Urine alkalization facilitates uric acid excretion

Protein Intake and High Uric Acid Stone Risk

Rationale & Objective

We evaluated the metabolic differences between pure and impure uric acid stone formers in this retrospective study of uric acid kidney stone formers diagnosed between 1996 and 2021.

Study Design

Demographics and medical history were compared by χ2 tests. Twenty-four-hour urine chemistries were compared using logistic regressions while controlling for demographics and comorbid conditions.

Setting & Participants

Patients from Yale Urology and Nephrology Clinics with a documented kidney stone analysis containing uric acid were included. In total, 4,294 kidney stone formers had a stone analysis, and 722 (16.8%) contained uric acid. Patients with all stone analyses  ≥ 50% uric acid were allocated to the pure group, while patients with ≥1 stone analysis <50% uric acid were allocated to the impure group.

Results

Among kidney stone formers, the prevalence of uric acid nephrolithiasis was 16.8%. Pure uric acid stone formers were more likely to be older, heavier, and were 1.5 times more likely to have chronic kidney disease. When controlling for age, sex, race, ethnicity, and body mass index, pure uric acid stone formers had lower urinary pH and lower urine citrate normalized for creatinine. Additionally, they had a higher protein catabolic rate, urine urea nitrogen, and urine sulfur normalized for creatinine, all markers of dietary protein intake. These findings persisted after controlling for chronic kidney disease.

Limitations

This is a retrospective study from a single center.

Conclusions

Pure uric acid stone formation is more common with diminished kidney function; however, after controlling for kidney function, pure uric acid stone formation is associated with protein intake, suggesting that modifying protein intake may reduce risk.

Association between vegetarian diet and gouty arthritis: A retrospective cohort study

BACKGROUND AND AIMS

A vegetarian diet is rich in vegetables, fruits, and soy products. Although vegetarian diet is beneficial for improving the health outcomes such as body mass index, metabolic syndrome, cardiovascular disease, and mortality rate, the association between a vegetarian diet and gout incidence is not well known.

METHODS AND RESULTS

We linked the MJ Health Survey Data and MJ Biodata 2000 with the National Health Insurance Research Database (NHIRD) and the National Registration of Death (2000-2018). Information on the diet was collected from the MJ Health Survey Data, and the incidence of gouty arthritis was confirmed using the NHIRD. The Kaplan-Meier survival curve and log-rank test were used to compare the differences between vegetarian and non-vegetarian participants. Cox regression models were used to estimate the risk of the incidence of gouty arthritis. Among 76,972 participants, 37,297 (48.46%) were men, 2488 (3.23%) were vegetarians and the mean age was 41.65 ± 14.13 years. The mean baseline uric acid level was 6.14 ± 1.65 mg/dL. A total of 16,897 participants developed gouty arthritis, including 16,447 (22.08%) non-vegetarians and 450 (18.9%) vegetarians over a mean follow-up of 19 years. Significant differences were observed in the Kaplan-Meier survival curves between vegetarians and non-vegetarians (log-rank p < 0.001). Vegetarians had a significantly decreased incidence of gouty arthritis compared with non-vegetarians (hazard ratio = 0.87, 95% confidence interval = 0.78-0.98, p = 0.02) after adjusting for potential confounders.

CONCLUSION

People with a vegetarian diet had a significantly decreased risk of developing gouty arthritis compared with non-vegetarians in Taiwan.

Association between Dietary Acid Load and Hyperuricemia in Chinese Adults: Analysis of the China Health and Nutrition Survey (2009)

BACKGROUND

This study evaluates the association between dietary acid load (DAL) and hyperuricemia in Chinese adults.

METHODS

The China Health and Nutrition Survey (CHNS) in 2009 was used in this cross-sectional study. Potential renal acid load (PRAL) and net endogenous acid production (NEAP) were applied to estimate DAL. A multiple logistic regression model was used to test the relationship between DAL and hyperuricemia risk.

RESULTS

A total of 7947 participants were included in this study, of whom 1172 had hyperuricemia. The PRAL score was positively related to the prevalence of hyperuricemia, even when potential covariates were taken into account. In comparison with Q1, the ORs were 1.12 (95% CI, 0.92-1.38), 1.20 (95% CI, 0.97-1.47) and 1.42 (95% CI, 1.16-1.75) in Q2, Q3 and Q4. However, there was no significant relationship between NEAP scores and hyperuricemia. Every 10 g increase in energy-adjusted fat, protein and animal protein intakes caused a 10%, 17% and 18% increase in hyperuricemia risk, respectively (OR: 1.10, 95% CI: 1.04-1.16; OR: 1.17, 95% CI: 1.11-1.25; OR: 1.18, 95% CI: 1.12-1.24, respectively). An obvious linear correlation was also suggested by the restricted cubic spline.

CONCLUSIONS

Hyperuricemia risk was associated with higher PRAL among Chinese adults. This means that a diet low in PRAL scores could be a very valuable uric acid-lowering dietary pattern.

