration rate an urine concentrating ability in those receiving only colchicine. The renal function of patients given allopurinol did not change. Treatment with allopurinol resulted ina significant reduction of ammonium excretion, a phenomenon which could not be readily explained. Urate clearance also declined during allopurinol treatment, and the impaired urate clearance associated with gout became more evident. The most important observation was that allopurinol retarded an apparent decline of renal function. Presumably this was achieved through its hypouricaemic effect and implies that the hyperuricaemia of gouty patients is deleterious to the kidneys.
Gout is a common disease caused by hyperuricemia, which shows elevated serum uric acid (SUA) levels. From a viewpoint of urate handling in humans, gout patients can be divided into those with renal overload (ROL) gout with intestinal urate underexcretion, and those with renal underexcretion (RUE) gout. Recent genome-wide association studies (GWAS) revealed an association between SUA and a variant in human monocarboxylate transporter 9 (MCT9/SLC16A9) gene. Although the function of MCT9 remains unclear, urate is mostly excreted via intestine and kidney where MCT9 expression is observed. In this study, we investigated the relationship between a variant of MCT9 and gout in 545 patients and 1,115 healthy volunteers. A missense variant of MCT9 (K258T), rs2242206, significantly increased the risk of ROL gout (p = 0.012), with odds ratio (OR) of 1.28, although it revealed no significant association with all gout cases (p = 0.10), non-ROL gout cases (p = 0.83), and RUE gout cases (p = 0.34). In any case groups and the control group, minor allele frequencies of rs2242206 were >0.40. Therefore, rs2242206 is a common missense variant and is revealed to have an association with ROL gout, indicating that rs2242206 relates to decreased intestinal urate excretion rather than decreased renal urate excretion. Our study provides clues to better understand the pathophysiology of gout as well as the physiological roles of MCT9.
Gouty arthritis; Single nucleotide polymorphism (SNP); Gut urate excretion; Carnitine; Solute carrier (SLC) family transporter
Serum creatinine level is the most commonly used indices for assessment of glomerular filtration rate (GFR), even though these indices have been shown to have some limitations in clinical practice. We investigated the diagnostic efficacy of serum cystatin C compared to that of serum creatinine levels and identified the relating factors associated with changes in serum cystatin C levels in gout patients with renal impairment. A total of 68 gouty patients with renal impairment were enrolled in this study. Diagnostic efficacy of serum cystatin C levels was evaluated through non-parametric receiver operating characteristic (ROC) analysis. The risk factors for changes in serum cystatin C levels were confirmed using multivariate regression analysis. With 24-hr urine creatinine clearance (Ccr) as the reference for GFR, 1/cystatin C (r=0.702, P<0.001) showed a significantly higher correlation with Ccr than 1/creatinine (r=0.665, P<0.001). Multivariate correlation analysis demonstrated that the clinical parameters for increased serum cystatin C are a higher stage of chronic kidney disease, older age, use of allopurinol, and lower high density lipoprotein-cholesterol. The area under the curve (AUC) at ROC plots identified that of serum cystatin C was significantly greater than that of serum creatinine (AUC 0.804 of cystatin C and AUC 0.745 of creatinine). The study suggests that serum cystatin C is a reliable endogenous marker for the assessment of renal function or GFR in gout patients with renal impairment.
Cystatin C; Gout; Creatinine; Kidney Failure; Glomerular Filtration Rate
Allopurinol (4-hydroxypyrazolo (3,4-d)-pyrimidine) is a potent xanthine oxidase inhibitor which inhibits the oxidation of naturally occurring oxypurines, thus decreasing uric acid formation. The clinical and metabolic effects of this agent were studied in 80 subjects with primary and secondary gout and other disorders of uric acid metabolism. Allopurinol has been universally successful in lowering the serum uric acid concentration and uric acid excretion to normal levels, while not significantly affecting the clearance of urate or other aspects of renal function. Oxypurine excretion increased concomitantly with the fall in urine uric acid. The agent is particularly valuable in the management of problems of gout with azotemia, acute uric acid nephropathy and uric acid urolithiasis. The minor side effects, clinical indications and theoretical complications are discussed.
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.
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.
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.
