Effects of benzbromarone and allopurinol on adiponectin in vivo and in vitro

When treating gout patients, we have incidentally found elevated serum levels of adiponectin in some after administration of benzbromarone. In the present study, we determined whether benzbromarone increases the serum level of adiponectin in gout patients and investigated the mechanism involved. Sixty-nine patients with gout were separated into two groups, and then treated for 1 year with uric acid-lowering therapy using benzbromarone or allopurinol. After overnight fasting, blood samples were drawn before and at 1 year after beginning of treatment. In an in vitro study, 3T3L1 cells were incubated in medium containing benzbromarone, allopurinol, pioglitazone, or uric acid, after which real time PCR assays were performed for messenger RNA of adiponectin, aP2, and CD36. Furthermore, 3T3L1 cells were incubated in medium containing GW9662 (PPARgamma antagonist) together with benzbromarone or pioglitazone, after which real-time PCR assays were performed for messenger RNA of adiponectin. In the in vivo study, benzbromarone increased the serum concentration of adiponectin in the subjects, whereas allopurinol did not. In vitro, benzbromarone and pioglitazone each increased the levels of messenger RNA of adiponectin, aP2, and CD36 in 3T3 cells, whereas allopurinol and uric acid did not. Also, GW9662 suppressed the increase in adiponectin mRNA induced by benzbromarone as well as that by pioglitazone. Together, our results suggest that benzbromarone enhances the production of adiponectin via activation of PPARgamma, which is a weak agonist for PPARgamma.

Effect of acarbose on the increased plasma concentration of uric acid induced by sucrose ingestion

Sucrose is converted fructose and glucose, which may increase plasma uric acid concentration (pUA) through increased purine degradation and/or decreased uric acid (UA) excretion. To investigate effects of acarbose, an inhibitor of alpha-glucosidase, on the increased pUA from sucrose administration, we measured pUA and urinary UA excretion in 6 healthy subjects before and after administering sucrose, with and without co-administration of acarbose. Sucrose raised pUA by 10% (p < 0.01). However, excretion and fractional clearance of UA were unchanged. Sucrose and acarbose coadministration also increased pUA, but less than did sucrose alone (sucrose: 4.9 to 5.4 mg/dl; sucrose + acarbose, 4.7 to 4.9 mg/dl, p < 0.05) without changes in urinary excretion and fractional clearance of UA. Acarbose appears to attenuate the rise in pUA by sucrose ingestion by inhibiting sucrose absorption.

Relationship between insulin resistance and low urinary pH in patients with gout, and effects of PPARalpha agonists on urine pH

Patients with gout frequently have low urinary pH, though the underlying mechanism has not been identified. Recently, nephrolithiasis has been reported to be involved with renal manifestation of metabolic syndrome. The present study was conducted to clarify the mechanism of low urinary pH in gout patients. The relationships between urine pH and factors contributing to metabolic syndrome were investigated. In addition, the effects of PPAR alpha agonists on urine pH were examined. Patients with 24-hour urine samples below a level of pH 5.5 showed higher values for factors constituting metabolic syndrome, compared with those with 24-hour urine pH equal to or greater than 5.5. Multiple regression analysis demonstrated that HOMA index was the only contributing factor to low urinary pH in gout patients, except for serum uric acid. Administrations of PPAR alpha agonists significantly raised 24-hour urine pH levels in gout patients in accordance with a reduction in serum triglyceride concentration, probably through their activities to improve insulin resistance. Our results suggest that insulin resistance plays an important role in the development of low urinary pH in patients with gout and that PPAR alpha agonist is preferable for raising urinary pH of the gout patients with hypertriglyceridemia.

Effect of beer ingestion on the plasma concentrations and urinary excretion of purine bases: one-month study

To investigate the effect of long-term beer ingestion on the plasma concentrations and urinary excretion of purine bases, 5 healthy males participated in the present study, during which they ingested beer every evening for 30 days. Blood and 24-hour urine samples were collected in the morning one day before and 14 and 30 days after the initiation of the beer ingestion. During the beer ingestion period, the plasma concentration and the urinary excretion of uric acid were increased significantly, while uric acid clearance was not decreased. Further, purine ingestion was not significantly different throughout the study. These results suggest that production of uric acid by ethanol ingestion was the main contributor to the increased plasma uric acid. Therefore, patients with gout should be encouraged to avoid drinking large amounts of beer on a daily basis.

Effects of a fenofibrate/losartan combination on the plasma concentration and urinary excretion of purine bases

OBJECTIVE

To assess the effects of a combination of fenofibrate and losartan on the plasma concentrations and urinary excretion of purine bases in healthy male subjects.

METHODS

5 healthy males participated in a fenofibrate plus losartan combination study. The plasma concentrations and urinary excretion of purine bases (hypoxanthine, xanthine, uric acid) were measured before and after administrations of losartan (100 mg o.d.) alone for 2 weeks, losartan and fenofibrate together for 2 weeks and fenofibrate (300 mg o.d.) alone for 2 weeks, which were given consecutively over a 6-week period.

RESULTS

Losartan alone significantly reduced the serum uric acid concentration and increased uric acid excretion, whereas the combination of losartan and fenofibrate reduced serum uric acid concentrations further with a concomitant increased uric acid excretion. Fenofibrate alone also reduced plasma uric acid concentration with an increase in urinary excretion, although the effect was weak when compared with the combination treatment. The plasma concentrations and urinary excretion of oxypurines remained unchanged throughout the entire study.

CONCLUSION

A combination of fenofibrate and losartan demonstrated an additive urate-lowering effect which may be beneficial in the treatment of patients with gout and hypertriglyceridemia.

