Hormonal and cytokine effects of uric acid

Impact of hyperuricemia on 5-year clinical outcomes in patients with critical limb ischemia following percutaneous transluminal angioplasty

BACKGROUND

A growing evidence on the correlation between hyperuricemia and cardiovascular disease (CVD) has been previously reported. However, there have been limited data on the impact of hyperuricemia on long-term clinical outcomes in patients with critical limb ischemia (CLI) who underwent percutaneous transluminal angioplasty (PTA).

METHODS

A total of 425 peripheral artery disease patients who underwent PTA for CLI were enrolled. The patients were divided into the hyperuricemia group (n = 101) and the normal group (n = 324). The primary endpoint was major adverse cerebral and cardiovascular event (MACCE), including death, myocardial infarction, any coronary revascularization, and stroke, up to 5 years. The secondary endpoint was a major adverse limb event (MALE), including any repeated PTA, and target extremity surgery. Inverse probability weighting (IPTW) analysis, derived from the logistic regression model, was performed to adjust for potential confounders.

RESULTS

After IPTW matching analysis, compared to the normal group, the hyperuricemia group was associated with a higher incidence of MACCE (20.7% vs. 13.6%, hazard ratio [HR], 1.65; 95% confidence interval [CI], 1.15-2.38, P  = 0.006) including non-cardiac death (11.7% vs. 6.3%, HR: 1.95, 95% CI: 1.19-3.19, P  = 0.006) and MALE (47.7% vs. 36.0%, HR: 1.62, 95% CI: 1.23-2.13, P  = 0.001) including non-target extremity revascularization (15.0% vs. 6.8%, HR: 2.42, 95% CI: 1.52-3.84, P  < 0.001).

CONCLUSION

In the present study, hyperuricemia was associated with worse clinical outcomes in patients with CLI following PTA during 5-year clinical follow-up. Efficacy of controlling hyperuricemia in improving clinical outcomes should be evaluated in further studies.

Impact of hyperuricemia on 5-year clinical outcomes following percutaneous transluminal angioplasty

BACKGROUND

Although the correlation between hyperuricemia and cardiovascular disease (CVD) is well known, there have been limited data regarding the impact of hyperuricemia on long-term clinical outcomes in patients with peripheral arterial disease (PAD) after percutaneous transluminal angioplasty (PTA).

METHODS

A total of 718 patients who underwent PTA for PAD were enrolled. The patients were divided into the hyperuricemia group (N = 168) and the normal group (N = 550). Hyperuricemia was defined as a uric acid level ≥ 7.0 mg/dL in men, and ≥ 6.5 mg/dL in women. The primary endpoint was major adverse cerebral and cardiovascular event (MACCE), including death, myocardial infarction (MI), any coronary revascularization, and stroke, up to 5 years. The secondary endpoint was major adverse limb event (MALE), including any repeated PTA, and target extremity surgery (TES). Inverse probability weighting (IPTW) analysis, derived from the logistic regression model, was performed to adjust potential confounders.

RESULTS

After IPTW matching analysis, compared to the normal group, the hyperuricemia group was not associated with increased MACCE but was associated with an increased incidence of MI (2.6 % vs. 0.5 %, p = 0.001), and coronary revascularization (6.7 % vs. 3.9 %, p = 0.018). Also, the hyperuricemia group was associated with a higher incidence of MALE (45.3 % vs. 28.9 %, p < 0.001), including target extremity revascularization (TER; 25.1 % vs. 15.9 %, p < 0.001), non-TER (11.5 % vs. 5.6 %, p < 0.001), and TES (22.8 % vs. 16.2 %, p = 0.002).

CONCLUSIONS

In the present study, hyperuricemia was associated with worse clinical outcomes in PAD patients following PTA during 5-year clinical follow-up. Further investigations should be made regarding the clinical benefit of controlling hyperuricemia on clinical outcomes.

Dose-response relationships of tea and coffee consumption with gout: a prospective cohort study in the UK Biobank

OBJECTIVES

The association of tea or coffee consumption with gout is inconsistently reported. Few prospective studies have explored their dose-response relationship. Therefore, we aimed to quantitatively investigate the association between tea, coffee and the risk of developing gout.

METHODS

The study included 447 658 participants in the UK Biobank who were initially free of gout. Tea and coffee consumption were assessed at baseline. We used Cox proportional hazards models to estimate the associations between tea/coffee consumption and incident gout, with restricted cubic spline added to the Cox models to evaluate the dose-response relationships.

RESULTS

During a median follow-up period of 13.42 years, we recorded 3,053 gout cases. The associations between tea, coffee and gout were nonlinear, with a significant reduction in the risk by ∼ six cups/day of tea and three cups/day of coffee. Compared with those who were not tea and coffee drinkers, those who consumed >6 cups/day of tea or coffee were associated with 23% (HR 0.77, 95% CI, 0.66, 0.91) and 40% (HR 0.60, 95% CI, 0.47, 0.77) lower risks of gout, respectively, and both caffeinated and decaffeinated coffee consumption were associated with a decreased risk. Moreover, hyperuricaemia may modify the association between coffee and gout. Compared with non-coffee consumers with hyperuricaemia, those with ≥4 cups/day coffee intake without hyperuricaemia had the lowest risk (HR 0.34, 95% CI, 0.28, 0.41).

CONCLUSION

Consumption of tea or coffee had a strong nonlinear association in gout risk reduction. Hyperuricaemia status had a potential effect modification on the association of coffee intake with gout.

Sex-specific association of serum uric acid trajectories with risk of incident retinal arteriosclerosis in Chinese population: A population-based longitudinal study

Background

The impact of serum uric acid (SUA) trajectories on the development of retinal arteriosclerosis is uncertain. The purpose of this study was to identify adult SUA trajectories by sex and determine their association with risk of retinal arteriosclerosis.

Methods

In this longitudinal study, 4,324 participants who were aged between 18 and 60 years without retinal arteriosclerosis at or before baseline (from January 1, 2010, through December 31, 2010) were included. Group-based trajectory modeling was used to identify SUA trajectories during the exposure period (from January 1, 2006, through December 31, 2010). Cox proportional-hazards models were applied to evaluate the associations between SUA trajectories and the risk of incident retinal arteriosclerosis during the outcome period (from January 1, 2011, through December 31, 2019).

Results

4 distinct SUA trajectories were identified in both women and men: low, moderate, moderate-high, and high. During a median follow-up of 9.54 years (IQR 9.53-9.56), 97 women and 295 men had developed retinal arteriosclerosis. In the fully adjusted model, a significant association between the moderate-high SUA trajectory group and incidence of retinal arteriosclerosis was observed only in men (HR: 1.76, 95% CI: 1.17-2.65) compared with the low trajectory group, but not in women (HR: 0.77, 95% CI: 0.39-1.52). Also, the high SUA trajectory group had the highest risk with an adjusted HR of 1.81 (95% CI, 1.04-3.17) in men. However, they did not exhibit a substantially increased risk in women.

