Elevated serum uric acid levels in metabolic syndrome: an active component or an innocent bystander?

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.

Serum uric acid and metabolic syndrome in Taiwanese adults

A positive association between serum uric acid and metabolic syndrome has been reported, but little information is available about the association between serum uric acid and metabolic syndrome in Taiwanese adults. The purpose of this study was to investigate the association between serum uric acid levels and metabolic syndrome in Taiwanese adults. We performed a cross-sectional study of 2085 men and 1557 women. All of the participants underwent a health screening during the period from January 2005 to December 2005 at a health center of the Shin Kong Wu Ho-Su Memorial Hospital. Metabolic syndrome was defined according to the National Cholesterol Education Program Adult Treatment Panel III criteria. The results showed that hyperuricemia was significantly associated with increased risk for hypertriglyceridemia, low high-density lipoprotein cholesterol level, and high blood pressure in men and women. The risk of metabolic syndrome was significantly higher in the fourth quartile than in the first quartile of uric acid level in men (odds ratio [OR], 1.50; 95% confidence interval [CI], 1.06-2.14) and women (OR, 2.33; 95% CI, 1.39-3.93). In addition, uric acid level was inversely associated with hyperglycemia in men. The ORs of hyperglycemia for the second, third, and fourth quartile of uric acid were 0.69 (95% CI, 0.46-1.03), 0.55 (95% CI, 0.37-0.83), and 0.45 (95% CI, 0.29-0.69), respectively, compared with the lowest quartile of uric acid. The results demonstrate that there is a positive association between serum uric acid levels and metabolic syndrome and an inverse association between uric acid and fasting plasma glucose in Taiwanese adults.

Serum glycated albumin, but not glycated haemoglobin, is low in relation to glycemia in hyperuricemic men

Measurements of glycated albumin (GA) as well as glycated haemoglobin (HbA(1C)) have been applied in order to monitor chronic glycemic control in diabetic patients. Since the levels of both glycated proteins are influenced by various factors other than glycemia, cautions are necessary to evaluate such measures in some specific conditions. In this study, we examined the effects of serum uric acid (UA) levels on these glycemic markers. One hundred and ninety-three men with normal glucose tolerance were enrolled in this study. Association of serum UA with BMI, plasma glucose (PG), high sensitivity CRP (hs-CRP), serum GA and HbA(1C) was analysed. Serum UA showed a significant positive correlation with BMI (R = 0.329, P < 0.0001) and hs-CRP (R = 0.306, P < 0.0001). Multivariate analysis revealed serum UA to be a significant positive explanatory variable for hs-CRP. There was a significant positive correlation of serum UA with the 2-h PG after 75 g OGTT but not fasting PG. Although there was no correlation of serum UA with HbA(1C), serum UA showed a significant inverse correlation with both serum GA (R = -0.402, P < 0.0001) as well as BMI-adjusted serum GA (R = -0.327, P < 0.0001). By multivariate analysis, serum UA was an explanatory variable for serum GA. Serum GA, but not HbA(1C), is set lower in relation to plasma glucose levels in hyperglycemic men. This may be caused by microinflammation associated with hyperuricemic state.

Association between serum uric acid and non-alcoholic fatty liver disease in Korean adults

BACKGROUND

Increased uric acid is associated with the metabolic syndrome, conditions linked to oxidative stress and insulin resistance. Non-alcoholic fatty liver disease (NAFLD) is now considered a hepatic manifestation of insulin resistance. However, little has been written regarding the association between uric acid and NAFLD.

METHODS

We examined the association between uric acid and the presence of NAFLD in 3768 Koreans (2133 men, 1635 women; aged 20-75 years) in a health examination program. Uric acid quartiles were categorized separately as follows: Q1: <or=291.5, Q2: 291.6-333.1, Q3: 333.2-380.7, and Q4: >or=380.8 micromol/L for men; Q1: <or=202.2, Q2: 202.3-232.0, Q3: 231.1-267.7, and Q4: >or=267.8 micromol/L for women. Hepatic steatosis was diagnosed based on abdominal ultrasonographic findings by hyperechogenicity of liver tissue, difference of echogenicity between the liver and diaphragm, and visibility of vascular structures. The odds ratios (ORs) and 95% confidence intervals (CIs) for NAFLD were calculated across each quartile of serum uric acid.

