Effect of insulin on uric acid excretion in humans

Longitudinal association between serum urate and subclinical atherosclerosis: the Coronary Artery Risk Development in Young Adults (CARDIA) study

OBJECTIVE

The aim of the present study was to determine whether serum urate (sUA) concentration is positively associated with subclinical atherosclerosis, independent of body mass index (BMI), amongst generally healthy adults.

DESIGN AND SETTING

The CARDIA study followed 5115 Black and White individuals aged 18-30 years in 1985-1986 (year 0). Subclinical atherosclerosis comprised coronary artery calcified plaque (CAC; years 15, 20 and 25), and maximum common carotid intima-media thickness (IMT; year 20). sUA (years 0, 10, 15 and 20) was modelled as gender-specific quartiles that were pooled. Discrete-time hazard regressions and generalized linear regressions were used for analyses.

RESULTS

Mean sUA concentration was lower in women than in men and increased with age. Adjusting for demographic and lifestyle factors, the highest versus lowest quartile of sUA at year 0 was associated with a 44% [95% confidence interval (CI) 20%, 73%] greater risk of CAC progression from years 15 to 25 (Ptrend  < 0.001), which was attenuated by adjustment for BMI at year 0 (Ptrend  = 0.45). A stronger association was found between sUA at year 15 and CAC progression at year 20 or 25 (hazard ratio 2.07, 95% CI 1.66, 2.58 for the highest versus lowest sUA quartile Ptrend  < 0.001), which was attenuated, but remained significant with additional adjustment for BMI at year 15 (Ptrend  = 0.01). A greater increment in sUA concentration from year 0 to year 15, independent of change in BMI, was related to a higher risk of CAC progression (Ptrend  < 0.001). Similar associations were found between sUA and IMT, but only in men.

CONCLUSION

sUA may be an early biomarker for subclinical atherosclerosis in young adults; starting in early middle age, sUA predicts subclinical atherosclerosis independently of BMI.

Hyperuricemia is independently associated with endothelial dysfunction in postmenopausal women but not in premenopausal women

OBJECTIVES

The purpose of this study was to determine the relationships between uric acid, endothelial function and cardiovascular risk factors and to investigate whether menopausal status was associated with the relationship between uric acid and endothelial function in women.

DESIGN

Cross-sectional study.

SETTING

3 general hospitals in Japan.

PARTICIPANTS

749 Japanese women aged 30-74 years recruited from people who underwent health-screening examinations with agreement for measurement of vascular function.

MEASURES

We measured serum concentrations of uric acid and flow-mediated vasodilation (FMD). Percentage of FMD (peak diameter-baseline diameter/baseline diameter) was used for analysis. Endothelial dysfunction was defined as FMD ≤4.90%, division point for the lowest tertile and the middle tertile of FMD. Menopause women were defined as participants without menstruation for over 1 year or participants with a history of hysterectomy or bilateral oophorectomy.

RESULTS

Of the 749 participants, 368 (49.1%) were premenopausal women and 381 (50.9%) were postmenopausal women. Age, body mass index, systolic blood pressure, total cholesterol, triglycerides, glucose, estimated glomerular filtration rate and Framingham risk score were significantly correlated with serum uric acid level. FMD showed a gradual decrease in accordance with the serum uric acid level in the entire study population (<4 mg/dL, 6.85±3.65%; 4 to <5 mg/dL, 6.79±3.60%; 5 to <6 mg/dL, 6.24±3.58%; ≥6 mg/dL, 5.27±3.18%; p=0.01). Multivariate analysis revealed that uric acid was a significantly independent risk factor for endothelial dysfunction in postmenopausal women (OR 1.23, 95% CI 1.01 to 1.50), but not in premenopausal women.

CONCLUSIONS

These findings suggest that uric acid can be used as a risk marker of endothelial dysfunction in a female population, and particularly as an independent risk factor in postmenopausal women but not in premenopausal women.

REGISTRATION NUMBER OF THE STUDY

UMIN000003409.

Hyperuricemia as an independent predictor of vascular complications and mortality in type 2 diabetes patients: a meta-analysis

Background

Recent data have suggested that serum uric acid (SUA) level is positively associated with the development of type 2 diabetes (T2DM). Whether SUA is also independently associated with the development of vascular complications and mortality in T2DM is controversial.

Methods

A computerized literature search of MEDLINE, Embase and PubMed database was conducted and the odds ratio (OR) or hazard ratio (HR) for per 0.1mmol/l increase in SUA in each study was calculated. Cochrane’s Q and I² statistics were used to evaluate heterogeneity among studies and pooling OR and HR with 95% confidence intervals (CIs) were calculated using random-effects models and fixed-effects models. The pooled analysis was performed using Stata 10.0.

Results

Our search yielded 9 eligible articles (16 ORs and HRs) including 20,891 T2DM patients. Pooled estimates for the relationship suggested that each 0.1 mmol/l increase in SUA resulted in a 28% increase in the risk of diabetic vascular complications and a 9% increase in the risk of diabetic mortality. In stratification-analysis, the positive relationship between SUA and vascular complications remained significant irrespective of mean age, adjustment for metabolic variables and medications. However, it was inconsistent in different populations (significantly positive in the Asian but not in Australian and Italian population) and sample sizes (significantly positive in the relatively large sample size [≥1000] but non-significant in the small sample size [<1000]).

Conclusions

Results of this meta-analysis supported elevated SUA as an independent predictor of vascular complications and mortality in T2DM patients. SUA-lowering therapies might be helpful for prevention and treatment of vascular complications in this population.

The pathophysiology of hyperuricaemia and its possible relationship to cardiovascular disease, morbidity and mortality

Uric acid is the end product of purine metabolism in humans. High levels are causative in gout and urolithiasis. Hyperuricaemia has also been implicated in the pathophysiology of hypertension, chronic kidney disease (CKD), congestive heart failure (CHF), the metabolic syndrome, type 2 diabetes mellitus (T2DM), and atherosclerosis, with or without cardiovascular events. This article briefly reviews uric acid metabolism and summarizes the current literature on hyperuricaemia in cardiovascular disease and related co-morbidities, and emerging treatment options.

Serum uric acid is more strongly associated with impaired fasting glucose in women than in men from a community-dwelling population

Serum uric acid (SUA) levels are associated with metabolic syndrome (MetS) and its components such as glucose intolerance and type 2 diabetes. It is unknown whether there are gender-specific differences regarding the relationship between SUA levels, impaired fasting glucose (IFG) and newly detected diabetes. We recruited 1,209 men aged 60±15 (range, 19–89) years and 1,636 women aged 63±12 (range, 19–89) years during their annual health examination from a single community. We investigated the association between SUA levels and six categories according to fasting plasma glucose (FPG) level {normal fasting glucose (NFG), <100 mg/dL; high NFG-WHO, 100 to 109 mg/dL; IFG-WHO, 110 to 125 mg/dL; IFG-ADA, 100 to 125 mg/dL; newly detected diabetes, ≥126 mg/dL; known diabetes} SUA levels were more strongly associated with the different FPG categories in women compared with men. In women, the associations remained significant for IFG-WHO (OR, 1.23, 95% CI, 1.00–1.50) and newly detected diabetes (OR, 1.33, 95% CI, 1.03–1.72) following multivariate adjustment. However, in men all the associations were not significant. Thus, there was a significant interaction between gender and SUA level for newly detected diabetes (P = 0.005). SUA levels are associated with different categories of impaired fasting glucose in participants from community-dwelling persons, particularly in women.

Is there a link between hyperuricemia, morning blood pressure surge, and non-dipping blood pressure pattern in metabolic syndrome patients?

Background:

Hypertensive patients usually have a blunted nocturnal decrease, or even increase, in blood pressure during sleep. There is also a tendency for increased occurrence of cardiovascular events between 6 and 12 am due to increased morning blood pressure surge (MBPS). Co-occurrence of metabolic syndrome (MetS) and hypertension is also a common problem. Hyperuricemia might trigger the development of hypertension, chronic renal failure, and insulin resistance. In this study, we aimed to determine whether there is a relationship between hyperuricemia, MetS, nocturnal blood pressure changes, and MBPS.

Method:

A total of 81 newly diagnosed hypertensive MetS patients were included in this study. Ambulatory blood pressure monitoring of patients was done and patients’ height, weight, and waist and hip circumferences were recorded. Fasting blood glucose (FBG), lipid profile, creatinine, potassium, uric acid, hematocrit levels were studied.