Conclusion

Higher SUA trajectory groups were significantly associated with an increased risk of incident retinal arteriosclerosis in men but not in women.

Sirtuin deficiency and the adverse effects of fructose and uric acid synthesis

Fructose metabolism and hyperuricemia have been shown to drive insulin resistance, metabolic syndrome, hepatic steatosis, hypertension, inflammation, and innate immune reactivity in experimental studies. We suggest that these adverse effects are at least in part the result of suppressed activity of sirtuins, particularly Sirtuin1. Deficiency of sirtuin deacetylations is a consequence of reduced bioavailability of its cofactor nicotinamide adenine dinucleotide (NAD+). Uric acid-induced inflammation and oxidative stress consume NAD+ and activation of the polyol pathway of fructose and uric acid synthesis also reduces the NAD+-to-NADH ratio. Variability in the compensatory regeneration of NAD+ could result in variable recovery of sirtuin activity that may explain the inconsistent benefits of treatments directed to reduce uric acid in clinical trials. Here, we review the pathogenesis of the metabolic dysregulation driven by hyperuricemia and their potential relationship with sirtuin deficiency. In addition, we discuss therapeutic options directed to increase NAD+ and sirtuins activity that may improve the adverse effects resulting from fructose and uric acid synthesis.

Hyperuricemia and Its Association With Ischemic Stroke

Elevated serum uric acid (SUA) levels have been associated with an increased risk of cardiovascular (CV) disease and acute ischemic stroke (AIS) as well as many other medical conditions. AIS is a CV complication that is the second most common cause of mortality worldwide. It results from reduced blood flow to the brain by means of thrombosis, embolism, or systemic hypoperfusion. Studies have demonstrated an association between SUA levels and CV events, with a significant dose-response relationship between elevated SUA levels and stroke risk. Since the relationship between SUA levels and AIS risk has been established, studies are also being conducted in order to evaluate whether antihyperuricemic drugs can lower this risk. Allopurinol use in hyperuricemic patients has been shown to decrease the risk of major CV events, which include AIS. This narrative review aims to investigate the role of SUA as an independent risk factor for AIS along with the proposed biological mechanisms by thoroughly appraising research findings from relevant full-text articles and abstracts indexed in PubMed and the Cochrane Library. In this literature, we will be discussing hyperuricemia, AIS, the association between the two, and the use of antihyperuricemic medications on stroke prognosis. This review will also shed new light on studies that have begun to provide insight into the predictive role of hyperuricemia in AIS.

The Different Relationship between Homocysteine and Uric Acid Levels with Respect to the MTHFR C677T Polymorphism According to Gender in Patients with Cognitive Impairment

In an elderly population with cognitive impairment, we investigated the association between serum uric acid (sUA) and serum homocysteine (sHcy), known risk factors for cerebrovascular disease. We also investigated the potential effect of the C677T polymorphism in the gene encoding methylenetetrahydrofolate reductase (MTHFR) to the sUA level in different dementia types. Participants underwent a battery of tests including measurements of sUA, sHcy, folic acid, and vitamin B12 as well as genotyping of the MTHFR locus. Data from 861 subjects (597 females to 264 males) were retrospectively analyzed. Subjects with hyperhomocysteinemia had lower serum folic acid and vitamin B12 and higher sUA than those with normal sHcy. sUA was significantly associated with serum creatinine, HbA1c, and sHcy regardless of gender. The TT genotype was found to be associated with hyperhomocysteinemia in both genders (p = 0.001). The levels of hyperlipidemia, sHcy, and sUA differed according to dementia subtypes. High sUA were associated with hyperhomocystenemia in TT genotype only in dementia with vascular lesion. This study reveals that sUA is positively associated with sHcy. We speculate that the two markers synergistically increase cerebrovascular burden and suggested that dietary intervention for sUA and sHcy would be helpful for cognitive decline with vascular lesion.

Association between serum uric acid levels and metabolic markers in patients with type 2 diabetes from a community with high diabetes prevalence

BACKGROUND

The importance of uric acid has been increasingly appreciated because of its association with the development of diabetes mellitus and related diseases.

OBJECTIVE

This study was undertaken to evaluate the association of serum uric acid (SUA) level with different clinical and biochemical parameters in patients with type 2 diabetes from Saudi Arabia.

METHODS

Clinical and biochemical data from the patients were obtained and assessed in a cross-sectional design. Relationships between SUA level and various clinical and biochemical parameters were analysed.

RESULTS

SUA level was positively associated with increased incidence of cardiovascular diseases (CVD) in patients with abnormal eGFR (<90 mL/min/1.73 m² ). HbA1c was found to be inversely associated with hyperuricemia in patients with normal eGFR level (≥90 mL/min/1.73 m² ). Incidence of metabolic syndrome did not show any relationship with SUA level. However, the incidence of hypertension, a component of metabolic syndrome, was significantly higher among patients with hyperuricemia. Waist circumference and serum triglycerides were higher, whereas serum high-density lipoprotein level was lower in patients with higher SUA level. Patients with hyperuricemia had higher incidence of CVDs than those of the normouricemic group.

CONCLUSION

SUA level was positively associated with incidence of cardiovascular diseases CVD in patients with abnormal eGFR. HbA1c correlated significantly with SUA level in patients with normal eGFR. Incidence of metabolic syndrome did not show any association with SUA level. Incidence of hypertension, waist circumference and serum triglycerides were significantly higher and serum high-density lipoprotein level was lower in patients with higher SUA level.

Safety and effectiveness of low-protein diet supplemented with ketoacids in diabetic patients with chronic kidney disease

BACKGROUND

The impact of the low-protein diet on nutrition in CKD diabetics is uncertain.

METHODS

The metabolic and nutritional effects of a low-protein (0.5-0.6 g/kg/d), normal-high energy (30-35 kcal/kg/d) diet supplemented with ketoacids (LPD-KA) were prospectively evaluated in CKD patients with (DM) and without (non-DM) diabetes mellitus.

RESULTS

197 patients on CKD stages 3-5 were enrolled. DM (n = 81) and non-DM (n = 116) were comparable for gender (Male 58 vs 55%), age (66 ± 9 vs 63 ± 18 years), renal function (eGFR 23 ± 13 vs 24 ± 13 mL/min). After 6-month, serum urea (DM: 131 ± 58 to 105 ± 49 mg/dl, p < 0.05; non-DM: 115 ± 52 to 88 ± 36, p < 0.05) and phosphate (DM: 4.5 ± 1.3 to 4.1 ± 1.2 mg/dl, p = 0.06; non-DM: 4.3 ± 1.0 to 3.7 ± 0.8, p < 0.05) declined. Fasting glucose decreased in DM (126 ± 52 to 103 ± 29 mg/dl, p < 0.05) without insulin dose increase. These effects were preserved after 3-year. Serum albumin did not change after 6 months (DM: 3.7 ± 0.6 to 3.8 ± 0.4 mg/dl; non-DM: 4.0 ± 0.6 to 4.0 ± 0.4) and in the long-term. Body weight (BW) declined after the diet start (DM: 68.9 ± 14.3 to 65.1 ± 12.1 kg, p < 0.05; non-DM: 66.6 ± 15.1 to 64.1 ± 15.1, p < 0.05) and was stable at 6 months and 3 years. Muscle strength at baseline was reduced in all patients and remained stable during the diet period. Changes of nutritional markers during the study were similar among groups and diabetes was not associated to any nutritional change at the multivariate analysis. As attain wasting, lower BMI (< 23 kg/m²) and albumin (< 3.8 g/dl) levels were present in 1/3 patients at start and along 3 years, cholesterol never dropped below the lower threshold (< 100 mg/dl) and poorer FM (< 10%) was less than 10% during the study in both groups.