Risk factors and management of hyperuricemia after renal transplantation

Hyperuricemia (HUA) is a common complication after renal transplantation. Currently, there is no uniform consensus on factors which increase the risk for and treatment of HUA in renal transplant recipients. The purpose of this review is to summarize current and proposed risk factors and strategies to manage HUA after renal transplantation in order to assist renal function protection and prolong graft survival time.

Uric Acid as a Risk Factor for Cardiovascular Diseases

Recently, hyperuricemia and its association with cardiovascular disease have been receiving more and more attention. The article talks about the role of uric acid in the body, the reasons for its increase and the impact of elevated uric acid levels on the cardiovascular system. The mechanisms of influence of hyperuricemia on the development and progression of cardiovascular diseases are presented. Medicinal and non-drug ways to reduce the level of uric acid in the blood are considered. From non-drug methods, attention is focused on the hypopurine diet, adequate drinking regimen and normalization of body weight. Separately, the effect on the level of uric acid of various drugs used in clinical practice is considered. In the light of current clinical guidelines, the issue of the need to prescribe drug therapy for asymptomatic hyperuricemia is discussed.

Higher HEI-2015 scores are associated with lower risk of gout and hyperuricemia: Results from the national health and nutrition examination survey 2007-2016

Gout, the most prevalent inflammatory arthritis, is becoming increasingly prevalent in the United States and across the world, and it adversely impacts people’s quality of life and their health. Few studies have focused on the relationship between daily dietary quality and gout, so the topic requires further exploration. Data were derived from the National Health and Nutrition Examination Survey 2007–2016, and the inclusion criteria of the analytic sample were (1) adults, age ≥20 years, with complete information about HEI-2015, gout, and uric acid; (2) complete information of demographics, lifestyle (BMI, smoking, drinking), and disease history [hypertension, chronic kidney disease (CKD), diabetes]. The quality of the daily diet was reflected using the Healthy Eating Index 2015 (HEI-2015). The baseline features of different groups were examined using the Scott-Rao chi-square tests, and the association between the HEI-2015 score and the risk of gout/hyperuricemia (HUA) was investigated using weighted logistic regression models. The effects of different dietary components in the HEI-2015 on reducing the risk of gout/HUA were evaluated by weighted quantile sum (WQS) regression models. After adjusting for demographic characteristics, behavioral covariates, and disease history, higher HEI-2015 scores were associated with a significantly lower risk of gout (OR: 0.878, 95% CI: 0.876–0.880) and HUA (OR: 0.978, 95% CI: 0.976–0.979) in weighted logistic regression. Dairy, whole grains, plant proteins, and added sugar contributed greatly in HEI-2015 to reducing gout risk (weights of WQS index: 42, 17.18, 16.13, and 7.93%, respectively). Dairy, total fruits, greens and beans, and plant proteins contributed greatly in HEI-2015 to reducing HUA risk (weights of WQS index: 28.9, 17.13, 16.84, and 11.39%, respectively). As the result, adherence to the American Dietary Guidelines may assist to decrease the risk of gout/HUA in American adults, and greater emphasis should be placed on dairy products, whole grains, fruits, legumes, and added sugars.

Purine content of hospital meals and its effect on serum uric acid, urine pH, and urinary uric acid excretion

Hospital meals are prepared with the nutrients required by the patient's medical condition in consideration. However, no research on the purine content of hospital meals has been conducted, and it is not shown on the purine content. The recommended purine consumption for patients with gout and hyperuricemia is 400 mg/day based on the Japanese guidelines for the management of hyperuricemia and gout. In this study, the purine content in hospital meals was evaluated using the purine content of foods previously determined by our laboratory as a reference. The serum uric acid levels and uric acid excretion in admitted patients who consumed these diets were examined.

Higher Levels of Serum Uric Acid Have a Significant Association with Lower Incidence of Lower Urinary Tract Symptoms in Healthy Korean Men

Gout has been correlated with the risk of incident benign prostatic hyperplasia. In line with increasing prevalence of hyperuricemia, the aim of this study was to investigate the relationship between serum uric acid (SUA) level and the incidence of lower urinary tract symptoms (LUTS) among clinically healthy middle-aged men. We performed a cohort study in 101,091 Korean men without LUTS at baseline who completed health checkups between 2011 and 2016. LUTS were evaluated using the International Prostate Symptom Score, where a score ≥ 8 was defined as significant LUTS. Men were divided into six groups according to their SUA levels in mg/dL (<5.5, 5.5−6.4, 6.5−7.4, 7.5−8.4, 8.5−9.4, and ≥9.5). Throughout the follow-up—encompassing a total of 358,982.6 person years—13,424 people had significant LUTS (37.3 per 1000 person years for incidence rate). The multivariable models demonstrated that the highest level of SUA (≥9.5 mg/dL) was related to the lowest risk of significant LUTS compared with the reference category (<5.5 mg/dL) (0.77 (95% CI 0.59−0.99) for adjusted HR). In this large cohort composed of middle-aged men, higher SUA levels were related to a reduced risk of LUTS. This result suggests another potential role of SUA in restraining LUTS. Additional studies are needed to explain the underlying biological mechanisms of this phenomenological relationship.