RESULTS

The prevalence of NAFLD was 25.8% (32.2% in men and 17.4% in women). After adjustment for age, body mass index (BMI), smoking, regular exercise, blood pressure, fasting plasma glucose (FPG), triglycerides, and high-density lipoprotein (HDL) cholesterol, the ORs (95% CIs) for NAFLD according to each quartile of uric acid were 1.00, 1.55 (1.13-2.14), 1.77 (1.30-2.41), and 2.01 (1.45-2.78) for men and 1.00, 0.69 (0.40-1.20), 1.12 (0.67-1.88), and 1.94 (1.21-3.13) for women.

CONCLUSIONS

Serum uric acid is independently associated with the presence of NAFLD, and uric acid may be a useful additional measure in assessing the risk of NAFLD in the clinical setting.

Association between carotid atherosclerosis and metabolic syndrome: results from the ISMIR study

The metabolic syndrome (MetS) has previously been associated with an early marker of atherosclerosis, the carotid intima-media thickness (IMT). From the ISMIR (Ispessimento Medio Intimale e Rischio cardiovascolare [media-intima thickness and cardiovascular risk]) study population of 479 asymptomatic participants, we identified 80 participants with MetS. Carotid IMT and plaques were evaluated by ultrasonography. Blood samples were obtained from all participants. Participants with MetS had a significantly higher prevalence of a carotid IMT > 0.80 mm (P = .004) and of carotid plaques (P < .001) as compared with participants without MetS. Carotid IMT was significantly correlated with fasting triglycerides and fibrinogen levels both in participants with MetS and in those without MetS (all P < .01). In contrast, IMT correlated with fasting plasma glucose, serum creatinine, and uric acid levels only in participants without MetS. Our study confirms the association between MetS and carotid atherosclerosis. In MetS, a significant correlation between carotid IMT and triglycerides and fibrinogen levels was found.

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.

Clinical review: The pathogenetic role of cortisol in the metabolic syndrome: a hypothesis

CONTEXT

The metabolic syndrome (MetS) is a cluster of metabolic abnormalities that increase the risk for type 2 diabetes mellitus and vascular disease. The common characteristics of MetS and hypercortisolemic conditions such as Cushing's syndrome (CS) suggest that the pathogenesis of MetS and central obesity might involve prolonged and excessive exposure to glucocorticoids. The present review summarizes the evidence on the potential role of cortisol in the pathogenesis of MetS and discusses new therapeutic approaches for these patients.

EVIDENCE ACQUISITION

Using PubMed, we searched for publications during the last 20 yr regarding the possible pathogenetic role of cortisol in the development of MetS.

EVIDENCE SYNTHESIS

Emerging data suggest that patients with MetS show hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis, which leads to a state of "functional hypercortisolism." The cause for this activation of the HPA axis remains uncertain but may be partly associated with chronic stress and/or low birth weight, which are both associated with increased circulating cortisol levels and greater responsiveness of the HPA axis. Increased exposure to cortisol contributes to increased fat accumulation in visceral depots. However, cortisol metabolism is not only centrally regulated. The action of 11beta-hydroxysteroid dehydrogenase-1 at the tissue level also modulates cortisol metabolism. Increased 11beta-hydroxysteroid dehydrogenase-1 activity in adipose tissue and liver might contribute to the development of several features of the MetS.

CONCLUSIONS

MetS shares many characteristics of CS, and cortisol might play a role in the development of MetS at both a central and a peripheral level.

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

Introduction

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

Methods

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

Results

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

Conclusions

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

Genetic influence on variation in serum uric acid in American Indians: the strong heart family study

Hyperuricemia is associated with the metabolic syndrome, gout, renal and cardiovascular disease (CVD). American Indians have high rates of CVD and 25% of individuals in the strong heart family study (SHFS) have high serum uric acid levels. The aim of this study was to investigate the genetic determinants of serum uric acid variation in American Indian participants of the SHFS. A variance component decomposition approach (implemented in SOLAR) was used to conduct univariate genetic analyses in each of three study centers and the combined sample. Serum uric acid was adjusted for age, sex, age x sex, BMI, estimated glomerular filtration rate, alcohol intake, diabetic status and medications. Overall mean +/- SD serum uric acid for all individuals was 5.14 +/- 1.5 mg/dl. Serum uric acid was found to be significantly heritable (0.46 +/- 0.03 in all centers, and 0.39 +/- 0.07, 0.51 +/- 0.05, 0.44 +/- 0.06 in Arizona, Dakotas and Oklahoma, respectively). Multipoint linkage analysis showed significant evidence of linkage for serum uric acid on chromosome 11 in the Dakotas center [logarithm of odds score (LOD) = 3.02] and in the combined sample (LOD = 3.56) and on chromosome 1 (LOD = 3.51) in the combined sample. A strong positional candidate gene in the chromosome 11 region is solute carrier family22, member 12 (SLC22A12) that encodes a major uric acid transporter URAT1. These results show a significant genetic influence and a possible role for one or more genes on chromosomes 1 and 11 on the variation in serum uric acid in American Indian populations.

