Purine-free Diet Research Articles

The effect of depurinized milk draught diet on rat serum uric acid, lipid status and haematological parameters

Hyperuricaemia and gout are closely related, but hyperuricaemia is an independent risk factor for endothelial damage, autoinflammation and haemodynamic abnormalities. Milk, generally known as a 'purine-free diet', is an essential protein source for patients suffering from hyperuricaemia and gout. As milk still contains different purine ribonucleotides, the new product, depurinized milk, almost free of purine nucleotides and uric acid, was produced. The potential effect of depurinized milk diet on serum uric acid (SUA) level, lipid parameters and blood haematological parameters was explored in rats after 72 h and 15 days, in relation to standard laboratory chow or the untreated milk diet. The beneficial effect on SUA was achieved when depurinized milk draught was given instead of standard chow for 72 h [28.39 ± 4.76 μm; p < 0.001 vs. standard diet (STD) 47.6 ± 6.12, vs. untreated milk diet 31.55 ± 8.50; p < 0.05] or as a supplement for STD for 15 days experiment (35.38 ± 6.40 μm; p < 0.05 vs. STD only 48.05 ± 4.32; vs. untreated milk + STD 46.02 ± 9.48). Depurinized milk diet significantly decreased the low density lipoproteins/high density lipoproteins (LDL/HDL) ratio (p < 0.001), triglycerides (p < 0.05) and leucocyte count (p < 0.001), while both milk draughts enhanced haemoglobin concentration (p < 0.01). In conclusion, considering the detrimental effect of persisting hyperuricaemia, the depurinized milk draught may meet the demand of healthy dairy product for population under hyperuricaemic risk.

Dietary purines in vegetarian meat analogues

The meat alternatives market offers a wide range of products resembling meat in taste, flavour or texture but based on vegetable protein sources. These high protein-low purine foods may find application in a low purine or purine-free diet, which is sometimes suggested for subjects with increased serum urate levels, i.e. hyperuricaemia. We determined purine content (uric acid, adenine, guanine, hypoxanthine, xanthine) in 39 commercially available meat substitutes and evaluated them in relation to their protein content. Some of the products contained a comparable sum of adenine and hypoxanthine per protein as meat. Analysis of variance showed an influence of protein source used. Mycoprotein-based products had significantly higher contents (2264 mg kg(-1)) of adenine and hypoxanthine per kg of 100% protein than soybean-based products (1648 mg kg(-1)) or mixtures consisting of soybean protein and wheat protein (1239 mg kg(-1)). Protein-rich vegetable-based meat substitutes might be generally accepted as meat alternatives for individuals on special diets. The type of protein used to manufacture these products determines the total content of purines, which is relatively higher in the case of mycoprotein or soybean protein, while appearing lower in wheat protein and egg white-based products. These are therefore more suitable for dietary considerations in a low-purine diet for hyperuricaemic subjects.

Urinary excretion and blood plasma allantoin in lambs and young goats starved and refed with a purine-free diet

An experiment was carried out to determine endogenous excretion of allantoin (AN) in lambs and kids fasted and fed on a purine-free diet (milk replacer: MR). After weaning (40–50 days after birth), the animals were reared by feeding on MR until they were 120 days old. At 8 months of age, they were fasted for 8 days, and then re-fed on MR for 13 days. After weaning, AN excretion gradually decreased almost to a constant level at 80–120 days after birth (mean 0·14 mmol/kgW0·75/day). In goat kids, there was variation but no definite trend in urinary AN excretion in the period 40–120 days (mean 0·35 mmol/kgW0·75/day). Urinary AN excretion was very low after fasting for 8 days, mean values (per kgW0·75/day) being 0·13 mmoles for lambs and 0·17 mmoles for goat kids. In lambs, urinary AN excretion did not increase following subsequent re-feeding of MR, and for goat kids the increase was small. Changes in plasma AN concentration after fasting and re-feeding showed a similar response to that of urinary AN excretion for both sheep and goats so that there was a high positive correlation between the plasma AN and urinary AN excretion (r=0·881 for lambs and r=0·853 for kids). It is concluded that, in these young animals, urinary AN excretion rapidly responds to changes in plasma AN and is therefore likely to be a useful practical indication of endogenous PD excretion.

