Uric acid and cardiovascular risk

The rs2231142 variant of the ABCG2 gene is associated with uric acid levels and gout among Japanese people

OBJECTIVES

Recent genome-wide association and functional studies have shown that the ABCG2 gene encodes for a urate transporter, and a common causal ABCG2 variant, rs2231142, leads to elevated uric acid levels and prevalent gout among Whites and Blacks. We examined whether this finding is observed in a Japanese population, since Asians have a high reported prevalence of the T-risk allele.

METHODS

A total of 3923 Japanese people from the Circulatory Risk in Communities Study aged 40-90 years were genotyped for rs2231142. Associations of the rs2231142 variant with serum uric acid levels and prevalence of gout and hyperuricaemia were examined.

RESULTS

The frequency of the T-risk allele was 31% in this Japanese sample. Multivariable adjusted mean uric acid levels were 7-9 micromol/l higher for TG and TT than GG carriers (P-additive = 0.0006). The multivariable-adjusted odds ratio (OR) of prevalent gout was 1.37 (95% CI 0.68, 2.76) for TG and 4.37 (95% CI 1.98, 9.62) for TT compared with the GG carriers (P-additive = 0.001). When evaluating the combined outcome of hyperuricaemia and gout, the respective ORs were 1.40 (95% CI 1.04, 1.87) for TG and 1.88 (95% CI 1.23, 2.89) for TT carriers. The population attributable risk was 29% for gout and 19% for gout and/or hyperuricaemia.

CONCLUSIONS

The association of the causal ABCG2 rs2231142 variant with uric acid levels and gout was confirmed in a sample of Japanese ancestry. Our study emphasizes the importance of this common causal variant in a population with a high risk allele frequency, especially as more Japanese adopt a Western lifestyle with a concomitant increase in mean serum uric acid levels.

A roadmap for education to improve the quality of care in gout

PURPOSE OF REVIEW

To describe obstacles to optimum management of gout by primary care physicians and to propose educational interventions to improve care.

RECENT FINDINGS

In the past, gout education has been hampered by infrequency of continuing medical education courses, loss of excitement for a disease in which therapies have not changed (until recently), insufficient evidence-based medicine, and the lack of motivation by physicians to re-learn this disease once in active practice. We identify 10 common myths that impede appropriate treatment of gout, identify gaps in evidence-based medicine that perpetuate those myths, and propose opportunities to improve education on these myths. It is through better gout-centered education that quality of care in gout can be enhanced. Residency may be one of the key points of intervention. As more evidence-based medicine publications address the optimum management of gout, national re-education can occur. More outreach by community rheumatologists to primary care physicians through educational programs and improved referral letters can help re-educate practitioners. Lastly, an often overlooked engine to change physician practices is consumer education, but current patient education programs are lacking.

SUMMARY

Novel education interventions for physician trainees, primary care physicians, and patients are proposed to improve the care of patients with gout.

The effects of salsalate on glycemic control in patients with type 2 diabetes: a randomized trial

BACKGROUND

Salsalate, a nonacetylated prodrug of salicylate, has been shown to decrease blood glucose concentration in small studies.

OBJECTIVE

To compare the efficacy and safety of salsalate at different doses in patients with type 2 diabetes.

DESIGN

Parallel randomized trial with computer-generated randomization and centralized allocation. Patients and investigators, including those assessing outcomes and performing analyses, were masked to group assignment. (ClinicalTrials.gov registration number: NCT00392678)

SETTING

3 private practices and 14 universities in the United States.

PATIENTS

Persons aged 18 to 75 years with fasting plasma glucose concentrations of 12.5 mmol/L or less (< or = 225 mg/dL) and hemoglobin A1c (HbA1c) levels of 7.0% to 9.5% treated by diet, exercise, and oral medication at stable doses for at least 8 weeks.

INTERVENTION

After a 4-week, single-masked run-in period, patients were randomly assigned to receive placebo or salsalate in dosages of 3.0, 3.5, or 4.0 g/d for 14 weeks (27 patients each) in addition to their current therapy.

MEASUREMENTS

Change in HbA1c was the primary outcome. Adverse effects and changes in measures of coronary risk and renal function were secondary outcomes.

RESULTS

Higher proportions of patients in the 3 salsalate treatment groups experienced decreases in HbA1c levels of 0.5% or more from baseline (P = 0.009). Mean HbA1c changes were -0.36% (P = 0.02) at 3.0 g/d, -0.34% (P = 0.02) at 3.5 g/d, and -0.49% (P = 0.001) at 4.0 g/d compared with placebo. Other markers of glycemic control also improved in the 3 salsalate groups, as did circulating triglyceride and adiponectin concentrations. Mild hypoglycemia was more common with salsalate; documented events occurred only in patients taking sulfonylureas. Urine albumin concentrations increased in all salsalate groups compared with placebo. The drug was otherwise well tolerated.

LIMITATION

The number of patients studied and the trial duration were insufficient to warrant recommending the use of salsalate for type 2 diabetes at this time.

CONCLUSION

Salsalate lowers HbA1c levels and improves other markers of glycemic control in patients with type 2 diabetes and may therefore provide a new avenue for treatment. Renal and cardiac safety of the drug require further evaluation.

PRIMARY FUNDING SOURCE

National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health.

Association of uric acid with change in kidney function in healthy normotensive individuals

BACKGROUND

Despite recent evidence, the role of uric acid as a causal factor in the pathogenesis and progression of kidney disease remains controversial, partly because of the inclusion in epidemiologic studies of patients with hypertension, diabetes, and/or proteinuria.

STUDY DESIGN

Prospective observational cohort.

SETTING & PARTICIPANTS

900 healthy normotensive adult blood donors (153 women, 747 men) evaluated at baseline and after 5 years.

PREDICTOR

Serum uric acid level.

OUTCOMES

Decrease in estimated glomerular filtration rate (eGFR) >10 mL/min/1.73 m(2), computed using the Modification of Diet in Renal Disease (MDRD) Study equation, with secondary analyses examining similar decreases using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and Cockcroft-Gault equations.