Results:

Non-dipper (ie, those whose blood pressure did not drop overnight) patients had higher waist–hip ratios (WHR) (P = 0.003), uric acid (P = 0.0001), FBG (P = 0.001), total and low-density lipoprotein cholesterol levels (P = 0.0001). Risk analysis revealed that hyperuricemia was a risk factor for non-dipping pattern (P < 0.0001, odds ratio = 8.1, 95% confidence interval = 1.9–33.7). Patients in the highest quadrant for uric acid levels had higher FBG (P = 0.001), low-density lipoprotein cholesterol (P = 0.017), WHR (P = 0.01), MBPS (P = 0.003), and night diastolic blood pressure compared with lowest quadrant patients (P = 0.013). Uric acid levels were also positively correlated with night ambulatory blood pressure (ABP) (r = 0.268, P =0.05), night diastolic blood pressure (r =0.3, P =0.05), and MBPS (r =0.3, P =0.05).

Conclusion:

Evaluation of hypertensive patients should also include an assessment of uric acid level and anthropometric measurements such as abdominal obesity. Hyperuricemia seems to be closely related to undesired blood pressure patterns and this may signal to the clinician that an appropriate therapeutic approach is required.

Uric acid and chronic kidney disease: which is chasing which?

Serum uric acid is commonly elevated in subjects with chronic kidney disease (CKD), but was historically viewed as an issue of limited interest. Recently, uric acid has been resurrected as a potential contributory risk factor in the development and progression of CKD. Most studies documented that an elevated serum uric acid level independently predicts the development of CKD. Raising the uric acid level in rats can induce glomerular hypertension and renal disease as noted by the development of arteriolosclerosis, glomerular injury and tubulointerstitial fibrosis. Pilot studies suggest that lowering plasma uric acid concentrations may slow the progression of renal disease in subjects with CKD. While further clinical trials are necessary, uric acid is emerging as a potentially modifiable risk factor for CKD. Gout was considered a cause of CKD in the mid-nineteenth century, and, prior to the availability of therapies to lower the uric acid level, the development of end-stage renal disease was common in gouty patients. In their large series of gouty subjects Talbott and Terplan found that nearly 100% had variable degrees of CKD at autopsy (arteriolosclerosis, glomerulosclerosis and interstitial fibrosis). Additional studies showed that during life impaired renal function occurred in half of these subjects. As many of these subjects had urate crystals in their tubules and interstitium, especially in the outer renal medulla, the disease became known as gouty nephropathy. The identity of this condition fell in question as the presence of these crystals may occur in subjects without renal disease; furthermore, the focal location of the crystals could not explain the diffuse renal scarring present. In addition, many subjects with gout also had coexistent conditions such as hypertension and vascular disease, leading some experts to suggest that the renal injury in gout was secondary to these latter conditions rather than to uric acid per se. Indeed, gout was removed from the textbooks as a cause of CKD, and the common association of hyperuricemia with CKD was solely attributed to the retention of serum uric acid that is known to occur as the glomerular filtration rate falls. Renewed interest in uric acid as a cause of CKD occurred when it was realized that invalid assumptions had been made in the arguments to dismiss uric acid as a risk factor for CKD. The greatest assumption was that the mechanism by which uric acid would cause kidney disease would be via the precipitation as crystals in the kidney, similar to the way it causes gout. However, when laboratory animals with CKD were made hyperuricemic, the renal disease progressed rapidly despite an absence of crystals in the kidney. Since this seminal study, there has been a renewed interest in the potential role uric acid may have in both acute and CKD. We briefly review some of the major advances that have occurred in this field in the last 15 years.

Genome-wide association analyses identify 18 new loci associated with serum urate concentrations

Elevated serum urate concentrations can cause gout, a prevalent and painful inflammatory arthritis. By combining data from >140,000 individuals of European ancestry within the Global Urate Genetics Consortium (GUGC), we identified and replicated 28 genome-wide significant loci in association with serum urate concentrations (18 new regions in or near TRIM46, INHBB, SFMBT1, TMEM171, VEGFA, BAZ1B, PRKAG2, STC1, HNF4G, A1CF, ATXN2, UBE2Q2, IGF1R, NFAT5, MAF, HLF, ACVR1B-ACVRL1 and B3GNT4). Associations for many of the loci were of similar magnitude in individuals of non-European ancestry. We further characterized these loci for associations with gout, transcript expression and the fractional excretion of urate. Network analyses implicate the inhibins-activins signaling pathways and glucose metabolism in systemic urate control. New candidate genes for serum urate concentration highlight the importance of metabolic control of urate production and excretion, which may have implications for the treatment and prevention of gout.

Association between serum uric acid and nonalcoholic fatty liver disease in the US population

BACKGROUND/PURPOSE

Studies conducted in Eastern Asia suggest that serum uric acid (SUA) level is highly related to nonalcoholic fatty liver disease (NAFLD). However, limited information is available in the USA. Our objective was to determine the association between NAFLD and SUA levels in the USA and to determine if this is independent of age, sex, and components of metabolic syndrome (MetS).

METHODS

We analyzed 5370 men and women aged 20-74 years from the Third National Health and Nutrition Examination Survey (NHANES III) (1988-1994) in the USA. We calculated the prevalence and odds ratio (OR) of NAFLD and elevated liver enzymes by SUA and sex-specific quintiles of SUA, adjusting for multiple factors.

RESULTS

The prevalence of NAFLD was higher in participants with higher SUA levels (10.9%, 9.6%, 15.9%, 21.8% and 33.1%, respectively, from the second to the fifth sex-specific quintile of uric acid). After adjustment, individuals with hyperuricemia were more likely to have NAFLD (OR: 1.4, 95% CI: 1.1-1.9). Similarly, the adjusted odds of NAFLD were increasingly higher from the second to the fifth quintile of SUA (ORs: 0.8, 1.2, 1.5 and 1.7, respectively; p < 0.01) as compared to the lowest quintile. Finally, individuals with hyperuricemia were more likely to have elevated liver enzymes (aspartate aminotransferase or alanine aminotransferase) (adjusted OR: 1.8, 95% CI: 1.1-2.7).

CONCLUSION

NAFLD and SUA levels were strongly and independently associated in this nationally representative sample of men and women after adjustment for multiple factors.

Changes in uric acid levels following bariatric surgery are not associated with SLC2A9 variants in the Swedish Obese Subjects Study

Context and Objective

Obesity and SLC2A9 genotype are strong determinants of uric acid levels. However, data on SLC2A9 variants and weight loss induced changes in uric acid levels are missing. We examined whether the changes in uric acid levels two- and ten-years after weight loss induced by bariatric surgery were associated with SLC2A9 single nucleotide polymorphisms (SNPs) in the Swedish Obese Subjects study.

Methods

SNPs (N = 14) identified by genome-wide association studies and exonic SNPs in the SLC2A9 gene locus were genotyped. Cross-sectional associations were tested before (N = 1806), two (N = 1664) and ten years (N = 1201) after bariatric surgery. Changes in uric acid were compared between baseline and Year 2 (N = 1660) and years 2 and 10 (N = 1172). A multiple testing corrected threshold of P = 0.007 was used for statistical significance.

Results

Overall, 11 of the 14 tested SLC2A9 SNPs were significantly associated with cross-sectional uric acid levels at all three time points, with rs13113918 showing the strongest association at each time point (R² = 3.7−5.2%, 3.9×10⁻²²≤p≤7.7×10⁻¹¹). One SNP (rs737267) showed a significant association (R² = 0.60%, P = 0.002) with change in uric acid levels from baseline to Year 2, as common allele homozygotes (C/C, N = 957) showed a larger decrease in uric acid (−61.4 µmol/L) compared to minor allele carriers (A/X: −51.7 µmol/L, N = 702). No SNPs were associated with changes in uric acid from years 2 to 10.

Conclusions

SNPs in the SLC2A9 locus contribute significantly to uric acid levels in obese individuals, and the associations persist even after considerable weight loss due to bariatric surgery. However, we found little evidence for an interaction between genotype and weight change on the response of uric acid to bariatric surgery over ten years. Thus, the fluctuations in uric acid levels among the surgery group appear to be driven by the weight losses and gains, independent of SLC2A9 genotypes.

Serum uric acid and adiposity: deciphering causality using a bidirectional Mendelian randomization approach

Background

Although the relationship between serum uric acid (SUA) and adiposity is well established, the direction of the causality is still unclear in the presence of conflicting evidences. We used a bidirectional Mendelian randomization approach to explore the nature and direction of causality between SUA and adiposity in a population-based study of Caucasians aged 35 to 75 years.