Update on Uric Acid and the Kidney

PURPOSE OF REVIEW

In this review, we report on new findings regarding associations of uric acid with kidney health. We discuss kidney stones, effects of uric acid in chronic kidney disease (CKD), and management of gout in CKD. Recent studies on neuroprotective effects of raising uric acid provide interesting data regarding nephrolithiasis.

RECENT FINDINGS

Elevated urate levels have been implicated in the progression of chronic kidney disease (CKD), but the results from PERL and CKD-FIX studies did not demonstrate that allopurinol slowed CKD progression. The SURE-PD3 sought to determine if increasing uric acid would slow the progression of Parkinson's disease. Results ultimately did not support this hypothesis, but high urinary uric acid levels caused uric acid stones, not calcium stones. Low urinary pH remains the key to the formation of uric acid stones. Thiazolidinediones improve insulin resistance, which is associated with an increase in urine pH. The most recent research has not supported the hypothesis that lowering serum uric acid levels will slow the progression of CKD or provide neuroprotection in Parkinson's disease. It is still unclear as to why uric acid stone formers have a high net acid excretion. The STOP-GOUT trial demonstrates that there was a lack of significant adverse events with higher urate-lowering dosages of allopurinol and febuxostat, despite patients' kidney function. This may push other studies to administer higher dosages per ACR guidelines. Future studies could then demonstrate decreased progression of CKD.

Association of acidic urine pH with impaired renal function in primary gout patients: a Chinese population-based cross-sectional study

Background

Patients with gout frequently have low urinary pH, which is associated with the nephrolithiasis. However, the specific distribution of urinary pH and potential relationship of acidic urine pH to broader manifestations of kidney disease in gout are still poorly understood.

Methods

A 2016–2020 population-based cross-sectional study was conducted among 3565 gout patients in the dedicated gout clinic of the Affiliated Hospital of Qingdao University to investigate the association between low urinary pH and kidney disease. We studied patients that we defined to have “primary gout”, based on the absence of > stage 2 CKD. All subjects underwent 14 days of medication washout and 3-day standardized metabolic diet. We obtained general medical information, blood and urine biochemistries, and renal ultrasound examination on the day of the visit. The primary readouts were urine pH, eGFR, nephrolithiasis, renal cysts, microhematuria, and proteinuria. Patients were assigned into 5 subgroups (urine pH ≤5.0, 5.0 <pH≤ 5.5, 5.5 <pH< 6.2, 6.2 ≤pH≤ 6.9, and pH >6.9), aligning with the clinical significance of urine pH.

Results

Overall, the median urine pH and eGFR of all patients was 5.63 (IQR 5.37~6.09), and 98.32 (IQR 86.03~110.6), with acidic urine in 46.5% of patients. The prevalence of nephrolithiasis, microhematuria, and proteinuria were 16.9%, 49.5%, and 6.9%, respectively. By univariate analysis, eGFR was significantly associated with age, sex, duration of gout, tophus, body mass index, systolic blood pressure, diastolic blood pressure, fasting blood glucose, total cholesterol, serum utare, hypertension, diabetes, and urine pH. On multivariable analysis, eGFR was associated with age, sex, diastolic blood pressure, serum uric acid, hypertension, diabetes, and urine pH. Acidic urine pH, especially urine pH < 5.0, was significantly associated with the prevalence of kidney disease, including > stage 1 CKD, nephrolithiasis, kidney cyst, and microhematuria. Patients with 6.2 ≤ urine pH ≤ 6.9 and SU ≤ 480 μmol/L had the highest eGFR with the lowest prevalence of nephrolithiasis, microhematuria, and proteinuria.

Conclusions

Approximately half of gout subjects had acidic urine pH. Urine pH < 5.0 was associated with significantly increased nephrolithiasis, renal cyst, microhematuria, and proteinuria. The results support prospective clinical investigation of urinary alkalinization in selected gout patients with acidic urine pH.

Hyperuricemia: Features of the Diet

The association of hyperuricemia (HU) with cardiovascular disease (CVD), diabetes, metabolic syndrome, and kidney disease has been demonstrated in numerous studies. НU is the main pathogenetic factor in the development of gout and is associated with an increase in overall and cardiovascular mortality. НU is included in the list of factors determining cardiovascular risk. According to epidemiological studies, there is a high prevalence of HU in the world and its increase in recent decades. A number of factors have been identified that contribute to the increased risk of НU. Non-modifiable factors include gender, age, genetic factors, and modifiable factors include diet and lifestyle. Nutritional unbalances, increased life expectancy, increased prevalence of obesity, and increased use of drugs (especially diuretics) are seen as contributing factors to the rise in НU. The review was carried out to summarize the available information on the effect of dietary habits, individual foods and nutrients on serum uric acid (SUA) levels and the risk of developing HU. The review presents the results of scientific studies demonstrating the relationship of НU with the consumption of foods rich in purines (offal, red meat, fish, seafood, legumes), alcohol consumption, drinks sweetened with fructose, coffee, dairy products, vegetables and fruits. Diet correction is an important and necessary step in the prevention and treatment of НU. The article reviews the basic principles of dietary management in HU and provides dietary recommendations for patients. For effective prevention and treatment of НU, a mandatory correction of the diet is required.