Urinary excretion of purine derivatives as an index of microbial-nitrogen intake in growing rabbits.

Three experiments were carried out to establish a response model between intake and urinary excretion of purine compounds. In Expt 1 the relationship between the intake of purine bases (PB) and the excretion of total purine derivatives (PD) was determined in seven growing rabbits with a mean initial live weight (LW) of 2.03 (SE 0.185) kg, aged 70 d, each fitted with a wooden neck collar to prevent caecotrophagy. They were fed on five experimental diets formulated with different levels of nucleic acids (0.00, 3.75, 7.50, 11.25, 15.00 g yeast-RNA/kg diet). The relationship between intake of purine (x, mumol/kg W0.75) and total urinary PD excretion (y, mumol/kg W0.75), y= 0.56 + 0.67x (r2 O.86; RSD 0.338), indicated that about 70% of duodenal PB were recovered as urinary PD and that the endogenous contribution was constant and independent of dietary PB supply. Endogenous excretion of PD (allantoin and uric acid) was measured in a second experiment using six rabbits fed on a purine-free diet and fitted with neck collars to avoid caecotrophagy. Basal daily urinary excretion values for allantoin and uric acid were 532 (SE 33.9) and 55 (SE 7.3) mumol/kg W0.75 respectively; xanthine and hypoxanthine were not found in urine samples and therefore the sum of allantoin and uric acid should comprise the total excretion of PD (588 (SE 40.1) mumol/kg W0.75). The xanthine oxidase (EC 1.2.3.2) activity in plasma, liver, duodenum, jejunum and kidney was measured in a third experiment. The activities of xanthine oxidase in duodenal and jejunal mucosa, liver and kidney were: 0.61 (SE 0.095), 0.37 (SE 0.045), 0.035 (SE 0.001) and 0 units/g fresh tissue respectively and in plasma 2.96 (SE 0.094) units/1. The results show that urinary excretion of PD may be a useful tool to estimate duodenal PB input and microbial protein intake once the relationship between PB and N has been established in caecal micro-organisms.

Interaction of allopurinol and hydrochlorothiazide during prolonged oral administration of both drugs in normal subjects

The kinetics of allopurinol and hydrochlorothiazide were investigated in seven healthy male subjects during prolonged coadministration of two drugs. Subjects were maintained on an isoenergetic, purine-free formula diet with RNA supplementation for 24 days. Allopurinol (300 mg) was given orally on days 1-24. Hydrochlorothiazide (50 mg daily) was added to days 11-21. On day 43 a single oral dose of 50 mg hydrochlorothiazide was administered. Plasma concentration-time profiles of allopurinol and its main metabolite oxipurinol were obtained on days 1, 10, and 21; hydrochlorothiazide profiles were assessed on days 21 and 43. In addition, 24-h plasma concentrations of oxipurinol were measured repetitively, and 24 h urine samples were collected for the determination of allopurinol, oxipurinol, and hydrochlorothiazide. For oxipurinol, mean Cmax was not altered on hydrochlorothiazide treatment (13.8 +/- 1.4 micrograms/ml and 14.7 +/- 2.6 micrograms/ml, respectively); mean AUC0-24 was 259 and 290 micrograms h-1 ml-1, respectively. The small difference in AUC0-24 values does not explain the increase in plasma uric acid concentration during hydrochlorothiazide treatment, nor do the variations in allopurinol and hydrochlorothiazide kinetics.

Excretion of purine derivatives by ruminants: endogenous excretion, differences between cattle and sheep

The endogenous urinary excretion of the purine derivatives allantoin, uric acid and xanthine plus hypoxanthine were measured in twenty-nine lambs, ten cattle (six steers, one cow and three preruminant calves) and four pigs. The sheep and mature cattle were nourished by intragastric infusion and the calves were given a milk-substitute. The pigs were fed on a purine-free diet. The excretion of total purine derivatives was substantially greater by the cattle, being 514 (SE 20.6) mumol/kg live weight (W)0.75 per d compared with 168 (SE 5.0) mumol/kg W0.75 per d by the sheep and 166 (SE 2.6) mumol/kg W0.75 per d by the pigs. Plasma from normally fed sheep, cows and pigs was incubated with either xanthine or uric acid. Sheep and pig plasma had no xanthine oxidase (EC 1.2.3.2) activity whereas plasma from cattle did. Uricase (EC 1.7.3.3) was not present in plasma of cattle and pigs and appeared to be present in trace amounts only in sheep plasma. It is suggested that the species differences in endogenous purine derivative excretion were probably due to the different profiles of xanthine oxidase activity in tissues and particularly in the blood. This is because a high xanthine oxidase activity would reduce the chance to recycle purines, by increasing the probability of degradation to compounds which could not be salvaged.