Methods and Findings

We used, as instrumental variables, rs6855911 within the SUA gene SLC2A9 in one direction, and combinations of SNPs within the adiposity genes FTO, MC4R and TMEM18 in the other direction. Adiposity markers included weight, body mass index, waist circumference and fat mass. We applied a two-stage least squares regression: a regression of SUA/adiposity markers on our instruments in the first stage and a regression of the response of interest on the fitted values from the first stage regression in the second stage. SUA explained by the SLC2A9 instrument was not associated to fat mass (regression coefficient [95% confidence interval]: 0.05 [−0.10, 0.19] for fat mass) contrasting with the ordinary least square estimate (0.37 [0.34, 0.40]). By contrast, fat mass explained by genetic variants of the FTO, MC4R and TMEM18 genes was positively and significantly associated to SUA (0.31 [0.01, 0.62]), similar to the ordinary least square estimate (0.27 [0.25, 0.29]). Results were similar for the other adiposity markers.

Conclusions

Using a bidirectional Mendelian randomization approach in adult Caucasians, our findings suggest that elevated SUA is a consequence rather than a cause of adiposity.

Elevated uric acid, the metabolic syndrome and cardiovascular disease: cause, consequence, or just a not so innocent bystander?

For more than 200 years initially seen as a cause of gout, speaking in a politically correct 21st century term, a disease of the rich and very well nourished people, many experimental and epidemiological studies have associated increased levels of serum uric acid (UA) with the classical components of the metabolic syndrome (MS), type 2 diabetes, and cardiovascular disease [1]. This association with components of the MS is seen even in children and adolescents [2]. The topic of increased UA concentrations, its consequences or associations is getting more important nowadays due to the increments in the prevalence of obesity and the MS in both developed and developing countries.

Uric acid is more strongly associated with impaired glucose regulation in women than in men from the general population: the KORA F4-Study

Objective

High serum uric acid (UA) levels are associated with the metabolic syndrome, type 2 diabetes and cardiovascular disease. It is largely unknown whether there are gender-specific differences regarding the association between UA and prediabetic states. We examined the possible association between UA levels and known as well as newly diagnosed diabetes (NDD), isolated impaired fasting glucose (i-IFG), isolated impaired glucose tolerance (i-IGT), and combined IFG/IGT in a population-based sample of 32-to-81-year-old men and women.

Research Design and Methods

An oral glucose tolerance test was carried out in all 2,740 participants without known diabetes of the Cooperative Health Research in the Region of Augsburg (KORA) F4 Study conducted between 2006 and 2008 in Southern Germany. Serum UA was analysed by the uricase method.

Results

In women after multivariable adjustment the associations between UA and i-IFG (OR 1.57, 95% CI 1.15–2.14), IFG/IGT (OR 1.52, 1.07–2.16), NDD (OR 1.67, 95% CI 1.28–2.17), and known diabetes (OR 1.47, 95% CI 1.18–1.82) remained significant, but the association with i-IGT (OR 1.14, 95% CI 0.95–1.36) lost significance. In contrast in men, after multivariable adjustment there was only a significant association between UA levels and i-IFG (OR 1.49, 95% CI 1.21–1.84), all other associations were non-significant (i-IGT: OR 1.09, IFG/IGT: OR 1.06, NDD: OR 0.91, known diabetes: OR 1.04; all p-values>0.05).

Conclusions

Serum UA concentrations were associated with different categories of impaired glucose regulation in individuals from the general population, particularly in women. Further studies investigating the role of UA in the development of derangements in glucose metabolism are needed.

Nephrolithiasis: Endocrine evaluation

Nephrolithias is a common problem in populations around the world, and contribute significantly to the development of end stage renal disease. It is a matter of debate whether the metabolic factors responsible for renal stone formation are similar or variable in different populations around the globe. This review discusses the influence of different metabolic and dietary factor, and some other co-morbid conditions on the etiopathogenesis Nephrolithiasis. Evaluation and medical management of Nephrolithiasis is summarized in the later part of the article.

SGLT2 inhibition in diabetes mellitus: rationale and clinical prospects

This Review covers the rationale, physiological consequences and clinical application of pharmacological sodium-glucose cotransporter 2 (SGLT2) inhibition. In patients with type 2 diabetes mellitus, in whom renal glucose reabsorption might be upregulated, orally active, selective SGLT2 inhibitors improve glycaemic control to a therapeutically useful extent. Chronic administration of several SGLT2 inhibitors dose-dependently lowers HbA(1c) levels by 0.5-1.5% without causing hypoglycaemia. The unique mechanism of action of SGLT2 inhibitors-which does not hinge upon β-cell function or tissue insulin sensitivity-means that they can exert their antihyperglycaemic effects in combination with any other oral antidiabetic drug as well as insulin. Available phase III studies confirm a good tolerability profile. Weight loss owing to urinary calorie leakage may be less than expected, but the negative energy balance offers a valuable clinical benefit. Offloading of sodium can assist blood pressure control. The progressive loss of efficacy in patients with reduced glomerular function will have to be balanced against the possibility of renal protection. The safety issues of genitourinary infections and cancer risk requires careful, proactive monitoring and analysis of robust exposure data, particularly in elderly, frail patients and in patients with impaired kidney function and/or high cardiovascular/cancer risk, who represent an increasing fraction of the population with diabetes mellitus.

The relationship between the regional abdominal adipose tissue distribution and the serum uric acid levels in people with type 2 diabetes mellitus

BACKGROUND

Hyperuricemia is associated with obesity. The visceral adiposity and subcutaneous adiposity may be associated with the differential metabolic risk, and the distribution of abdominal adipose tissue was significantly altered in people with type 2 diabetes mellitus (DM) compared to healthy people. Our study was performed to determine to the association between the regional abdominal adipose tissue distribution and serum uric acid levels in people with type 2 DM.

METHODS

A total of 699 people with type 2 DM and who had undergone abdominal computed tomography assessment of the visceral fat area and subcutaneous fat area were included. The serum uric acid levels were measured by the uricase method. Hyperuricemia was defined by cut-off value of > 7 mg/dl for men and > 6 mg/dl for women.

RESULTS

The visceral fat area was positively associated with the serum uric acid levels after adjustment for age, sex, systolic blood pressure, diastolic blood pressure, serum creatinine, hemoglobin, serum albumin, serum high-density lipoprotein, serum triglyceride and hemoglobin A1c (β-coefficient = 0.117, p < 0.001). The logistic regression analysis showed that the visceral fat area was the significant independent predictor of hyperuricemia (OR 2.33, 95% CI, 1.21-4.50, p = 0.012). But there was no significant association between the subcutaneous fat area and the serum uric acid levels (β-coefficient = 0.061, p = 0.255).

CONCLUSIONS

our data shows that the visceral fat area was positively associated with the serum uric acid levels, but the subcutaneous fat area was not in people with type 2 DM.

A structural equation model for assessment of links between changes in serum triglycerides, -urate, and -glucose and changes in serum calcium, -magnesium and -phosphate in type 2 diabetes and non-diabetes metabolism

Background

This study investigates the associations between changes in serum Triglycerides (S-TG), -Urate (S-Urate), and -Glucose (S-Glu) and changes in serum Calcium (S-Ca), -Magnesium (S-Mg), and -Phosphate (S-P) in patients with type 2 diabetes compared with non-diabetic patients.

Methods

The analysis is based on data collected from a secondary prevention population of women and men (W/M) at risk for cardiovascular disease (type 2 diabetes, 212/200; non-diabetes 968/703). The whole population (n = 2083) had a mean age of 51.0 (9.7) years and was stratified for sex and according to type 2 diabetes or non-diabetes. The patients were followed for, either half a year or one year and changes in risk factors were calculated from follow-up to baseline, the time when patients were admitted to the health center. The pattern of relationships was evaluated using a structural equation model.

Results

Higher S-TG and S-Glu but lower S-Urate was revealed at baseline in type 2 diabetes women and men as compared to their counterparts, non-diabetes patients. Women with type 2 diabetes had higher S-Ca and lower S-Mg than non-diabetes women. Changes in S-Glu were associated with changes in S-Ca (+), baseline S-Ca (+), and S-Urate (-) in type 2 diabetes men. Changes in S-Urate were associated with changes in S-Mg (+) in type 2 diabetes women and non-diabetes men. In men with non-diabetes, changes in S-Glu were associated with changes in S-Mg (-). In women with non-diabetes, changes in S-Glu were associated with changes in S-P (-) and changes in S-Urate with changes in S-Ca (+).