Effects of allopurinol on beer-induced increases in plasma concentrations and urinary excretion of purine bases (uric acid, hypoxanthine, and xanthine)

To determine the effects of allopurinol on beer-induced increases in plasma and urinary excretion of purine bases (hypoxanthine, xanthine, and uric acid), we performed three experiments on five healthy study participants. In the first experiment (combination study), the participants ingested beer (10 ml/kg body weight) eleven hours after taking allopurinol (300 mg). In the second experiment (beer-only study), the same participants ingested beer (10 ml/kg body weight) alone, while in the third experiment (allopurinol-only study), they took allopurinol (300 mg) alone. There was a two-week interval between each of the studies. Beer-induced increases in plasma concentration and urinary excretion of hypoxanthine in the combination study were markedly higher than those in the beer-only study. On the other hand, the sum of increases in plasma concentrations of purine bases in the beer-only study was greater than in the combination study, whereas the increase in plasma uridine concentration in the combination study did not differ from the beer-only study. In addition, allopurinol administration inhibited the beer-induced increase in plasma concentration of uric acid. These results suggest that abrupt adenine nucleotide degradation may increase plasma concentration and urinary excretion of hypoxanthine under conditions of low xanthine dehydrogenase activity, which is mostly ascribable to allopurinol. Further, the difference in the sum of increases in plasma concentrations of purine bases between the combination study and beer-only study was largely ascribable to a greater increase in urinary excretion of hypoxanthine in the combination study. In addition, allopurinol intake seems to be effective in controlling the rapid increase in plasma uric acid caused by ingestion of alcoholic beverages.

Effects of long-term beer ingestion on plasma concentrations and urinary excretion of purine bases

To investigate the long-term effects of beer ingestion on plasma concentrations of purine bases (hypoxanthine, xanthine, and uric acid), ten healthy males ingested beer (15 ml/kg body weight) every evening for three months. Blood and 24-hour urine samples were collected in the morning on one day before and one, two, and three months after starting the experiment to determine the plasma concentrations and urinary excretion of uric acid, hypoxanthine, and xanthine. Plasma concentrations and urinary excretion of uric acid, hypoxanthine, and xanthine in five of the participants that did not regularly ingest beer at a quantity of more than 15 ml/kg body weight in a single day prior to the experiment were not increased during the experimental period. In contrast, plasma concentrations and urinary excretion of uric acid were increased in five participants who regularly ingested more than 15 ml/kg body weight of beer in a single day prior to the experiment, although hypoxanthine and xanthine levels were not significantly increased during the experimental period. In both groups, uric acid clearance and purine ingestion were not significantly different throughout the study. Our results suggest that the production of uric acid caused by ethanol ingestion from beer is a significant contributor to the increase in plasma uric acid concentration in patients that regularly consume more than 15 ml/kg body weight of beer each day. Therefore, patients with gout should be encouraged to refrain from drinking large amounts of beer on a daily basis.

Effect of purine-free low-malt liquor (happo-shu) on the plasma concentrations and urinary excretion of purine bases and uridine--comparison between purine-free and regular happo-shu

To determine whether purine-free and regular low-malt liquor beverages (happo-shu) increase the plasma concentration and urinary excretion of purine bases (hypoxanthine, xanthine, uric acid) and uridine, 6 healthy males were given regular (10 ml/kg of body weight) and purine-free happo-shu (10 ml/kg of body weight). Plasma concentration-time curves were plotted, and the areas under the curves for uric acid and total purine bases (the sum of hypoxanthine, xanthine, and uric acid) were greater in the regular than in the purine-free happo-shu ingestion experiment (both p < 0.05). In addition, the total urinary excretion of xanthine, total purine bases, and uridine was greater in the regular than in the purine-free happo-shu ingestion experiment (p < 0.05 in all cases), although the total urinary excretion of hypoxanthine and uric acid was no different between the regular and the purine-free happo-shu ingestion experiments. These results suggest that uridine contained in regular happo-shu might contribute to an increase in the urinary excretion of uridine along with ethanol, and that the purines contained in regular happo-shu may contribute to the increase in plasma concentration of uric acid due to purine degradation.

Hyperosmolar non-ketotic diabetic syndrome associated with rhabdomyolysis and acute renal failure: a case report and review of literature

A 64-year-old man was admitted to our hospital because of general fatigue and drowsiness. On admission, a physical examination disclosed dehydration and a laboratory investigation revealed the following values: plasma glucose, 1309 mg/dl; serum sodium, 160 mmol/l; potassium, 3.0 mmol/l; urea nitrogen, 65 mg/dl; creatinine, 2.73 mg/dl; and plasma osmolarity, 403 mOsm/kg. Urine ketone bodies were negative. A diagnosis of hyperosmolar non-ketotic diabetic syndrome was made, and hydration with an infusion of hypotonic saline (0.45%) and insulin therapy were immediately started. However, despite adequate rehydration and correction of blood glucose, his serum creatinine level increased to 3.1 mg/dl, while oliguria and myoglobinuria developed on the 4th hospital day, with serum creatine kinase increasing up to a maximum level of 16,749 IU/l, suggesting rhabdomyolysis. A final diagnosis of hyperosmolar non-ketotic diabetic syndrome associated with rhabdomyolysis and acute renal failure was made. His renal function gradually improved without hemodialysis, though acute renal failure due to rhabdomyolysis with hyperosmolar non-ketotic diabetic syndrome can sometimes be fatal. This rare case is presented along with a review of literature.

Effects of combination treatment using anti-hyperuricaemic agents with fenofibrate and/or losartan on uric acid metabolism

OBJECTIVE

To assess the effect of a combination treatment using anti-hyperuricaemic agents with fenofibrate and/or losartan on uric acid metabolism in hypertriglyceridaemic and/or hypertensive patients with gout.

METHODS

Twenty seven patients with gout were included in a fenofibrate plus anti-hyperuricaemic agents combination study, and 25 in a losartan plus anti-hyperuricaemic agents combination study. Serum uric acid concentration, uric acid clearance, and 24 hour urinary uric acid excretion were measured before and two months after the addition of fenofibrate (300 mg once daily) or losartan (50 mg once daily) to anti-hyperuricaemic agents.

RESULTS

Combination therapy of fenofibrate or losartan with anti-hyperuricaemic agents, which included benzbromarone (50 mg once daily) or allopurinol (200 mg twice a day), significantly reduced serum uric acid concentrations in accordance with increased uric acid excretion.

CONCLUSION

A combination of fenofibrate or losartan with anti-hyperuricaemic agents is a good option for the treatment of gout patients with hypertriglyceridaemia and/or hypertension, though the additional hypouricaemic effect may be modest.