Behavior of oxypurines in normal subjects after an 8 day purine-free diet.

We have already reported1 that gouty patients have a tendency to higher urinary levels excretion of purine bases in comparison to normal subjects. Since diet plays a very important role in this pathology, we analyzed the behavior of oxypurines (hypoxanthine and xanthine) and uric acid in gouty subjects after an 8 day purine-free diet (this diet is reported in table 1). This type of diet limits the ingestion of preformed purines to add to the burden of the uric acid pool and urinary disposal, as well as the ingestion of dietary constituents which can promote endogenous production of purines.2

32 BEHAVIOR OF OXYPURINES IN NORMAL SUBJECTS AFTER AN 8 DAY PURINE-FREE DIET

Seven normal adult volunteers (aged between 22 and 60 years) received a purine free diet for eight days (meat, fish, ham, salami and sausages, eggs, legumes, chocolate, wine, beer, superalcoholics, coca-cola, tea and coffee were rigorously excluded; noodles, rice, tomato, bread, cheese and sweets were allowed). Plasma and 24 h urine were analyzed both before and after the experiment for uric acid, hypoxanthine and xanthine content by high performance liquid chromatography (HPLC), as previously described (1). Urinary excretion of uric acid and xanthine was reduced, that of hypoxanthine rose: changes were more evident in plasma, where there was a highly significant rise (P < 0.01) in both oxypurines and lower values for uric acid. Results were surprising in part and interpretation was difficult. Increased purine catabolism, associated with a tendency of the body to spare oxypurines, provoked with a subsequent increase in exchange of oxypurines between tissues: the behavior of xanthine oxidase - which is sensitive to dietary changes and to purine-intake: could partially explain the results.(1) M.Lorenzi et al., Tumori 73, 289–294, 1987.

A study of dose-response relationships of allpurinol in the presence of low or high purine turnover

Effects of allopurinol (125-500 mg/m2 body surface) were studied in normal subjects during periods of 18 days both during a purine-free, isoenergetic liquid formula diet and additional intake of ribonucleic acid, 4 g/day. Plasma uric acid and renal excretion of uric acid, oxypurines (hypoxanthine plus xanthine) and orotic acid were measured and total purine excretion calculated. Effects of allopurinol were evaluated by comparison of the results obtained in the steady state during diet alone (average of days 7-10) with those during allopurinol administration (days 16-18). During the purine-free diet, plasma uric acid was lowered more than urinary uric acid by allopurinol on doses of 250-500 mg/m2 (44%-54% of control values on 500 mg/m2), demonstrating an increase in renal clearance. At the same dose, the uric acid lowering effect of allopurinol was more pronounced with than without purine loads (plasma 41%, urine 32% of control on 500 mg/m2 during purine intake), while renal uric acid clearance was decreased. The more pronounced reduction of uric acid excretion during purine administration was balanced to the greater part by a more pronounced increase in oxypurine excretion. Total purine excretion was reduced by about 20% during the purine-free diet irrespective of dose. The size of this purine deficit was doubled, but was also independent of dose during addition of purines. Orotic acid excretion increased with dose during allopurinol treatment and was reduced by addition of purines.(ABSTRACT TRUNCATED AT 250 WORDS)