Conclusion

With respect to metabolic disturbances in non-diabetes and the awareness of risk for type 2 diabetes, changes in S-Glu and changes in S-Ca, S-Mg, and S-P should be considered as risk factors for cardiovascular disease. Increased early detection and corrections of high S-Ca, low S-Mg, and S-P in obese patients may improve their metabolism and reduce the risk of CVD in patients with type 2 diabetes.

Trial registration number

ISRCTN: ISRCTN79355192

Gender-specific relationship between serum uric acid level and atrial fibrillation prevalence

BACKGROUND

Although various kinds of cardiovascular risk factors have been reported to be associated with atrial fibrillation (AF), the relationship between serum uric acid level and AF has not been fully examined.

METHODS AND RESULTS

Data were collected from a single hospital-based cohort in the Shinken Database 2004-2008 (n=11,123), and consisted of serum uric acid level for 7,155 patients. The association between serum uric acid level and AF prevalence was evaluated on logistic regression. Uric acid significantly increased the crude AF prevalence in both men and women (both, P<0.001). The odds ratio (OR) and 95% confidence interval (95%CI) in the highest tertile compared with the lowest one were 3.368 (2.478-4.578) and 1.408 (1.169-1.695) in women and men, respectively. Uric acid was also significantly associated with other various cardiovascular risk factors for AF. Even after the multivariate model was adjusted using these variables, the effect of uric acid on AF was independent in women (OR, 1.888; 95%CI: 1.278-2.790), but not in men.

CONCLUSIONS

Reflecting the composite of various cardiovascular risk factors, serum uric acid level was apparently associated with AF prevalence. The independent association in women might imply some sex-specific mechanisms. The results should be confirmed in prospective studies.

Uric acid levels and all-cause and cardiovascular mortality in the hemodialysis population

BACKGROUND AND OBJECTIVES

Hyperuricemia is associated with hypertension, coronary artery disease, and chronic kidney disease. However, there are no specific data on the relationship of uric acid to cardiovascular disease in the chronic hemodialysis setting.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Data from 5827 patients on chronic hemodialysis from six countries affiliated with the Dialysis Outcomes and Practice Patterns Study (DOPPS) were analyzed. All laboratory data were based upon the initial cross-section of patients in DOPPS I and II. Cox regression was used to calculate the hazard ratio (HR) of all-cause and cardiovascular (CV) mortality with adjustments for case-mix including 14 classes of comorbidity.

RESULTS

There were no clinically significant differences in baseline characteristics between those who had measured uric acid (n = 4637) and those who did not (n = 1190). Uric acid level was associated with lower all-cause mortality (HR: 0.95, 95% confidence interval [CI]: 0.90 to 1.00 per 1 mg/dl higher uric acid level) and CV mortality (HR: 0.92, 95% CI: 0.86 to 0.99). When analyzed as a dichotomous variable, the adjusted HR at uric acid ≤8.2 mg/dl compared with >8.2 mg/dl was 1.24 (95% CI: 1.03 to 1.49) for all-cause mortality and 1.54 (95% CI: 1.15 to 2.07) for CV mortality.

CONCLUSIONS

Higher uric acid levels were associated with lower risk of all-cause and CV mortality in the hemodialysis population. These results are in contrast to the association of hyperuricemia with higher cardiovascular risk in the general population and should be the subject of further research.

No evidence for a causal link between uric acid and type 2 diabetes: a Mendelian randomisation approach

AIMS/HYPOTHESIS

Epidemiological and experimental evidence suggests that uric acid has a role in the aetiology of type 2 diabetes. Using a Mendelian randomisation approach, we investigated whether there is evidence for a causal role of serum uric acid for development of type 2 diabetes.

METHODS

We examined the associations of serum-uric-acid-raising alleles of eight common variants recently identified in genome-wide association studies and summarised this in a genetic score with type 2 diabetes in case-control studies including 7,504 diabetes patients and 8,560 non-diabetic controls. We compared the observed effect size to that expected based on: (1) the association between the genetic score and uric acid levels in non-diabetic controls; and (2) the meta-analysed uric acid level to diabetes association.

RESULTS

The genetic score showed a linear association with uric acid levels, with a difference of 12.2 μmol/l (95% CI 9.3, 15.1) by score tertile. No significant associations were observed between the genetic score and potential confounders. No association was observed between the genetic score and type 2 diabetes with an OR of 0.99 (95% CI 0.94, 1.04) per score tertile, significantly different (p = 0.046) from that expected (1.04 [95% CI 1.03, 1.05]) based on the observed uric acid difference by score tertile and the uric acid to diabetes association of 1.21 (95% CI 1.14, 1.29) per 60 μmol/l.

CONCLUSIONS/INTERPRETATION

Our results do not support a causal role of serum uric acid for the development of type 2 diabetes and limit the expectation that uric-acid-lowering drugs will be effective in the prevention of type 2 diabetes.

The relationship between normal serum uric acid and nonalcoholic fatty liver disease

The objective of the present study was to determine the relationship between serum uric acid (SUA) level and the presence of nonalcoholic fatty liver disease (NAFLD). We analyzed data of 9,019 Koreans who visited a health check up center. The SUA levels of all of these subjects were within the normal range. The participants were divided into 4 groups according to the quartiles of the SUA levels for both sexes. Hepatic steatosis was diagnosed on the basis of ultrasonographic findings. Multivariate logistic regression modeling was performed across the SUA quartiles. The presence of NAFLD and metabolic abnormalities were found significantly in subjects with high-normal SUA levels. After adjustment for age, metabolic components, and the liver-function test, the adjusted odds ratio (OR, 95% CIs) for the presence of NAFLD in the subjects with the highest SUA level was 1.46 (1.17-1.82) for men and 2.13 (1.42-3.18) for women, as compared to the subjects with the lowest SUA level. Our results suggest that increased SUA concentrations, even within the normal range, are independently associated with the presence of NAFLD.

Insulin resistance: pathophysiology and rationale for treatment

After binding to its receptor and activating the β-subunit, insulin is faced with two divergent pathways: one is phosphatidylinositol 3-kinase (PI 3-K) dependent, while another is dependent upon activation of mitogen-activated protein kinase (MAP-K). The former is absolutely necessary for mediating most metabolic and antiapoptotic effects; the latter is linked to nonmetabolic, proliferative and mitogenic effects. In obese patients, especially with type 2 diabetes mellitus (DM2), only the PI 3-K, but not the MAP-K, is resistant to insulin stimulation: hence insulin resistance is better defined as metabolic insulin resistance. The resulting 'compensatory hyperinsulinemia' is an unsuccessful attempt to overcome the inhibition of the metabolic pathway at the price of unopposed stimulation of the MAP-K pathway, and the administration of exogenous insulin might worsen the metabolic dysfunction. As the preferential activation of the MAP-K pathway in insulin-resistant patients has atherogenic and mitogenic properties, this leads to atherosclerosis and cancer. Metformin may carry out direct protective action on human β cells, inasmuch as it improves both primary and secondary endpoints through selective inhibition of fatty acyl oxidation.

Hyperuricaemia, chronic kidney disease, and outcomes in heart failure: potential mechanistic insights from epidemiological data

AIM

To determine if the association between hyperuricaemia and poor outcomes in heart failure (HF) varies by chronic kidney disease (CKD).

METHODS AND RESULTS

Of the 2645 systolic HF patients in the Beta-Blocker Evaluation of Survival Trial with data on baseline serum uric acid, 1422 had hyperuricaemia (uric acid ≥6 mg/dL for women and ≥8 mg/dL for men). Propensity scores for hyperuricaemia, estimated for each patient, were used to assemble a matched cohort of 630 pairs of patients with and without hyperuricaemia who were balanced on 75 baseline characteristics. Associations of hyperuricaemia with outcomes during 25 months of median follow-up were examined in all patients and in those with and without CKD (estimated glomerular filtration rate of <60 mL/min/1.73 m(2)). Hyperuricaemia-associated hazard ratios (HRs) and 95% confidence intervals (CI) for all-cause mortality and HF hospitalization were 1.44 (1.12-1.85, P = 0.005) and 1.27 (1.02-1.58, P = 0.031), respectively. Hazard ratios (95% CIs) for all-cause mortality among those with and without CKD were 0.96 (0.70-1.31, P = 0.792) and 1.40 (1.08-1.82, P = 0.011), respectively (P for interaction, 0.071), and those for HF hospitalization among those with and without CKD were 0.99 (0.74-1.33, P = 0.942) and 1.49 (1.19-1.86, P = 0.001), respectively (P for interaction, 0.033).