RESULTS

During a median follow-up of 59 months, eGFR decreased from 97 +/- 16 to 88 +/- 14 mL/min/1.73 m(2). Higher serum uric acid levels were associated with a greater likelihood of eGFR decrease in both women and men (HR, 1.13 [95% CI, 1.04-1.39] per each 1-mg/dL increase in uric acid level); in multivariable analyses adjusting for age, sex, body mass index, blood glucose level, total cholesterol level, mean blood pressure, urine albumin-creatinine ratio, and serum triglyceride level, the association remained highly significant (HR, 1.28 [95% CI, 1.12-1.48]). Results were similar using different estimating equations and when the association was examined in sex-specific subgroups.

LIMITATIONS

Analyses were based on a single baseline uric acid measurement. Women are underrepresented.

CONCLUSIONS

In healthy normotensive individuals, serum uric acid level is an independent risk factor for decreased kidney function.

Hyperuricemia and coronary heart disease: a systematic review and meta-analysis

OBJECTIVE

The role of serum uric acid as an independent risk factor for cardiovascular disease remains unclear, although hyperuricemia is associated with cardiovascular disease such as coronary heart disease (CHD), stroke, and hypertension.

METHODS

A systematic review and meta-analysis using a random-effects model was conducted to determine the risk of CHD associated with hyperuricemia in adults. Studies of hyperuricemia and CHD were identified by searching major electronic databases using the medical subject headings and keywords without language restriction (through February 2009). Only prospective cohort studies were included if they had data on CHD incidences or mortalities related to serum uric acid levels in adults.

RESULTS

Twenty-six eligible studies of 402,997 adults were identified. Hyperuricemia was associated with an increased risk of CHD incidence (unadjusted risk ratio [RR] 1.34, 95% confidence interval [95% CI] 1.19-1.49) and mortality (unadjusted RR 1.46, 95% CI 1.20-1.73). When adjusted for potential confounding, the pooled RR was 1.09 (95% CI 1.03-1.16) for CHD incidence and 1.16 (95% CI 1.01-1.30) for CHD mortality. For each increase of 1 mg/dl in uric acid level, the pooled multivariate RR for CHD mortality was 1.12 (95% CI 1.05-1.19). Subgroup analyses showed no significant association between hyperuricemia and CHD incidence/mortality in men, but an increased risk for CHD mortality in women (RR 1.67, 95% CI 1.30-2.04).

CONCLUSION

Hyperuricemia may marginally increase the risk of CHD events, independently of traditional CHD risk factors. A more pronounced increased risk for CHD mortality in women should be investigated in future research.

Hyperuricemia and coronary heart disease: a systematic review and meta-analysis

OBJECTIVE

The role of serum uric acid as an independent risk factor for cardiovascular disease remains unclear, although hyperuricemia is associated with cardiovascular disease such as coronary heart disease (CHD), stroke, and hypertension.

METHODS

A systematic review and meta-analysis using a random-effects model was conducted to determine the risk of CHD associated with hyperuricemia in adults. Studies of hyperuricemia and CHD were identified by searching major electronic databases using the medical subject headings and keywords without language restriction (through February 2009). Only prospective cohort studies were included if they had data on CHD incidences or mortalities related to serum uric acid levels in adults.

RESULTS

Twenty-six eligible studies of 402,997 adults were identified. Hyperuricemia was associated with an increased risk of CHD incidence (unadjusted risk ratio [RR] 1.34, 95% confidence interval [95% CI] 1.19-1.49) and mortality (unadjusted RR 1.46, 95% CI 1.20-1.73). When adjusted for potential confounding, the pooled RR was 1.09 (95% CI 1.03-1.16) for CHD incidence and 1.16 (95% CI 1.01-1.30) for CHD mortality. For each increase of 1 mg/dl in uric acid level, the pooled multivariate RR for CHD mortality was 1.12 (95% CI 1.05-1.19). Subgroup analyses showed no significant association between hyperuricemia and CHD incidence/mortality in men, but an increased risk for CHD mortality in women (RR 1.67, 95% CI 1.30-2.04).

CONCLUSION

Hyperuricemia may marginally increase the risk of CHD events, independently of traditional CHD risk factors. A more pronounced increased risk for CHD mortality in women should be investigated in future research.

The independent association between serum uric acid and graft outcomes after kidney transplantation

BACKGROUND

Improving long-term outcomes of kidney transplantation depends on identifying novel risk factors that lead to poor outcomes. We sought to evaluate the predictive value of mean uric acid (UA) level during the first 6 months posttransplant for graft survival and function.

METHODS

Two hundred twelve recipients of living donor kidneys transplanted during January 2000 to December 2001 were included. The study outcome included graft and patient survival and graft function at 1 year posttransplant. Regression models were used to adjust for the confounding variables including graft function during first 6 months.

RESULTS

During 68.3 + or - 27.2 months follow-up, UA level (mg/dL) and hyperuricemia (n=45) were associated with graft loss (hazard ratio [HR]=1.26, P=0.026, 95% confidence interval [CI]=1.03-1.53, and HR=1.92, P=0.029, 95% CI=1.1-3.4, respectively) independent of graft function and other confounders. UA also seemed to be associated with risk of death with borderline significance (HR=1.2, P=0.096, 95% CI=0.97-1.46). Examining the predictive value for graft function, UA level and hyperuricemia were independent predictors of 1-year serum creatinine (beta=0.10, P=0.013, 95% CI=0.02-0.18, and beta=0.25, P<0.04, 95% CI=0.01-0.49, respectively). Similarly, both were associated with 1-year estimated glomerular filtration rate (beta=-3.9, P<0.001, 95% CI=-5.7 to -1.5 for UA, and beta=-7.6, P<0.02, 95% CI=-13.6 to -1.5 for hyperuricemia). Notably, these associations were all independent of renal function during first 6 months.

CONCLUSION

The results of this study suggest that mean UA level during the first 6 months posttransplant is an independent predictor of long-term graft survival and short-term graft function. Further investigations are needed to evaluate its causal association with chronic allograft injury and cardiovascular disease.