An atypical case of primary renal tubular hypokalaemic metabolic alkalosis with chronic tophaceous gout

A 55-year-old woman was referred to our ward for further evaluation of marked hyperuricaemia and suspected tophi. On physical examination, huge subcutaneous nodules were observed on the knee joints as well as a small nodule on the lateral side of the left sole. Blood chemistry showed marked hyperuricaemia (0.85 mmol/l), hypokalaemia (2.7 mmol/l) and a mild degree of renal insufficiency. Arterial blood gas analysis showed signs of metabolic alkalosis. Daily urinary uric acid excretion on a purine non-restricted diet was 8.9 mmol/day. Uric acid clearance and fractional uric acid clearance were 0.8 ml/min and 2.6%, respectively. Plasma renin activity was 21.8 ng/ml/h, and plasma angiotensin II and aldosterone concentrations were 61 and 121 pg/ml, respectively. However, pressor response to an intravenous administration of angiotensin II was normal. The urinary calcium to creatinine molar ratio was 0.069, and serum magnesium concentration was normal to supranormal. A biopsy of the subcutaneous nodule showed a typical appearance of tophus. Based on these findings, the patient was diagnosed with an atypical case of renal tubular hypokalaemic metabolic alkalosis, with marked hyperuricaemia and tophi as the initial manifestations. So far, only four cases of Bartter's syndrome with gout and/or hyperuricaemia have been described in Japan. This rare case is presented and its mechanism of hyperuricaemia discussed.

Functioning adrenal black adenoma with pulmonary and cutaneous cryptococcosis: a case report and review of English literature

A 53-year-old woman experienced progressive general weakness and lumbago in the 2 years prior to a physical examination which disclosed cushingoid manifestations and a skin ulcer on the back of her right knee joint. Her plasma cortisol concentration ranged from 24.7 to 31.1 microg/dl, with an ACTH level <5 pg/ml. Urinary excretions of 17-hydroxycorticosteroid (17-OHCS) and 17-ketosteroid (17-KS) were 20.5 mg/day and 5.1 mg/day, respectively, and urinary cortisol was also increased (421 microg/day). Cortisol was not suppressed after the administration of 8 mg dexamethasone. Abdominal ultrasound sonography, computed tomography (CT) scan, and magnetic resonance imaging (MRI) studies demonstrated a left adrenal tumor and further, a chest X-ray examination showed a cavitary lesion containing a fungus ball-like mass in the left lower lung field. The serum cryptococcal antigen titer was positive at 1:128 and a bronchoalveolar lavage fluid culture yielded a growth of Cryptococcus neoformans. A biopsy specimen of the skin ulcer also suggested cryptococcosis. As a result, a left adrenectomy was performed, and the excised specimen was shown to be an adenoma consisting of compact cells with abundant pigmentation (black adenoma). A diagnosis of functioning black adenoma of the adrenal gland, complicated with pulmonary and cutaneous cryptococcosis was made.

Effect of norepinephrine on the urinary excretion of purine bases and oxypurinol

To examine whether norepinephrine affects the plasma concentrations and urinary excretion of purine bases and oxypurinol, we orally administered allopurinol (300 mg) to 5 healthy subjects and 9 hours later intravenously administered norepinephrine (12 to 20 microg/kg body weight), which causes a more than 10 mm Hg increase in diastolic pressure for 2 hours. Norepinephrine decreased the urinary excretion of uric acid by 33% (P <.01), oxypurinol by 32% (P <.01), and xanthine by 51% (P <.01), as well as the fractional clearance of uric acid by 32% (P <.01), oxypurinol by 24% (P <.05), and xanthine by 21% (P <.05) when measured 1 to 2 hours after administration. These results indicate that norepinephrine decreases the urinary excretion of uric acid, oxypurinol, and xanthine, probably via hemodynamic change. It is also suggested that the hypouricemic effect of allopurinol may be more potent than that expected in gout patients with enhanced sympathetic tone, such as in salt-sensitive hypertension.

Effect of fenofibrate on plasma concentration and urinary excretion of purine bases and oxypurinol

OBJECTIVE

To investigate whether fenofibrate increases the clearance of purine bases (hypoxanthine, xanthine, uric acid) and oxypurinol.

METHODS

We administered fenofibrate (150 mg) 3 times a day for 3 days, and then allopurinol (300 mg) 4 h after the last administration of fenofibrate, to 5 healthy subjects. Ten hours later, a clearance study was done.

RESULTS

Following 3 day administration of fenofibrate, fractional clearance of xanthine, uric acid, and oxypurinol increased by 41% (p < 0.05), 101% (p < 0.01), and 51% (p < 0.01), respectively, compared to baseline values, while the respective plasma concentrations decreased by 46% (p < 0.05), 46% (p < 0.05), and 19% (p < 0.05).

CONCLUSION

Our results suggest that fenofibrate, fenofibric acid, or fenofibrate derivatives can increase fractional clearance of xanthine, uric acid, and oxypurinol by acting on their common renal pathways. It is suggested that the hypouricemic effect of combination therapy using allopurinol and fenofibrate may be less than additive.

Decreased activities of lipoprotein lipase and hepatic triglyceride lipase in patients with gout

Postheparin plasma lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL) activities were measured in 30 male primary gout patients as well as in control subjects. The activities of these lipolytic enzymes were significantly decreased in the patients as compared with the controls (gout v control; LPL, 5.4 +/- 0.4 v 7.9 +/- 0.9 U; HTGL, 14.6 +/- 2.0 v 17.9 +/- 3.4 U) when matched with serum triglyceride concentration. Further, LPL activity was negatively correlated with serum- and very-low-density lipoprotein (VLDL)-triglyceride in gout patients, while that of HTGL was negatively correlated with low-density lipoprotein (LDL)-triglyceride in both gout patients and control subjects. These results suggest that decreased activities of LPL and HTGL may contribute, in part, to the increased concentrations of serum-, VLDL-, and LDL-triglyceride seen in gout patients, leading to a higher risk for coronary atherosclerotic diseases in gout.

