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PubMed1988

[An architectural study of mixed uric acid and calcium oxalate stones by polarized light microscopy of thin section].

The architecture of mixed uric acid and calcium oxalate stones was studied by polarized light microscopy. Some uric acid stones contained calcium oxalate stones (whewellite or weddellite) as a nucleus. Other uric acid stones contained calcium oxalate crystals in the nucleus or inner portion. A uric acid stone covered with layers of calcium oxalate was also found. In the mixed stones, nuclei of randomly mixed fine grained whewellite and uric acid were seen and both crystals appeared in alternating sequence in the outer layers. Weddellite crystals dissolved layers of uric acid and invaded into them in the nuclear or peripheral zones. Whewellite may precipitate in the same or a similar condition as uric acid precipitates, whereas weddellite may precipitate in a different condition. We discussed the pathogenesis of mixed uric acid and calcium oxalate stones, heterogeneous nucleation and epitaxial growth based on a morphologic study of the mixed stones.

Calcium Oxalate↗
PubMed1997

Serum uric acid as an index of impaired oxidative metabolism in chronic heart failure.

BACKGROUND: Elevated serum uric acid concentrations have been observed in clinical conditions associated with hypoxia. Since chronic heart failure is a state of impaired oxidative metabolism, we sought to determine whether serum uric acid concentrations correlate with measures of functional capacity and disease severity. METHODS: Fifty nine patients with a diagnosis of chronic heart failure due to coronary heart disease (n = 34) or idiopathic dilated cardiomyopathy (n = 25) and 20 healthy controls underwent assessment of functional capacity. Maximal oxygen uptake (MVO2) and regression slope relating to minute ventilation to carbon dioxide output (VE-VCO2) were measured during a maximal treadmill exercise test. Metabolic assessment consisted of measuring serum uric acid and fasting lipids, and insulin sensitivity, obtained by minimal modelling analysis of glucose and insulin responses during an intravenous glucose tolerance test. Clustering of indices of functional disease capacity and metabolic factors was explored using factor analysis and multivariate regression analysis. RESULTS: Compared to 20 healthy controls, patients with chronic heart failure had a 52% lower MVO2 (P < 0.001), 56.8% higher serum uric acid concentrations (P < 0.001) as well as a 60.5% lower insulin sensitivity (P < 0.001). Salient univariate correlations in the chronic heart failure group included serum uric acid concentrations with exercise time during the exercise test (r = -0.53), MVO2 (r = -0.50) (both P < 0.001), VE-VCO2 slope (r = 0.45), and NYHA functional class (r = 0.36) (both P < 0.01). In factor analysis of the chronic heart failure group, serum uric acid formed part of a principal cluster of metabolic variables which included MVO2 and VE-VCO2 slope. In multivariate regression analysis, serum uric acid concentrations emerged as a significant predictor of MVO2, exercise time (both P < 0.001,) VE-VCO2 slope and NYHA functional class (both P < 0.02), independent of diuretic dose, age, body mass index, serum creatinine, alcohol intake, plasma insulin levels, and insulin sensitivity index. CONCLUSIONS: There is an inverse relationship between serum uric acid concentrations and measures of functional capacity in patients with cardiac failure. The strong correlation between serum uric acid and MVO2 suggests that in chronic heart failure, serum uric acid concentrations reflect an impairment of oxidative metabolism.

Aged↗
PubMed2004

Correlation studies of plasma paraoxonase activity and uric acid concentration with AAPH-Induced erythrocyte hemolysis in hemodialysis patients.

Uric acid possesses antioxidant properties and is an important determinant of total plasma antioxidant capacity. Uric acid concentrations tend to be elevated in patients with renal failure requiring maintenance hemodialysis but are abruptly reduced by the dialysis procedure itself. Paraoxonase (PON1), an enzyme which circulates in association with high density lipoprotein (HDL), confers protection against free radicals by limiting the oxidation of phospholipids. The relationship between pre- and postdialysis uric acid concentration, PON1 activity, and high density lipoprotein cholesterol (HDL-C) level and the resistance of erythrocytes from hemodialysis patients to hemolysis induced by the free radical generator 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) was studied. Red cells were washed free of plasma prior to the assay, and no plasma was added to the hemolysis assay tubes. Postdialysis erythrocytes were found to be more susceptible to hemolysis compared to blood samples obtained at the initiation of the session (784 +/- 713 vs. 256 +/- 256 micro mol/L hemoglobin released after 60 min incubation and 1530 +/- 696 vs. 1354 +/- 757 micro mol/L at 90 min). Hemolysis correlated negatively with the concentration of uric acid and positively with PON1 arylesterase activity but not with HDL-C level in the corresponding plasma samples. There was a strong negative correlation between uric acid and PON1 in predialysis blood samples (r2 = 0.4, P < 0.001). The conclusion is that the reciprocal relationship between uric acid and PON1 may reflect a mechanism that protects erythrocytes from subsequent oxidative stress.