CONCLUSIONS

In diabetic CKD patients a low-protein diet supplemented with ketoacids improves uremia and diabetes, causes sudden decline of body weight which remains stable over time and has not a negative effect on wasting and muscle mass and fitness. In diabetic CKD patients the LPD-KA is safe and the nutritional impact is the same as in non-diabetics CKD.

Prevalence of peripheral artery disease (PAD) and factors associated: An epidemiological analysis from the population-based Screening PRE-diabetes and type 2 DIAbetes (SPREDIA-2) study

AIM

To describe the prevalence of Peripheral Artery Disease (PAD) in a random population sample and to evaluate its relationship with Mediterranean diet and with other potential cardiovascular risk factors such as serum uric acid and pulse pressure in individuals ranged 45 to 74 years.

METHODS

Cross-sectional analysis of 1568 subjects (mean age 6.5 years, 43% males), randomly selected from the population. A fasting blood sample was obtained to determine glucose, lipids, and HbA1C levels. An oral glucose tolerance test was performed in non-diabetic subjects. PAD was evaluated by ankle-brachial index and/or having a prior diagnosis.

RESULTS

PAD prevalence was 3.81% (95% CI, 2.97-4.87) for all participants. In men, PAD prevalence was significantly higher than in women [5.17% (95% CI, 3.74-7.11) vs. 2.78% (95% CI, 1.89-4.07); p = 0.014]. Serum uric acid in the upper quartile was associated with the highest odds ratio (OR) of PAD (for uric acid > 6.1 mg/dl, OR = 4.31; 95% CI, 1.49-12.44). The remaining variables more strongly associated with PAD were: Heart rate >90 bpm (OR = 4.16; 95%CI, 1.62-10.65), pulse pressure in the upper quartile (≥ 54 mmHg) (OR = 3.82; 95%CI, 1.50-9.71), adherence to Mediterranean diet (OR = 2.73; 95% CI, 1.48-5.04), and former smoker status (OR = 2.04; 95%CI, 1.00-4.16).

CONCLUSIONS

Our results show the existence of a low prevalence of peripheral artery disease in a population aged 45-74 years. Serum uric acid, pulse pressure and heart rate >90 bpm were strongly associated with peripheral artery disease. The direct association between Mediterranean diet and peripheral artery disease that we have found should be evaluated through a follow-up study under clinical practice conditions.

Physiological functions and pathogenic potential of uric acid: A review

Uric acid is synthesized mainly in the liver, intestines and the vascular endothelium as the end product of an exogenous pool of purines, and endogenously from damaged, dying and dead cells, whereby nucleic acids, adenine and guanine, are degraded into uric acid. Mentioning uric acid generates dread because it is the established etiological agent of the severe, acute and chronic inflammatory arthritis, gout and is implicated in the initiation and progress of the metabolic syndrome. Yet, uric acid is the predominant anti-oxidant molecule in plasma and is necessary and sufficient for induction of type 2 immune responses. These properties may explain its protective potential in neurological and infectious diseases, mainly schistosomiasis. The pivotal protective potential of uric acid against blood-borne pathogens and neurological and autoimmune diseases is yet to be established.

Influence of Normo- and Hypogonadal Condition, Hyperuricemia, and High-Fructose Diet on Renal Changes in Male Rats

Background. There is a gender disparity in the incidence, prevalence, and progression of renal disease. The object of this paper is to evaluate the presence and type of renal lesion in normogonadic and hypogonadic male rats in a mild hyperuricemia induced condition and exposed to a high-fructose diet. Methods. 56 adult male Wistar rats were used. Animals were divided into two groups, one normogonadic (NGN) and one hypogonadic (HGN), and each group was divided into four subgroups in accordance with the treatment: control with only water (C), fructose (F), oxonic acid (OA), and fructose + oxonic acid (FOA). Renal changes were evaluated by measuring glomerulosclerosis, fibrosis, and arteriolar media/lumen (M/L) ratio. Results. The OA and FOA groups presented significantly hypertension (p < 0.001). The OA group significantly increased (p < 0.05) the percentage of glomerulosclerosis as well as the FOA group (p < 0.001). When comparing NGN versus HGN, we observed a trend to a lower glomerulosclerosis in the latter. A higher arteriolar M/L ratio was observed in the OA (p < 0.05) and FOA (p < 0.001). Conclusion. Hyperuricemia conditions and a high-fructose diet favor blood pressure increase together with changes in the arteriolar media/lumen ratio and renal glomerular damage. These changes were more apparent in normogonadic animals.

Uric acid stimulates proliferative pathways in vascular smooth muscle cells through the activation of p38 MAPK, p44/42 MAPK and PDGFRβ

Hyperuricemia and angiotensin II (Ang II) may have a pathogenetic role in the development of hypertension and atherosclerosis as well as cardiovascular disease (CVD) and its prognosis. The purpose of this study was to investigate whether uric acid can induce proliferative pathways of vascular smooth muscle cell (VSMC) that are thought to be responsible for the development of CVD. The phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK), p44/42 mitogen-activated protein kinase (p44/42 MAPK) and platelet-derived growth factor receptor β (PDGFRβ) was measured by Elisa and Western blot techniques to determine the activation of proliferative pathways in primary cultured VSMCs from rat aorta. Results demonstrated that uric acid can stimulate p38 MAPK, p44/42 MAPK and PDGFRβ phosphorylation in a time- and concentration-dependent manner. Furthermore, treatment of VSMCs with the angiotensin II type I receptor (AT1R) inhibitor losartan suppressed p38 MAPK and p44/42 MAPK induction by uric acid. The stimulatory effect of uric acid on p38 MAPK was higher compared to that of Ang II. The results of this study show for the first time that uric acid-induced PDGFRβ phosphorylation plays a crucial role in the development of CVDs and that elevated uric acid levels could be a potential therapeutical target in CVD patients.

Uric acid in metabolic syndrome: From an innocent bystander to a central player

Uric acid, once viewed as an inert metabolic end-product of purine metabolism, has been recently incriminated in a number of chronic disease states, including hypertension, metabolic syndrome, diabetes, non-alcoholic fatty liver disease, and chronic kidney disease. Several experimental and clinical studies support a role for uric acid as a contributory causal factor in these conditions. Here we discuss some of the major mechanisms linking uric acid to metabolic and cardiovascular diseases. At this time the key to understanding the importance of uric acid in these diseases will be the conduct of large clinical trials in which the effect of lowering uric acid on hard clinical outcomes is assessed. Elevated uric acid may turn out to be one of the more important remediable risk factors for metabolic and cardiovascular diseases.