Widespread cellular distribution of aldehyde oxidase in human tissues found by immunohistochemistry staining

Aldehyde oxidase (EC 1.2.3.1) is a xenobiotic metabolizing enzyme that catalyzes a variety of organic aldehydes and N-heterocyclic compounds. However, its precise pathophysiological function in humans, other than its xenobiotic metabolism, remains unknown. In order to gain a better understanding of the role of this enzyme, it is important to know its exact localization in human tissues. In this study, we investigated the distribution of aldehyde oxidase at the cellular level in a variety of human tissues by immunohistochemistry. The enzyme was found to be widespread in respiratory, digestive, urogenital, and endocrine tissues, though we also observed a cell-specific localization in the various tissues studied. In the respiratory system, it was particularly abundant in epithelial cells from the trachea and bronchium, as well as alveolar cells. In the digestive system, aldehyde oxidase was observed in surface epithelia of the small and large intestines, in addition to hepatic cells. Furthermore, the proximal, distal, and collecting tubules of the kidney were immunostained with various intensities, while glomerulus tissues were not. In epididymus and prostate tissues, staining was observed in the ductuli epididymidis and glandular epithelia. Moreover, the adrenal gland, cortex, and notably the zona reticularis, showed strong immunostaining. This prevalent tissue distribution of aldehyde oxidase in humans suggests some additional pathophysiological functions besides xenobiotic metabolism. Accordingly, some possible roles are discussed.

Spot urine uric acid to creatinine ratio used in the estimation of uric acid excretion in primary gout

OBJECTIVE

Uric acid overexcretion in patients with gout is frequently assessed by the measurement of 24 hour urinary uric acid excretion, which is cumbersome with ambulatory patients, and requires accurate timing and complete collection of the specimen. We assessed whether uric acid to creatinine ratio (Uua/Ucr) in spot urine is useful for the estimation of uric acid overexcretion in patients with gout.

METHODS

One hundred thirty male patients with gout and 33 non-gout male control subjects were studied. Early morning urine and/or a portion of 24 h collected urine (24 h urine) were used as spot urine samples. Uric acid overexcreters were defined as those with a 24 h urinary uric acid excretion > or = 1000 mg/day, while uric acid underexcreters were defined as those with uric acid clearance < 6 ml/min.

RESULTS

There was a significant relationship between 24 h urinary uric acid excretion and early morning urine Uua/Ucr in patients with gout, while no such relationship was observed in controls. No significant difference in Uua/Ucr was observed between patients with gout and controls, or in Uua/Ucr between gout uric acid overexcreters and underexcreters in early morning urine. A significant difference in this value was observed between the 2 groups in the 24 h urine specimens. Although the diagnostic accuracy of gout uric acid overexcretion was 87.2% using early morning urine and 89.6% using 24 h urine, the sensitivity of gout uric acid overexcretion was only 25.0% when using early morning urine and 25.0% when using 24 h urine, when the cutoff value of Uua/Ucr was 0.63 and 0.64, respectively.

CONCLUSION

Uua/Ucr using spot urine, especially early morning urine, is not an accurate indicator of uric acid overexcretion in patients with gout.

Increased visceral fat accumulation further aggravates the risks of insulin resistance in gout

We performed the present study to determine the degree of visceral fat accumulation and incidence of visceral fat obesity in 138 gout patients who were classified as overexcretion type (n = 53) and underexcretion type (n = 85) by their levels of uric acid clearance and urinary uric acid excretion. We also investigated the relationship between visceral fat accumulation and insulin resistance expressed by the homeostasis model assessment (HOMA) index. Visceral fat area (VFA)/surface body area (SBA) was significantly increased in patients with gout as compared with control subjects (79.7 +/- 30.8 cm(2)/m(2) v 65.1 +/- 24.1 cm(2)/m(2), P <.001). It was also shown that VFA/SBA in the gout overexcretion group was significantly increased as compared with the gout underexcretion group (88.3 +/- 32.8 cm(2)/m(2) v 74.3 +/- 28.3 cm(2)/m(2), P <.01). Although the incidence of visceral fat obesity (VFO) was not different between gout patients and control subjects, the incidence of VFO was significantly higher in the gout overexcretion type than the gout underexcretion type (19 of 53 v 11 of 85, P <.01). Further, there was a significant relationship between visceral fat area and HOMA index. Gout patients possess some factors that are included in the insulin resistance syndrome, irrespective of the presence of VFO, and the insulin resistance risk factors observed in gout become more prominent when it is complicated with VFO. Our results suggest that gout patients, especially the overexcretion type who have greater levels of visceral fat accumulation, may be more vulnerable to atherosclerotic diseases.

Human xanthine dehydrogenase cDNA sequence and protein in an atypical case of type I xanthinuria in comparison with normal subjects

To investigate the properties of xanthine dehydrogenase/xanthine oxidase (XDH/XO) deficiency in a patient with atypical type I xanthinuria, as indicated by oxypurine data, a cDNA sequence encoding XDH, XDH/XO immunoblot analysis and a competitive PCR assay were performed, and the results were compared with those of normal subjects. The xanthine dehydrogenase cDNA sequence of the patient was consistent with the controls, while immunologically reactive 150 kD XDH/XO protein was not present in the xanthinuric duodenal mucosa, unlike the control duodenal mucosa. In addition, a decrease in XDH/XO messenger RNA was found by competitive PCR. These results suggest that atypical type I xanthinuria is due to a decrease in messenger RNA of XDH/XO. Furthermore, it was considered that this decrease could explain the normal plasma level and near normal urinary excretion of hypoxanthine seen in this case of xanthinuria, though XDH/XO activity and protein were not detected spectrophotometrically and immunologically, respectively.

Effect of furosemide on renal excretion of oxypurinol and purine bases

To examine whether furosemide affects the plasma concentration and urinary excretion of purine bases and oxypurinol, we administered allopurinol (300 mg) orally to 6 healthy subjects and then administered furosemide (20 mg) intravenously 10 hours later. Furosemide (20 mg) decreased the urinary excretion of uric acid by 40% (P < .01), oxypurinol by 39% (P < .05), and xanthine by 43% (P < .05) and the fractional clearance of uric acid by 45% (P < .01) and oxypurinol by 34% (P < .05) when measured 1 to 2 hours after administration. Moreover, furosemide increased the plasma concentration of uric acid by 6% at 1.5 hours after administration. These results indicate that furosemide may decrease the urinary excretion of uric acid and oxypurinol by acting on their common renal transport pathway(s). In addition, it is suggested that the effect of furosemide on oxypurinol is clinically important, since the hypouricemic effect of allopurinol may become more potent as a result.

Effect of losartan potassium, an angiotensin II receptor antagonist, on renal excretion of oxypurinol and purine bases

OBJECTIVE

To examine whether losartan affects the plasma concentrations and urinary excretion of purine bases and oxypurinol.

METHODS

We administered allopurinol (300 mg) and then 9 h later losartan potassium (100 mg) to 5 healthy subjects.