DOSE DEPENDENCY OF THE URIC ACID LOWERING EFFECTS OF ALLOPURINOL WITH AND WITHOUT ORAL PURINES: 111

Healthy young volunteers received a purine-free formula diet for 18 days. Allopurinol (A) was given from day 11-18 in single oral doses of 125, 250, 375 and 500 mg/m2 body surface to 4, 8, 4 and 8 subjects, respectively. In a second study 4 of the 8 subjects on 250 and 500 mg/m2 took the same doses with the formula diet being supplemented by 4 g RNA/d. Maximum reduction of renal uric acid excretion was 55% and 70% during purine-free diet and RNA intake, respectively. On 250 and 500 mg/m2 reduction of endogenous renal uric acid was 36 and 46%, while exogenous uric acid was reduced by 74 and 86%, respectively in the 4 subjects. Renal uric acid clearance was increased by A during purine-free diet, but was not during RNA loading. In a different series of experiments A was given alone first followed by additional purine intake. On this regimen uric acid excretion did not increase during purine ingestion in most instances. This suggests previous inhibition by A or stimulation by oral purines of xanthine oxydase to be a factor in determining the influence of A on exogenous uric acid production.

APRT PARTIAL DEFICENCY IN A FAMILY: 34

A APRT partial deficency case in a 30 years old woman with gout, nephrolithiasis and renal failure had been, previously, described.(Acta Reuma. Port. 2,125,1974). We have, recently, studied the purine metabolism in this patient and in her family (Guido,17; Giorgia,16; Giulia,13 years-old). Giulia is apparently healty with normal uricemic value; Giorga showed an increasing serum urate levels (8 mg%) in 1980, when she was treted with purine free diet and henceforth she is normal uricemic. Guido shows several attacks of gout from the age of 12 years. In they all we have investigated HGPRT, APRT activity (nmol/mg prot./h) and erythocyte level of PRPP (nmol/mg prot.).HGPRT, and APRT, were determined as in Clinical Rheumat. 3, 229, 1984. Levels of PRPP were determined measuring the amount of IMP synthesized without adding any exogenous PRPP. The data are reported in table:Turnover of [14C] uric acid and its plasma disappearence has been evaluated in everyone.

Orotic acid excretion during starvation and refeeding in normal men

The effects of acute food deprivation and subsequent refeeding on urinary orotic acid excretion were examined in nine healthy adult male subjects. During inpatient metabolic ward conditions, the volunteers were fed a nutritionally complete, pyrimidine- and purine-free diet for three days and subsequently underwent a ten-day fast followed by a ten-day period of refeeding by total parenteral nutrition. Mean daily excretion of 4.33 ± 0.23 mg (2.77 ± 0.12 mg/g creatinine) of orotic acid during the enterally fed state was significantly reduced (mean 46 ± 5%) in all subjects during starvation. This reduction in the excretion of orotic acid during starvation is more likely related to a lowered rate of production and utilization. The starvation adaptation of orotate excretion occurred more rapidly than did the decrease in urinary nitrogen loss. All subjects showed an increase (mean 48 ± 14%) in the excretion of orotic acid during the first day of refeeding which continued throughout the refeeding phase. A significant positive correlation was shown between the daily orotic acid excretion and nitrogen intake ( r = 0.98) or protein balance (r = 0.83). The response to refeeding of acutely malnourished normal male is an increase in orotic acid excretion with a decrease in whole body protein catabolism.

Renal handling of uric acid in patients with recurrent calcium nephrolithiasis and hyperuricosuria.

Hyperuricosuria is a frequent finding in patients with recurrent calcium nephrolithiasis (RCN) that has been related to purine overingestion . The influence of diet and the renal handling of uric acid were investigated in patients with RCN to assess the pathogenic mechanism of excessive urate excretion. Among 50 patients with recurrent nephrolithiasis 42 formed renal stones containing calcium and 9 of these 42 patients demonstrated concomitant asymptomatic hyperuricosuria while on a self-selected diet. Ingestion of a purine-free diet normalized the uric acid excretion in 4 of these 9 patients. The other 5 patients showed persistent hyperuricosuria while on a purine-free diet. In order to assess a possible dysfunction in the renal handling of uric acid, pharmacological tests were undertaken in these 9 patients. Pyrazinamide administration almost completely suppressed urate excretion, excluding a presecretory reabsorption defect. Urate excretion in response to probenecid administration was decreased in 4 patients and increased in 1. This finding is in accordance with a postsecretory reabsorption defect in the former and an augmented tubular secretion of urate in the latter. This study proves that both dietary factors and tubular transport defects are involved in patients with recurrent calcium nephrolithiasis and hyperuricosuria.

Isotope studies of uric acid metabolism during dietary purine administration.