Carotid intima-media thickness, dietary intake, and cardiovascular phenotypes in adolescents: relation to metabolic syndrome

Little is known about the interrelationships between metabolic syndrome (MS), uric acid, and early carotid atherosclerosis with diet in adolescents. We investigated associations among diet, carotid intima-media thickness (cIMT), MS, uric acid, and other cardiovascular risk factors in adolescents. Two hundred forty-nine adolescents from 3 high schools in Central California-a predominately Hispanic (n = 119, 16.1 +/- 0.9 years old, 94% Hispanic), a mixed-ethnicity (n = 94, 15.7 +/- 1.2 years old), and a Seventh-day Adventist (SDA) (n = 33, 17.0 +/- 1.3 years old) high school-were assessed for cIMT, blood lipids, uric acid, blood glucose, systolic and diastolic blood pressure, body mass index (BMI), and dietary intake. Compared with SDA adolescents, the predominately Hispanic and mixed-ethnicity high school adolescents exhibited higher low-density lipoprotein and BMI percentile, whereas adolescents from the SDA and mixed-ethnicity high schools exhibited lower uric acid and fasting glucose levels than those from the Hispanic high school. After adjusting for age and sex, cIMT was only correlated with systolic blood pressure percentile (r = 0.16, P < .01). Controlling for age, levels of uric acid were correlated with BMI percentile (males: r = 0.59, P < .001; females: r = 0.24, P < .01), low-density lipoprotein (males: r = 0.40, P < .001; females: r = 0.20, P < .01), and total cholesterol in males (r = 0.38, P < .001). Despite no significant differences in the high school frequency of MS risk factors, 59% of adolescents had one or more MS risk factors. A relationship was noted between the number of MS risk factors and uric acid (P < .002). Most of the adolescents presented MS risk factors independent of ethnicity or a purportedly healthier lifestyle (SDA). Uric acid association with MS and its risk factors suggests its potentially heightened importance for the assessment of adolescent cardiovascular health.

Macula densa sensing and signaling mechanisms of renin release

Macula densa cells in the distal nephron, according to the classic paradigm, are salt sensors that generate paracrine chemical signals in the juxtaglomerular apparatus to control vital kidney functions, including renal blood flow, glomerular filtration, and renin release. Renin is the rate-limiting step in the activation of the renin-angiotensin system, a key modulator of body fluid homeostasis. Here, we discuss recent advances in understanding macula densa sensing and suggest these cells, in addition to salt, also sense various chemical and metabolic signals in the tubular environment that directly trigger renin release.

Update on gout: new therapeutic strategies and options

Gout, a disease recognized since antiquity, has increased in prevalence in recent years and the clinical profile of this disease has become increasingly complex, owing to large numbers of cases with iatrogenic factors, multiple comorbidities, advanced age, and hyperuricemia and arthritis refractory to treatment. In this Review, key advances in gout research made during the past decade are summarized. Revised strategies for safe and effective employment of dietary measures and pharmacologic treatments for active gouty arthritis, prevention of gout flares and urate lowering are also reviewed, with an emphasis on dosing of colchicine and allopurinol, and the evidence-based approach to systemic glucocorticosteroid treatment of acute gout. Also discussed are new and emerging treatments for gout and hyperuricemia, and the potential influence of dual energy CT imaging on treatment. In this context, the therapeutic role of febuxostat, and clinical development of pegylated uricase urate-lowering therapy and interleukin 1 antagonism for gouty inflammation are reviewed. Collectively, novel approaches will hopefully lead to improved management of hyperuricemia and gout, and also to improvements in patient-centered outcomes, even for those who have previously failed to respond to treatment.

Bayesian methods for instrumental variable analysis with genetic instruments ('Mendelian randomization'): example with urate transporter SLC2A9 as an instrumental variable for effect of urate levels on metabolic syndrome

The ‘Mendelian randomization’ approach uses genotype as an instrumental variable to distinguish between causal and non-causal explanations of biomarker–disease associations. Classical methods for instrumental variable analysis are limited to linear or probit models without latent variables or missing data, rely on asymptotic approximations that are not valid for weak instruments and focus on estimation rather than hypothesis testing. We describe a Bayesian approach that overcomes these limitations, using the JAGS program to compute the log-likelihood ratio (lod score) between causal and non-causal explanations of a biomarker–disease association. To demonstrate the approach, we examined the relationship of plasma urate levels to metabolic syndrome in the ORCADES study of a Scottish population isolate, using genotype at six single-nucleotide polymorphisms in the urate transporter gene SLC2A9 as an instrumental variable. In models that allow for intra-individual variability in urate levels, the lod score favouring a non-causal over a causal explanation was 2.34. In models that do not allow for intra-individual variability, the weight of evidence against a causal explanation was weaker (lod score 1.38). We demonstrate the ability to test one of the key assumptions of instrumental variable analysis—that the effects of the instrument on outcome are mediated only through the intermediate variable—by constructing a test for residual effects of genotype on outcome, similar to the tests of ‘overidentifying restrictions’ developed for classical instrumental variable analysis. The Bayesian approach described here is flexible enough to deal with any instrumental variable problem, and does not rely on asymptotic approximations that may not be valid for weak instruments. The approach can easily be extended to combine information from different study designs. Statistical power calculations show that instrumental variable analysis with genetic instruments will typically require combining information from moderately large cohort and cross-sectional studies of biomarkers with information from very large genetic case–control studies.

The effects of salsalate on glycemic control in patients with type 2 diabetes: a randomized trial

BACKGROUND

Salsalate, a nonacetylated prodrug of salicylate, has been shown to decrease blood glucose concentration in small studies.

OBJECTIVE

To compare the efficacy and safety of salsalate at different doses in patients with type 2 diabetes.

DESIGN

Parallel randomized trial with computer-generated randomization and centralized allocation. Patients and investigators, including those assessing outcomes and performing analyses, were masked to group assignment. (ClinicalTrials.gov registration number: NCT00392678)

SETTING

3 private practices and 14 universities in the United States.