RESULTS

The urinary excretion of uric acid increased by 3.9- and 2.6-fold, and that of oxypurinol by 2- and 1.8-fold, at 1 to 2 h and at 2 to 3 h, respectively, after administration of losartan potassium. The fractional clearance of uric acid was increased by 4.3- and 3.2-fold, oxypurinol by 2.3- and 2.1-fold, and xanthine by 1.32- and 1.26-fold, at 1 to 2 h and at 2 to 3 h, respectively, after administration of losartan potassium. The plasma concentrations of uric acid decreased by 8% and 16%, oxypurinol by 7% and 11%, and xanthine by 42% and 45%, at 1.5 and 2.5 h, respectively, after oral administration.

CONCLUSION

These results suggest that losartan potassium could increase urinary excretion of uric acid, xanthine, and oxypurinol by acting on their common renal transport pathways, since it was found that uric acid may share a renal transport pathway with oxypurinol and xanthine. It is also suggested that the effect of losartan potassium on oxypurinol and uric acid is clinically important, since the hypouricemic effect of a combination therapy using allopurinol and losartan potassium may be less than additive, while the uricosuric effect of losartan potassium may increase the frequency of calculi in the urinary tract.

Effect of furosemide on the plasma concentration and urinary excretion of purine bases, adenosine, and uridine

To examine whether furosemide affects the plasma concentration and urinary excretion of purine bases, adenosine, and uridine, we administered 20 mg furosemide intravenously to 6 healthy subjects. Furosemide decreased the plasma concentration of hypoxanthine by 39% and increased plasma renin activity (PRA) and the plasma concentration of protein by 3.4-fold and 9%, respectively, at 90 minutes after administration. Furthermore, it decreased the urinary excretion of hypoxanthine, xanthine, and uric acid by 47%, 49%, and 49%, respectively, and the fractional clearance of xanthine and uric acid by 44% and 47%, respectively, during the 1-hour period between 60 and 120 minutes after administration. However, furosemide did not affect the plasma concentration or urinary excretion of adenosine and uridine. In addition, in an in vitro incubation study of erythrocytes, furosemide (10 microg/mL) did not affect the concentration of hypoxanthine in the incubation medium or the activity of erythrocyte purine nucleoside phosphorylase and 5'-nucleotidase. These results imply that xanthine may share a renal transport pathway with uric acid. Further, it is suggested that the furosemide-induced decrease in hypoxanthine may be ascribable to a decrease in adenosine triphosphate (ATP) degradation related to the inhibition of chloride transport in the body.

Effect of urine storage on urinary uric acid concentrations

Accurate determination of serum and urinary uric acid concentrations is essential for the diagnosis and classification of gout according to uric acid metabolism derangement. Urine and/or serum samples are often kept at either 4 degrees C or -20 degrees C until assayed, when a large number of samples are handled simultaneously. Our preliminary study indicated a significant decrease in urinary uric acid concentration after preservation, regardless of the storage temperature. Uric acid crystals were often observed in these cases which showed a marked decrease in urinary uric acid concentration after storage. In the present study, we sought the factor(s) that might cause this decrease in urinary uric acid concentration, as well as measures to overcome the problem. High urinary uric acid concentration and low pH proved to play major roles in the decrease in urinary uric acid concentration after storage. In contrast, dilution of the urine samples before storage resulted in no significant change in urinary uric acid concentration. Based on these results, we recommend diluting urine before storage for determination of uric acid concentration and avoiding underestimation.

Effect of branched-chain amino acids on the plasma concentration of uridine does not occur via the action of glucagon or insulin

To examine whether branched-chain amino acids affect the plasma concentration of uridine, we administered branched-chain amino acids (L-isoleucine, 2.85 g, L-leucine 5.71 g, and L-valine, 3.43 g) orally to 6 healthy subjects. Plasma uridine and glucose decreased by 44% and 12%, respectively, together with an increase in plasma isoleucine, leucine, and valine 90 minutes after administration. However, branched-chain amino acids did not affect the plasma concentration and urinary excretion of purine bases (hypoxanthine, xanthine, and uric acid) and uridine or the plasma concentration of insulin, glucagon, and cyclic adenosine monophosphate (cAMP). Since small amounts of regular insulin, which were found to decrease plasma glucose more than the amino acids, did not decrease the plasma concentration of uridine, these results suggest that plasma uridine was decreased by a direct effect of the branched-chain amino acids on the cellular uptake and/or release of uridine.

Effect of TEI-6720, a xanthine oxidase inhibitor, on the nucleoside transport in the lung cancer cell line A549

To examine the effect of 2-(3-cyano-4-isobutoxyphenyl)-4-methyl-5-thiazolecarboxylic acid (TEI-6720), an inhibitor of xanthine oxidase, on purine metabolism in the lung cancer cell line A549, the activities of adenosine deaminase, purine nucleoside phosphorylase, adenine phosphoribosyltransferase, hypoxanthine guanine phosphoribosyltransferase, xanthine oxidase, and guanase together with pyrimidine nucleoside phosphorylase were measured with or without the addition of TEI-6720, and the extracellular concentrations of hypoxanthine, xanthine, inosine, uracil, and uridine were measured after the addition of inosine or uridine to the incubation medium with or without TEI-6720. Moreover, the Na-independent nucleoside transport was determined in A549 cells with or without TEI-6720. TEI-6720 inhibited the activity of xanthine oxidase in A549 cells, but did not affect other enzymes. During incubation, TEI-6720 not only prevented a decrease in the inosine concentration in inosine-containing medium, but also a decrease in the uridine concentration in uridine-containing medium. Furthermore, the Na-independent transport of uridine was inhibited by TEI-6720 with a K(i) value of 4.1 micromol/l. These results indicate that TEI-6720 is an inhibitor of the Na-independent nucleoside transport of uridine and inosine, as well as xanthine oxidase.

Effect of amino acids on the plasma concentration and urinary excretion of uric acid and uridine

To determine the effect of amino acids on the plasma level and urinary excretion of uric acid and uridine, 200 mL 12% amino acid solution, and 2 weeks later, 100 mL physiological saline solution containing glucagon (1.2 microg/kg weight), was infused into five healthy men. Both increased the urinary excretion of uric acid and the concentration of glucagon, insulin, and glucose in plasma and pyruvic acid in blood, whereas they decreased the concentration of uridine and inorganic phosphate in plasma. However, neither the amino acid infusion nor glucagon infusion affected the concentration of purine bases (hypoxanthine, xanthine, and uric acid), cyclic adenosine monophosphate (cAMP) in plasma, or lactic acid in blood or the urinary excretion of oxypurines (hypoxanthine and xanthine), uridine, or sodium. These results suggest that glucagon may have an important role in the amino acid-induced increase in urinary excretion of uric acid and decrease in plasma uridine.