CONCLUSION

Hyperuricaemia has a significant association with poor outcomes in HF patients without CKD but not in those with CKD, suggesting that hyperuricaemia may predict poor outcomes when it is primarily a marker of increased xanthine oxidase activity, but not when it is primarily due to impaired renal excretion of uric acid.

Influence of physical activity intensity and aerobic fitness on the anthropometric index and serum uric acid concentration in people with obesity

BACKGROUND AND OBJECTIVE

Physical activity (PA) is considered an important approach to prevent and treat obesity and hyperuricemia. The purpose of the present study was to examine the influence of PA intensity and aerobic fitness on anthropometric indices and serum uric acid in obese individuals.

METHODS

PA was examined using a single-axial accelerometer and aerobic fitness was assessed by electric cycle ergometry in obese middle-aged men (n=71, 47.2 ± 4.4 years). PA was defined as light (<3 metabolic equivalents [METs]), moderate (3.0-6.0 METs) or vigorous (>6.0 METs) intensity from the corresponding METs multiplied by time spent at the corresponding intensity levels. Serum uric acid was measured by the uricase peroxidase method.

RESULTS

The association between aerobic fitness index (lactate threshold) and serum uric acid did not reach statistical significance after adjustment for potential confounding factors (age, body mass index [BMI], and alcohol consumption) (β=-0.110, p=0.138). Light intensity PA was inversely associated with BMI and waist circumference, even after adjustment for age and alcohol consumption (BMI: β=-0.543, p=0.023; waist circumference: β=-1.333, p=0.016). Moderate intensity PA, but not light or vigorous intensity PA, was inversely correlated with the uric acid level and this remained significant after adjustment for age, BMI, and alcohol consumption (β=-0.222, p=0.036).

CONCLUSION

Our results suggest that light intensity PA may have an important role in weight control while moderate intensity PA may be associated with the lower uric acid concentrations in obese individuals.

Association of renal manifestations with serum uric acid in Korean adults with normal uric acid levels

Several studies have reported that hyperuricemia is associated with the development of hypertension and cardiovascular disease. Increasing evidences also suggest that hyperuricemia may have a pathogenic role in the progression of renal disease. Paradoxically, uric acid is also widely accepted to have antioxidant activity in experimental studies. We aimed to investigate the association between glomerular filtration rate (GFR) and uric acid in healthy individuals with a normal serum level of uric acid. We examined renal function determined by GFR and uric acid in 3,376 subjects (1,896 men; 1,480 women; aged 20-80 yr) who underwent medical examinations at Gangnam Severance Hospital from November 2006 to June 2007. Determinants for renal function and uric acid levels were also investigated. In both men and women, GFR was negatively correlated with systolic and diastolic blood pressures, fasting plasma glucose, total cholesterol, uric acid, log transformed C reactive protein, and log transformed triglycerides. In multivariate regression analysis, total uric acid was found to be an independent factor associated with estimated GFR in both men and women. This result suggests that uric acid appears to contribute to renal impairment in subjects with normal serum level of uric acid.

APOE polymorphism is associated with lipid profile, but not with arterial stiffness in the general population

Background

Cardiovascular diseases (CVD) are the main cause of death and disability in developed countries. In most cases, the progress of CVD is influenced by environmental factors and multifactorial inheritance. The purpose of this study was to investigate the association between APOE genotypes, cardiovascular risk factors, and a non-invasive measure of arterial stiffness in the Brazilian population.

Methods

A total of 1493 urban Brazilian individuals were randomly selected from the general population of the Vitoria City Metropolitan area. Genetic analysis of the APOE polymorphism was conducted by PCR-RFLP and pulse wave velocity analyzed with a noninvasive automatic device.

Results

Age, gender, body mass index, triglycerides, creatinine, uric acid, blood glucose, blood pressure phenotypes were no different between ε2, ε3 and ε4 alleles. The ε4 allele was associated with higher total-cholesterol (p < 0.001), LDL-C (p < 0.001), total-cholesterol/HDL-C ratio (p < 0.001), LDL/HDL-C ratio (p < 0.001), lower HDL-C values (p < 0.001) and higher risk to obesity (OR = 1.358, 95% CI = 1.019-1.811) and hyperuricemia (OR = 1.748, 95% CI = 1.170-2.611). Nevertheless, pulse wave velocity (p = 0.66) measures were no different between genotypes. The significant association between APOE genotypes and lipid levels persisted after a 5-year follow-up interval, but no interaction between time and genotype was observed for lipids longitudinal behavior.

Conclusion

The ε4 allele of the APOE gene is associated with a worse lipid profile in the Brazilian urban population. In our relatively young sample, the observed effect of APOE genotype on lipid levels was not translated into significant effects in arterial wall stiffness.

Effect of serum insulin on the association between hyperuricemia and incident heart failure

Increased serum uric acid (UA) is associated with incident heart failure (HF). However, whether it is a direct effect of UA or an effect of increased xanthine oxidase (XO) is unknown. Because hyperuricemia in hyperinsulinemia is primarily due to impaired renal UA excretion, its association with incident HF would suggest a direct UA effect. In contrast, hyperuricemia in normoinsulinemia is likely due to increased UA production and thus its association with incident HF would suggest an XO effect. To clarify this, we examined the association of hyperuricemia with centrally adjudicated incident HF in Cardiovascular Health Study participants with and without hyperinsulinemia. Of the 5,411 participants ≥ 65 years of age without baseline HF, 1,491 (28%) had hyperuricemia (serum UA ≥ 6 mg/dl for women and ≥ 7 mg/dl for men). Propensity scores for hyperuricemia were estimated using 63 baseline characteristics. Mean serum UA levels were 6.0 and 5.3 mg/dl in those with (n = 2,731) and those without (n = 2,680) hyperinsulinemia (median serum insulin ≥ 13 mU/L), respectively (p < 0.001). Propensity-adjusted hazard ratios (95% confidence intervals) for hyperuricemia-associated incident HF during 8 years of median follow-up were 0.99 (0.83 to 1.18, p = 0.886) and 1.32 (1.04 to 1.67, p = 0.021) for those with and without hyperinsulinemia respectively (p for interaction = 0.014). In conclusion, the absence of an association of hyperuricemia with incident HF in those with hyperinsulinemia (despite a significantly higher mean serum UA) and a significant association in normoinsulinemia suggest that UA has no intrinsic association with incident HF and that it may predict incident HF when it is a marker of increased of XO activity.

Uric acid and hypertension: cause or effect?

Uric acid was first associated with primary hypertension in 1874, yet its role in this condition remains unclear. Historically, uric acid was thought to be a secondary response to hypertension or its associated conditions. However, more recent experimental and clinical studies suggest that uric acid could have a contributory role in the pathogenesis of elevated blood pressure. More studies are needed to help dissect the potential mechanisms by which uric acid could initiate this response. It remains possible that uric acid is a marker for xanthine oxidase-associated oxidants and that the latter could be driving the hypertensive response. However, the weight of the evidence suggests that uric acid is a true modifying and possibly causal factor for human primary hypertension. Hence, early management of hyperuricemia might delay the development of essential hypertension.

Hyperuricemia in obese children and adolescents: the relationship with metabolic syndrome

The prevalence of hyperuricemia in obese children and adolescents and its association with metabolic syndrome are largely unknown. The objective of our study was to characterize hyperuricemia in relation to metabolic syndrome in Japanese children and adolescents with obesity. Between 2005 and 2008, we performed a cross-sectional study of 1,027 obese children and adolescents aged 6-14 years. Based on the reference value of serum uric acid we had established previously, hyperuricemia was defined as one standard deviation over the mean value at each age. The diagnosis of metabolic syndrome was made based on the Japanese criteria for children. A total of 213 children and adolescents (20.7%) was found to have hyperuricemia. The prevalence of hyperuricemia was significantly higher in the male gender and older age group. Sixty-five out of 213 subjects with hyperuricemia (30.5%) had metabolic syndrome, whereas 111 out of 814 subjects without hyperuricemia (13.6%) had metabolic syndrome. The most common abnormal component of metabolic syndrome was triglyceride, followed by diastolic blood pressure, systolic blood pressure, fasting blood glucose, and HDL-cholesterol. Such a tendency was almost identical between the two groups. We concluded that considering the association between hyperuricemia and metabolic syndrome in obese Japanese children and adolescents, the role of hyperuricemia in metabolic syndrome should receive more attention, beginning in early childhood.

Could uric acid be a modifiable risk factor in subjects with pulmonary hypertension?