Dietary Acid Load Is Positively Associated with the Incidence of Hyperuricemia in Middle-Aged and Older Korean Adults: Findings from the Korean Genome and Epidemiology Study

Hyperuricemia has been associated with a number of chronic diseases, such as type 2 diabetes mellitus, hypertension, and cardiovascular diseases. Dietary acid load plays a key role in regulating uric acid levels. We hypothesized that potential renal acid load (PRAL) and net endogenous acid production (NEAP) score would be positively associated with the incidence of hyperuricemia. Data from the Health Examinees study, a part of the Korean Genome and Epidemiology Study were used. The PRAL and NEAP scores were calculated to evaluate the dietary acid load. Hyperuricemia was defined as follows: >7.0 mg/dL and >6.0 mg/dL of serum uric acid levels in men and women, respectively. Multivariable Cox proportional hazard models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the incidence of hyperuricemia. We identified 2500 new cases of hyperuricemia during a mean follow-up of 5.0 years (223,552 person years). The participants in the highest quartiles of the PRAL and NEAP score had 21% (HR: 1.21, 95% CI: 1.07–1.35, p for trend <0.0001) and 17% (HR: 1.17, 95% CI: 1.04–1.31, p for trend <0.0001) higher risks for hyperuricemia, respectively, than those in the lowest quartiles, after adjusting for covariates. In this prospective cohort study, a higher dietary acid load was positively associated with a higher incidence of hyperuricemia in Korean adults. This suggests that an alkaline diet may be an effective strategy to reduce the future risk of elevated uric acid levels.

Plasma Xanthine Oxidoreductase Activity Associated with Glycemic Control in Patients with Pre-Dialysis Chronic Kidney Disease

INTRODUCTION

Xanthine oxidoreductase (XOR) activity plays an important role as a pivotal source of reactive oxygen species, which is associated with cardiovascular disease (CVD) events. Patients with CKD have increased risk of CVD events. In the present study, factors associated with plasma XOR activity in pre-dialysis CKD patients were investigated.

METHODS

In this cross-sectional study, plasma XOR activity in 118 pre-dialysis CKD patients (age 68 [57-75] years; 64 males, 26 with diabetes mellitus [DM]) was determined using a newly established highly sensitive assay based on (13C2,15N2) xanthine and liquid chromatography/triple quadrupole mass spectrometry.

RESULTS

Plasma glucose, hemoglobin A1c, and estimated glomerular filtration (eGFR) were significantly and positively correlated with plasma logarithmically transformed XOR (ln-XOR) activity. In multiple regression analyses, eGFR and hemoglobin A1c or plasma glucose were significantly, independently, and positively associated with plasma ln-XOR activity after adjusting for several confounders. Plasma XOR activity was significantly higher in CKD patients with (n = 26) than in those without (n = 92) DM (62.7 [32.3-122] vs. 25.7 [13.4-45.8] pmol/h/mL, p < 0.001). A total of 38 patients were taking uric acid-lowering drugs. Multiple regression analysis of CKD patients not administered uric acid-lowering drugs (n = 80) showed no significant association between eGFR and plasma ln-XOR activity. In contrast, association between glycemic control and plasma ln-XOR activity was significant even in CKD patients without uric acid-lowering drug treatment.

CONCLUSIONS

These results indicate the importance of glycemic control in CKD patients in regard to decreased XOR, possibly leading to a decrease in CVD events.

Pathophysiology of hyperuricemia and its clinical significance - a narrative review

Hyperuricemia, i.e. increased serum uric acid (UA) concentration, is a common problem in clinical practice. While there are clear guidelines concerning management of symptomatic hyperuricemia in acute conditions such as gout, urolithiasis or acute urate nephropathy, less is known about their secondary prevention. Moreover, despite the ongoing debate on the role of UA in the pathogenesis of chronic kidney disease, hypertension, cardiovascular disease and heart failure, the management of asymptomatic hyperuricemia in patients with these chronic conditions is still mainly up to physicians' judgement. Individual considerations should always be taken into account when prescribing urate-lowering therapy. In this narrative review study, we attempt to present current trends concerning treatment of patients with either symptomatic or asymptomatic hyperuricemia in the light of the available knowledge on the role of hyperuricemia in the development of gout, renal, cardiovascular and other diseases.