'Pseudohypouricosuria' in alcaptonuria: homogentisic acid interference in the measurement of urinary uric acid with the uricase-peroxidase reaction

Urinary excretion of uric acid was found to be extremely low in a 58-year-old female patient with alcaptonuria. This was due to interference with the uricase-peroxidase method used, because analysis using high-performance liquid chromatography (HPLC) showed a normal urinary concentration of uric acid. In vitro experiments demonstrated that a high concentration of homogentisic acid in the patient's urine inhibited the peroxidase reaction, possibly due to inhibition of the colour development of 3-methyl-N-ethyl-N-(beta-hydroxyethyl)aniline (MEHA) and 4-aminoantipyrine, via the peroxidase reaction. A homogentisic acid concentration equivalent to that in plasma did not affect the uricase-peroxidase reaction. This result suggests that any assay based on a peroxidase method is affected by a high urinary concentration of homogentisic acid in patients with alcaptonuria.

Effect of interferon-gamma on purine catabolic and salvage enzyme activities in rats

To determine whether interferon-gamma affects rat purine catabolic and salvage enzyme activities, rats were injected with interferon-gamma (600000 U/kg, i.p.) and, similarly to a vehicle-injected control group, killed before or after injection at 6, 12, and 24 h. Organ homogenates were prepared and enzymatic reactions with substrates were carried out, after which the products were measured either chromatographically or spectrophotometrically. Western and Northern blotting also were performed. In contrast to the vehicle-injected rats, interferon-gamma-injected rats showed a significant rise in xanthine oxidoreductase activity in the liver, while enzyme activity was unchanged in the spleen, kidney, and lung. Western analysis of hepatic xanthine oxidoreductase showed an increased concentration of this protein 12 and 24 h after interferon-gamma injection. Northern analysis disclosed an enhanced mRNA expression coding for this enzyme, peaking 12 h after injection. Contrastingly, the activities of adenosine deaminase, purine nucleoside phosphorylase, hypoxanthine guanine phosphoribosyltransferase, and adenine phosphoribosyltransferase were not affected by interferon-gamma in any organ tested. While interferon-gamma causes an increased hepatic biosynthesis of xanthine oxidoreductase, the physiologic role of this enzyme induction remains undetermined.

Effects of fructose and xylitol on the urinary excretion of adenosine, uridine, and purine bases

To examine whether fructose and xylitol increase the plasma concentration and urinary excretion of adenosine, as well as uridine and purine bases (hypoxanthine, xanthine, and uric acid), we intravenously administered xylitol and, 2 weeks later, fructose, to five healthy subjects. Analyses of blood and urine samples obtained during these infusion studies demonstrated that fructose increased the urinary excretion of adenosine and uridine 11.9- and 105.5-fold, respectively, and caused only a small increase in the plasma concentrations of uridine and purine bases. It was further demonstrated that xylitol increased the urinary excretion of uridine 58.4-fold, with a marked increase in the plasma concentrations of purine bases and uridine but without an increase in the urinary excretion of adenosine. However, neither infusion increased the plasma concentration of adenosine. These results suggest that in addition to many organs, including the liver, fructose is significantly metabolized by an abrupt adenosine triphosphate (ATP) consumption in the kidney, leading to an increase in the urinary excretion of adenosine and uridine. They also suggest that xylitol is not significantly metabolized in the kidney.

Effect of glucose on the plasma concentration and urinary excretion of uridine and purine bases

To examine whether glucose increases the plasma concentration of purine bases and uridine, 75 g glucose was administered orally to eight healthy subjects and two patients with hyperuricemia. The plasma concentration of uridine increased by 21%, 25%, and 20% 30, 60, and 90 minutes after administration of glucose, respectively. However, urinary excretion of uridine was not affected, nor were the plasma concentrations and urinary excretion of purine bases (hypoxanthine, xanthine, and uric acid). These results suggest that the glucose-induced increase in plasma uridine was not concomitant with adenosine triphosphate (ATP) consumption-induced purine degradation, but instead was ascribable to a uridine diphosphate (UDP)-glucose consumption-induced pyrimidine degradation (UDP-glucose-->UDP-->uridine monophosphate [UMP]-->uridine).

Determination of adenosine and deoxyadenosine in urine by high-performance liquid chromatography with column switching

The means of measurement of adenosine and deoxyadenosine in urine was developed by separating adenosine and deoxyadenosine from other compounds using high-performance liquid chromatography with column switchings. This method is simple and convenient since no pretreatment of the urine is needed. Using this method, it could be demonstrated that urinary adenosine was higher in an adenosine deaminase (ADA) deficient patient who had a bone marrow transplant treatment (1.97 micromol/mmol creatinine) and in a heterozygote who had a markedly low erythrocyte ADA activity (1% of control ADA activity) (1.33 micromol/mmol creatinine) as compared to normal subjects (0.22+/-0.09 micromol/mmol creatinine, n=11). It was also noted that urinary deoxyadenosine was below the detection limits in the ADA-deficient bone marrow transplant patient, but it was detected in the heterozygote (3.7 micromol/mmol creatinine). Furthermore, it was also demonstrated that a fructose infusion increased the urinary concentration of adenosine from 0.21+/-0.03 to 2.66+/-1.21 micromol/mmol creatinine in five normal subjects.