A high serum uric acid is common in subjects with pulmonary hypertension. The increase in serum uric acid may be a consequence of the local tissue ischemia and/or hypoxia, and it may also result from other factors independent of ischemia or hypoxia that occur in various forms of pulmonary hypertension. While classically viewed as a secondary phenomenon, recent studies suggest that hyperuricemia may also have a role in mediating the local vasoconstriction and vascular remodeling in the pulmonary vasculature. If uric acid does have a contributory role in pulmonary hypertension, we may see an increasing prevalence of pulmonary hypertension as hyperuricemia is common in subjects with obesity and metabolic syndrome. We propose studies to investigate the role of uric acid in pulmonary hypertension and to determine if lowering serum uric acid may have clinical benefit in this condition.

Serum uric acid is associated with metabolic risk factors for cardiovascular disease in the Uygur population

The prevalence of hyperuricemia is low in Uygurs, who have a high prevalence of cardiovascular risk factors such as hypertension, overweight-obesity, dyslipidemia, hyperglycemia, and insulin resistance (IR). This study sought to investigate the relationships between serum uric acid (UA) and these risk factors in this population. A cross-sectional study was conducted in Uygurs (859 males, 1268 females) aged 20 to 70 years. Demographic data, systolic blood pressure (SBP), diastolic blood pressure (DBP), body mass index (BMI), and fasting and postprandial blood were obtained, and biological measurements were determined. The mean of BMI, SBP, DBP, total cholesterol, high-density lipoprotein cholesterol (HDL-c), low-density lipoprotein cholesterol (LDL-c), triglycerides, fasting blood glucose, fasting insulin, and homeostasis model assessment insulin resistance index (HOMA-IR), and the prevalence of hypertension, IR, hyperglycemia, overweight-obesity, hypercholesteremia, hyper-LDL-c, and hypertriglyceridemia increased with UA but the prevalence of hypo-HDL-c decreased (p < 0.05). Logistic regression analysis showed that the odds ratios for IR, overweight-obesity, hypercholesteremia, hyper-LDL-c, and hypertriglyceridemia against the lowest UA group increased but decreased for hypo-HDL-c (p < 0.05). The UA in the hypo-HDL-c group was lower than that of the controls; the prevalence of hypo-HDL-c in hyperuricemia subjects was lower than in those with normal UA (p < 0.05). But the opposite results were observed between overweight-obesity, hyperglycemia, IR, hypercholesteremia, hypertriglyceridemia, and hyper-LDL-c and correspondence controls, respectively (p < 0.05). In Uygur, elevated UA is associated with overweight-obesity, hypercholesteremia, hyper-LDL-c, hypertriglyceridemia, hyperglycemia, and IR. The HDL-c level significantly increases with UA, whereas the prevalence of hypo-HDL-c decreases. Further studies are needed to clarify why UA is positively correlated to HDL-c.

Carbohydrate exerts a mild influence on fluid retention following exercise-induced dehydration

Rapid and complete rehydration, or restoration of fluid spaces, is important when acute illness or excessive sweating has compromised hydration status. Many studies have investigated the effects of graded concentrations of sodium and other electrolytes in rehydration solutions; however, no study to date has determined the effect of carbohydrate on fluid retention when electrolyte concentrations are held constant. The purpose of this study was to determine the effect of graded levels of carbohydrate on fluid retention following exercise-induced dehydration. Fifteen heat-acclimatized men exercised in the heat for 90 min with no fluid to induce 2–3% dehydration. After a 30-min equilibration period, they received, over the course of 60 min, one of five test beverages equal to 100% of the acute change in body mass. The experimental beverages consisted of a flavored placebo with no electrolytes (P), placebo with electrolytes (P + E), 3%, 6%, and 12% carbohydrate solutions with electrolytes. All beverages contained the same type and concentration of electrolytes (18 meq/l Na+, 3 meq/l K+, 11 meq/l Cl−). Subjects voided their bladders at 60, 90, 120, 180, and 240 min, and urine specific gravity and urine volume were measured. Blood samples were taken before exercise and 30, 90, 180, and 240 min following exercise and were analyzed for glucose, sodium, hemoglobin, hematocrit, renin, aldosterone, and osmolality. Body mass was measured before and after exercise and a final body mass was taken at 240 min. There were no differences in percent dehydration, sweat loss, or fluid intake between trials. Fluid retention was significantly greater for all carbohydrate beverages compared with P (66.3 ± 14.4%). P + E (71.8 ± 9.9%) was not different from water, 3% (75.4 ± 7.8%) or 6% (75.4 ± 16.4%) but was significantly less than 12% (82.4 ± 9.2%) retention of the ingested fluid. No difference was found between the carbohydrate beverages. Carbohydrate at the levels measured exerts a mild influence on fluid retention in postexercise recovery.

What lies behind serum urate concentration? Insights from genetic and genomic studies

Many factors, including genetic components and acquired factors such as obesity and alcohol consumption, influence serum uric acid (urate) concentrations. Since serum urate concentrations are determined by the balance between renal urate excretion and the volume of urate produced via purine metabolism, urate transporter genes as well as genes coding for enzymes involved in purine metabolism affect serum urate concentrations. URAT1 was the first transporter affecting serum urate concentrations to be identified. Using the characterization of this transporter as an indicator, several transporters have been shown to transport urate, allowing the construction of a synoptic renal urate transport model. Notable re-absorptive urate transporters are URAT1 at apical membranes and GLUT9 at basolateral membranes, while ABCG2, MRP4 (multidrug resistance protein 4) and NPT1 are secretive transporters at apical membranes. Recent genome-wide association studies have led to validation of the in vitro model constructed from each functional analysis of urate transporters, and identification of novel candidate genes related to urate metabolism and transport proteins, such as glucokinase regulatory protein (GKRP), PDZK1 and MCT9. However, the function and physiologic roles of several candidates, as well as the influence of acquired factors such as obesity, foods, or alcoholic beverages, remain unclear.

Uric acid concentrations are associated with insulin resistance and birthweight in normotensive pregnant women

OBJECTIVE

We sought to investigate whether uric acid concentrations are increased in pregnant women with insulin resistance and to correlate both with fetal growth.

STUDY DESIGN

Uric acid, glucose, and insulin were measured in plasma at 20.4 (+/-2.0) weeks' gestation in 263 women. The association between uric acid and insulin resistance, as estimated using the homeostasis model assessment (HOMA), was analyzed and related to birthweights.

RESULTS

In 212 (80.6%) women who remained normotensive throughout pregnancy, HOMA increased 1.23 U per 1-mg/dL increase in uric acid (95% confidence interval, 1.07-1.42; P=.003). Infants born to normotensive women in the upper quartile of uric acid and lowest HOMA quartile weighed 435.6 g less than infants of women with highest uric acid and HOMA quartiles (P<.005).

CONCLUSION

Increasing uric acid concentrations were associated with insulin resistance in midpregnancy. Hyperuricemia was associated with lower birthweight in normotensive women, and this effect was attenuated by insulin resistance.

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.

Association between serum uric acid and development of type 2 diabetes

OBJECTIVE

To systematically evaluate the association between serum uric acid (SUA) level and subsequent development of type 2 diabetes.

RESEARCH DESIGN AND METHODS

We searched Medline (31 March from 1966 to 2009) and Embase (31 March from 1980 to 2009) for observational cohort studies examining the association between SUA and the risk of type 2 diabetes by manual literature search. Relative risks (RRs) for each 1 mg/dl increase in SUA were pooled by using a random-effects model. The studies included were stratified into subgroups representing different study characteristics, and meta-regression analyses were performed to investigate the effect of these characteristics on the association between SUA level and type 2 diabetes risk.

RESULTS

The search yielded 11 cohort studies (42,834 participants) that reported 3,305 incident cases of type 2 diabetes during follow-up periods ranging from 2.0 to 13.5 years. The pooled RR of a 1 mg/dl increase in SUA was 1.17 (95% CI 1.09-1.25). Study results were consistently significant (i.e., >1) across characteristics of participants and study design. Publication bias was both visually and statistically suggested (P = 0.03 for Egger's test, 0.06). Adjustment for publication bias attenuated the pooled RR per mg/dl increase in SUA (RR 1.11 [95% CI 1.03-1.20]), but the association remained statistically significant (P = 0.009).

CONCLUSIONS

The current meta-analysis suggests that SUA level is positively associated with the development of type 2 diabetes regardless of various study characteristics. Further research should attempt to determine whether it is effective to utilize SUA level as a predictor of type 2 diabetes for its primary prevention.