Obesity and metabolic changes are common in young childhood brain tumor survivors

BACKGROUND

A population based cross-sectional study was used to examine the prevalence of metabolic syndrome and its components in childhood brain tumor survivors.

PROCEDURE

Fifty-two survivors were examined at a mean age of 14.4 years (range 3.8-28.7). Lipid and glucose metabolism, thyroid function, and plasma uric acid were evaluated. Fat mass and fat percentage were assessed by dual-energy X-ray absorptiometry (DXA). Metabolic syndrome was defined on International Diabetes Federation criteria.

RESULTS

Ten (19%) patients were overweight and four (8%) were obese. According to DXA, 16/46 (35%) patients were obese. Central obesity was found in 11 (21%) patients. Cranial irradiation, hypothalamic/hypophyseal damage, growth hormone (GH) deficiency and impaired mobility were associated with overweight/obesity and central obesity. Thirteen (25%) subjects had hypercholesterolemia, 14 (27%) had raised low-density lipoprotein cholesterol (LDL-C), 12 (23%) had raised blood pressure, four (8%) had metabolic syndrome, two (4%) had hyperinsulinemia and five (10%) had hyperuricemia. Cranial irradiation was associated with hypercholesterolemia (P = 0.019), raised LDL-C (P = 0.028), raised blood pressure (P = 0.040), and metabolic syndrome (P = 0.018). Impaired mobility was associated with hypercholesterolemia (P = 0.034). Hypothalamic/hypophyseal damage was associated with metabolic syndrome (P = 0.003) and hyperuricemia (P = 0.011) as was GH deficiency (P = 0.034 and P = 0.008). GH supplementation alleviated adverse metabolic outcomes among brain tumor survivors with GH deficiency.

CONCLUSIONS

Obesity/overweight, dyslipidemia, hypertension, metabolic syndrome, and hyperuricemia were common in young childhood brain tumor survivors. Cranial irradiation, hypothalamic/hypophyseal damage, growth hormone deficiency, and/or impaired mobility were associated with higher risk for obesity and metabolic changes among these patients.

Diabetes mellitus and cerebrovascular disease: which are the actual data?

Cerebrovascular disease (CeVD) represents a major cause of morbidity and mortality worldwide. Diabetes mellitus (DM) represents an independent risk factor for CeVD. The aim of the present review is to describe the epidemiology of CeVD in patients with DM and to explain how DM and diabetic autonomic neuropathy can increase the risk of CeVD. The prevention and management of CeVD in the diabetic population are also analyzed.

Insulin resistance acts as an independent risk factor exacerbating high-purine diet induced renal injury and knee joint gouty lesions

OBJECTIVE AND DESIGN

Insulin resistant Otsuka-Long-Evans-Tokushima Fatty (OLETF) and its control Long-Evans Tokushima Ohtsuka (LETO) rats were used to generate a model for acute hyperuricemia. Upon the onset of insulin resistance OLETF rats were feed with high-purine diet, and the development of acute hyperuricemic renal injury and gouty-like lesions was monitored. Rosiglitazone was also administered to demonstrate whether improved insulin sensitivity would prevent high-purine diet induced renal injury and gouty-like lesions.

RESULTS

Otsuka-Long-Evans-Tokushima Fatty rats showed significant higher incidence of hyperuricemia as compared to the control LETO rats (77 vs. 36.1%, P < 0.05), indicating that insulin resistance exacerbates the development of hyperuricemia following high-purine load. Consistent with this observation, improvement of insulin sensitivity by administration of rosiglitazone significantly reduced high-purine diet induced renal injury and gouty-like lesions. It was found that insulin resistance is associated with impaired capability for maintaining the homeostasis of renal uric acid excretion and reabsorption. Upon high-purine load, insulin resistance enhances urate reabsorption as manifested by up-regulated URAT1 expression and reduces urate excretion as characterized by down-regulated UAT expression.