Uric acid is excreted by the kidneys and intestinal tract, while other routes are negligible. By addition of purines to a purine-free or low purine diet changes in uric acid turnover and excretion occur, which cannot be investigated by metabolic balance methods as that part of the uric acid turnover secreted into the gut is completely destroyed by the intestinal flora (Sorensen, 1960). We therefore studied uric acid pool size and turnover in normal subjects both during a purine-free diet and during purine supplementation by stable isotope methods.

Effect of purine restriction on serum and urine urate in normal subjects.

We sought to determine in individual patients with gout the contribution which the diet was making to the serum urate concentration and the urine urate excretion. In order to interpret the results, we needed to know the findings in healthy subjects studied under similar conditions. Previous studies in 22 normal male subjects in USA (1) had shown an upper limit of urinary urate excretion on a purine-free diet of 575 mg (3.4 mmol) per 24 hours. The serum urate concentration and urine urate excretion reached a nadir after 5 days purine restriction, with a mean fall in the serum urate concentration of 1 mg/100 ml (0.06 mmol/1). Accordingly, we planned to compare the serum urate concentration and the mean 24 hour urinary urate excretion on a normal diet with values obtained after 5 days of a low purine diet. The resulting change would reflect the contribution by the purines in the normal Australian diet to the serum and the urine urate. The values during purine restriction would also provide information concerning the normal range for the 24 hour urinary urate excretion on a low purine food diet.KeywordsNormal DietSerum UrateSerum Urate ConcentrationPrincess Alexandra HospitalUric Acid ProductionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Purine synthesis de novo in lymphocytes from patients with gout.

1. Variables that affect the measurement of purine synthesis de novo in human lymphocytes were studied and a reliable method of measurement of purine synthetic activity in these cells was established. 2. Purine synthesis de novo was measured as the rate of incorporation of [14C] formate into alpha-N-formylglycinamide ribonucleotide when further steps in the biosynthetic pathway had been blocked by azaserine. Incubation was carried out in a synthetic medium with a high phosphate concentration (25 mmol/l). 3. Purine synthesis de novo was measured in lymphocytes obtained on several occasions both from control subjects and from patients with gout, particularly those who tended to overproduce urate as suggested by high values of urinary urate. 4. Lymphocytes obtained from each individual on different occasions showed considerable variations in purine biosynthetic activity. This variation was such that there was no difference between the mean values obtained for the gouty subjects and the control subjects. 5. No correlation was obtained between the mean purine synthetic activity de novo in lymphocytes and either the serum urate concentration or the 24 h urinary urate excretion on a purine-free diet. 6 Apart from those with recognized enzyme mutations, no subgroup of the gouty population has been demonstrated in whom isolated lymphocytes demonstrate an intrinsic abnormality of purine synthesis de novo.

Uric acid metabolism in normal subjects and in gouty patients by chromatographic measurement of 14C-uric acid in plasma and urine

The turnover kinetics of uric acid were determined in a group of 25 subjects, including 6 controls, 17 gouty patients, and 2 subjects with asymptomatic hyperuricemia. According to their daily urate excretion while on a purine-free diet, the gouty patients (none of whom had evidence of tophi at the time of the study) were classified as follows: five overexcretor patients (“metabolic” gout), six normo-excretor patients (“renal” gout), and six borderline patients. Uric acid-2- 14C was used as the tracer, and the uric acid radioactivity in plasma and urine samples was measured after column chromatography through a polyacrylamide gel that specifically adsorbs uric acid. The experimental data of plasma disappearance curves and urine radioactivities of 14C-uric acid (followed up to 3 days after injection) were analyzed by the noncompartmental approach and by the urine/plasma ratio method, in order to calculate the total removal rate of uric acid, its distribution volumes, and the removal rate of uric acid through the renal route. The monocompartmental approach and the urine specific radioactivity methods were also employed to compute the uric acid turnover data, and the results were compared with those of noncompartmental analysis. The overexcretor patients were found to have normal metabolic clearance rate and fractional catabolic rate values, but significantly higher-than-normal total turnover rate values ( p < 0.005), whereas the normo-excretors had normal total turnover rate values but significantly lower metabolic clearance rate and fractional catabolic rate values compared to the controls ( p < 0.001). Uric acid excretion through the kidneys was found to be about two-thirds of the total removal both in the control subjects and in the gouty patients. The results obtained allowed the exclusion of any significant delay in the excretion of uric acid through the kidneys. The use of monocompartmental analysis led to a significant overestimation of both the total turnover rate ( p < 0.005) and the total pool of uric acid ( p < 0.001), and the urine specific radioactivity approach implied a significant overestimation of the total turnover rate ( p < 0.001). The gouty patients as a whole had a significantly larger-than-normal ( p < 0.001) total pool of uric acid, however determined. On the basis of the results obtained, a metabolic differentiation was made possible for the two pathophysiologic types of gout. In fact, the metabolic gout patients were all characterized by normal metabolic clearance rate values and increased total pool values, whereas the renal gout patients were all characterized by reduced metabolic clearance rate values and increased total pool values.