Dopamine D1 receptor (DRD1) genetic polymorphism: pleiotropic effects on heritable renal traits

Because dopamine D(1) receptors (DRD1) influence renal sodium transport and vascular hemodynamics, we examined whether genetic polymorphisms play a role in renal function. We conducted polymorphism discovery across the DRD1 open reading frame and its 5'-UTR and then performed association studies with estimated glomerular filtration rate (eGFR), plasma creatinine (pCr), and fractional excretion of uric acid (FeUA). We used a twin/family group of 428 subjects from 195 families and a replication cohort of 677 patients from the Kaiser health-care organization sampled from the lower percentiles of diastolic blood pressures. Although the coding region lacked common non-synonymous variants, we identified two polymorphisms in the DRD1 5'-UTR (G-94A, A-48G) that occurred with frequencies of 15 and 30%, respectively. In the twin/family study, renal traits were highly heritable, such that DRD1 G-94A significantly associated with eGFR, pCr, and FeUA. Homozygotes for the G-94A minor allele (A/A) exhibited lower eGFR, higher pCr, and lower FeUA. No effects were noted for DRD1 A-48G. Patients in the Kaiser group had similar effects of G-94A on eGFR and pCr. Kidney cells transfected with the -94A variant but not the wild type vectors had increased receptor density. Because the -94A allele is common and may reduce glomerular capillary hydrostatic pressure, G-94A profiling may aid in predicting survival of renal function in patients with progressive renal disease.

Allopurinol, rutin, and quercetin attenuate hyperuricemia and renal dysfunction in rats induced by fructose intake: renal organic ion transporter involvement

Fructose consumption has been recently related to an epidemic of metabolic syndrome, and hyperuricemia plays a pathogenic role in fructose-induced metabolic syndrome. Fructose-fed rats showed hyperuricemia and renal dysfunction with reductions of the urinary uric acid/creatinine ratio and fractional excretion of uric acid (FE(ur)), as well as other features of metabolic syndrome. Lowering serum uric acid levels with allopurinol, rutin, and quercetin increased the urinary uric acid/creatinine ratio and FE(ur) and attenuated other fructose-induced metabolic abnormalities in rats, demonstrating that hyperuricemia contributed to the deficiency of renal uric acid excretion in this model. Furthermore, we found that fructose upregulated the expression levels of rSLC2A9v2 and renal-specific transporter (rRST), downregulated the expression levels of organic anion transporters (rOAT1 and rUAT) and organic cation transporters (rOCT1 and rOCT2), with the regulators prostaglandin E(2) (PGE(2)) elevation and nitric oxide (NO) reduction in rat kidney. Allopurinol, rutin, and quercetin reversed dysregulations of these transporters with PGE(2) reduction and NO elevation in the kidney of fructose-fed rats. These results suggested that dysregulations of renal rSLC2A9v2, rRST, rOAT1, rUAT, rOCT1, and rOCT2 contributed to fructose-induced hyperuricemia and renal dysfunction. Therefore, these renal transporters may represent novel therapeutic targets for the treatment of hyperuricemia and renal dysfunction in fructose-induced metabolic syndrome.

Associations of serum uric acid with cardiovascular events and mortality in moderate chronic kidney disease

BACKGROUND

It is unclear whether the presence of kidney disease modifies the associations of uric acid with cardiovascular events and death.

METHODS

In the limited access, public use Atherosclerosis Risk In Communities (ARIC) database, associations of serum uric acid levels with cardiovascular events and death were analysed using a parametric proportional hazards model and the modification of these associations by the presence of CKD was assessed using a likelihood ratio test.

RESULTS

Of the 15 366 ARIC participants included in this analysis, 461 had CKD (eGFR <60 ml/min/1.73 m(2)). In both non-CKD and CKD sub-groups, participants with hyperuricaemia (> or = 7 mg/dl in men and > or = 6 mg/dl in women) compared to those with normal serum uric acid levels had higher waist circumference and fasting serum insulin levels. In the entire cohort, in a multivariate parametric proportional hazards model, each mg/dl increase in serum uric acid was associated with an increased hazard of cardiovascular events (HR 1.09, 95% CI 1.05-1.12) and death. A multiplicative interaction term of serum uric acid and CKD when added to the above models was significant (P < 0.001). The likelihood ratio test of the models with and without the interaction term was also significant (P < 0.001). In the non-CKD population, a multivariate analysis after adjusting for comorbidities and metabolic syndrome showed a significant association between hyperuricaemia and mortality (HR 1.18, 95% CI 1.04-1.33) but not for cardiovascular events (HR 1.07, 95% CI 0.96-1.19). In the CKD population, the association was not significant for both mortality and cardiovascular events.

CONCLUSION

We conclude that hyperuricaemia is associated with insulin resistance and mortality in the non-CKD population. The presence of CKD attenuates the associations of uric acid with mortality. Interventional studies are warranted to establish the biological role of hyperuricaemia in mortality in non-CKD and CKD populations.

Association between hyperuricemia and incident heart failure among older adults: a propensity-matched study

BACKGROUND

The association between hyperuricemia and incident heart failure (HF) is relatively unknown.

METHODS

Of the 5461 community-dwelling older adults, >or=65 years, in the Cardiovascular Health Study without HF at baseline, 1505 had hyperuricemia (baseline serum uric acid >or=6 mg/dL for women and >or=7 mg/dL for men). Using propensity scores for hyperuricemia, estimated for each participant using 64 baseline covariates, we were able to match 1181 pairs of participants with and without hyperuricemia.

RESULTS

Incident HF occurred in 21% and 18% of participants respectively with and without hyperuricemia during 8.1 years of mean follow-up (hazard ratio {HR} for hyperuricemia versus no hyperuricemia, 1.30; 95% confidence interval {CI}, 1.05-1.60; P=0.015). The association between hyperuricemia and incident HF was significant only in subgroups with normal kidney function (HR, 1.23; 95% CI, 1.02-1.49; P=0.031), without hypertension (HR, 1.31; 95% CI, 1.03-1.66; P=0.030), not receiving thiazide diuretics (HR, 1.20; 95% CI, 1.01-1.42; P=0.044), and without hyperinsulinemia (HR, 1.35; 95% CI, 1.06-1.72; P=0.013). Used as a continuous variable, each 1 mg/dL increase in serum uric acid was associated with a 12% increase in incident HF (HR, 1.12; 95% CI, 1.03-1.22; P=0.006). Hyperuricemia had no association with acute myocardial infarction or all-cause mortality.

CONCLUSIONS

Hyperuricemia is associated with incident HF in community-dwelling older adults. Cumulative data from our subgroup analyses suggest that this association is only significant when hyperuricemia is a marker of increased xanthine oxidase activity but not when hyperuricemia is caused by impaired renal elimination of uric acid.

Hypothesis: could excessive fructose intake and uric acid cause type 2 diabetes?

We propose that excessive fructose intake (>50 g/d) may be one of the underlying etiologies of metabolic syndrome and type 2 diabetes. The primary sources of fructose are sugar (sucrose) and high fructose corn syrup. First, fructose intake correlates closely with the rate of diabetes worldwide. Second, unlike other sugars, the ingestion of excessive fructose induces features of metabolic syndrome in both laboratory animals and humans. Third, fructose appears to mediate the metabolic syndrome in part by raising uric acid, and there are now extensive experimental and clinical data supporting uric acid in the pathogenesis of metabolic syndrome. Fourth, environmental and genetic considerations provide a potential explanation of why certain groups might be more susceptible to developing diabetes. Finally, we discuss the counterarguments associated with the hypothesis and a potential explanation for these findings. If diabetes might result from excessive intake of fructose, then simple public health measures could have a major impact on improving the overall health of our populace.

The effect of the interaction between obesity and drinking on hyperuricemia in Japanese male office workers

BACKGROUND

Obesity and drinking are acknowledged risk factors for hyperuricemia. However, the effect of the interaction between obesity and drinking on hyperuricemia is not well understood.

METHODS

The cases comprised 3028 male office workers with hyperuricemia (serum uric acid level >or=7.0 mg/dL); the controls were 5348 men with a serum uric acid level less than 6.0 mg/dL. Logistic regression analysis was used to assess risk factors for hyperuricemia and the interaction between obesity and drinking in hyperuricemia. Participants were divided into 2 groups according to their BMI: individuals with a BMI of 25 or higher were classified as obese and those with a BMI less than 25 were classified as non-obese. In addition, participants were divided into 5 groups based upon their ethanol consumption. The 2 variables were then combined to create 10 groups.