The effects of fruit consumption in patients with hyperuricaemia or gout

The consumption of fructose has gained increased attention as a potential cause of hyperuricaemia since fructose metabolism produces urate as a byproduct. In addition to sucrose and high fructose corn syrup, fresh fruits also contain fructose, suggesting that patients with hyperuricaemia or gout might also avoid fresh fruit. However, the effect of fruits is complex. Some studies reported that fruit intake was associated with gout flares while other studies showed that fruits rather lowered the risk for gout. Thus, fruits should not be simply viewed as a source of fructose. The complexity of fruits is accounted for by several nutrients existing in fruits. Vitamin C, epicatechin, flavonols, potassium and fibre are all nutrients in fruits, and these factors could modify fructose and urate effects. In this review, we discuss clinical studies evaluating the effect of fruit and fruit juice intake on hyperuricaemia and gout, and propose potential mechanisms for how fruit may influence urate levels.

Low-Purine Diet Is More Effective Than Normal-Purine Diet in Reducing the Risk of Gouty Attacks After Sleeve Gastrectomy in Patients Suffering of Gout Before Surgery: a Retrospective Study

BACKGROUND

Obese patients with preoperative gout often suffer of gouty attacks after bariatric surgery (BS), probably due to the lack of an adequate postoperative diet.

OBJECTIVES

The objectives of the study are to assess whether sleeve gastrectomy (SG) is effective in reducing the frequency of gouty attacks and also whether a postoperative low-purine diet (LPD) may further reduce these attacks as compared to a normal-purine diet (NPD) in a series of patients suffering of gout before SG.

METHODS

In this retrospective study, we measured and compared total body weight (TBW), body mass index (BMI), uric acid levels (UAL), anti-gout medication (allopurinol) requirements, and frequency in gouty attacks in 40 patients that underwent SG and who received either a LPD (n = 24) or NPD (n = 16). Compliance in following the prescribed diet was assessed in both groups study.

RESULTS

Before surgery, LPD and NPD patients had hyperuricemia and were receiving allopurinol. One year after SG, LPD and NPD groups showed a significant decrease in serum UAL (p < 0.001 and p = 0.00175, respectively). However, serum UAL decreased more significantly with the LPD compared to the NPD (p < 0.001). Furthermore, while NPD group showed a significant decrease in allopurinol requirements (p = 0.00130) and on the frequency in gouty attacks (p < 0.001), LPD group were off allopurinol therapy and had no gouty attacks 12 months after SG. Both groups showed high compliance in following the prescribed diets.

CONCLUSION

LPD is more effective in reducing the frequency of gouty attacks after SG compared with NPD in patients suffering of gout before surgery.

Hyperuricemia and acute gout after laparoscopic sleeve gastrectomy

The aim of this study was to evaluate the prevalence of hyperuricemia and acute gout after laparoscopic sleeve gastrectomy (LSG). Risk factors for developing gout were also examined. Eighty-five patients underwent LSG were enrolled in this prospective study. Serum uric acid levels, gout attacks and total water levels % derived by bioimpedance were examined pre-operatively and 1 month post-operatively. Hyperuricemia was identified in 30.6% pre-operatively and in 18.82% of patients post-operatively. From the patients' group with pre-operative hyperuricemia, 53.9% were normalized, 46.2% had increased uric acid post-operatively while gout was observed in 11.5%. From the patients group without pre-operative hyperuricemia, hyperuricemia and gout were observed in 6.8% and 5.1% post-operatively, respectively. The relative risk for developing hyperuricemia was 6.2 (95% confidence interval [CI] 2.2-17.8) and for developing gout was 2.3 (95% CI 2.2-17.8). Statistical significant differences for gout among the groups with and without gout were indicated concerning pre-operative use of medications (P < 0.001), age (P = 0.025), post-operative uric acid levels (P < 0.001) and post-operative total water levels % (P = 0.048). The prevalence of hyperuricemia was 18.8% and gout attack of 7.1% 1 month after LSG. From the cohort of patients with pre-operative hyperuricemia, a significant proportion normalized uric acid, while 11.5% developed gout. Patients without hyperuricemia pre-operatively developed hyperuricemia and gout in 6.8% and 5.1% post-operatively, respectively. The patients who had gout were younger and had 37% water levels post-operatively.

Effect of immediate and prolonged GLP-1 receptor agonist administration on uric acid and kidney clearance: Post-hoc analyses of four clinical trials

AIMS

To determine the effects of glucagon-like peptide (GLP)-1 receptor agonists (RA) on uric acid (UA) levels and kidney UA clearance.

MATERIAL AND METHODS

This study involved post-hoc analyses of 4 controlled clinical trials, which assessed actions of GLP-1RA administration on kidney physiology. The immediate effects of GLP-1RA exenatide infusion vs placebo were determined in 9 healthy overweight men (Study-A) and in 52 overweight T2DM patients (Study-B). The effects of 12 weeks of long-acting GLP-1RA liraglutide vs placebo in 36 overweight T2DM patients (Study-C) and of 8 weeks of short-acting GLP-1RA lixisenatide vs once-daily titrated insulin glulisine in 35 overweight T2DM patients (Study-D) were also examined. Plasma UA, fractional (inulin-corrected) and absolute urinary excretion of UA (UE_UA ) and sodium (UE_Na ), and urine pH were determined.