The urinary cytokine/chemokine signature of renal hyperfiltration in adolescents with type 1 diabetes

OBJECTIVE

Urinary cytokine/chemokine levels are elevated in adults with type 1 diabetes (T1D) exhibiting renal hyperfiltration. Whether this observation extends to adolescents with T1D remains unknown. Our first objective was to determine the relationship between hyperfiltration and urinary cytokines/chemokines in normotensive, normoalbuminuric adolescents with T1D using GFR(cystatin). Our second aim was to determine the relationship between urine and plasma levels of inflammatory biomarkers, to clarify the origin of these factors.

METHODS

Urine and serum cytokines/chemokines (Luminex platform) and GFR(cystatin) were measured in normofiltering (n = 111, T1D-N, GFR<135 ml/min/1.73 m(2)) and hyperfiltering (n = 31, T1D-H, GFR ≥ 135 ml/min/1.73 m(2)) adolescents with T1D (ages 10-16), and in age and sex matched healthy control subjects (HC, n = 59).

RESULTS

We noted significant step-wise increases in urinary cytokine/chemokine excretion according to filtration status with highest levels in T1D-H, with parallel trends in serum analyte concentrations. After adjusting for serum glucose at the time of sampling, differences in urinary cytokine excretion were not statistically significant. Only serum IL-2 significantly differed between HC and T1D (p = 0.0076).

CONCLUSIONS

Hyperfiltration is associated with increased urinary cytokine/chemokine excretion in T1D adolescents, and parallel trends in serum cytokine concentration. The GFR-associated trends in cytokine excretion may be driven by the effects of ambient hyperglycemia. The relationship between hyperfiltration, glycemia, and variations in serum and urine cytokine expression and their impact on future renal and systemic vascular complications requires further study.

Sweetened beverage consumption and the risk of hyperuricemia in Mexican adults: a cross-sectional study

BACKGROUND

The prevalence of hyperuricemia has doubled worldwide during the last few decades. The substantial increase in sweetened beverage (SB) consumption has also coincided with the secular trend of hyperuricemia. Recent studies do show that the consumption of SB can induce hyperuricemia. However, the association between SB and hyperuricemia remains unclear. The aim of this study was to evaluate the association between SB consumption and levels of uric acid in Mexican adults.

METHODS

We performed a cross-sectional analysis of data from selected adults participating in the baseline assessment of the Health Workers Cohort Study. A total of 6,705 participants of both sexes between ages 18 and 70 years were included. SB intake was estimated using a validated semi-quantitative food frequency questionnaire. Biochemical and anthropometric information was collected using standard procedures. Hyperuricemia was defined as uric acid levels ≥ 7.0 mg/dL in men and ≥ 5.8 mg/dL in women. The association of interest was assessed by multiple logistic regression models.

RESULTS

The odds ratios (OR) for hyperuricemia in men who consume 0.5-1 SB/day was 1.59 (95% CI; 1.05-2.40) and 2.29 (95% CI; 1.55-3.38) for those who consume ≥3 SB/day when compared to men who consume less than half a SB/day. In women, the OR for hyperuricemia for those who consume >1.0- < 3.0 SB/day was 1.33 (95% CI; 1.04-1.70) and 1.35 (95% CI; 1.04-1.75) for those who consume ≥3 SB/day when compared to women who consume less than half a SB/day, independent of other covariables. Men and women with high SB consumption and a body mass index (BMI) ≥ 25 Kg/m2 had greater risk for hyperuricemia than men and women with low SB consumption and normal BMI < 25 Kg/m2.

CONCLUSIONS

Our findings suggest that the consumption of SB is associated with an increased risk of hyperuricemia in Mexican adults. However, longitudinal research is needed to confirm the association between SB intake and hyperuricemia.

Associations of serum uric acid levels with arterial wave reflections and central systolic blood pressure

BACKGROUND

Uric acid may be involved in the pathogenesis of hypertension. We investigated the roles of four major hemodynamic parameters of blood pressure, including arterial stiffness, wave reflections, cardiac output (CO), and total peripheral resistance (TPR), in the association between uric acid and central systolic blood pressure (SBP-c).

METHODS

A sample of 1303 normotensive and untreated hypertensive Taiwanese participants (595 women, aged 30-79 years) was drawn from a community-based survey. Study subjects' baseline characteristics, biochemical parameters, carotid-femoral pulse wave velocity (cf-PWV), amplitude of the backward pressure wave decomposed from a calibrated tonometry-derived carotid pressure waveform (Pb), CO, TPR, and SBP-c were analyzed.

RESULTS

In multi-variate analyses adjusted for age, waist circumference, body mass index, creatinine, total cholesterol, smoking, and heart rate, uric acid significantly correlated with Pb and cf-PWV in men, and Pb and TPR in women. The correlation between uric acid and Pb remained significant in men and women when cf-PWV was further adjusted. In the final multi-variate prediction model (model r(2)=0.839) for SBP-c, the significant independent variables included uric acid (partial r(2)=0.005), Pb (partial r(2)=0.651), cf-PWV (partial r(2)=0.005), CO (partial r(2)=0.062), TPR (partial r(2)=0.021), with adjustment for age, sex, waist circumference, body mass index, creatinine, total cholesterol, smoking, and heart rate.

CONCLUSIONS

Uric acid was significantly independently associated with wave reflections, which is the dominant determinant of SBP-c. Uric acid was also significantly associated with SBP-c independently of the major hemodynamic parameters.

Uric acid for diagnosis and risk stratification in suspected myocardial infarction

BACKGROUND

Hypoxia precedes cardiomyocyte necrosis in acute myocardial infarction (AMI). We therefore hypothesized that uric acid - as a marker of oxidative stress and hypoxia - might be useful in the early diagnosis and risk stratification of patients with suspected AMI.

MATERIALS AND METHODS

In this prospective observational study, uric acid was measured at presentation in 892 consecutive patients presenting to the emergency department with suspected AMI. The final diagnosis was adjudicated by two independent cardiologists. Patients were followed 24 months regarding mortality. Primary outcome was the diagnosis of AMI, secondary outcome was short- and long-term mortality.

RESULTS

Uric acid at presentation was higher in patients with AMI than in patients without (372 μM vs. 336 μM; P < 0·001). The diagnostic accuracy of uric acid for AMI as quantified by the area under the receiver operating characteristic curve (AUC) was 0·60 (95%Cl 0·56-0·65). When added to cardiac troponin T (cTnT), uric acid significantly increased the AUC of cTnT from 0·89 (95%Cl 0·85-0·93) to 0·92 (95%Cl 0·89-0·95, P = 0·020 for comparison). Cumulative 24-month mortality rates were 2·2% in the first, 5·4% in the second and the third and 15·6% in the fourth quartile of uric acid (P < 0·001 for log-rank). Uric acid predicted 24-month mortality independently. Adding uric acid to TIMI and GRACE risk score improved their prognostic accuracy as shown by an integrated discrimination improvement of 0·04 (P = 0·007) respective 0·02 (P = 0·021).