RESULTS

With non-obese non-drinkers as the reference category, the odds ratio for hyperuricemia was 1.80 for non-obese drinkers of less than 25 mL/day of ethanol, 2.15 for non-obese drinkers of 25-49 mL/day, 2.60 for non-obese drinkers of 50-74 mL/day, 2.56 for non-obese drinkers of 75+ mL/day, 4.40 for obese non-drinkers, 5.74 for obese drinkers of less than 25 mL/day, 6.57 for obese drinkers of 25-49 mL/day, 5.55 for obese drinkers of 50-74 mL/day, and 7.77 for obese drinkers of 75+ mL/day. The interaction between obesity and drinking in hyperuricemia was statistically significant.

CONCLUSION

Our results suggest that although combining the effects of obesity and drinking did not result in a multiplicative increase in the risk for hyperuricemia, the combined risk was greater than the sum of the effects of obesity and drinking.

Comparison of alanine aminotransferase, white blood cell count, and uric acid in their association with metabolic syndrome: a study of Korean adults

The aim of this study is to investigate the respective associations of alanine aminotransferase (ALT), white blood cell (WBC) count, and uric acid with metabolic syndrome and compare the magnitude in their association with metabolic syndrome, using modified Adult Treatment Panel III (ATP III) and its components. We studies 5,020 Korean adults (20-70 years of age; 2,501 men and 2,519 women) who visited Center for Health Promotion in Pusan National University Hospital for routine health examinations. Metabolic parameters and biochemical markers including ALT, WBC count, and uric acid were obtained. Alcohol intake, smoking status, and the presence of fatty liver were also evaluated. The prevalence of metabolic syndrome was 17.3%. In the partial correlation coefficients adjusted for age, alcohol consumption, smoking status, and presence of fatty liver, ALT was correlated significantly with all components of metabolic syndrome among three markers in men and women respectively. Moreover, ALT showed the highest correlation with HOMA-IR (r=0.311, P<0.001 in men and r=0.285, P<0.001 in women) in both genders. With the increase in the number of metabolic syndrome components, the mean values of all three markers were also significantly increased. In addition, the adjusted mean values of each marker were all significantly increased in metabolic syndrome. In ALT, the adjusted mean values were significantly increased in subjects with all metabolic component disorders. When we calculated odd ratios (ORs) for metabolic syndrome prevalence of the highest quartiles in three markers using multivariate logistic regression analyses, ALT was associated most strongly with metabolic syndrome in both genders (OR 5.65 [95% CI, 3.80 to 8.40]; P<0.001 in men, OR 3.23 [95% CI, 2.15 to 4.86]; P<0.001 in women). The cut-off value for ALT using the ROC curve was 27 IU/L (area under the curve=0.717, sensitivity 62.5%, specificity 70.4%, P<0.001) in men and 18 IU/L (area under the curve=0.735, sensitivity 61.3%, specificity 72.3%, P<0.001) in women. In conclusion, ALT, WBC count, and uric acid play important role as an additional markers for metabolic syndrome. Among three markers, in overlap the multiple risk factors, ALT might have a strong association with metabolic syndrome in Korean adults.

The conundrum of hyperuricemia, metabolic syndrome, and renal disease

The level of serum uric acid in human has been increasing over the last decades, and correlates with an increase prevalence of renal disease and metabolic syndrome. Understanding the role of uric acid in these conditions may provide clues for preventing the current epidemic of renal disease. Controversy still remains if hyperuricemia is simply a consequence or a cause of renal disease although epidemiological studies have attempted to resolve this issue. In this review, we discuss the clinical and experimental evidence for a causal role of hyperuricemia in renal diseases and potential relationships of hyperuricemia with metabolic syndrome.

Associations between serum uric acid and adipokines, markers of inflammation, and endothelial dysfunction

AIM

Serum uric acid is associated with the metabolic syndrome and its components, while its relationship with cardiovascular disease is controversial. The aim of the study was to evaluate the association between uric acid and adipokines, markers of inflammation, oxidative stress, and endothelial dysfunction, which are all linked to cardiovascular disease.

METHODS

The associations between uric acid and adiponectin, resistin, leptin, high-sensitivity-C-reactive protein (hs-CRP), interleukin-6, tumor necrosis factor-alpha, nitrotyrosine, Total Antioxidant Status (TAS), E-selectin, vascular adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1) were cross-sectionally evaluated in a randomly collected sample of 100 men from a population-based cohort.

RESULTS

Subjects within the highest uric acid quartile showed a worse metabolic pattern and a higher prevalence of the metabolic syndrome [odds ratio (OR)=3.6; 95% confidence interval (CI) 1.6-8.2; p<0.001 for each 50 micromol/l uric acid increment in a logistic regression model after multiple adjustments]. Nitrotyrosine and adiponectin were significantly lower, while TAS, hs-CRP, E-selectin, ICAM-1, and VCAM-1 were higher in the groups with increased uric acid levels. In a multiple regression model, after adjustments for multiple confounders, uric acid levels were inversely associated with nitrotyrosine (p<0.001) and adiponectin (p=0.02), and directly with TAS (p<0.001), and E-selectin (p=0.006).

CONCLUSION

Serum uric acid showed opposite relationships, being associated with both beneficial (inverse association with nitrotyrosine, direct association with TAS) and detrimental (inverse association with adiponectin, direct association with E-selectin) markers, thus providing a possible explanation for the previously reported controversial and not linear association between uric acid and cardiovascular disease.

Uric acid as a pathogenic factor in preeclampsia

Hyperuricemia is a common finding in preeclamptic pregnancies evident from early pregnancy. Despite the fact that elevated uric acid often pre-dates the onset of clinical manifestations of preeclampsia, hyperuricemia is usually considered secondary to altered kidney function. Increased serum uric acid is associated with hypertension, renal disease and adverse cardiovascular events in the non-pregnant population and with adverse fetal outcomes in hypertensive pregnancies. We hypothesize that an elevated concentration of uric acid in preeclamptic women is not simply a marker of disease severity but rather contributes directly to the pathogenesis of the disorder. Using epidemiological and experimental evidence, gained largely outside of pregnancy, we will propose pathogenic roles for uric acid in preeclamptic pregnancies. Uric acid's ability to promote inflammation, oxidative stress and endothelial dysfunction will be highlighted with discussions of the potential impact on placental development and function and maternal vascular health.

Diabetes and nephrolithiasis

Type 2 diabetes is associated with an increased risk of nephrolithiasis, specifically in the form of uric acid (UA) nephrolithiasis. Diabetic patients who produce uric stones exhibit a low urine pH, the key factor of UA crystallization. Production of such acidic urine appears to result from the insulin-resistant state characteristic of diabetes mellitus. Insulin resistance is also involved in the pathogenesis of primary UA nephrolithiasis observed in overweight subjects with the metabolic syndrome. Therefore, UA nephrolithiasis should be considered a possible manifestation of insulin resistance, as it already is for hyperuricemia. Occurrence of UA stones in a patient, especially if overweight or hypertensive, should prompt a search for components of the metabolic syndrome in order to implement therapeutic intervention aimed at preventing the development of type 2 diabetes and atherosclerotic complications. Reciprocally, diabetologists should be aware of the risk of UA stones in their patients.

Ten-year change in serum uric acid and its relation to changes in other metabolic risk factors in young black and white adults: the CARDIA study

Elevated serum uric acid is commonly seen in association with obesity, glucose intolerance, hypertension and dyslipidemia. There is currently no satisfactory explanation for the relation of uric acid and the metabolic syndrome (MetSyn). This study aimed to evaluate the relations of change in serum uric acid with changes in components of the MetSyn in young adults. We studied 1,249 male and 1,362 female black and white subjects aged 17-35 years (baseline) from the Coronary Artery Risk Development in Young Adults (CARDIA) Study, which attended a 10-year follow-up. Metabolic factors assessed at both time periods included BMI, waist circumference, blood pressure, fasting glucose, insulin, and lipids. Confounders examined (baseline and change variables) were serum creatinine, alcohol, smoking, physical activity, and oral contraceptives. Mean uric acid increased the most in black males (+0.5 mg/dl), followed by white males (+0.3 mg/dl) and black females (+0.2 mg/dl) (all P < 0.01), with the least change among white females (+0.1 mg/dl) (ns). Although change in all of the metabolic factors was associated with change in uric acid in the anticipated directions, in multivariable analyses only BMI and triglycerides had a significant independent association with uric acid in all race-sex-groups. Among confounders, only change in serum creatinine showed a strong independent association with uric acid. In conclusion, besides weight gain and renal excretion, increasing uric acid concentrations in young adults are strongly related to corresponding changes in triglycerides. The correlation of uric acid and triglycerides was found within the normal range and could not be explained by obesity.