RESULTS

Median baseline plasma UA level was 5.39 to 6.33 mg/dL across all studies (17%-22% of subjects were hyperuricaemic). In Study-A, exenatide infusion slightly increased plasma UA (+0.07 ± 0.02 mg/dL, P = .04), and raised absolute-UE_UA (+1.58 ± 0.65 mg/min/1.73 m² , P = .02), but did not affect fractional UE_UA compared to placebo. Fractional UE_UA and absolute UE_UA correlated with increases in urine pH (r:0.86, P = .003 and r:0.92, P < .001, respectively). Fractional UE_UA correlated with increased fractional UE_Na (r:0.76, P = .02). In Study-B, exenatide infusion did not affect plasma UA, but increased fractional UE_UA (+0.76 ± 0.38%, P = .049) and absolute UE_UA (+0.75 ± 0.27 mg/min/1.73 m² , P = .007), compared to placebo. In regression analyses, both parameters were explained by changes in urine pH and, in part, by changes in UE_Na . In Study-C, liraglutide treatment did not affect plasma UA, UE_UA, UE_Na or urine pH, compared to placebo. In Study-D, lixisenatide treatment increased UE_Na and urine pH from baseline, but did not affect plasma UA or UE_UA .

CONCLUSION

Immediate exenatide infusion increases UE_UA in overweight healthy men and in T2DM patients, probably by inhibiting Na⁺ /H⁺ -exchanger type-3 in the renal proximal tubule. Prolonged treatment with a long-acting or short-acting GLP-1RA does not affect plasma UA or UE_UA in T2DM patients with normal plasma UA levels and at relatively low cardiovascular risk. Our results suggest that the cardio-renal benefits of GLP-1RA are not mediated through changes in UA.

Long-term in vivo evolution of high-purity Mg screw degradation - Local and systemic effects of Mg degradation products

Magnesium (Mg) based materials are the focus of research for use as degradable materials in orthopedics and cranio-maxillofacial surgery. However, corrosion rate control and biosecurity are still the key issues that need to be solved prior to their clinical applications. In the present study, as-rolled high-purity magnesium (HP Mg, 99.99 wt%) screws were implanted in rabbit tibiae for up to 52 weeks in order to investigate their long-term in vivo degradation and the local and systemic effects of their degradation products. A series of long-term monitoring were performed at various time points (4w, 12w, 26w and 52w) after implantation using numerous investigations such as micro-CT assay, histomorphometric analysis, local micro-environment testing and biochemical analysis of serum and urine. It was revealed that HP Mg screws had a uniform degradation morphology and a slow degradation rate in vivo during the period of 52 weeks. Their degradation products not only increased the local pH values but also changed the local Mg²⁺ ions concentration and gas cavity area in the peri-implant tissues in a dynamic manner. More importantly, both the new bone formation and bone-implant contact rate were increased at bone-implant interfaces at 26 weeks and 52 weeks post-implantation. Furthermore, neither abnormal elevation of serum magnesium and urine magnesium level, nor liver and kidney dysfunction were detected during the monitoring period of 26 weeks. All these results of long-term investigation suggest that HP Mg screws possess a slow degradation rate, desirable bone repair capacity and long-term local/systemic biosafety, and consequently may have good potential for application as bone fixation devices.

STATEMENT OF SIGNIFICANCE

The corrosion resistance control and biosecurity issues of Mg alloys limited their clinical applications in some extent. Mg purification is another effective way to improve corrosion resistance of Mg-based materials. However, the long-term in vivo degradation of high-purity magnesium (HP Mg) and the local and systemic effects of its degradation products have not been fully investigated yet, which are the key factors to determine the clinical application prospect of HP Mg. Especially the changes in peri-implant microenvironment may greatly influence the local physiological response and bone repair. In this study, the long-term evolution tendency of in vivo degradation behavior of HP Mg screws was discovered from the view of space-time. Furthermore, not only the dynamic changes of local microenvironment and the long-term evolution process of bone repair, but also the dynamic systemic responses were systematically revealed. Conclusions of this study may help us to further understand the long-term in vivo evolution of HP Mg degradation and the local/systemic effects of its degradation products and help to guide the design of biodegradable bone fixation material.

The effects of apples and apple juice on acute plasma uric acid concentration: a randomized controlled trial

Background

The consumption of large amounts of fructose from added sugars results in the hepatic production and export of uric acid into the circulation.

Objective

Our aim was to test whether fructose present in fruit is of sufficient quantity or in a form that will increase uric acid concentration.

Design

Seventy-three participants were randomly assigned to 1 of 3 groups to ingest small (205 g) and large (410 g) servings of apple segments, small (170 mL) and large (340 mL) servings of apple juice, or a glucose and a fructose control beverage. Within each group, participants ingested both treatments in a crossover design. The fructose control and the large servings of apple and juice contained 26.7 g fructose. Test foods were ingested within 10 min. Blood samples were taken at baseline and at 30 and 60 min after intake.