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 21 year old man with a family history of gout and neurological deficits, developed severe idiopathic congestive cardiomyopathy after a long history of typical gouty attacks and neurological abnormalities. Clinical and laboratory evaluations showed borderline mental retardation, ataxia, sensorineural deafness, marked hyperuricaemia, and excessive uric acid excretion in the presence of impaired renal function. None of the known causes of cardiomyopathy was found. Even though red cell hypoxanthine guanine phosphoribosyltransferase enzyme activity was normal, this case probably represents an inborn error of purine metabolism. The association of cardiomyopathy with gout is very unusual. Previously it has been only once described in a single case.
OBJECTIVES—Insulin resistance (IR) has been increasingly implicated in the pathogenesis of gout. The lipoprotein abnormalities described in hyperuricaemic subjects are similar to those associated with IR, and insulin influences renal urate excretion. In this study it was investigated whether dietary measures, reported to be beneficial in IR, have serum uric acid (SU) and lipid lowering effects in gout.
METHODS—Thirteen non-diabetic men (median age 50, range 38-62) were enrolled. Each patient had had at least two gouty attacks during the four months before enrolment. Dietary recommendations consisted of calorie restriction to 6690 kJ (1600 kcal) a day with 40% derived from carbohydrate, 30% from protein, and 30% from fat; replacement of refined carbohydrates with complex ones and saturated fats with mono- and polyunsaturated ones. At onset and after 16 weeks, fasting blood samples were taken for determination of SU, serum cholesterol (C), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), and triglycerides (TGs). Results were expressed as median (SD).
RESULTS—At onset, the body mass index (BMI) was 30.5 (8.1) kg/m2. Dietary measures resulted in weight loss of 7.7 (5.4) kg (p=0.002) and a decrease in the frequency of monthly attacks from 2.1 (0.8) to 0.6 (0.7) (p=0.002). The SU decreased from 0.57 (0.10) to 0.47 (0.09) mmol/l (p=0.001) and normalised in 7 (58%) of the 12 patients with an initially raised level. Serum cholesterol decreased from 6.0 (1.7) to 4.7 (0.9) mmol/l (p=0.002), LDL-C from 3.5 (1.2) to 2.7 (0.8) mmol/l (p=0.004), TGs from 4.7 (4.2) to 1.9 (1.0) mmol/l (p=0.001), and C:HDL-C ratios from 6.7 (1.7) to 5.2 (1.0) (p=0.002). HDL-C levels increased insignificantly. High baseline SU, frequency of attacks, total cholesterol, LDL-C and TG levels, and total C:HDL-C ratios correlated with higher decreases in the respective variables upon dietary intervention (p<0.05).
CONCLUSION—The results suggest that weight reduction associated with a change in proportional macronutrient intake, as recently recommended in IR, is beneficial, reducing the SU levels and dyslipidaemia in gout. Current dietary recommendations for gout may need re-evaluation.
Fifteen patients with clinical gout occurring after long term treatment with diuretics were studied retrospectively. In all 15 patients one or more additional factors were present which might have contributed to the hyperuricaemia and gout. The most common of these was the impairment of the glomerular filtration rate. Twenty five other patients receiving long term treatment with diuretics who did not have gout were also studied. The concentrations of uric acid, urea, and creatinine were, in general, markedly lower in these patients than in those who had developed gout. It is concluded that diuretic induced gout occurs in patients in whom there is an additional cause of hyperuricaemia, usually impaired renal function.
Measurement of the plasma free amino acids by column chromatography (AutoAnalyzer) in 32 patients with primary gout showed statistically significant increases or decreases in several components when compared with the spectrum in 18 control subjects, but the absolute amounts involved were small and the mean total plasma amino acid concentrations in both groups were the same. In the urine all major amino acid components, notably glutamine, serine, threonine, and leucine, were lower in our gouty than in our nongouty subjects, as were also the corresponding renal clearance ratios. These deficits could be reproduced by restricting dietary protein, so appear to be due largely to the some-what reduced mean dietary protein intake of our gouty subjects. However, the low renal clearance of glutamine, the most striking and consistent of the deficits in urinary amino acids noted, could not be accounted for by dietary or other relevant factors, and is interpreted as indicating increased tubular reabsorption of glutamine in primary gout. This interpretation was supported by the results of glutamine loading. The possible compensatory relationship of the abnormality in renal handling of glutamine to the deficiency in renal production of ammonia previously reported is discussed.