PATIENTS

Persons aged 18 to 75 years with fasting plasma glucose concentrations of 12.5 mmol/L or less (< or = 225 mg/dL) and hemoglobin A1c (HbA1c) levels of 7.0% to 9.5% treated by diet, exercise, and oral medication at stable doses for at least 8 weeks.

INTERVENTION

After a 4-week, single-masked run-in period, patients were randomly assigned to receive placebo or salsalate in dosages of 3.0, 3.5, or 4.0 g/d for 14 weeks (27 patients each) in addition to their current therapy.

MEASUREMENTS

Change in HbA1c was the primary outcome. Adverse effects and changes in measures of coronary risk and renal function were secondary outcomes.

RESULTS

Higher proportions of patients in the 3 salsalate treatment groups experienced decreases in HbA1c levels of 0.5% or more from baseline (P = 0.009). Mean HbA1c changes were -0.36% (P = 0.02) at 3.0 g/d, -0.34% (P = 0.02) at 3.5 g/d, and -0.49% (P = 0.001) at 4.0 g/d compared with placebo. Other markers of glycemic control also improved in the 3 salsalate groups, as did circulating triglyceride and adiponectin concentrations. Mild hypoglycemia was more common with salsalate; documented events occurred only in patients taking sulfonylureas. Urine albumin concentrations increased in all salsalate groups compared with placebo. The drug was otherwise well tolerated.

LIMITATION

The number of patients studied and the trial duration were insufficient to warrant recommending the use of salsalate for type 2 diabetes at this time.

CONCLUSION

Salsalate lowers HbA1c levels and improves other markers of glycemic control in patients with type 2 diabetes and may therefore provide a new avenue for treatment. Renal and cardiac safety of the drug require further evaluation.

PRIMARY FUNDING SOURCE

National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health.

Relationship between hyperuricemia (HUC) and metabolic syndrome (MS) in institutionalized elderly men

This study investigated the relationship between hyperuricemia (HUC) and the components of the metabolic syndrome (MS) among elderly institutionalized men. In addition, this study explored the relationship between HUC and serum inflammatory markers. A total of 333 participants from Chang-Hua Veterans Care Home were enrolled. The MS was defined using a modified ATP III definition issued in 2004 by the Bureau of Health Promotion, Department of Health, ROC (Taiwan). The participants' mean age was 78.6+/-3.9 years, and their mean serum uric acid level was 6.9+/-1.7 mg/dl. The prevalence of HUC was 46.2% (n = 154). The prevalence of the MS was 38.4% (n = 128). HUC was correlated with components of the MS, including waist circumference (WC), triglyceride (TG), and high density lipoprotein cholesterol (HDL-C) but it was not related to blood pressure (BP) and fasting plasma glucose (FPG). Moreover, increased serum creatinine, albumin, prealbumin, and body fat were also associated with HUC. The plasma activator inhibitor-1 (PAI-1) levels were significantly elevated in the HUC group, but serum interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), serum intercellular cell adhesion molecule-1 (sICAM-1), serum levels of vascular cell adhesion molecule-1 (sVCAM-1), and P-selectin were not related to HUC. HUC in elderly men may represent poorer renal function, better nutritional status, and increased body fat.

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.

Higher serum uric acid on admission is associated with higher short-term mortality and poorer long-term survival after myocardial infarction: retrospective prognostic study

AIM

To assess serum uric acid (SUA) levels determined on admission as a potential predictor of short-term mortality and long-term survival in acute myocardial infarction (AMI) patients.

METHOD

Data for this retrospective prognostic study were drawn from the patient database of the Varazdin County General Hospital in Varazdin, Croatia. We included consecutive patients with verified AMI admitted within 48 hours since the symptom onset during the period between 1 January 1996 and 31 December 2001. Long-term survival/mortality data were collected through direct contacts with patients and search of the community death registries. Relative risks (RR) and hazard ratios (HR) by 10 micromol/L increase in SUA were determined using modified Poisson regression with robust error variance and proportional hazard regression, respectively.

RESULTS

A total of 621 patients (age 27-90 years, 64.7% men, 77.5% AMI with ST elevation, SUA 63-993 micromol/L) were included. Higher SUA on admission was independently associated with higher in-hospital mortality (RR, 1.016; 95% confidence interval [CI], 1.001-1.031, P=0.043) and higher thirty-day mortality (RR, 1.016; 95% CI, 1.003-1.029, P=0.018). Considered covariates were demographics, pre-index event cardiovascular morbidity and treatment, on-admission serum creatinine, total cholesterol and triglycerides, AMI characteristics, and peak creatine phosphokinase. Higher SUA on admission was also independently associated with poorer long-term survival (ie, higher all-cause mortality) (HR, 1.105; 95% CI, 1.020-1.195, P=0.010). Considered covariates were demographics, laboratory variables on admission, AMI characteristics, peak creatine phosphokinase, acute complications, and treatment at discharge.

CONCLUSION

Higher serum uric acid determined on admission is associated with higher in-hospital mortality and thirty-day mortality and poorer long-term survival after AMI.

Correlation of asymptomatic hyperuricaemia and serum uric acid levels with arterial stiffness in women with systemic lupus erythematosus without clinically evident atherosclerotic cardiovascular disease

The objective of this article was to evaluate whether serum uric acid (SUA) correlates with arterial stiffness and inflammation markers in a cohort of women with systemic lupus erythematosus (SLE) without overt atherosclerotic cardiovascular diseases, who attended a community hospital. One hundred and two women with SLE were assessed as part of this cross-sectional study. Carotid-femoral pulse wave velocity (PWV) was measured using an automatic device (Complior). C-reactive protein (CRP), fibrinogen and homocysteine levels as well as other metabolic results were recorded. Duration and activity of SLE, damage accrual and treatments were recorded. SLE women were categorized as having or not having hyperuricaemia (HU) according to SUA levels (greater than or up to 6.2 mg/dl, respectively). A multiple linear regression analysis was used to determine the independent link between SUA levels and other variables. Women with SLE and HU (n = 15, 15%) had a worse cardiovascular risk profile that included ageing, hypertension, obesity, higher total cholesterol levels, renal failure and presence of metabolic syndrome. Also, the duration of SLE was increased and damage accrual was greater. In the unadjusted analysis, SUA levels correlated with PWV, CRP, fibrinogen and homocysteine. However, in a multivariate linear regression analysis, SUA levels independently correlated with the duration of SLE, creatinine, total cholesterol and homocysteine levels but did not correlate with PWV. In conclusion, SUA was associated with arterial stiffness, but not independently of age and homocysteine levels. Nevertheless, SUA might be an ancillary indicator of subclinical atherosclerosis in SLE women without clinically evident atherosclerotic cardiovascular disease.