Results

Plasma uric acid concentrations increased after the intake of all fructose-containing treatments and decreased after the glucose beverage. The mean (95% CI) increase in uric acid at 30 min was 15 µmol/L (10, 21 µmol/L) for the fructose control and 19 µmol/L (8, 30 µmol/L) and 17 µmol/L (9, 24 µmol/L) for the large servings of apple and apple juice, respectively. There was no difference in change in uric acid between baseline and 30 min when comparing the apple (3 µmol/L; 95% CI: -8, 14 µmol/L) and apple juice (-7 µmol/L; 95% CI: -18, 5 µmol/L) with the fructose control. Blood pressure taken 70 min after ingestion was unaffected by any treatment (P > 0.05). There was no difference in change in satiety scores between the fructose and glucose control beverages (P > 0.05). Participants felt more satiated 30 min after ingesting whole apple than after apple juice. The glycemic response reflected the amount of glucose in each treatment.

Conclusions

The body acutely responds to fructose regardless of source. Longer-term studies are required to assess how small and transient increases in plasma uric acid contribute to health. This trial was registered with the Australian New Zealand Clinical Trials Registry at https://www.anzctr.org.au/trial/registration/trialreview.aspx?id=367974 as ACTRN12615000215527.

Dietary Potential Renal Acid Load Is Positively Associated with Serum Uric Acid and Odds of Hyperuricemia in the German Adult Population

Background

Initial interventional data indicate that a reduction in dietary acid load (e.g., by an increased consumption of alkalizing fruit and vegetables) can increase renal uric acid excretion and decrease serum uric acid (SUA).

Objective

Against this background, we examined the association between dietary potential renal acid load (PRAL) and SUA in a representative population sample.

Methods

Cross-sectional analyses were performed in 6894 participants (aged 18-79 y) of the German Health Interview and Examination Survey for Adults (DEGS1). Dietary intake was assessed with a food-frequency questionnaire. Nutritive acid load and the intake of uric acid equivalents (UAEs) were characterized by assigning PRAL and UAE values to reported food consumption. In multiple linear regression models, the associations of PRAL, UAEs, and relevant food groups with SUA were analyzed. Multiple logistic regressions were used to calculate ORs for hyperuricemia comparing lower and upper tertiles of the predictors.

Results

After adjustment for relevant confounders, PRAL (P = 0.003), alcohol (P < 0.0001), and UAE (P = 0.03) intakes were positively associated with SUA, whereas the intake of dairy products and fruit and vegetables was inversely associated (both P < 0.0001). Subgroup analyses among participants without interacting medication use confirmed these results. In addition, participants with lower PRAL had lower odds for hyperuricemia (OR: 0.60; 95% CI: 0.43, 0.83).

Conclusions

Apart from observing known dietary influences on SUA, we found in this population-based, cross-sectional study in adults that low PRAL may represent a potentially SUA-reducing dietary pattern. This highlights dietary alkalization as a possible nonpharmacologic option to influence elevated SUA concentrations.

Effects of the Dietary Approaches to Stop Hypertension (DASH) Diet and Sodium Intake on Serum Uric Acid

OBJECTIVE

Randomized trial data guiding dietary recommendations to lower serum uric acid (UA), the etiologic precursor of gout, are scarce. We undertook this study to examine the effects of the Dietary Approaches to Stop Hypertension (DASH) diet (a well-established diet that lowers blood pressure) and levels of sodium intake on serum UA.

METHODS

We conducted an ancillary study of a randomized, crossover feeding trial in 103 adults with prehypertension or stage I hypertension. Participants were randomly assigned to receive either the DASH diet or a control diet (typical of the average American diet) and were further fed low, medium, and high levels of sodium for 30 days, each in random order. Body weight was kept constant. Serum UA levels were measured at baseline and following each feeding period.

RESULTS

Trial participants were 55% women and 75% black with a mean ± SD age of 51.5 ± 9.7 years and a mean ± SD serum UA level of 5.0 ± 1.3 mg/dl. The DASH diet reduced serum UA (-0.35 mg/dl [95% confidence interval (95% CI) -0.65, -0.05], P = 0.02), with a higher effect (-1.29 mg/dl [95% CI -2.50, -0.08]) among participants (n = 8) with a baseline serum UA level of ≥7 mg/dl. Increasing sodium intake from the low level decreased serum UA during the medium sodium intake period (-0.3 mg/dl [95% CI -0.5, -0.2], P < 0.001) and during the high sodium intake period (-0.4 mg/dl [95% CI -0.6, -0.3], P < 0.001).

CONCLUSION

The DASH diet lowered serum UA, and this effect was greater among participants with hyperuricemia. Moreover, we found that higher sodium intake decreased serum UA, which enhances our knowledge of urate pathophysiology and risk factors for hyperuricemia.

Association of plasma xanthine oxidoreductase activity with severity and clinical outcome in patients with chronic heart failure

BACKGROUND

Oxidative stress due to purine degradation is associated with the development of chronic heart failure (CHF). Xanthine oxidoreductase (XOR) is a rate-limiting enzyme of purine degradation that plays a key role in uric acid (UA) production with a resultant increase in reactive oxygen species. However, the relationship between plasma XOR activity and CHF severity and clinical outcome remains unclear.