CONCLUSIONS

Our data demonstrated strong evidence indicating that insulin resistance acts as an independent risk factor predisposing OLETF rats more susceptible to the development of hyperuricemia and gouty arthritis following high-purine load.

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.

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.

Elevated uric acid increases the risk for kidney disease

Recent epidemiologic studies suggest that uric acid predicts the development of new-onset kidney disease, but it is unclear whether uric acid is an independent risk factor. In this study, data from 21,475 healthy volunteers who were followed prospectively for a median of 7 yr were analyzed to examine the association between uric acid level and incident kidney disease (estimated GFR [eGFR] <60 ml/min per 1.73 m(2)). After adjustment for baseline eGFR, a slightly elevated uric acid level (7.0 to 8.9 mg/dl) was associated with a nearly doubled risk for incident kidney disease (odds ratio 1.74; 95% confidence interval 1.45 to 2.09), and an elevated uric acid (> or =9.0 mg/dl) was associated with a tripled risk (odds ratio 3.12; 95% confidence interval 2.29 to 4.25). These increases in risk remained significant even after adjustment for baseline eGFR, gender, age, antihypertensive drugs, and components of the metabolic syndrome (waist circumference, HDL cholesterol, blood glucose, triglycerides, and BP). In a fully adjusted spline model, the risk for incident kidney disease increased roughly linearly with uric acid level to a level of approximately 6 to 7 mg/dl in women and 7 to 8 mg/dl in men; above these levels, the associated risk increased rapidly. In conclusion, elevated levels of uric acid independently increase the risk for new-onset kidney disease.

Role of oxidative stress in the renal abnormalities induced by experimental hyperuricemia

Endothelial dysfunction is a characteristic feature during the renal damage induced by mild hyperuricemia. The mechanism by which uric acid reduces the bioavailability of intrarenal nitric oxide is not known. We tested the hypothesis that oxidative stress might contribute to the endothelial dysfunction and glomerular hemodynamic changes that occur with hyperuricemia. Hyperuricemia was induced in Sprague-Dawley rats by administration of the uricase inhibitor, oxonic acid (750 mg/kg per day). The superoxide scavenger, tempol (15 mg/kg per day), or placebo was administered simultaneously with the oxonic acid. All groups were evaluated throughout a 5-wk period. Kidneys were fixed by perfusion and afferent arteriole morphology, and tubulointerstitial 3-nitrotyrosine, 4-hydroxynonenal, NOX-4 subunit of renal NADPH-oxidase, and angiotensin II were quantified. Hyperuricemia induced intrarenal oxidative stress, increased expression of NOX-4 and angiotensin II, and decreased nitric oxide bioavailability, systemic hypertension, renal vasoconstriction, and afferent arteriolopathy. Tempol treatment reversed the systemic and renal alterations induced by hyperuricemia despite equivalent hyperuricemia. Moreover, because tempol prevented the development of preglomerular damage and decreased blood pressure, glomerular pressure was maintained at normal values as well. Mild hyperuricemia induced by uricase inhibition causes intrarenal oxidative stress, which contributes to the development of the systemic hypertension and the renal abnormalities induced by increased uric acid. Scavenging of the superoxide anion in this setting attenuates the adverse effects induced by hyperuricemia.

Uric acid and the development of metabolic syndrome in women and men

Associations between serum uric acid (UA) levels and metabolic syndrome (MetS) have been reported in cross-sectional studies. Limited information, however, is available concerning the prospective association of UA and the risk of developing MetS. The authors evaluated UA as a risk factor for incident MetS in a prospective study of 8429 men and 1260 women (aged 20-82 years) who were free of MetS and for whom measures of waist girth, resting blood pressure, fasting lipids, and glucose were taken during baseline and follow-up examinations between 1977 and 2003. Hyperuricemia was defined as >7.0 mg/dL in men and >6.0 mg/dL in women. Metabolic syndrome was defined with the National Cholesterol Education Program Adult Treatment Panel III criteria. The overall prevalence of hyperuricemia was 17%. During a mean follow-up of 5.7 years, 1120 men and 44 women developed MetS. Men with serum UA concentrations > or =6.5 mg/dL (upper third) had a 1.60-fold increase in risk of MetS (95% confidence interval, 1.34-1.91) as compared with those who had concentrations <5.5 mg/dL (lowest third). Among women, the risk of MetS was at least 2-fold higher for serum UA concentrations > or =4.6 mg/dL (P for trend = .02). Higher serum UA is a strong and independent predictor of incident MetS in men and women.