Adult↗
PubMed1987

Is thiazide-produced uric acid elevation harmful? Analysis of data from the Hypertension Detection and Follow-up Program.

Interaction of thiazide diuretics and the serum uric acid and creatinine levels was studied in 3693 stepped care participants in the Hypertension Detection and Follow-up Program not receiving treatment at baseline. Among men grouped into quartiles by their level of uric acid at baseline, the upper quartile (average uric acid, 7.7 mg/dL [458 mumol/L]) had an average serum creatinine level of 1.2 mg/dL (106 mumol/L) and the lowest quartile (uric acid, 4.9 mg/dL [291 mumol/L]) had an average serum creatinine level of 1.1 mg/dL (97 mumol/L). Similar findings were present in women. Therapy with chlorthalidone or other thiazide-type diuretics tended to increase levels of uric acid and creatinine, but the increase in both was less in the upper quartile than in the lower quartile. Among individuals who were prescribed uric acid-lowering drugs, the level of serum creatinine increased just as much as in those whose uric acid level was not pharmacologically lowered. Baseline uric acid level was a weak predictor of mortality in men; the introduction of an interaction term for creatinine suggested that this effect was primarily restricted to those with elevated levels of both uric acid and creatinine at baseline. Change in uric acid level at one year after therapy was inversely correlated with mortality in men. There were few episodes of gout (only 15 recorded in five years among 3693 participants at risk). These results suggest that neither the baseline uric acid level nor the change in uric acid level produced by therapy injures the kidney. These results suggest no reason to lower uric acid levels pharmacologically in the treated hypertensive patient who is not gouty. They leave unanswered whether there is a predictive value to baseline uric acid level not explainable by other correlated cardiovascular risk factors.

Adult↗
PubMed2006

Uric acid nephrolithiasis: proton titration of an essential molecule?

PURPOSE OF REVIEW: The majority of uric acid nephrolithiasis in humans occurs in the absence of frank hyperuricosuria and is primarily a disease of excessively low urinary pH. Uric acid is substantially less soluble than urate salts so in low urine pH urate is protonated, thus favoring precipitation even under what is considered physiologic concentrations of total urinary uric acid/urate. This commentary examines the rationales behind the existence of uric acid in urine and body fluids in vertebrate evolution. RECENT FINDINGS: The purpose of uric acid in arthropod, avian and reptilian species is to enable nitrogen excretion in solid state without loss of water. The re-emergence of uric acid in higher primates as an end product of metabolism is intriguing since urea functions perfectly well as a nitrogenous waste. Uric acid must purvey important physiologic functions in primate biology. Numerous roles of uric acid as an antioxidant, immune signaling molecule, and a defender of circulatory integrity have recently been proposed. SUMMARY: There is little doubt that uric acid serves multiple important functions in higher primates. It is also conceivable, however, that this important molecule when present in the wrong concentration or context can lead to undesirable phenotypes.

Animals↗
PubMed1996

Uric acid, xanthine oxidase and other risk factors of hypertension in normotensive subjects.

Uric acid produced by xanthine oxidase (also a source of superoxide radicals) has been known to increase in hypertensive patients. In this study we evaluated the possible involvement of uric acid and xanthine oxidase in the pathogenesis of hypertension by examining their association with mean arterial pressure (MAP) and factors related to blood pressure. These factors include age, quetelet index (weight/height2), cholesterol, creatinine, calcium (Ca), magnesium (Mg), sodium (Na), potassium (K) and urea. Fifty Two (male-19, female-33) normal healthy individuals were studied. Correlation studies of demographic variables showed that age was positively correlated with MAP [r = 0.309, p = 0.026] and cholesterol [r = 0.503, p = 0.000] while quetelet index was positively correlated with age [r = 422, p = 0.000] MAP [r = 0.331, p = 0.016] and xanthine oxidase [r = 0.331, p = 0.016]. MAP was positively correlated with uric acid [r = 0.511, p = 0.000], cholesterol [r = 0.492, p = 0.000] and xanthine oxidase enzyme activity [r = 0.388, p = 0.004] and negatively correlated with plasma calcium [r = 0.603, p = 0.000]. Correlation studies of measured parameters with uric acid and xanthine oxidase showed that uric acid was positively correlated with creatinine [r = 0.627, p = 0.000], plasma magnesium [r 0.442, p = 0.001] and negatively correlated with plasma calcium [r = 0.546, p = 0.000] while xanthine oxidase was negatively correlated with plasma calcium [r = -0.404, p = 0.003] and plasma sodium [r = -0.288, p = 0.038]. Stepwise multiple regression with MAP as dependent variable showed that 65% of total variability of blood pressure can be accounted for by plasma calcium, cholesterol, creatinine, plasma K, plasma Na, uric acid and xanthine oxidase in order of increasing R2 [xanthine oxidase: T-value = 3.26, R2 = 0.653]. It can be concluded that in normotensive subjects, uric acid and xanthine oxidase have significant association with blood pressure and thus are one of the many factors which are involved in the cause or effect of hypertension.