Relationship between uric acid and hepatic steatosis among Koreans

AIM

The relationship between high uric-acid levels and hepatic steatosis, according to body mass index (BMI) categories, and their coexistence with the metabolic syndrome (MetS) were examined in the present study.

METHODS

The study involved a cross-sectional sample of 13,621 Koreans (7221 men and 6400 women) who visited a health checkup centre between 2005 and 2006. Hepatic steatosis was diagnosed using ultrasonography. Hyperuricaemia was defined as >7mg/dL for men and >6mg/dL for women. The MetS was defined as the presence of three or more MetS components-obesity (BMI >or=25.0kg/m(2)), high blood pressure, elevated levels of triglycerides and glucose, and low levels of high-density lipoprotein (HDL)-cholesterol.

RESULTS

In total, 26.2% were diagnosed with hepatic steatosis, of whom 11.9% were non-obese (BMI <25kg/m(2)) and 52.5% were obese. Hyperuricaemia was associated with hepatic steatosis in non-obese (adjusted odds ratio [AOR] of 1.4 in men and 2.2 in women) as well as in obese individuals (AOR of 1.8 in men and 2.3 in women) after adjusting for age, other MetS components and liver function tests. The AOR (95% CI) for hepatic steatosis in obese individuals with hyperuricaemia compared with non-obese individuals with normal uric-acid levels was 7.7 (6.4-9.3) in men and 12.4 (7.8-19.5) in women. The adjusted age and liver-function test ORs (95% CI) for hepatic steatosis in those with hyperuricaemia and no MetS compared with those who had normal uric acid levels and no MetS were 2.0 (1.7-2.4) in men and 3.2 (2.1-4.9) in women. The ORs (95% CI) in those with hyperuricaemia and the MetS increased to 6.9 (5.5-8.8) and 15.2 (8.4-27.4) in men and women, respectively.

CONCLUSION

Hyperuricaemia is independently associated with hepatic steatosis regardless of BMI category or the presence of the MetS in Korean adults. Further research into the causal relationship is needed.

Common variants in SLC17A3 gene affect intra-personal variation in serum uric acid levels in longitudinal time series

AIM

To investigate whether intra-personal variation in serum uric acid concentration is influenced by genes that were described to be associated with serum uric acid levels in cross-sectional studies.

METHODS

The study included 92 participants from the isolated community of the Croatian island of Vis. For each participant, two uric acid concentration measurements were available, one from 2002 and one from 2003. Changes in uric acid concentration were correlated with a set of 8 genes known to affect it: PDZK1, GCKR, SLC2A9, ABCG2, LRRC16A, SLC17A3, SLC16A9, and SLC22A12.

RESULTS

Thirteen participants (14%) had uric acid concentration change greater than 130 micromol/L. Greater variability of uric acid concentration was recorded in women (coefficient of variation 49% vs 12% in men). Two SNPs belonging to SLC17A3 gene (rs9393672 and rs942379) yielded significant association with serum uric acid concentration changes in women. These two single-nucleotide polymorphisms (SNP) explained 0.2%-1.3% of variance for 2002 or 2003 uric acid measurement and 1.1%-1.8% of variance for the average value of these two measurements.

CONCLUSIONS

Repeated measurements offer a possibility to enrich the percent of explained variance and contribute to the understanding of the "missing heritability" concept. Although a number of genes have been shown to affect serum uric acid concentration, SLC17A3 seems to have a major role in determination of serum uric acid repeated measurements variation.

Glucose transporters in the 21st Century

The ability to take up and metabolize glucose at the cellular level is a property shared by the vast majority of existing organisms. Most mammalian cells import glucose by a process of facilitative diffusion mediated by members of the Glut (SLC2A) family of membrane transport proteins. Fourteen Glut proteins are expressed in the human and they include transporters for substrates other than glucose, including fructose, myoinositol, and urate. The primary physiological substrates for at least half of the 14 Glut proteins are either uncertain or unknown. The well-established glucose transporter isoforms, Gluts 1-4, are known to have distinct regulatory and/or kinetic properties that reflect their specific roles in cellular and whole body glucose homeostasis. Separate review articles on many of the Glut proteins have recently appeared in this journal. Here, we provide a very brief summary of the known properties of the 14 Glut proteins and suggest some avenues of future investigation in this area.

Association between hyperuricemia and hypertension in a Chinese population at a high risk of hypertension

In this cross-sectional study, we examined whether hyperuricemia is associated with hypertension and the association exists in a Chinese population at a high risk of hypertension. The study population included 813 consecutively clinical patients with suspected cardiovascular disease, including the subjects with the current use of antihypertensive medications and self-reported diagnosis of hypertension. The subjects underwent three measures of blood pressure and were divided into two groups: 502 non-hypertensive subjects and 311 hypertensive subjects. Clinical and biochemical variables were measured. Results showed that uric acid level, fasting glucose, low-density lipoprotein (LDL)-cholesterol, total cholesterol and urea nitrogen were significantly higher (all p<0.05) in hypertension subjects than in non-hypertension subjects. The risk of hypertension was significantly higher in the group with higher uric acid (>400 micromol/l), compared with that with lower uric acid (<200 micromol/l) (odds ratio: 2.09, 95% CI 1.13-3.88). The odds ratio was 1.73, 95% CI 1.05-2.85 in the higher uric acid (200-400 micromol/l) group, compared with that with lower uric acid. In addition, age, gender, weight, fasting glucose, triglycerides and total cholesterol were also significantly associated with the incidence of hypertension. In age-adjusted logistic regression analysis, the effect of uric acid concentration on hypertension was attenuated. In conclusion, hyperuricemia is associated with hypertension in a Chinese population at a high risk of hypertension.