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.

Dysmetabolic changes associated with HCV: a distinct syndrome?

Although not associated with the metabolic syndrome, HCV is linked with impaired insulin signalling, insulin resistance, hypocholesterolemia and steatosis which represent a distinct HCV-associated dysmetabolic syndrome. Insulin resistance affects the development of diabetes, fibrosis, impaired response to antivirals and perhaps hepatocellular carcinoma risk. HCV infection is associated with hypocholesterolemia and steatosis reversible after sustained virologic response. A "viral", and a "metabolic" steatosis exist as function of viral genotypes. Little is known about the possible role of HCV in further components of the metabolic syndrome such as atherosclerosis, obesity, arterial hypertension, hyperuricemia and thrombotic risk factors.

Uric acid: A marker of increased cardiovascular risk

The relationship between uric acid and cardiovascular disease has been known since the 19th century, after that many authors reported the classical association of gout, hypertension, obesity and cardiovascular disease. With the exception of specific genetic defects in purine metabolism, increased uric acid is generally associated with important risk factors for atherosclerosis like hypertension, abdominal obesity, insulin resistance, the metabolic syndrome and renal failure. Studies have clearly shown an association between increased uric acid concentrations with oxidative stress, endothelial dysfunction, inflammation, subclinical atherosclerosis and an increased risk of cardiovascular events. Increased uric acid levels are independent markers of cardiovascular disease risk. Prospective studies are necessary to show that reduction of uric acid levels prevent cardiovascular events.

Effects of febuxostat on metabolic and renal alterations in rats with fructose-induced metabolic syndrome

Increased fructose consumption is associated with hyperuricemia, metabolic syndrome, and renal damage. This study evaluated whether febuxostat (Fx), an investigational nonpurine, and selective xanthine oxidase inhibitor, could alleviate the features of metabolic syndrome as well as the renal hemodynamic alterations and afferent arteriolopathy induced by a high-fructose diet in rats. Two groups of rats were fed a high-fructose diet (60% fructose) for 8 wk, and two groups received a normal diet. For each diet, one group was treated with Fx (5-6 mg.kg(-1).day(-1) in the drinking water) during the last 4 wk (i.e., after the onset of metabolic syndrome), and the other received no treatment (placebo; P). Body weight was measured daily. Systolic blood pressure and fasting plasma uric acid (UA), insulin, and triglycerides were measured at baseline and at 4 and 8 wk. Renal hemodynamics and histomorphology were evaluated at the end of the study. A high-fructose diet was associated with hyperuricemia, hypertension, as well as increased plasma triglycerides and insulin. Compared with fructose+P, fructose+Fx rats showed significantly lowered blood pressure, UA, triglycerides, and insulin (P < 0.05 for all comparisons). Moreover, fructose+Fx rats had significantly reduced glomerular pressure, renal vasoconstriction, and afferent arteriolar area relative to fructose+P rats. Fx treatment in rats on a normal diet had no significant effects. In conclusion, normalization of plasma UA with Fx in rats with metabolic syndrome alleviated both metabolic and glomerular hemodynamic and morphological alterations. These results provide further evidence for a pathogenic role of hyperuricemia in fructose-mediated metabolic syndrome.

Prevalence of metabolic syndrome in long-term survivors of hematopoietic stem cell transplantation

Our purpose was to determine the prevalence and features of metabolic syndrome (MS) in a series of long-term hematopoietic stem cell transplantation (HSCT) survivors. We assessed the clinical, metabolic and endocrinological data, and plasma TNF, leptin, resistin and adiponectin levels relating to 85 HSCT recipients. MS was diagnosed on the basis of the National Cholesterol Education Program-Adult Treatment Panel III criteria. Its prevalence was compared with that observed in an Italian population, and its relationship with the clinical and laboratory parameters was assessed univariately and multivariately. Twenty-nine HSCT recipients had MS instead of the 12.8 expected (P<0.0001), with hypertriglyceridemia being the most common feature. Univariate analysis indicated that high insulin and leptin levels, low-adiponectin levels and hypogonadism were significantly related to a diagnosis of MS; multivariate analysis indicated plasma leptin, insulin resistance, age and hypogonadism. We conclude that HSCT recipients are at increased risk of a form of MS that has particular clinical features. Plasma leptin levels are independently related to MS, thus suggesting that leptin resistance may play a role as a pathogenetic clue, as in other conditions in which MS occurs as a secondary phenomenon. MS deserves consideration as a life-threatening complication in patients who are probably cured of their underlying disease.