Adult↗
PubMed2006

Uric acid in patients with angiographically documented coronary heart disease.

OBJECTIVE: High serum uric acid levels have been associated with coronary heart disease (CHD). Hyperuricaemia is known to be related to several of the established aetiologic risk factors of CHD, such as obesity, insulin resistance, raised serum triglycerides, and hypertension, but it is still uncertain whether this relationship may cause the association between CHD and uric acid. We have investigated whether uric acid was an independent risk factor for CHD. METHODS AND RESULTS: Two-hundred and ninety patients with suspected CHD referred to elective coronary angiography were enrolled. The association between angiographically detected coronary stenosis > 50% in one or more of the 3 major coronary arteries and uric acid levels was examined. A significant association between high uric acid levels and the presence of one or more diseased vessels in women (p = 0.02) was observed, while no association was found in men (p = 0.25). After adjustment for several possible confounders such as smoking, triglycerides, HDL cholesterol, and a diagnosis of diabetes mellitus the association among women disappeared. CONCLUSION: The results indicate that uric acid should not be viewed as an independent risk factor for CHD, but more likely as a biological marker reflecting other causative parameters.

Age Factors↗
PubMed1987

The placental transfer and concentration difference in maternal and neonatal serum uric acid at parturition: comparison of normal pregnancies and gestosis.

The maternal uric acid (MUA) and neonatal uric acid (NUA) levels were measured simultaneously at parturition in three groups of pregnancies: group I - 83 cases of normal pregnancies, group II - 7 cases of mild gestosis and group III - 12 cases of severe gestosis, totaling 102 cases. Umbilical venous blood samples were taken in all of the cases. Maternal venous blood samples were obtained from 69 patients in group I, 6 cases in group II, and 12 cases in group III. The correlation coefficients of MUA and NUA values were 0.90, 0.91, and 0.95 (all p less than 0.01) in the three groups, respectively, and 0.93 in total series (p less than 0.0001). The high correlation and minimal concentration difference between MUA and NUA in either normal or gestosis suggested free transfer of uric acid via placenta in both directions. Moreover, not only MUA but also NUA levels were significantly different among normal and gestosis groups, and both MUA and NUA showed higher levels in accordance with the severity of gestosis. Both MUA and NUA had negative correlation with birth weight (BW), one-minute apgar score (AS-1) and five-minute apgar score (AS-5). It implied that the uric acid levels at parturition might provide as a reference index for fetal outcome in pregnancy with gestosis.

Female↗
PubMed2004

Effects of statin treatment on uric acid homeostasis in patients with primary hyperlipidemia.

BACKGROUND: Epidemiologic studies have shown that serum uric acid is a risk factor of coronary artery disease. In addition to fenofibrate, there is some evidence that atorvastatin may have a hypouricemic action, but the underlying mechanisms remain speculative. METHODS: This randomized trial was conducted to investigate the effects of atorvastatin and simvastatin on uric acid homeostasis in patients treated for primary hyperlipidemia. A total of 180 patients were enrolled; patients were randomly assigned to 40 mg/d of either atorvastatin or simvastatin. Serum lipid and metabolic parameters were measured at baseline and at 6 and 12 weeks of treatment; random urine samples were simultaneously obtained for creatinine, sodium, and uric acid determinations. RESULTS: Baseline serum uric acid levels correlated positively with the body mass index, serum insulin, creatinine, and triglyceride levels and inversely with serum HDL cholesterol levels. Both statins caused a favorable effect on lipids and a significant decrease in fibrinogen and high-sensitivity CRP levels. However, only atorvastatin reduced serum uric acid levels (from 5.6 +/- 1.7 to 4.9 +/- 1.5 mg/dL, P <.0001) by augmenting its urinary fractional excretion (from 10.4% +/- 7.9% to 12.0% +/- 7.4%, P <.01). In a multivariate logistic regression analysis, the reduction of uric acid levels was independently associated with baseline serum uric acid concentration but not to other variables, including lipid parameters (OR, 1.65; 95% CI, 1.14 to 2.40; P =.008). CONCLUSIONS: Atorvastatin (but not simvastatin) significantly lowered serum uric acid levels. This result may be in favor of a preferable choice of atorvastatin for the treatment of hyperlipidemic patients presenting with hyperuricemia.