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.

Concentration of uric acid removed during dialysis. Estimated by multi wavelength and processed ultra violet absorbance spectra

The aim of this study was to estimate the concentration of uric acid (UA) optically by using original and processed ultra violet (UV) absorbance spectra's of the spent dialysate. Also the effect of using several wavelengths for estimation was examined.

Clinical correlates of renal dysfunction in hypertensive patients without cardiovascular complications: the REDHY study

Our study was aimed to assess the clinical correlates of different degrees of renal dysfunction in a wide group of non-diabetic hypertensive patients, free from cardiovascular (CV) complications and known renal diseases, participating to the REDHY (REnal Dysfunction in HYpertension) study. A total of 1856 hypertensive subjects (mean age: 47+/-14 years), attending our hypertension centre, were evaluated. The glomerular filtration rate (GFR) was estimated by the simplified Modification of Diet in Renal Disease Study prediction equation. A 24-h urine sample was collected to determine albumin excretion rate (AER). Albuminuria was defined as an AER greater than 20 microg min(-1). We used the classification proposed by the US National Kidney Foundation's guidelines for chronic kidney disease (CKD) to define the stages of renal function impairment. In multiple logistic regression analysis, the probability of having stage 1 and stage 2 CKD was significantly higher in subjects with greater values of systolic blood pressure (SBP) and with larger waist circumference. SBP was also positively related to stage 3 CKD. Stage 3 and stages 4-5 CKD were inversely associated with waist circumference and directly associated with serum uric acid. Age was inversely related to stage 1 CKD and directly related to stage 3 CKD. The factors associated with milder forms of kidney dysfunction are, in part, different from those associated with more advanced stages of renal function impairment.

Uric acid: a novel mediator and marker of risk in chronic kidney disease?

PURPOSE OF REVIEW

To assess the current data suggesting that uric acid-lowering therapy may be useful in the prevention or mitigation of chronic kidney disease (CKD).

RECENT FINDINGS

Eleven observational studies assessing the potential role of serum uric acid in the prevalence and progression of CKD have been published in the past 2 years. Seven suggest an association, whereas four do not. Recent experimental models and clinical trials have mechanistically linked serum uric acid and hypertension, an established risk factor for CKD.

SUMMARY

Elevated serum uric acid is a marker for decreased renal function, may have a mechanistic role in the incidence and progression of renal functional decline and likely has a causal role in hypertension and vascular disease. Clinical trials are needed to determine whether uric acid-lowering therapy will be effective in preventing CKD.

Sugar-sweetened soda consumption, hyperuricemia, and kidney disease

The metabolism of high-fructose corn syrup used to sweeten soda drinks may lead to elevations in uric acid levels. Here we determined whether soda drinking is associated with hyperuricemia and, as a potential consequence, reduced kidney function. At baseline, 15,745 patients in the Atherosclerosis Risk in Communities Study completed a dietary questionnaire and had measurements of their serum creatinine and uric acid. After 3 and 9 years of follow-up, multivariate odds ratios from logistic regressions for binary outcome of hyperuricemia and chronic kidney disease (eGFR less than 60 ml/min per 1.73 m(2)) were evaluated. Compared to participants who drank less, consumption of over one soda per day was associated with increased odds of prevalent hyperuricemia and chronic kidney disease. The odds ratio for chronic kidney disease significantly increased to 2.59 among participants who drank more than one soda per day and had a serum uric acid level over 9.0 mg/dl. In longitudinal analyses, however, drinking more than one soda per day was not associated with hyperuricemia or chronic kidney disease. Neither preexistent hyperuricemia nor development of hyperuricemia modified the lack of association between soda drinking and incident chronic kidney disease. Thus our study shows that high consumption of sugar-sweetened soda was associated with prevalent but not incident hyperuricemia and chronic kidney disease.

Trp64Arg polymorphism of the ADRB3 gene predicts hyperuricemia risk in a population from southern Spain

OBJECTIVE

To study the role of Trp64Arg polymorphism of the ADRB3 gene in the risk of developing hyperuricemia in 1051 subjects from southern Spain, with a followup of 6 years. The inclusion of plasma levels of uric acid as a diagnostic criterion to define the metabolic syndrome is under discussion. Genes responsible for insulin resistance could contribute to the development of hyperuricemia. Previous cross-sectional studies have suggested ADRB3 as a possible candidate gene in the development of hyperuricemia and insulin resistance.

METHODS

A prospective, population-based, cohort study of 1051 persons examined in 1997-98 and reassessed at a second examination 6 years later. The metabolic phenotype was assessed at baseline and again at the followup. Insulin resistance was measured by homeostasis model assessment. The Trp64Arg polymorphism of ADRB3 was detected by real-time polymerase chain reaction. Subjects were considered normouricemic if their serum uric acid levels were <or=7 mg/dl for men or <or= 6 mg/dl for women.

RESULTS

Carriers of the Arg64 allele who were normouricemic at baseline had a higher risk of developing hyperuricemia 6 years later (p = 0.017, OR 2.3, 95% CI 1.1-4.6). Multivariate logistic regression analysis showed that the OR of having hyperuricemia at the 6-year followup was significantly associated with the Arg64 allele, after adjusting for age, weight gain, baseline levels of triglycerides, serum uric acid, and insulin resistance (OR 3.1, 95% CI 1.3-7.1).

CONCLUSION

Trp64Arg polymorphism of the ADRB3 gene predicted the risk of developing hyperuricemia in this adult population.