Effect of bucladesine sodium on the plasma concentrations and urinary excretion of purine bases and uridine

To examine whether bucladesine sodium affects the plasma concentrations of purine bases (hypoxanthine, xanthine, and uric acid) and uridine, 100 mL of physiological saline containing bucladesine sodium (6 mg/kg weight) was administered intravenously to eight healthy subjects for 1 hour after overnight fast except for water. Blood was drawn 30 minutes before, and 30 minutes and 1 hour after the beginning of the infusion, and 1-hour urine was collected before and after the beginning of the infusion. Two weeks later, 100 mL of only physiological saline was administered under the same protocol. Bucladesine sodium decreased the plasma concentrations of hypoxanthine by 36% and by 37%, and of xanthine by 16% and 33%, and of uridine by 17% and 30%, 30 minutes and 1 hour after the beginning of the infusion, respectively, and increased the urinary excretion of hypoxanthine and uric acid by 140% and 30%, respectively, after the beginning of the infusion. However, it did not affect the plasma concentration of uric acid or the urinary excretion of xanthine, and the urinary excretion of uridine was less than 0.2 micromol/h before or after bucladesine sodium infusion. On the other hand, physiological saline alone did not affect any of the values described. These results suggest that bucladesine sodium acts on the secretory process of the renal transport of hypoxanthine, resulting in the increased urinary excretion of hypoxanthine, and further suggest that bucladesine sodium enhances the uptake of uridine in plasma to liver cells.

Effect of glucagon on the plasma concentration of uridine

To determine whether glucagon affects the plasma concentration of uridine, we administered 100 mL physiological saline containing 1 mg glucagon or 100 mL physiological saline alone intravenously over 1 hour to healthy subjects. Glucagon decreased the plasma concentration of uridine from 5.72 +/- 1.05 to 4.80 +/- 0.60 micromol/L but increased the concentrations of cyclic adenosine monophosphate (cAMP) in plasma and pyruvic acid and lactic acid in blood 59-, 1.4-, and 1.3-fold, respectively. Although glucagon increased urinary excretion of uric acid, it did not affect the plasma concentration of purine bases (hypoxanthine, xanthine, and uric acid) or urinary excretion of oxypurines and uridine, indicating that glucagon does not affect purine degradation and suggesting that glucagon does not affect adenosine triphosphate (ATP) consumption-induced pyrimidine degradation. In contrast, physiological saline did not affect any of the measured variables. These results suggest that glucagon enhanced Na+-dependent uridine uptake from the blood into the cells, since glucagon stimulates Na+-dependent uridine uptake into cells in vitro.

Xylitol-induced increase in the plasma concentration and urinary excretion of uridine and purine bases

To determine whether xylitol increases the plasma concentration and urinary excretion of uridine together with purine bases, we administered xylitol (0.6 g/kg weight) intravenously to six normal subjects using a 10% xylitol solution. Xylitol infusion increased the plasma concentration and urinary excretion of uridine, as well as purine bases, while it decreased both the concentrations of inorganic phosphate in plasma and pyruvic acid in blood and increased the blood concentration of lactic acid. These results suggest that an increase in the plasma concentration and urinary excretion of uridine is ascribable to increased pyrimidine degradation following purine degradation induced by xylitol.

Zonal distribution of allopurinol-oxidizing enzymes in rat liver

We describe an enzymatic histochemical localization of two allopurinol-oxidizing enzymes, xanthine oxidase and aldehyde oxidase in rat hepatic tissues. This method is based on the tetrazolium salt procedures by use of a tissue protectant, polyvinyl alcohol, with tetra-nitro BT as the final electron acceptor. The present study demonstrated that both oxidases are present in the cytoplasm of hepatic cells. However, the distribution of the enzymes was uneven, being seen mainly in the pericentral rather than the periportal area. When allopurinol was used as a substrate, the specific staining by xanthine oxidase was more prominent than that of aldehyde oxidase. The results suggested that xanthine oxidase is more effective in oxidizing allopurinol than aldehyde oxidase.

Decreased serum concentrations of 1,25(OH)2-vitamin D3 in patients with gout

We measured the serum concentrations of 1,25(OH)2-vitamin D3, 25(OH)-vitamin D3, parathyroid hormone (PTH) in 82 male patients with primary gout whose serum uric acid was significantly higher than that of 41 normal control male subjects (8.8 +/- 0.2 vs 5.6 +/- 0.2 mg/dL, p < 0.001). The serum 1,25(OH)2-vitamin D3 concentration was significantly lower in the patients with gout compared with the control subjects (39.6 +/- 1.4 vs 44.8 +/- 1.7 pg/mL, p < 0.05), while no differences were observed between the two groups in either the serum concentration of 25(OH)-vitamin D3 or PTH. The administration of uric acid lowering agent to the patients for 1 year caused a significant increase in their serum 1,25(OH)2-vitamin D3 concentration which was associated with a significant decrease in their serum uric acid concentration. In contrast, the serum concentrations of 25(OH)-vitamin D3 and PTH were not affected by these drugs. These results suggest that uric acid per se may directly decrease the serum concentration of 1,25(OH)2-vitamin D3 in patients with gout by inhibiting 1-hydroxylase activity.

Decreased serum concentrations of 1,25(OH)2-vitamin D3 in patients with gout

We measured serum concentrations of 1,25(OH)2-vitamin D3, 25(OH)-vitamin D3, parathyroid hormone (PTH), and uric acid in 114 male patients with primary gout and 51 normal male control subjects. Serum 1,25(OH)2-vitamin D3 was significantly lower in patients with gout compared with control subjects (38.4 +/- 11.9 v 44.4 +/- 11.0 pg/mL, P < .005), whereas no differences were observed between the two groups for serum 25(OH)-vitamin D3 or PTH. Serum uric acid was significantly higher in patients with gout versus control subjects (8.8 +/- 1.3 v 5.7 +/- 1.0 mg/dL, P < .0001). In addition, there was a significant negative correlation between serum uric acid and 1,25(OH)2-vitamin D3 concentrations (r = .17, P < .05). Administration of allopurinol or benzbromarone to the patients for 1 year caused a significant increase in serum 1,25(OH)2-vitamin D3, which was associated with a significant decrease in serum uric acid. In contrast, serum concentrations of 25(OH)-vitamin D3 and PTH were not affected by these drugs. These results suggest that uric acid per se may directly decrease serum 1,25(OH)2-vitamin D3 in patients with gout by inhibiting 1alpha-hydroxylase activity.

Effect of Tofu (bean curd) ingestion and on uric acid metabolism in healthy and gouty subjects

The effect of Tofu (bean curd) ingestion on uric acid metabolism was examined in 8 healthy and 10 gout subjects. Ingestion of Tofu increased plasma concentration of uric acid, together with increases in uric acid clearance and urinary excretion of uric acid. However, the increase in plasma concentration of uric acid was fairy small. Interestingly, no significant rise in the plasma, urinary and clearance of uric acid was observed in gout patients with uric acid clearance > 6.0 mL/min (lower normal limit). The results suggest that tofu is a preferable source of protein, especially in gout patients with uric acid clearance > 6.0 mL/min.