CONCLUSIONS

Uric acid, an inexpensive widely available biomarker, improves both the early diagnosis and risk stratification of patients with suspected AMI.

Extracellular guanosine regulates extracellular adenosine levels

The aim of this investigation was to test the hypothesis that extracellular guanosine regulates extracellular adenosine levels. Rat preglomerular vascular smooth muscle cells were incubated with adenosine, guanosine, or both. Guanosine (30 μmol/l) per se had little effect on extracellular adenosine levels. Extracellular adenosine levels 1 h after addition of adenosine (3 μmol/l) were 0.125 ± 0.020 μmol/l, indicating rapid disposition of extracellular adenosine. Extracellular adenosine levels 1 h after addition of adenosine (3 μmol/l) plus guanosine (30 μmol/l) were 1.173 ± 0.061 μmol/l, indicating slow disposition of extracellular adenosine. Cell injury increased extracellular levels of endogenous adenosine and guanosine, and the effects of cell injury on endogenous extracellular adenosine were modulated by altering the levels of endogenous extracellular guanosine with exogenous purine nucleoside phosphorylase (converts guanosine to guanine) or 8-aminoguanosine (inhibits purine nucleoside phosphorylase). Extracellular guanosine also slowed the disposition of extracellular adenosine in rat preglomerular vascular endothelial cells, mesangial cells, cardiac fibroblasts, and kidney epithelial cells and in human aortic and coronary artery vascular smooth muscle cells and coronary artery endothelial cells. The effects of guanosine on adenosine levels were not mimicked or attenuated by 5-iodotubericidin (adenosine kinase inhibitor), erythro-9-(2-hydroxy-3-nonyl)-adenine (adenosine deaminase inhibitor), 5-aminoimidazole-4-carboxamide (guanine deaminase inhibitor), aristeromycin (S-adenosylhomocysteine hydrolase inhibitor), low sodium (inhibits concentrative nucleoside transporters), S-(4-nitrobenzyl)-6-thioinosine [inhibits equilibrative nucleoside transporter (ENT) type 1], zidovudine (inhibits ENT type 2), or acadesine (known modulator of adenosine levels). Guanosine also increases extracellular inosine, uridine, thymidine, and cytidine, yet decreases extracellular uric acid. In conclusion, extracellular guanosine regulates extracellular adenosine levels.

The uric acid metabolism pathway as a therapeutic target in hyperuricemia related to metabolic syndrome

INTRODUCTION

Uric acid (UA) increase is considered an important risk factor for the development of cardiovascular disease (CVD) favoring oxidative stress and endothelial dysfunction and is also involved in metabolic syndrome (MS) pathophysiology.

AREAS COVERED

Insulin has a physiological action on renal tubules, causing a reduction in UA clearance, what could explain the hyperuricemia found in MS. On the other hand, it was also hypothesized a causal role of UA in fructose-induced MS. Moreover, it has been suggested that higher UA levels predict the development of MS. MS subjects present a redox imbalance and UA participates in this process. UA can contribute to oxidative stress present in MS; however, it has also an important role in the antioxidant defense system. Although UA may have a protective effect due to its antioxidant properties, it is clear that the dominant effect of UA in MS is deleterious. All-cause mortality and CVD have been shown to be increased with higher UA levels.

EXPERT OPINION

It is extremely important to prescribe drugs which concomitantly decrease hyperuricemia and improve co-morbidities associated with hyperuricemia. Long-term studies to verify the consequences of decreasing UA concentration below current recommendations in asymptomatic patients are needed.

Prognostic value of uric acid in patients with acute coronary syndromes

The association between uric acid and cardiovascular disease is incompletely understood. In particular, the prognostic value of uric acid in patients with acute coronary syndromes who undergo percutaneous coronary intervention has not been studied. This study included 5,124 patients with acute coronary syndromes who underwent percutaneous coronary intervention: 1,629 with acute ST-segment elevation myocardial infarction, 1,332 with acute non-ST-segment elevation myocardial infarction, and 2,163 with unstable angina. The primary end point was 1-year mortality. Patients were divided into quartiles according to uric acid level as follows: quartile 1, 1.3 to <5.3 mg/dl; quartile 2, 5.3 to <6.3 mg/dl; quartile 3, 6.3 to <7.5 mg/dl; and quartile 4, 7.5 to 18.4 mg/dl. There were 450 deaths during follow-up: 80 deaths in quartile 1, 77deaths in quartile 2, 72 deaths in quartile 3, and 221 deaths in quartile 4 of uric acid (Kaplan-Meier estimates of 1-year mortality 6.4%, 6.2%, 5.6%, and 17.4%, respectively; unadjusted hazard ratio 3.05, 95% confidence interval 2.54 to 3.67, p <0.001 for fourth vs first quartile of uric acid). After adjustment for traditional cardiovascular risk factors, renal function, and inflammatory status, the association between uric acid and mortality remained significant, with a 12% increase in the adjusted risk for 1-year mortality for every 1 mg/dl increase in the uric acid level. Uric acid improved the discriminatory power of the predictive model regarding 1-year mortality (absolute integrated discrimination improvement 0.008, p = 0.005). In conclusion, elevated levels of uric acid are an independent predictor of 1-year mortality across the whole spectrum of patients with acute coronary syndromes treated with percutaneous coronary intervention.

Uric acid is an independent risk factor for carotid atherosclerosis in a Japanese elderly population without metabolic syndrome

Background

Carotid intima-media thickness (IMT) is an useful surrogate marker of cardiovascular disease. Associations between uric acid (UA), metabolic syndrome (MetS) and carotid IMT have been reported, but findings regarding the relationship have been inconsistent.

Methods

A total of 1,579 Japanese elderly subjects aged ≥65 years {663 men aged, 78 ± 8 (mean ± standard deviation) years and 916 women aged 79 ± 8 years} were divided into 4 groups according to UA quartiles. We first investigated the association between UA concentrations and confounding factors including MetS; then, we assessed whether there is an independent association of UA with carotid IMT and atherosclerosis in participants subdivided according to gender and MetS status.

Results

Carotid IMT was significantly increased according to the quartiles of UA in both genders without MetS and women with MetS. Multivariate logistic regression analysis showed that odds ratio (OR) {95% confidence interval (CI)} in men for carotid atherosclerosis was significantly increased in the third (OR, 1.75; 95% CI, 1.02-3.02), and fourth quartiles (OR, 2.01; 95% CI, 1.12-3.60) of UA compared with that in the first quartile of UA, and the OR in women was significantly increased in the fourth quartile (OR, 2.10; 95% CI, 1.30-3.39). Similarly, the ORs were significantly associated with increasing quartiles of UA in both genders without MetS, but not necessarily increased in those with MetS.

Conclusions

UA was found to be an independent risk factor for incidence of carotid atherosclerosis in both genders without MetS.