Homozygous SLC2A9 mutations cause severe renal hypouricemia

Hereditary hypouricemia may result from mutations in the renal tubular uric acid transporter URAT1. Whether mutation of other uric acid transporters produces a similar phenotype is unknown. We studied two families who had severe hereditary hypouricemia and did not have a URAT1 defect. We performed a genome-wide homozygosity screen and linkage analysis and identified the candidate gene SLC2A9, which encodes the glucose transporter 9 (GLUT9). Both families had homozygous SLC2A9 mutations: A missense mutation (L75R) in six affected members of one family and a 36-kb deletion, resulting in a truncated protein, in the other. In vitro, the L75R mutation dramatically impaired transport of uric acid. The mean concentration of serum uric acid of seven homozygous individuals was 0.17 +/- 0.2 mg/dl, and all had a fractional excretion of uric acid >150%. Three individuals had nephrolithiasis, and three had a history of exercise-induced acute renal failure. In conclusion, homozygous loss-of-function mutations of GLUT9 cause a total defect of uric acid absorption, leading to severe renal hypouricemia complicated by nephrolithiasis and exercise-induced acute renal failure. In addition to clarifying renal handling of uric acid, our findings may provide a better understanding of the pathophysiology of acute renal failure, nephrolithiasis, hyperuricemia, and gout.

Common polymorphisms influencing serum uric acid levels contribute to susceptibility to gout, but not to coronary artery disease

Background

Recently, a large meta-analysis including over 28,000 participants identified nine different loci with association to serum uric acid (UA) levels. Since elevated serum UA levels potentially cause gout and are a possible risk factor for coronary artery disease (CAD) and myocardial infarction (MI), we performed two large case-control association analyses with participants from the German MI Family Study. In the first study, we assessed the association of the qualitative trait gout and ten single nucleotide polymorphisms (SNP) markers that showed association to UA serum levels. In the second study, the same genetic polymorphisms were analyzed for association with CAD.

Methods and Findings

A total of 683 patients suffering from gout and 1,563 healthy controls from the German MI Family Study were genotyped. Nine SNPs were identified from a recently performed genome-wide meta-analysis on serum UA levels (rs12129861, rs780094, rs734553, rs2231142, rs742132, rs1183201, rs12356193, rs17300741 and rs505802). Additionally, the marker rs6855911 was included which has been associated with gout in our cohort in a previous study. SNPs rs734553 and rs6855911, located in SLC2A9, and SNP rs2231142, known to be a missense polymorphism in ABCG2, were associated with gout (p = 5.6*10⁻⁷, p = 1.1*10⁻⁷, and p = 1.3*10⁻³, respectively). Other SNPs in the genes PDZK1, GCKR, LRRC16A, SLC17A1-SLC17A3, SLC16A9, SLC22A11 and SLC22A12 failed the significance level. None of the ten markers were associated with risk to CAD in our study sample of 1,473 CAD cases and 1,241 CAD-free controls.

Conclusion

SNP markers in SLC2A9 and ABCG2 genes were found to be strongly associated with the phenotype gout. However, not all SNP markers influencing serum UA levels were also directly associated with the clinical manifestation of gout in our study sample. In addition, none of these SNPs showed association with the risk to CAD in the German MI Family Study.

Replication of the five novel loci for uric acid concentrations and potential mediating mechanisms

Uric acid (UA) is the final catabolic product of purine metabolism and elevated levels are associated with diabetes and cardiovascular disease. A recent meta-analysis of genome-wide association studies totalling 28,141 participants identified five novel loci associated with serum UA levels. In our population-based cohort of 7795 subjects, we replicated four of these five loci; PDZK1 (rs12129861, P = 1.07 x 10(-3)), glucokinase regulator protein (GCKR) (rs780094, P = 4.83 x 10(-4)), SLC16A9 (rs742132, P = 0.047) and SLC22A11 (rs17300741, P = 6.13 x 10(-3)), but not LRRC16A (rs742132, P = 0.645). Serum UA concentration is a complex trait, closely associated to renal UA handling (fractional UA excretion, P < 1 x 10(-300)), renal function (serum creatinine, P < 1 x 10(-300)) and the metabolic syndrome (including fasting insulin, P = 2.48 x 10(-232); insulin resistance, P = 2.51 x 10(-258); waist circumference, P < 1 x 10(-300)) and systolic blood pressure (P = 1.93 x 10(-219)). Together these factors explain 67% of the variance in UA levels. Therefore, we sought to determine the potential contribution of these factors to the association of these novel loci with UA levels, by including them as additional explanatory variables in our analyses, and by considering them as alternative response variables. The association with the GCKR locus is attenuated by serum triglycerides and fractional UA excretion. We also observed the GCKR locus to be associated with total cholesterol (P = 7.52 x 10(-6)), triglycerides (P = 2.65 x 10(-9)), fasting glucose (P = 0.011), fractional UA excretion (P = 3.36 x 10(-5)) and high-sensitive CRP (P = 1.18 x 10(-3)) also after adjusting for serum UA levels. We argue that GCKR locus affects serum UA levels through a factor that also affects triglycerides.

Differential changes in serum uric acid concentrations in sibutramine promoted weight loss in diabetes: results from four weeks of the lead-in period of the SCOUT trial

Background and aims

Elevated levels of serum uric acid are associated with an increased risk of cardiovascular morbidity and mortality. The response of uric acid to weight loss therapy (lifestyle plus sibutramine) in an overweight and obese cardiovascular high risk population was studied.

Methods and results

Data from a four week single-blind lead-in period of the Sibutramine Cardiovascular OUTcomes (SCOUT) study were analyzed. 2584 patients (24%) had diabetes mellitus (DM) only, 1748 (16%) had cardiovascular disease (CVD) only and 6397 (60%) had both DM + CVD. Uric acid concentrations (mean ± standard deviation) at screening were significantly higher among patients with CVD compared to patients without CVD (p < 0.0001): 369 ± 86 μmol/L, 374 ± 98 μmol/L and 342 ± 87 μmol/L in CVD only, CVD+DM and DM only groups, respectively. During treatment uric acid decreased significantly more in patients without DM (p < 0.0001): -15.0 μmol/L (95% confidence interval -17.7;-12.4), -4.6 μmol/L (-6.2;-3.0), and -6.6 μmol/L (-8.7;-4.5) in CVD only, CVD+DM, and DM only groups, respectively. In patients who failed to lose weight, sibutramine induced lower uric acid levels, but greater weight loss and diabetes were associated with smaller falls in blood uric acid levels; decreasing fasting and urinary glucose concentrations in diabetes were associated with increases in uric acid levels.