The prevalence of gout is increasing with increased life expectancy. Approximately half of the patients with gout have some degree of renal impairment. If both conditions persistently coexist, and in severe tophaceous gout, in particular, treatment has been difficult. We here report on the case of an 87-year-old woman, who had been suffering from recurrent gouty arthritis over 4 years. Monthly polyarthritis attacks were accompanied by subcutaneous tophi. Serum uric acid levels were constantly above 600 μmol/L (10 mg/dL). Allopurinol was no option because of intolerance, while benzbromarone was ineffective because of renal impairment. Therefore, the novel xanthin oxidase inhibitor febuxostat was started, achieving rapid control of serum urate levels (<360 μmol/L). After initial worsening of inflammation in the first weeks, gouty attacks stopped and all tophi resolved within the following 10 months. Renal function remained stable.
Under inpatient controlled conditions 4 patients with gout and hypertension were treated with varying doses of tienilic acid, a new uricosuric diuretic. Plasma urate levels were reduced by an average of 50% in association with significantly increased urinary urate excretion. A twice-daily regimen was considerably more effective than a single morning dosage in reduction of plasma urate, though both regimens were equally effective in antihypertensive potency. The single daily regimen produced greater diurnal fluctuations in plasma urate and was more frequently associated with the development of acute gout attacks.
Hypercalcemia has been widely associated with granulomatous processes. This is due to enhanced extra-renal conversion of calcidiol to calcitriol by activated macrophages within the granuloma. Symptomatic hypercalcemia due to granulomatous disorders is not common, with the incidence in sarcoidosis ranging from 10–20%. Large aggregates of monosodium urate crystals in patients with longstanding chronic tophaceous gout can serve as the inciting antigen for the development of granuloma, but hypercalcemia has not been described in this context. We report a case of symptomatic hypercalcemia due to gouty tophi induced granulomatous inflammation. Long term treatment with immunosuppressants, in addition to bisphosphonates and uric acid lowering therapy, has led to stabilization of serum calcium levels and other lab parameters indicative of granulomatous burden.
A report of 20 cases of gout considered to be secondary to chronic renal disease is presented. Studies of renal function and of uric acid metabolism were carried out in 16 patients. The daily production of urate remained within normal limits in the face of progressive renal dysfunction. Renal excretion of uric acid was decreased to a mean of 35.5% of the turnover. The cumulative urinary recovery of intravenously injected 14C-uric acid averaged 32.0%. In 3 patients 14C was successively retrieved in urinary allantoinand urea, in carbon dioxide of expired air, and in faeces. As in normal man, carbon dioxide and ammonia were the principal uricolytic products. The extrarenal excretion of uric acid assumes a greater role in chronic renal disease and eventually becomes the major route of elimination of uric acid. The possibility that gout may be secondary to intrinsic renal disease should be entertained when azotaemia is present.
To study the prevalence of chronic kidney disease (CKD) and its impact on allopurinol dosing and uric acid control among patients with gout.
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.
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.
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.
In mammals, excess purine nucleosides are removed from the body by breakdown in the liver and excretion from the kidneys. Uric acid is the end product of purine metabolism in humans. Two-thirds of uric acid in the human body is normally excreted through the kidney, whereas one-third undergoes uricolysis (decomposition of uric acid) in the gut. Elevated serum uric acid levels result in gout and could be a risk factor for cardiovascular disease and diabetes. Recent studies have shown that human ATP-binding cassette transporter ABCG2 plays a role of renal excretion of uric acid. Two non-synonymous single nucleotide polymorphisms (SNPs), i.e., 421C>A (major) and 376C>T (minor), in the ABCG2 gene result in impaired transport activity, owing to ubiquitination-mediated proteosomal degradation and truncation of ABCG2, respectively. These genetic polymorphisms are associated with hyperuricemia and gout. Allele frequencies of those SNPs are significantly higher in Asian populations than they are in African and Caucasian populations. A rapid and isothermal genotyping method has been developed to detect the SNP 421C>A, where one drop of peripheral blood is sufficient for the detection. Development of simple genotyping methods would serve to improve prevention and early therapeutic intervention for high-risk individuals in personalized healthcare.