Gender-specific association of serum uric acid with metabolic syndrome and its components in juvenile obesity

BACKGROUND

Hyperuricemia has been implicated in the pathogenesis of obesity and related metabolic abnormalities. Studies on the association between serum uric acid (sUA) and metabolic syndrome (MetS) in juvenile obesity are scant. The effect of gender has not been evaluated.

METHODS

sUA (uricase method), anthropometric and biochemical indices were measured in gender-stratified children/adolescents consisting of 113 overweight/obese and 71 lean individuals.

RESULTS

In males, sUA was significantly elevated in overweight as well as obese patients. sUA was strongly associated with obesity indices and reflected sexual development, decreases in high density lipoprotein-cholesterol, and moderately, the number of MetS components. Waist circumference (WC) and Tanner stage explained 40% of sUA variability. Controlling for body mass index (BMI) and other MetS components, sUA was associated with abdominal obesity, explaining 30% of variability in WC. In females, sUA was significantly increased in obesity, high blood pressure (BP), and MetS and corresponded with the number of MetS components, indices of glucose metabolism, triglycerides (TG), and the atherogenecity index. Insulin-resistance (IR) (homeostasis model assessment; HOMA) and high BP explained 29% of sUA variability, whereas sUA, while controlling for BMI, age, and other MetS components, was associated with hypertriglyceridemia, hyperglycemia, high BP, and abdominal obesity. IR mediated the associations with high TG and glucose.

CONCLUSIONS

The association between sUA and MetS components in juvenile obesity is gender-specific, with females being related more closely and to more metabolic abnormalities. It may explain why, despite its lower concentrations, sUA is an independent predictor of mortality from all causes and from vascular diseases exclusively in females. Our findings may help in identifying metabolic abnormalities which may possibly be targeted by reducing sUA in males and females.

Association between endothelial dysfunction and hyperuricaemia

OBJECTIVE

We used high-resolution peripheral vascular ultrasound imaging to assess endothelial function in hyperuricaemic patients.

METHODS

Hyperuricaemia was defined as a serum uric acid concentration of > 7.7 mg/dl in men or > 6.6 mg/dl in women. Measurements of endothelium-dependent flow-mediated vasodilation (FMD) and endothelium-independent nitroglycerin-mediated vasodilation were performed in 46 hyperuricaemic patients and an equal number of healthy age- and gender-matched normal controls by high-resolution two-dimensional ultrasonographic imaging of the brachial artery. The serum levels of glucose, creatinine, alanine aminotransferase (ALT), lipid profiles and high-sensitivity CRP were measured for both the study groups.

RESULTS

The serum uric acid levels averaged 9.24 (1.16) and 6.18 (0.99)  mg/dl in the hyperuricaemic and control groups, respectively. Body weight and BMI were significantly higher in the hyperuricaemic group than in the control group. The serum levels of creatinine, ALT, triglyceride and high-sensitivity CRP were significantly different between the two groups. The FMD values were significantly lower in the hyperuricaemic patients than in the controls [4.45% (3.13%) vs 7.10% (2.48%); P < 0.001]. The FMD values were negatively associated with serum uric acid levels (r = -0.273; P = 0.009). Multivariate regression analysis showed that the presence of hyperuricaemia (β = -0.384; P < 0.001) and body weight (β = 0.215; P = 0.017) were independent determinants of low FMD values.

CONCLUSION

Hyperuricaemia is associated with endothelial dysfunction. Decreased nitric oxide bioavailability may be the main reason.

Influence of fish oil or folate supplementation on the time course of plasma redox markers during pregnancy

Maternal supplementation with long-chain PUFA, to improve infant neurological development, might cause additional increase of oxidative stress. Pregnant women aged 18-41 years were randomised into one of four supplementation groups. From week 22 on, they received supplements containing either modified fish oil (n 69), 5-methyl-tetrahydro-folate (n 65), both (n 64), or placebo (n 72). Plasma Trolox-equivalent antioxidative capacity (TEAC), concentrations of alpha-tocopherol, retinol, beta-carotene, free thiol groups, uric acid and thiobarbituric acid-reactive substances (TBARS) were determined at weeks 20 and 30 and at delivery. The studied antioxidants showed no significant differences between the four supplementation groups. At week 30 plasma TBARS levels were found to be significantly higher in the fish oil group (0.80 (sem 0.04) micromol/l) than in the folate (0.67 (sem 0.03) micromol/l; P = 0.024) and control (0.69 (sem 0.04) micromol/l; P = 0.01) groups. Concentrations of retinol and free thiol groups decreased during pregnancy, whereas uric acid increased and beta-carotene as well as TEAC showed only minor changes. Fish oil supplementation during the second half of pregnancy appears not to decrease antioxidant status. The increased TBARS levels at week 30 may indicate a period of increased oxidative stress in plasma at this time.

Uric acid levels are associated with all-cause and cardiovascular disease mortality independent of systemic inflammation in men from the general population: the MONICA/KORA cohort study

OBJECTIVE

The purpose of this study was to assess whether increasing serum uric acid (UA) levels are related to cardiovascular disease (CVD) mortality, all-cause mortality, and incident (fatal and nonfatal) myocardial infarction (MI) in men from the general population taking into account C-reactive protein (CRP), a sensitive marker of systemic inflammation.

METHODS AND RESULTS

The study was based on 3604 men (45 to 74 years of age) who participated in 1 of the 3 MONICA Augsburg surveys between 1984 and 1995. All participants were prospectively followed within the framework of the Cooperative Health Research in the Region of Augsburg (KORA). Up to December 31, 2002, there occurred 809 total deaths, 359 CVD deaths, and 297 incident MIs. In a Cox model, comparing extreme quartiles of the UA distribution, the hazard ratio for CVD mortality was 1.44 (95% confidence interval [CI] 1.04 to 2.0), and for all-cause mortality it was 1.40 (95% CI 1.13 to 1.74) after adjustment for conventional cardiovascular risk factors, CRP, and diuretic intake. However, UA was not associated with incident MI after multivariable adjustment.

CONCLUSIONS

High UA levels were independently associated with CVD mortality as well as all-cause mortality but not with incident MI in middle-aged men from the general population.

Plasmodium-induced inflammation by uric acid

Infection of erythrocytes with the Plasmodium parasite causes the pathologies associated with malaria, which result in at least one million deaths annually. The rupture of infected erythrocytes triggers an inflammatory response, which is induced by parasite-derived factors that still are not fully characterized. Induced secretion of inflammatory cytokines by these factors is considered a major cause of malaria pathogenesis. In particular, the inflammatory cytokine tumor necrosis factor (TNF) is thought to mediate most of the life-threatening pathologies of the disease. Here we describe the molecular characterization of a novel pathway that results in the secretion of TNF by host cells. We found that erythrocytes infected by Plasmodium accumulate high concentrations of hypoxanthine and xanthine. Degradation of Plasmodium-derived hypoxanthine/xanthine results in the formation of uric acid, which triggers the secretion of TNF. Since uric acid is considered a "danger signal" released by dying cells to alert the immune system, Plasmodium appears to have co-evolved to exploit this warning system. Identifying the mechanisms used by the parasite to induce the host inflammatory response is essential to develop urgently needed therapies against this disease.