A NEW SYNDROME OF HYPERURICEMIA, PULMONARY FIBROSIS, AND RENAL DISEASE IN A KINDRED

A three month old male manifested failure to thrive, neurological dysfunction, moderate renal insufficiency, extreme hyperuricemia (16.5 mg%), and arterial hypoxemia and a radiographic picture compatible with idiopathic pulmonary fibrosis (IPF). A sister had died at age 6 months with IPF proven at autopsy, mild glomerular insufficiency and a disproportionate elevation in serum urate (10.6). There was no parental consanguinity nor positive family history for similar abnormalities. On a purine-free diet and 50 mg allopurinol the proband's serum urate was controlled at 5.5-7 mg%. N-15 uric acid tracer was administered intravenously while continuing allopurinol. Miscible urate pool size was considerably increased (55 mg/kg). Urate turnover was 11 mg/kg/24h; this figure may reflect increased de novo purine synthesis but sufficient data on children receiving allopurinol are not available to warrant a firm conclusion. Known enzymatic causes for purine overproduction were excluded since the following activities (nmol/hr/mg prot.) in RBC hemolysates were normal: hypoxanthine-guanine phosphoribosyltransferase, 79-83 (nl. 81±13 S.D.); adenine phosphoribosyltransferase, 18-19 (nl. 21±5); phos-phoribosylpyrophosphate synthetase, 84 (nl. 66±18), with normal inhibition by ADP, GDP, and 2,3-diphosphoglycerate. We conclude that the proband and his sister are examples of a previously undescribed disease state, inherited in autosomal recessive manner.

The Influence of Dietary Purines and Pyrimidines on Purine and Pyrimidine Biosynthesis in Man

Allopurinol-induced orotaciduria is reduced by dietary ribonucleic acid (RNA), RNA hydrolysate and different nucleotides. These findings are compatible with feedback regulation of pyrimidine biosynthesis by dietary nucleotides. Serum uric acid and urinary uric acid excretion on a purine-free isoenergetic diet reach a minimum after about 10 days and remain constant thereafter. When purines from different biochemical sources are added to such a diet there is always a linear relationship between dietary purines and serum uric acid level and urinary uric acid excretion. The findings suggest that dietary purines play a minor role if any in the regulation of purine biosynthesis in man.

Lipoproteins in Golgi Apparatus and GERL of Rat Hepatocytes: A CytoChemical Study

Our laboratory has recently reported that the marked fatty liver induced in rats by feeding a purine-free diet with 1% orotic acid (OA) can be reversed by addition of ethyl chlorophenoxyiso- butyrate (clofibrate or CPIB) to the OA diet (1). Hepatocyte ultrastructure returns to normal, as do the triacylglycerol levels in liver and serum. During reversal, GERL becomes prominent, distended with particles interpreted as lipoproteins undergoing degradation.This communication reports cytochemical observations on such hepatocytes. Thiamine pyrophosphatase (TPPase) activity in hepatocytes, as in various cell types (2), is localized to the inner (trans) element of the Golgi apparatus (Figure 1). GERL, in contrast, shows no TPPase activity but displays acid phosphatase (AcPase) activity (Figure 2). Particles resembling very low density lipoproteins (VLDL) are found in both GERL and elements of the Golgi apparatus. The presence of both AcPase activity and VLDL-like particles strengthens our earlier suggestion that lipoproteins may undergo transformations in GERL.