ABC transporter; ABCG2; gout; hyperuricemia; kidney; SNP; uric acid
In the majority of patients with gout and excessive uric acid production, underlying enzyme abnormalities have not been identified. In the present study, measurement of both the rate of generation and concentration of phosphoribosylpyrophosphate (PP-ribose-P) and the concentration of ribose-5-phosphate in cultured cells were undertaken to establish a classification of purine overproducers to direct study of additional enzyme defects. Fibroblasts were cultured from 24 individuals assigned to 4 groups: group 1, 5 normal controls; group 2, 5 patients with gout and normal dialy urinary uric acid excretion (gouty controls); group 3, 7 patients with well-defined enzyme abnormalities and excessive urinary acid excretion (4 with hypoxanthine-guanine phosphoribosyltransferase deficiency and 3 with excessive PP-ribose-P synthetase activity); and group 4, 7 patients with gout and excessive uric acid excretion but without grossly abnormal activities of the above enzymes in erythrocyte lysates. In all 14 fibroblast strains from patients showing excessive production of uric acid (groups 3 and 4), rates of purine synthesis de novo and PP-ribose-P concentrations exceeded values for cells from control groups. Cells from group 3 patients with hypoxanthine-guanine phosphoribosyltransferase deficiency showed normal PP-ribose-P generation, while those with excessive PP-ribose-P synthetase activity demonstrated increased generation of this regulatory substrate. All strains from group 3 patients had normal ribose-5-phosphate concentrations. Five cell strains from group 4 patients showed one of the two patterns of abnormalities in these measurements seen in strains from group 3 patients: two resembled hypoxanthine-guanine phosphoribosyltransferase-deficient cells, and three resembled cells with excessive PP-ribose-P synthetase activity. Analyses of erythrocyte enzyme preparations from two of these patients in group 4 have led to identification of a kinetic variant of each enzyme as predicted from the foregoing patterns. Two additional group 4 cell lines that showed increased ribose-5-phosphate concentrations in addition to increased PP-ribose-P concentrations and generation were classified in a separate subgroup, since in the individuals excessive purine synthesis appeared to result from increases ribose-5-phosphate concentration, leading to increased availability of PP-ribose-P. No abnormality in either hypoxanthine-guanine phosphoribosyltransferase or PP-ribose-P synthetase has been found in erythrocyte preparations from one patient so classified.
Gout is a metabolic disorder characterized by elevated uric acid levels in the body, associated with painful arthritis, tophi and nephropathy. The most frequently used pharmacologic urate lowering strategies involve reducing urate production with a xanthine oxidase inhibitor and enhancing urinary excretion of uric acid with a uricosuric agent. Urate lowering agents are limited in number, availability and effectiveness. The emergence of a new medication, febuxostat, to lower serum urate levels is welcome as no new drug have been approved since the introduction of allopurinol, in 1964, and the drugs that are available have limitations owing to inefficacy or toxicity. Febuxostat is a novel, nonpurine selective inhibitor of xanthine oxidase, is a potential alternative to allopurinol for patients with hyperuricemia and gout.