Atorvastatin↗
PubMed1986

Warfarin administration increases uric acid concentrations in plasma.

The effect of warfarin administration on plasma uric acid was investigated. A representative sample of patients on long-term warfarin treatment had a significantly higher concentration of uric acid in plasma than did age-matched patients with comparable plasma urea concentrations who were not taking warfarin. In women, this association was observed only in patients with normal values for plasma urea, not in those with high values. In contrast, in men this association was present in both groups (normal and high plasma urea). In a longitudinal study involving patients, their plasma uric acid significantly increased after warfarin administration. There was no significant change in the renal clearance of uric acid after a single dose of warfarin in normal, healthy volunteers; this contrasts with the increase observed with other coumarin anticoagulants. Our findings suggest that the increase in plasma uric acid noted with warfarin administration is probably due to an increase in uric acid production and may predispose to gout those patients who are on long-term therapy with warfarin.

Adult↗
PubMed1988

Renal handling of uric acid under cyclosporin A treatment.

The renal handling of uric acid during cyclosporin A (CyA) treatment was investigated by clearance studies using 24-h urine collections in 28 paediatric renal transplant recipients (CyA group), and the results were compared with those of 19 renal transplanted children treated with azathioprine and prednisolone (AZA group), 35 children with chronic renal failure (CRF) and 10 children with normal renal function (N group). Serum uric acid levels were significantly higher in the CyA group (567 +/- 156 mumol/l) compared with the AZA group (378 +/- 98), the CRF group (415 +/- 119) and the N group (290 +/- 68). Mean uric acid clearances in each group measured 3.9 +/- 2.8 ml/min per 1.73 m2 (CyA), 5.6 +/- 3.4 (AZA), 4.0 +/- 2.2 (CRF) and 8.4 +/- 3.7 (N). Calculation of the net tubular uric acid reabsorption per millilitre glomerular filtration rate revealed a significantly increased value of 0.53 +/- 0.15 mumol/ml in the CyA group (P less than 0.01) compared with 0.34 +/- 0.08, 0.29 +/- 0.15 and 0.27 +/- 0.07 mumol/l for the AZA, CRF and N groups respectively. We therefore conclude that CyA treatment is associated with an increased net tubular reabsorption of uric acid, which may lead to hyperuricaemia.

Azathioprine↗
PubMed1980

Family resemblances in serum uric acid level.

There is substantial relation between individuals serum uric acid level and their heights and weights. Even when the association of uric acid level with height/weight is partialed out, significant resemblances in uric acid level are found between biologically related persons (parents and offspring; siblings) but not between spouses. When the association of height/weight is partialed out, uric acid level does not have a significant association with measures of cognitive ability or with educational or occupational attainment.

Body Height↗
PubMed2006

Therapeutic value of serum uric acid levels increasing in the treatment of multiple sclerosis.

BACKGROUND/AIM: Uric acid was successfully used in both, prevention and treatment of the animal model of multiple sclerosis (MS). Recently it has been shown that inosine, a ribosylated precursor of uric acid, might be used to elevate serum uric acid levels in MS patients. The aim of this study was to evaluate the safety and efficacy of oral inosine as a single drug treatment in patients with MS. METHOD: We administered inosine orally to 32 MS patients from 2001-2004 year at doses from 1-2 g daily (given twice) depending on the pretreatment serum uric acid levels. The mean follow-up interval was 37.69+/-6.55 months. The other 32 MS patients, without any treatment except for a relapse period (matched by age, sex, duration of disease and functional disability), were used as controls. The follow-up interval of these patients was 36.39 +/- 2.68 months. The neurological disability was evaluated by the Expanded Disability Status Scale score (EDSS). RESULTS: During the observed period the treated MS patients were found to have the lower relapses rate than the non-treated MS patients (Chi-square test, p = 0.001). None of the patients have showed any adverse effect of inosine treatment. The non-treated MS patients were found to have a higher increasing in the mean EDSS score than the treated ones (two-way ANOVA-repeated measures/factor times, p = 0.025). CONCLUSION: Our results suggested that the treatment approaches based on the elevation of serum uric acid levels might prove beneficial for some MS patients.