Conclusion

A four week daily intake of sibutramine and life style changes was associated with significant reductions in mean uric acid levels. Changes in renal glucose load in diabetes seem to counteract a potential uricosuric effect of sibutramine.

Trial Registration

The trial is registered at ClinicalTrial.gov number: NCT00234832.

Fibrinogen, Hematocrit, Platelets in Mild Kidney Dysfunction and the Role of Uric Acid: An Italian Male Population Study

Aim: To examine the relationship between some blood parameters and mild kidney dysfunction. Participants and Methods: A total of 719 Italian men aged 42 to 74 years from a population-based survey carried out in the town of Bollate (Milan). General linear models were used to examine the variations in plasma fibrinogen, hematocrit, platelet counts, mean platelet volume, and uric acid across levels of kidney function (estimated on the basis of glomerular filtration rate [GFR]), adjusting for age, education, smoking, alcohol consumption, physical activity (evaluated as TV watching, engaging in sport practice, and walking/cycling), waist circumference, arm muscle area, high-density lipoprotein (HDL)-cholesterol, triglycerides, hypertension, diabetes, cardiovascular disease history, and nonsteroid anti-inflammatory, diuretic, and antihypertensive drug use. Results: Plasma fibrinogen and hematocrit levels increased, and platelet counts and mean platelet volume significantly decreased as GFR fell to <80 or <70 mL/min per 1.73 m2; stratified analysis revealed an association with serum uric acid levels. Alterations compatible with an increased cardiovascular risk were particularly evident among the participants with higher uric acid levels, whereas those indicative of platelet dysfunction were found among participants with lower levels. Conclusions: Parameters affecting hemostasis and blood viscosity are altered when kidney function is only slightly reduced, and the patterns of these relationships seem to be influenced by the levels of serum uric acid, whose easy and inexpensive measurement could have prognostic value.

Gout in young migrant Filipino women in Israel: a changing epidemiology. Case reports and review of the literature

Gout is rare among young women. The prevalence of gout is increasing in the western world and the Far East, probably owing to life style changes. The association between hyperuricemia and gout, the metabolic syndrome and atherosclerosis is stronger in women. 40 years ago, the increased prevalence of hyperuricemia and gout in Filipino men living in the United States was described. Recently, Filipino men and women living in the western world were found to have increased risk of the metabolic syndrome and atherosclerosis. We describe two unusual cases of gout in premenopausal Filipino women living in Israel, both of which suffered from hypertension. We also describe the current knowledge about gout in women, in general, and in migrant Asian women, in particular, with an emphasis on its relations to the metabolic syndrome and atherosclerosis. The occurrence of gout in relatively young migrant Filipino women might signal a change in the epidemiology of this disease, and might signal that these women are more prone to develop the metabolic syndrome and its complications.

Elevated first-trimester uric acid concentrations are associated with the development of gestational diabetes

OBJECTIVE

We sought to demonstrate that elevated first-trimester uric acid is associated with development of gestational diabetes mellitus (GDM).

STUDY DESIGN

Uric acid was measured in 1570 plasma samples collected at mean gestational age of 8.9 +/- 2.5 weeks. The primary outcome was GDM, diagnosed by 3-hour glucose tolerance test using Carpenter and Coustan criteria or by a 1-hour value of > or =200 mg/dL. Logistic regression was performed, adjusting for relevant covariates.

RESULTS

Almost half (46.6%) of the women with GDM had first-trimester uric acid concentrations in the highest quartile (>3.57-8.30 mg/dL). Women with uric acid in the highest quartile had a 3.25-fold increased risk (95% confidence interval, 1.35-7.83) of developing GDM after adjustment for body mass index and age. This effect was concentration dependent as risk increased with increasing uric acid quartiles (P = .003).

CONCLUSION

First-trimester hyperuricemia is associated with an increased risk of developing GDM, independent of body mass index.

Facilitative glucose transporter 9, a unique hexose and urate transporter

GLUT9 is a novel, facilitative glucose transporter isoform that exists as two alternative splice variants encoding two proteins that differ in their NH(2)-terminal sequence (GLUT9a and GLUT9b). Both forms of GLUT9 protein and mRNA are expressed in the epithelia of various tissues; however, the two splice variants are expressed differentially within polarized cells, with GLUT9a localized predominantly on the basolateral surfaces and GLUT9b expressed on apical surfaces. Protein expression of GLUT9 drops under conditions of starvation but increases with addition of glucose and under hyperglycemic conditions. The substrate specificity of GLUT9 is unique since, in addition to transporting hexose sugars, it also is a high-capacity uric acid transporter. Several recent large-scale human genetic studies show a correlation between SNPs mapped to GLUT9 and the serum uric acid levels in several different cohorts. The relationship between GLUT9 and uric acid is highly clinically significant. Elevated uric acid levels have been associated with metabolic syndrome, obesity, diabetes, hypertension, and chronic renal failure. Although some believe uric acid is elevated as a result of these diseases, there is now evidence that uric acid may play a role in the pathogenesis of these diseases. It is also known that GLUT9 is expressed in articular cartilage and is a uric acid transporter, and thus it is possible that GLUT9 plays a role in gout, a disease of uric acid deposition in the joints. In addition, some studies have suggested that intake of fructose plays an important role in causing elevated serum uric acid levels, especially in diabetes and obesity. It is possible that GLUT9, which seems to be both a fructose and a uric acid transporter, plays an important role in these conditions associated with hyperuricemia.