Obesity and hepatitis B infection are associated with increased risk of metabolic syndrome in university freshmen

OBJECTIVE

To investigate the prevalence of metabolic syndrome and its associated risk factors in a cohort of university freshmen.

DESIGN

A cross-sectional study in a university health center in North Taiwan.

SUBJECTS

A total of 8226 students (mean age: 19.2+/-2.3 years) receiving pre-entrance health examinations and lifestyle questionnaires during the 2005-2006 academic year were recruited.

MEASUREMENTS

A fasting plasma glucose, lipids, uric acid and hepatitis B serology were measured for each subject. The prevalence of metabolic syndrome and its individual components were examined using the America Heart Association and National Heart Lung Blood Institute criteria. The risk factors for metabolic syndrome were identified using a multivariate logistic regression analysis.

RESULTS

The prevalence of overweight, obesity and metabolic syndrome was 12.7% (17.0% in men and 7.6% in women), 13.0% (18.4% in men and 6.4% in women) and 4.6% (6.4% in men and 2.4% in women). The risk for metabolic syndrome increased with an increase of body mass index and plasma uric acid level, and decreased with the vigorous physical activity and current alcohol drinking. Furthermore, as compared to subjects with seroprotective titers from hepatitis B vaccination (anti-HBs(+) and anti-HBc(-)), those without protective titers of anti-HBs after vaccination or without hepatitis B infection (anti-HBs(-) and anti-HBc(-)) had 34% higher risk for metabolic syndrome, and those with natural infection of hepatitis B (anti-HBc(+)) had 58% higher risk for metabolic syndrome.

CONCLUSIONS

Overweight, obesity and metabolic syndrome were more common among men than women in university freshmen. Hepatitis B vaccination with anti-HBs(+) was associated with a lower risk of metabolic syndrome as compared to anti-HBs(-). However, hepatitis B infection presented with anti-HBc(+) was associated with a higher risk of metabolic syndrome. The interplay between hepatitis B infection, hepatitis B vaccination and metabolic syndrome needs further investigation.

A simple method for quantification of allopurinol and oxipurinol in human serum by high-performance liquid chromatography with UV-detection

OBJECTIVES

Allopurinol is a uric acid lowering drug used in the treatment of gout and the prevention of tumor lysis syndrome. Allopurinol and its active metabolite oxipurinol inhibit xanthine oxidase, which forms uric acid from xanthine and hypoxanthine. Therapeutic drug monitoring is an important option for evaluation and optimization of allopurinol treatment in case of renal impairment, interaction with uricosuric drugs or to verify patient adherence. In this study we developed and validated a simple quantitative assay using reverse phased high-performance liquid chromatography (HPLC) with UV-detection as a method for quantification of allopurinol and oxipurinol in human serum in the presence of different frequently used drugs.

METHODS

The HPLC-UV method uses a mobile phase consisting of sodium acetate (0.02 M; pH 4.5), at a flow rate of 1.0 mL/min. Allopurinol and oxipurinol are detected by UV-absorption at 254 nm with a retention time of 9.9 min for oxipurinol and 12.3 min for allopurinol. Aciclovir is used as internal standard.

RESULTS

Validation showed for allopurinol lower and upper limits of quantification of 0.5 and 10mg/L and for oxipurinol 1 and 40 mg/L, respectively. The assay was linear over the concentration range of 0.5-10mg/L (allopurinol) and 1-40 mg/L (oxipurinol). Intra- and inter-day precision showed coefficients of variation <15% over the complete concentration range; accuracy was within 5% for allopurinol and oxipurinol. Endogenous purine-like compounds were separated from allopurinol, oxipurinol and aciclovir with a resolution factor >1.5. Exogenous purine-like compounds and co-medication frequently used by gout patients did not hinder the analysis due to the dichloromethane washing step or to low UV-absorpion at 253 nm. Serum levels of 66 patients prescribed allopurinol 300 mg/day were determined using this HPLC-UV method. Measured serum allopurinol and oxipurinol concentrations in clinical practice showed large variability with a range of <0.5-4.3 mg/L for allopurinol and <1.0-39.2 mg/L for oxipurinol, respectively.