Administration, Oral↗
PubMed2004

Serum uric acid in traditional Pacific Islanders and in Swedes.

BACKGROUND: In some western populations, increased serum uric acid has been positively associated with cardiovascular disease, possibly because hyperuricaemia could be an untoward part of the insulin-resistant metabolic syndrome. However, there is evidence that uric acid is a free radical scavenger capable of inhibiting LDL oxidation. Amongst the traditional horticulturalists of Kitava, Trobriand Islands, Papua New Guinea, cardiovascular disease, hypertension, hyperinsulinaemia and abdominal obesity are absent or rare. In contrast, serum triglycerides are similar to Swedish levels. OBJECTIVE: To compare serum uric acid between nonwesternized and westernized populations. METHODS: Fasting levels of serum uric acid were measured cross-sectionally in 171 Kitavans aged 20-86 years and in 244 randomly selected Swedish subjects aged 20-80 years. RESULTS: There were small differences in serum uric acid between the two populations, although a slight increase with age was found only in Swedish males (r = 0.20; P = 0.03) and females (r = 0.36; P < 0.0001). Above 40 years of age, uric acid was approximately 10% lower in Kitavans, a difference which was statistically significant only in males, possibly because of the limited number of females. Regarding hyperuricaemia, two Kitavan males had uric acid above 450 micromol L-1 whilst none of the females was above 340 micromol L-1. Amongst the Swedish subjects, five of 117 males and 19 of 127 females had hyperuricaemia according to these definitions. CONCLUSION: The rather similar uric acid levels between Kitava and Sweden imply that uric acid is of minor importance to explain the apparent absence of cardiovascular disease in Kitava.

Adult↗
PubMed2001

Uric acid and cardiovascular disease: a renal-cardiac relationship?

Elevated serum uric acid is a frequent finding in patients with kidney disease and cardiovascular disease. Intrarenal ischaemia, induced by hypertension, increased sympathetic nervous system activity, and hyperinsulinaemia have all been implicated in reduced renal clearance of urate. This frequently results in elevated serum uric acid levels. The association of hyperuricaemia with cardiovascular disease remains controversial. Current evidence suggests that serum uric acid may provide additional prognostic information in patients with essential hypertension. However, there has been no test of the hypothesis that a reduction in serum uric acid would prevent cardiovascular disease. Furthermore, a critical review of the current literature does not support a causal role of serum uric acid in the development of cardiovascular disease. Serum uric acid probably reflects and integrates different risk factors and their possible interactions.

Cardiovascular Diseases↗
PubMed1990

On-line mass spectrometric investigation of the peroxidase-catalysed oxidation of uric acid.

The enzymatic and electrochemical oxidation pathways of uric acid were determined on-line with thermospray-tandem mass spectrometry. Products and intermediates formed as a result of electrooxidation were monitored as the electrode potential was varied. Electrochemical results served as a model for the enzymatic studies. In fact, electrochemical studies were essential for elucidating the structures of intermediates because of the high conversion efficiencies in electrooxidation. Products and intermediates formed as a result of enzymatic oxidation of uric acid were monitored as the reaction time was varied. When the enzymatic oxidation of uric acid with peroxidase and H2O2 was studied, the same intermediates and products were observed as in the electrochemical oxidation. The tandem mass spectrometric results provide convincing evidence that the primary intermediate produced during both the enzymatic and electrochemical oxidation of uric acid has a quinonoid diimine structure. The primary intermediate can follow three distinct reaction pathways to produce the identified final products. The final enzymatic and electrochemical oxidation products observed in these studies were urea, CO2, alloxan, alloxan monohydrate, allantoin, 5-hydroxyhydantoin-5-carboxamide and parabanic acid.

Chromatography, High Pressure Liquid↗
PubMed1977

Serum uric acid levels in England and Scotland.

A survey of serum uric acid levels in 766 subjects in England and 337 in Glasgow was carried out. There was no difference in the frequency distribution of uric acid or the mean levels in the two countries. A serum uric acid of 7 mg/100 ml or over was found in 7.2% of the men and 0.4% of the women. The previously described sex difference and association of serum uric acid with weight were confirmed. No association was found with social class. The suggestion of an increase in uric acid levels in the United Kingdom over the past 14 years is discussed.

Adult↗