Plasma Uric Acid and the Risk of Type 2 Diabetes in a Chinese Community

Background: Previous cross-sectional studies have shown hyperuricemia to be prevalent among individuals with metabolic syndrome, but the evidence from prospective studies of an association between uric acid and diabetes risk is limited. We prospectively investigated the association between plasma concentrations of uric acid and the incidence of type 2 diabetes in Chinese individuals.

Methods: We conducted a community-based prospective cohort study of 2690 participants (age range, 35–97 years) in the Chin-Shan Community Cardiovascular Cohort Study, who were found to be free of diabetes and cardiovascular disease during baseline assessment at study entry in 1990. During a median 9.0-year follow-up, 548 participants developed type 2 diabetes.

Results: High plasma uric acid concentrations were associated with a higher prevalence of metabolic syndrome. After adjustment for age, sex, body mass index, and other covariates, the relative risks (RR) of diabetes according to uric acid quintile were 1.11, 1.29, 1.40, and 1.63 [95% confidence interval (CI), 1.20–2.23; P for trend &lt;0.001]. After additional adjustment for metabolic syndrome, the RR for comparing the participants in the fifth and first uric acid quintiles was 1.40 (95% CI, 1.02–1.92; P for trend = 0.027). In joint analyses, participants who were in the highest uric acid quintile and also had metabolic syndrome had a 3.3-fold greater risk of diabetes (95% CI, 2.27–4.94) than those in the lowest uric acid quintile and without metabolic syndrome.

Conclusions: These findings suggest a modest positive association between plasma uric acid concentration and the incidence of type 2 diabetes in Chinese individuals. The association between hyperuricemia and diabetes was partly mediated through the metabolic syndrome.

Serum uric acid, mortality and glucose control in patients with Type 2 diabetes mellitus: a PreCIS database study

AIMS

To determine the association of serum uric acid with all-cause mortality and hyperglycaemia in patients with Type 2 diabetes.

METHODS

Retrospective cohort analysis of 535 consecutive patients who had uric acid determinations between 1998 and 2004 and whose subsequent vital status was determined at a median of 4.5 years. The association with mortality was analysed with Cox proportional hazards models. The incremental predictive value of uric acid was examined with concordance indexes. The proportional risk of mortality was represented with the Kaplan-Meier survival curves by uric acid quartiles.

RESULTS

We studied 370 men and 165 women aged 59.3 +/- 11.5 years. Mean uric acid was 371.7 +/- 106.2 micromol/l. Patients with glycated haemoglobin (HbA(1c)) > or = 9% had lower uric acid vs. the rest (342.2 +/- 112.1 vs. 383.5 +/- 106.2, P = 0.002). Overall mortality was 10.8%. For each 59 micromol/l increase in uric acid there was a 41% increase in risk of death (unadjusted analysis). The association of uric acid with mortality remained after adjustment for covariates (hazard ratio = 1.21, 95% confidence interval 1.07-1.45) and after gender subanalyses. Uric acid increased the accuracy of prediction when added to a model including Framingham risk factors, components of metabolic syndrome and fibrinogen (P = 0.03). Mortality was higher in patients taking diuretics vs. the rest (15.9 vs. 7.3%), but uric acid predicted mortality in both subgroups.

CONCLUSIONS

Serum uric acid predicts mortality in Type 2 diabetic patients regardless of gender, HbA(1c), renal function and diuretic use. Intervention studies should determine whether uric acid is a potential therapeutic target or only a marker of mortality risk.

Effect of bis (maltolato) oxovanadium (BMOV) in uric acid and sodium arsenite-induced vascular endothelial dysfunction in rats

The study has been designed to investigate the effect of BMOV, a protein tyrosine phosphatase (PTPase) inhibitor in uric acid and sodium arsenite-induced vascular endothelial dysfunction (VED). Uric acid (150 mg kg(-)(1) day(-)(1), i.p., 3 weeks) and sodium arsenite (1.5 mg kg(-)(1) day(-)(1), i.p., 2 weeks) were administered to produce VED in rats. VED was assessed by employing isolated aortic ring preparation, electron microscopy of thoracic aorta and estimating serum concentration of nitrite/nitrate. Further, serum thiobarbituric acid reactive substances (TBARS) and aortic production of superoxide anion were estimated to assess oxidative stress. Uric acid and sodium arsenite were noted to produce VED by attenuating acetylcholine-induced endothelium dependent relaxation, impairing the integrity of vascular endothelial lining, decreasing serum nitrite/nitrate concentration and increasing serum TBARS and aortic superoxide anion generation which were significantly attenuated by BMOV (0.2 mg ml(-)(1) day(-)(1) in drinking water) or atorvastatin (30 mg kg(-)(1) day(-)(1)p.o., a standard agent). However, these ameliorative effects of BMOV have been prevented by N-omega-nitro-L-arginine methyl ester (L-NAME) (25 mg kg(-)(1) day(-)(1), i.p.), an inhibitor of NOS and glibenclamide (5 mg kg(-)(1) day(-)(1), i.p.), a blocker of ATP-sensitive K(+) channel. It may be concluded that BMOV-induced inhibition of PTPase may activate eNOS by opening of ATP-sensitive K(+) channels and consequently decrease oxidative stress to prevent uric acid and sodium arsenite-induced vascular endothelial dysfunction.

Intake of added sugar and sugar-sweetened drink and serum uric acid concentration in US men and women

Fructose-induced hyperuricemia might have a causal role in metabolic syndrome, hypertension, and other chronic disease. However, no study has investigated whether sugar added to foods or sugar-sweetened beverages, which are major sources of fructose, are associated with serum uric acid concentration in free-living populations. We examined the relationship between the intakes of added sugars and sugar-sweetened beverages and serum uric acid concentrations in the National Health and Nutrition Examination Survey 2001-2002, a nationally representative sample of men and women. We included 4073 subjects (1988 men and 2085 women) >18 years of age in the current study. Dietary intake was assessed by a single 24-hour recall. We used multivariate linear regression to adjust for age, gender, intake of energy and alcohol, body mass index, use of diuretics, beta-blockers, and other covariates. Male subjects in the highest intake quartile of estimated intake of added sugars or sugar-sweetened drinks had higher plasma uric acid concentrations than those in the lowest intake quartiles (P<0.001 for both) after adjusting for potential confounders, whereas we did not observe significant associations for females (P for trend>0.2; P for interaction <0.01). Further research is needed to confirm causality of these associations and the observed difference by gender.