CONCLUSION

We developed an easy-to-operate and validated HPLC-UV method for the quantification of allopurinol and oxipurinol in human serum. This method was proven to be valid for samples of gout patients frequently using concomitant medications.

Effect of treatment of hyperuricemia with allopurinol on blood pressure, creatinine clearence, and proteinuria in patients with normal renal functions

BACKGROUND

Hyperuricemia has been associated with the development of hypertension, cardiovascular, and renal disease. However, there is no data about the effect of lowering uric acid level on hypertension, renal function, and proteinuria in patients with glomerular filtration rate (GFR) >60 ml/min. We therefore conducted a prospective study to investigate the benefits of allopurinol treatment in hyperuricemic patients with normal renal function.

MATERIALS AND METHODS

Forty-eight hyperuricemic and 21 normouricemic patients were included in the study. Hyperuricemic patients received 300 mg/day allopurinol for three months. All patients' serum creatinine level, 24-h urine protein level, glomerular filtration rate, and blood pressure levels were measured at baseline and after three months of treatment.

RESULTS

A total of 59 patients completed the three-month follow-up period of observation. In the allopurinol group, serum uric acid levels, GFR, systolic and diastolic blood pressure, and C-reactive protein (CRP) levels significantly improved (P < 0.05). However, urine protein excretion remained unchanged (P > 0.05). No correlation was observed between changes in GFR and changes in CRP, or blood pressure in the allopurinol group. No significant changes were observed in the control group (P > 0.05).

CONCLUSION

We bring indirect evidence that hyperuricemia increases blood pressure, and decreases GFR. Hence, management of hyperuricemia may prevent the progression of renal disease, even in patients with normal renal function, suggesting that early treatment with allopurinol should be an important part of the management of chronic kidney disease (CKD) patients. Long-term follow-up studies are warranted to identify the benefits of uric acid management on renal function and hypertension.

Should a statin be prescribed to every patient with heart failure?

Chronic heart failure (HF) represents an emerging epidemic since its prevalence is continuously increasing despite advances in treatment. Many recent clinical studies have clearly demonstrated that statin therapy is associated with improved outcomes in HF irrespective of aetiology (ischaemic or not) or baseline cholesterol levels. Indeed, most of the conducted large statin trials and trials in HF have demonstrated a positive effect of statins in HF patients. Furthermore, the use of statins in HF seems to be safe as none of the recent trials has resulted in worse outcomes for HF patients treated with statins. Potential mechanisms through which statins could benefit the failing myocardium include non-sterol effects of statins, as well as effects on nitric oxide and endothelial function, inflammation and adhesion molecules, apoptosis and myocardial remodelling and neurohormonal activation. This review discusses the pathophysiological basis of statin effects on HF and focuses on clinical data for the benefit from statin use in this setting. Until today there are no official recommendations in both the American and the European guidelines regarding the use of statins in HF patients, as the available data come from small observational or larger but retrospective, non-randomised studies. Therefore, HF patients should be treated according to current lipid guidelines. Large randomised clinical trials are underway and will further delineate the role of statin therapy in HF patients. Until more data are available, we could not recommend statin use to every patient with HF irrespective of HF aetiology and baseline cholesterol levels.

A growing burden: the pathogenesis, investigation and management of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most common hepatic disorder in western countries, and its incidence is increasing. This review outlines the significant health burden posed by NAFLD and discusses what is presently known about its pathogenesis, including the roles of the metabolic syndrome, obesity, insulin resistance, hepatic steatosis, reactive oxygen species, inflammatory cytokines and adipocytokines. The way in which NAFLD is clinically diagnosed is described, and areas of uncertainty surrounding its investigation are identified, before discussing the relative merits of the limited treatment options available and looking ahead to potential therapeutic strategies for the future.

The role of renin–angiotensin system inhibition in the treatment of hypertension in metabolic syndrome: are all the angiotensin receptor blockers equal?