Effect of allopurinol and benzbromarone on the concentration of uridine in plasma

To investigate whether allopurinol and benzbromarone affect the concentration of uridine in plasma, allopurinol or benzbromarone were administered to patients with gout for 3 to 6 months. Allopurinol decreased the concentrations of uridine and uric acid in plasma and the urinary excretion of uric acid, but increased the plasma concentration and urinary excretion of oxypurines and orotidine. Benzbromarone decreased the concentration of uric acid in plasma and increased the excretion of uric acid in urine. However, it did not affect the plasma concentration of uridine or oxypurines or the urinary excretion of oxypurines or orotidine. These results suggest that orotidilytic decarboxylase was inhibited by allopurinol and oxypurinol ribonucleotides and/or that phosphoribosyl pyrophosphate (PRPP) was consumed by conversion from hypoxanthine, allopurinol, and oxypurinol to the respective ribonucleotides, resulting in a decrease in the de novo synthesis of pyrimidine leading to the decreased concentration of uridine in plasma. Furthermore, it was suggested that benzbromarone did not affect the de novo synthesis of pyrimidine or purine.

Effect of muscular exercise on the concentration of uridine and purine bases in plasma--adenosine triphosphate consumption-induced pyrimidine degradation

To identify whether muscular exercise increases the plasma concentration of uridine and of purine bases, the effect of rigorous muscular exercise was determined in five healthy men with a bicycle ergometer. Twenty-five-minute muscular exercise at 65% maximum O2 consumption increased the concentration of uridine, purine bases, and inorganicphosphate in plasma and of NH3 and lactic acid in blood. These results suggest that exercise-induced excessive adenosine triphosphate (ATP) consumption enhanced not only purine degradation but also pyrimidine degradation (uridine triphosphate [UTP]-->uridine diphosphate [UDP]-->uridine monophosphate [UMP]-->uridine) in exercising muscles.

Close correlation between visceral fat accumulation and uric acid metabolism in healthy men

We evaluated the effect of accumulation of intraabdominal visceral fat on the metabolism of uric acid in 50 healthy male subjects to elucidate any relationship between such obesity and hyperuricemia. The area of abdominal fat (visceral fat and subcutaneous fat) was measured at the level of the umbilicus by abdominal computed tomographic scanning. Serum and urinary concentrations of uric acid and creatinine were determined with an autoanalyzer. Uric acid clearance and the ratio of urinary uric acid to creatinine excreted in urine were calculated. Univariate and multivariate analyses were used to evaluate the relationship between uric acid metabolism and body fat. The size of the area of visceral fat was significantly correlated with the serum concentration of uric acid (r = .37, P < .01), uric acid clearance (r = -.34, P < .05), and the urinary uric acid to creatinine ratio (r = .65, P < .0001). The size of the area of subcutaneous fat was significantly correlated only with the urinary uric acid to creatinine ratio (r = .38, P < .01). Multivariate analyses, including body mass index (BMI), showed that the size of the visceral fat area was the strongest contributor to an elevated serum concentration of uric acid, a decrease in uric acid clearance, and an increase in the urinary uric acid to creatinine ratio. These results suggest that accumulation of visceral fat may have a greater adverse effect on the metabolism of uric acid than BMI or accumulation of subcutaneous fat. Clearly, patients with hyperuricemia should lose weight to reduce excessive visceral fat stores, to help avoid attacks of gout.

Is the plasma uridine level a marker of the overproduction of uric acid?

To determine whether the plasma level of uridine can be used to identify patients with gout, the plasma concentration of uridine was determined in patients with gout and normal subjects. Plasma uridine was significantly higher in patients with gout than in normal subjects. It was also significantly higher in patients with gout of the overexcretion (of uric acid) type than in those with gout of the underexcretion type. Plasma uridine was used to classify gout patients into underexcretion and overexcretion types, with a diagnostic accuracy of 92.5%. Results indicate that the plasma uridine concentration may be a marker of uric acid production and can be used to separate hyperuricemia into the overexcretion and underexcretion types.

Effect of ethanol and fructose on plasma uridine and purine bases

To determine whether both ethanol and fructose increase the plasma concentration of uridine, we administered ethanol (0.6 g/kg) or fructose (1.0 g/kg) to seven normal subjects. Both ethanol and fructose increased the plasma concentration of uridine together with an increase in the plasma concentration of oxypurines, whereas fructose also increased the plasma concentration of uric acid, but ethanol did not. In ethanol ingestion and fructose infusion, an increase in the plasma concentration of purine bases correlated with that of uridine. These results strongly suggest that an increase in the plasma concentration of uridine is ascribable to increased pyrimidine degradation following purine degradation increased by ethanol and fructose.

Effect of glucagon on renal excretion of oxypurinol and purine bases

OBJECTIVE

To investigate whether glucagon increases the urinary excretion of oxypurinol and purine bases.

METHODS

We administered 1 mg glucagon intravenously to 5 healthy subjects taking 300 mg allopurinol orally, and determined plasma concentrations and urinary excretion of oxypurinol and purine bases.

RESULTS

Glucagon increased the urinary excretion and fractional clearances of uric acid, xanthine, and oxypurinol, together with an increase in creatinine clearance, while it decreased plasma concentrations of xanthine and hypoxanthine.

CONCLUSION

Glucagon-induced increases in urinary excretion of uric acid, xanthine, and oxypurinol were attributable to increases in the fractional clearances of uric acid, xanthine, and oxypurinol in addition to an increase in glomerular filtration rate. It is suggested that glucagon affects the renal common transport pathway of uric acid, xanthine, and oxypurinol by stimulating the release of a liver derived renal vasodilator.

[Gout and atherosclerosis]

Recently atherosclerotic diseases, such as coronary heart disease and cerebrovascular disease have been considered as an important complication of hyperuricemia and gout. However, it is still controversial whether or not hyperuricemia is an independent risk factor of atherosclerotic diseases. On the other hand, several risk factors for coronary heart disease, for example hyperlipidemia and hypertension, are frequently observed in the patients with gout. Atherosclerosis in relation to hyperuricemia was discussed in view of definite and probable risk factors.