Gout; hyperuricemia; xanthine oxidase inhibitor
Objective. To profile a sample of gouty patients treated with allopurinol, benzbromarone, or a combination of these two drugs and to describe the impact of this therapy in reducing uric acid levels. Methods. An observational, transversal study was performed. We evaluated 48 patients diagnosed with gout who were seen at the Outpatient Rheumatology Clinic of the Federal University of Paraná between January 2009 and November 2010. Clinical data, creatinine serum levels, and basal and posttreatment levels of serum urates, transaminases, and bilirubins were recorded. Uric acid levels were measured in a 24-hour urine sample. Patients were divided into three groups: patients given only allopurinol (A), only benzbromarone (B), and both in combined therapy (A + B). Results. The average age of these patients was 56.6 ± 11.4 years, varying from 35 to 81 years. The entire patient group experienced a significant drop in serum urate levels, from 8.5 ± 1.8 mg/dL (0.472 ± 0.1 mmol/L) to 6.7 ± 2.1 mg/dL (0.372 ± 0.116 mmol/L) (P < 0.001), regardless of the prescribed medication. The number of patients taking both drugs whose serum uric acid values fell within normal range (men <7 mg/dL (0.38 mmol/L) and women <6 mg/dL (0.33 mmol/L)) was 85.7% (6/7) while this value for the group taking benzbromarone alone was 75% (3/4) and for the group taking allopurinol alone this number was 51.8% (14/27). Conclusions. The therapeutic combination of benzbromarone and allopurinol significantly decreased serum urate levels in patients with gout when compared to individual use of each of these agents. This finding is especially important in treating patients who cannot control hyperuricemia with monotherapy. Benzbromarone alone or in combination with allopurinol has an important clinical role in controlling hyperuricemia in patients with gout.
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.
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.
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.
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
Gout is a common and disabling cause of arthritis in middle-aged and elderly populations, with its main predisposing factor being hyperuricemia (serum urate > 6.8 mg/dL). Options for treatment of chronic gout until 2008 were allopurinol, a xanthine oxidase inhibitor, and the group of drugs known as uricosurics that stimulate the renal excretion of uric acid. A proportion of patients, including some with chronic kidney disease and solid organ transplantations, could not be treated with the those therapies because of intolerance, drug interactions, or adverse events. Febuxostat is a nonpurine xanthine oxidase inhibitor, recently approved in Europe and the United States for the treatment of chronic gout.
To review the clinical evidence (phase II and III studies) of the effectiveness and safety of febuxostat for treatment of hyperuricemia and gout.
Febuxostat, at doses ranging from 40 to 240 mg/day, is efficacious in reducing serum urate in patients with hyperuricemia and gout, comparing favorably with fixed doses of allopurinol in that respect. Early safety signals with respect to liver test abnormalities and cardiovascular outcomes have not been confirmed in recent large prospective trials but need to be further monitored.
Given its low cost and extensive clinical experience, allopurinol will likely remain the first-line drug for management of hyperuricemia and gout. Febuxostat may provide an important option in patients unable to use allopurinol, those with very high serum urate levels, or in the presence of refractory tophi.
febuxostat; gout; hyperuricemia; evidence
Recent studies have confirmed that gout is an inborn error of metabolism. It has now become evident that the hyperuricemia associated with gout might occur either due to overproduction of uric acid, underexcretion of uric acid or a combination of these processes. Furthermore, patients with excessive purine synthesis may have a specific enzyme defect resulting in altered feedback inhibition of purine synthesis. A neurological disease manifest by mental retardation, choreo-athetosis, aggressive behavior, lip-biting and self-mutilation and associated with decidedly increased purine biosynthesis serves as a prototype of this kind of disorder. Other defects in regulation of purine biosynthesis have been postulated but their existence not yet confirmed.
It has been demonstrated that urate crystals which are deposited from hyperuricemic body fluids set up an acute inflammatory reaction by means of a variety of chemical mediators. Thus, acute gouty arthritis is now recognized as an example of “crystal induced” synovitis.
The treatment of gout consists of (1) the control of acute gouty attacks, and (2) the maintenance of normal serum uric acid concentrations. This latter may be achieved either with uricosuric drugs or with xanthine oxidase inhibition. With these principles in mind, it is now possible to avoid many of the severe crippling effects of gout and to restore the vast majority of gouty patients to useful and productive lives.
Hyperuricemia is a risk factor for the onset of chronic kidney disease (CKD) and is significantly associated with the progression of CKD. However, there is no sufficient evidence by interventional research supporting a cause-effect relationship. Hyperuricemic patients without gouty arthritis, whose serum urate (SUA) concentration is ≥8.0 mg/dL and who have a complication, are treated by pharmacotherapy in addition to lifestyle guidance. Nevertheless, there is no evidence that rationalizes pharmacotherapy for patients with hyperuricemia who have no complication and whose SUA concentration is below 9.0 mg/dL.