Serum uric acid is associated with microvascular function in hypertensive individuals

We investigated the relationship of serum uric acid (UA) with resting forearm blood flow (FBF), reactive hyperaemia (RH) and flow-mediated dilation (FMD) of the brachial artery in hypertensive adults (n=506, mean age 62 years, 59% women). UA was measured by a colorimetric method. FBF, RH and FMD were measured by brachial artery ultrasound. Regression analyses were used to assess whether UA was associated with FBF, RH and FMD before and after adjustment for age, sex, systolic BP, diabetes, total and high-density lipoprotein cholesterol, smoking, body mass index (BMI), C-reactive protein (CRP), serum creatinine, alcohol intake, statin and diuretic use and brachial artery diameter (BAD). UA was significantly associated with FBF (P<0.0001) and RH (P=0.0001) but not with FMD (P=0.43). After adjustment for the covariates listed above, higher UA level remained independently associated with a higher FBF (P=0.012) and lower RH (P=0.004). The independent predictors were as follows: (a) higher FBF: lower age, higher BMI, history of smoking, statin use, higher CRP, higher BAD and higher UA levels; (b) lower RH: higher BMI, diabetes and higher UA levels; (c) lower FMD: greater age, male sex, higher BMI, history of smoking, statin use and higher BAD. We conclude that in hypertensive individuals, higher UA levels are associated with higher resting FBF and lower RH, markers of microvascular function, but not with brachial artery FMD.

Uric acid heralds ischemic tissue injury to mobilize endothelial progenitor cells

Understanding the nature of endogenous mechanisms for mobilization of stem/progenitor cells is predicated on the identification of injury-induced substances that are released from a damaged organ and capable of producing a distant effect. Although different substances that mobilize endothelial progenitor cells (EPCs) have been proposed, their potential to signal injury and afford postischemic renoprotection and repair remains obscure. Uric acid (UA) is consistently overproduced by ischemic tissues and has been shown to exert immunomodulatory functions. It was hypothesized that UA and/or its precursors might serve as injury signals that are capable of mobilizing EPCs in acute renal ischemia. Indeed, FVB/NJ mice that were subjected to acute renal ischemia showed a transient surge in UA level in the peripheral blood. Single-dose treatment with UA, as well as acute hyperuricemia induced by the inhibition of uricase, caused a robust mobilization of EPCs, whereas administration of adenosine or inosine seemed to lack this effect. Moreover, pretreatment of mice with a single dose of UA afforded significant renoprotection against ischemic injury. In animals with chronic hyperuricemia (induced by continuous 2-wk treatment with a uricase inhibitor oxonic acid), EPC mobilization was blunted and renoprotective effects were absent. In conclusion, acute elevation of UA acts as "physiologic," fast-acting endogenous mediator of EPC mobilization and renoprotection, consistent with its novel function in pharmacologic preconditioning. Both of these actions are lacking in mice with chronic hyperuricemia. In summary, a transient surge in UA concentration may serve as a universal herald of tissue injury to accelerate the recruitment of EPCs.

Association between serum uric acid level and peripheral arterial disease

BACKGROUND

Higher serum uric acid levels have been implicated in the development and progression of atherosclerotic cardiovascular disease. However, it is not clear whether serum uric acid levels are related to subclinical measures of cardiovascular disease, including peripheral arterial disease (PAD). We examined the association between increasing serum uric acid levels and PAD in the US general population.

METHODS

A cross-sectional study was conducted among 3987 National Health and Nutrition Examination Survey 1999-2002 participants aged > or =40 years, without clinical history of cardiovascular disease. Main outcome-of-interest was PAD defined as ankle-brachial index <0.9 (n=229).

RESULTS

Higher serum uric acid levels were positively associated with PAD, independent of smoking, body mass index (BMI), hypertension, diabetes, serum total cholesterol, serum creatinine, and other confounders. Multivariable odds ratio (OR) [95 percent confidence intervals (CI)] comparing serum uric acid levels > or =75th percentile (> or =380.8 micromol/L) to uric acid levels <50th percentile (<315.6 micromol/L) was 1.62 (1.08-2.44), p-trend=0.015. This association persisted in separate analysis among men and women. Further, the results were consistent in subgroup analyses by categories of age, current smoking, BMI, and diabetes mellitus.

CONCLUSIONS

Higher serum uric acid levels are associated with PAD in the US general population. These results suggest that PAD may be an important indicator of the reported association between higher serum uric acid levels and clinical cardiovascular disease. Future prospective studies are required to clarify the temporal nature of this relationship.

Predicting initiation and progression of chronic kidney disease: Developing renal risk scores

Epidemiological studies have raised awareness of the problem of undiagnosed chronic kidney disease (CKD) and suggest that early identification and treatment will reduce the global burden of patients requiring dialysis. This has highlighted the twin problems of how to identify subjects for screening and target intervention to those with CKD most likely to progress to end-stage renal disease. Prospective studies have identified risk factors for CKD in the general population as well as risk factors for progression in patients with established CKD. Risk factors may thus be divided into initiating factors and perpetuating factors, with some overlap between the groups. In this paper, we review current data regarding CKD risk factors and illustrate how each may impact upon the mechanisms underlying CKD progression to accelerate loss of renal function. We propose that these risk factors should be used as a basis for developing a renal risk score, analogous to the Framingham risk score for ischemic heart disease, which will allow accurate determination of renal risk in the general population and among CKD patients.

Meeting report: ISN forefronts in nephrology on endothelial biology and renal disease: from bench to prevention

This ISN-sponsored Forefront in Nephrology meeting, which has brought together 120 scientists from 21 countries, has been concerned with various aspects of endothelial function and dysfunction and their contribution to progression of chronic kidney disease and/or its cardiovascular complications. The following themes were discussed in great depth: (1) phenotypical changes in the vascular endothelium - permeability, senescence, and apoptosis; (2) regulation of endothelial nitric oxide (NO) synthase function - caveolar and shear stress mechanisms, epigenetic regulation, S-nitrosylation, and Rho-kinase regulation; (3) oxidative stress and hypoxia-induced changes; (4) organellar dysfunction - lysosomes, mitochondria, and endoplasmic reticulum; (5) NO-independent mechanisms of vasomotion - epoxides, heme oxygenase-1 and carbon monoxide, thromboxane, tumor necrosis factor-alpha, and uric acid; (6) endothelial crosstalk with podocytes, monocytes, smooth muscle cells, and platelets; (7) candidate clinical biomarkers of endothelial dysfunction - functional testing of macro- and micro-vascular functions, surrogate markers, circulating detached endothelial cells, and endothelial precursor cells; and culminated in Round Table discussion on the diagnosis of endothelial dysfunction and its treatment options. In conclusion, this meeting has focused on several key problems of endothelial cell pathobiology relevant to chronic kidney disease.

Renal Urate Transport

Serum uric acid is determined by a balance between production and renal excretion. Luminal reabsorption of urate by the proximal tubule from the glomerular ultrafiltrate involves coupling between sodium-anion cotransport and urate-anion exchange. Apical sodium-coupled cotransport of lactate, ketoacids, nicotinate, and pyrazinoate increases intracellular levels of these anions in proximal tubular cells, stimulating the apical absorption of luminal urate via anion exchange. Hyperuricemia occurs when plasma levels of these anions increase; for example, hyperuricemia is a well-recognized concomitant of lactic acidosis and ketoacidosis. Relevant developments in the molecular and renal physiology of urate homeostasis are reviewed.