The metabolic syndrome (MetS) is a strong predictor of cardiovascular morbidity and mortality, as well as new Type 2 diabetes. MetS consists of visceral obesity, elevated blood pressure, impaired glucose metabolism, atherogenic dyslipidaemia (elevated triglycerides and low levels of high-density lipoprotein cholesterol), as well as other metabolic abnormalities. The underlying pathophysiology seems to be largely, but not uniquely, attributable to insulin resistance. Existing antihypertensive drugs were designed to lower blood pressure rather than to modify the metabolic abnormalities associated with hypertension. This review considers the role of renin-angiotensin system inhibition and especially the use of angiotensin receptor blockers (ARBs) in the treatment of hypertension in MetS. There are differences among ARBs. Among them is the uricosuric effect of losartan. Furthermore, telmisartan may function as a partial agonist of the peroxisome proliferator-activated receptor-gamma (PPAR-gamma).

Hypouricemic Action of Selected Flavonoids in Mice: Structure-Activity Relationships

Hyperuricemia and gout appear to be rapidly increasing worldwide and frequently cause symptoms of metabolic syndrome. Dietary flavonoids have their potential beneficial effects on human health. In the present study, 15 flavonoids (quercetin, morin, myricetin, kaempferol, icariin, apigenin, luteolin, baicalin, silibinin, naringenin, formonoetin, genistein, puerarin, daidzin and naringin dihydrochalcone) were selected to investigate for their hypouricemic action in mice. Oral administration of quercetin, morin, myricetin, kaempferol, apigenin and puerarin at 50 and 100 mg/kg for 3 d was able to elicit hypouricemic actions in hyperuricemic mice induced by potassium oxonate. Luteolin, formonoetin and naringenin showed the significant effects only at 100 mg/kg. Quercetin, puerarin, myricetin, morin and kaempferol significantly reduced liver uric acid level in hyperuricemic animals. In addition, quercetin, morin, myricetin, kaempferol and puerarin exhibited significant inhibition on the liver xanthine oxidase (XOD) activities. It seems to be likely that these flavonoids reduce serum urate levels by mainly inhibiting XOD activity. However, the hypouricemic effect of apigenin observed seemed not to parallel with the changes in liver uric acid level and liver XOD activity, implying that apigenin might act via other mechanisms apart from inhibiting enzyme activity simply. Analysis of the chemical structure showed that a planar structure with the hydroxyl groups played a crucial role in hypouricemic activity of flavonoids. The exact mechanism of the hypouricemic action of flavonoids in vivo should be investigated in the future.

Serum Uric Acid as an Independent Predictor of Early Death After Acute Stroke

BACKGROUND

The prognostic significance of uric acid (UA) levels in acute stroke is unclear, so the objective of this study was to determine the association between levels of serum UA (SUA) and mortality in acute stroke.

METHODS AND RESULTS

Consecutive patients (n=435) presenting with ischemic stroke and intracerebral hemorrhage were included in the study. The length of stay in hospital and the occurrence of death were recorded. On univariate analysis, the occurrence of death was associated with older age, smoking, presence of congestive heart failure or atrial fibrillation, absence of hyperlipidemia, and intracerebral hemorrhage as the index event. Furthermore, glucose, urea, creatinine and SUA at admission were significantly higher in patients who died, whereas total and high-density-lipoprotein cholesterol were significantly lower. On multiple logistic regression analysis, the independent relationship between higher SUA levels and death was confirmed (odds ratio (OR), 1.37; 95%confidence interval (CI), 1.13-1.67; p=0.001). The only other variables independently associated with the occurrence of death were urea concentration and presence of atrial fibrillation. If urate was >7.8 mg/dl (0.47 mmol/L), then there would be a high probability of early death (87%).

CONCLUSIONS

Elevated levels of SUA are independently associated with an increased risk of early death in acute stroke.

Statin-associated adverse effects beyond muscle and liver toxicity

Randomized controlled trials with 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) have consistently demonstrated significant reductions in cardiovascular morbidity and mortality. Statins are currently the most widely used drugs in many countries. The most important adverse effects are associated with muscle and liver toxicity. However, with increased use and dose of statins and their over-the-counter availability in some countries more cases of other rare side effects may be seen in clinical practice. In the present article we review the literature concerning the statin-related adverse effects other than muscle and liver injury and we provide insight into their clinical relevance and possible underlying mechanisms.