The FEATHER (FEbuxostat versus placebo rAndomized controlled Trial regarding reduced renal function in patients with Hyperuricemia complicated by chRonic kidney disease stage 3) study is a prospective, multicenter, double-blind, randomized, placebo-controlled trial of febuxostat—a novel, nonpurine, selective, xanthine oxidase inhibitor. The present study will enroll, at 64 medical institutions in Japan, 400 Japanese patients aged 20 years or older who have hyperuricemia without gouty arthritis, who present CKD stage 3, and whose SUA concentration is 7.1-10.0 mg/dL. Patients are randomly assigned to either the febuxostat or the control group, in which febuxostat tablets and placebo are administered orally, respectively. The dosage of the study drugs should be one 10-mg tablet/day at weeks 1 to 4 after study initiation, increased to one 20-mg tablet/day at weeks 5 to 8, and elevated to one 40-mg tablet/day at week 9 and then maintained until week 108. The primary endpoint is estimated glomerular filtration rate (eGFR) slope. The secondary endpoints include the amount and percent rate of change in eGFR from baseline to week 108, the amount and percent rate of change in SUA concentration from baseline to week 108, the proportion of patients who achieved an SUA concentration ≤6.0 mg/dL, and the incidence of renal function deterioration.
The present study aims to examine whether febuxostat prevents a further reduction in renal function as assessed with eGFR in subjects and will (1) provide evidence to indicate the inverse association between a reduction in SUA concentration and an improvement in renal function and (2) rationalize pharmacotherapy for subjects and clarify its clinical relevance.
UMIN Identifier: UMIN000008343
Xanthine oxidase inhibitor; Urate-lowering therapy; Reduced renal function; Hyperuricemia; Chronic kidney disease; Randomized controlled study; Placebo
Two major gout-causing genes have been identified, the urate transport genes SLC2A9 and ABCG2. Variation within the SLC17A1 locus, which encodes sodium-dependent phosphate transporter 1, a renal transporter of uric acid, has also been associated with serum urate concentration. However, evidence for association with gout is equivocal. We investigated the association of the SLC17A1 locus with gout in New Zealand sample sets.
Five variants (rs1165196, rs1183201, rs9358890, rs3799344, rs12664474) were genotyped across a New Zealand sample set totaling 971 cases and 1,742 controls. Cases were ascertained according to American Rheumatism Association criteria. Two population groups were studied: Caucasian and Polynesian.
At rs1183201 (SLC17A1), evidence for association with gout was observed in both the Caucasian (odds ratio (OR) = 0.67, P = 3.0 × 10-6) and Polynesian (OR = 0.74, P = 3.0 × 10-3) groups. Meta-analysis confirmed association of rs1183201 with gout at a genome-wide level of significance (OR = 0.70, P = 3.0 × 10-8). Haplotype analysis suggested the presence of a common protective haplotype.
We confirm the SLC17A1 locus as the third associated with gout at a genome-wide level of significance.
Gout is a disorder of purine metabolism, of varied etiology, associated with an increase in serum uric acid and a recurrent arthritis. The defect may be either metabolic or renal, or either unknown etiology or associated with other disease states. The acute arthritis has been shown to be due to a crystal (sodium urate) synovitis. The many chronic complications, arthritic, renal and vascular, necessitate a vigorous and longterm treatment program. With the advent of the xanthine oxidase inhibiter Allopurinol, excellent control of gout and its complications can be achieved in a large number of patients, with good control in the remainder.
In the past few decades, gout has increased not only in prevalence, but also in clinical complexity, the latter accentuated in part by a dearth of novel advances in treatments for hyperuricemia and gouty arthritis. Fortunately, recent research reviewed here, much of it founded on elegant translational studies of the past decade, highlights how gout can be better managed with cost-effective, well-established therapies. In addition, the advent of both new urate-lowering and anti-inflammatory drugs, also reviewed here, promises for improved management of refractory gout, including in subjects with co-morbidities such as chronic kidney disease. Effectively delivering improved management of hyperuricemia and gout will require a frame shift in practice patterns, including increased recognition of the implications of refractory disease and frequent noncompliance of patients with gout, and understanding the evidence basis for therapeutic targets in serum urate-lowering and gouty inflammation.