METHODS AND RESULTS

We measured XOR activity in 440 patients with CHF and 44 control subjects. Abnormally high and low XOR activities were identified based on the results for 95% of the control subjects (high and low XOR activities ≥120 and <33pmol/100μL/h, respectively). The prevalence rates of high and low XOR activities increased with advancing New York Heart Association functional class. There were 158 cardiac events during a median follow-up period of 1034days. Multivariate Cox proportional hazard regression analysis showed that both high and low XOR activities were significantly associated with cardiac events in patients with CHF after adjustment for confounding risk factors including serum UA and loop diuretic use. Kaplan-Meier analysis revealed that the cardiac event rate was significantly higher in patients with either high or low XOR activity. The net reclassification index was significantly improved by adding XOR activity to the basic risk factors.

CONCLUSIONS

We provide the first evidence of an association of plasma XOR activity with CHF severity and clinical outcome. Plasma XOR activity could be used to identify high-risk CHF patients and could be a therapeutic target for XOR inhibitors.

Nonpharmacological Management of Gout and Hyperuricemia: Hints for Better Lifestyle

We reviewed lifestyle factors that influence serum uric acid levels and risk of gout flare, and how to improve their deleterious effects. Since obesity increases uric acid and weight gain increases gout risk, weight reduction by daily exercise and limiting intake of excess calories is recommended. However, strenuous exercise, which causes adenine nucleotide degradation; starvation, which decreases uric acid excretion; and dehydration may raise the level of uric acid in serum and trigger gout. Increased intake of purine-rich foods, such as meat and seafood, raise the level of uric acid in serum and is associated with increased risk of gout, whereas dairy products, especially low-fat types, are associated with a lower risk of gout. Also, heavy alcohol drinking raises the uric acid level and increases the risk of gout through adenine nucleotide degradation and lactate production. Sweet fruits and soft drinks containing fructose should be moderated, since fructose may raise uric acid and increase gout risk through uric acid production and/or decreased excretion. On the other hand, the Mediterranean diet is recommended for gout patients, since it may also help prevent hyperuricemia. Furthermore, coffee and vitamin C supplementation could be considered as preventive measures, as those can lower serum uric acid levels as well as the risk of gout.

Cross-sectional analysis of nutrition and serum uric acid in two Caucasian cohorts: the AusDiab Study and the Tromsø study

Background

Hyperuricemia can lead to gout, and may be a risk factor for cardiovascular events, hypertension, diabetes and renal disease. There is well-known link between gout and habitual intake of meat and seafood, however the association between hyperuricemia and micro-and macro-nutrient intake has not been established.

Methods

We studied associations between intakes of food categories, macro-and micronutrients and serum uric acid (SUA) levels in two cross-sectional surveys of Caucasian adults deriving from different food traditions: Australian Diabetes, Obesity and Lifestyle Study 1999/00 (n=9734, age 25–91) and Tromsø Study 4 1994/95 (n = 3031, age 25–69). Dietary intake was calculated from self-administered Food Frequency Questionnaires. In some analyses we stratified according to abdominal obesity status and gender.

Results

In both cohorts, lower levels of SUA were found in subjects with higher consumption of carbohydrates, calcium and vitamin B2, while higher fat intake was associated with higher SUA, after adjustment for age, body mass index, estimated glomerular filtration rate, physical activity, total energy intake, use of diuretics, presence of hypertension, diabetes and gout. Among individual food items, high consumption of dairy products, high-fibre bread, cereals and fruits were associated with lower SUA in most subject groups while consumption of meat, eggs, beer and spirits, but not wine, with elevated levels.

Conclusions

Healthy food choices with high intake of carbohydrates, dairy products, fiber and micronutrient-rich foods, and limited intake of fat, beer and spirits, might be recommended to prevent high SUA. Dietary factors seem to have qualitatively similar impact on SUA in obese and non-obese men and women from Australia and Norway.

Electronic supplementary material

The online version of this article (doi:10.1186/s12937-015-0032-1) contains supplementary material, which is available to authorized users.

The association between hyperuricemia and betel nut chewing in Taiwanese men: a cross-sectional study

Background

Studies have associated betel nut chewing with cancers, metabolic syndrome, cardiovascular disorders, chronic kidney disease, and proteinuria. This study investigated whether hyperuricemia is associated with betel nut chewing in men who participated in a health check-up program.

Methods

From hospital records, we identified a total of 11,991 men who participated in the health check-up program from 2003 to 2009. They were divided into hyperuricemic group and non-hyperuricemic group. Laboratory tests, medical history, and status of cigarette smoking, alcohol consumption, and betel nut chewing were compared between the 2 groups. We calculated odds ratio (OR) and 95% confidence interval (CI) of hyperuricemia in association with betel nut consumption and other factors.

Results

Compared with the non-hyperuricemic group, the hyperuricemic group was slightly older (59.4 vs. 58.6 years) but less prevalent with betel nut use (11.8 vs. 13.6%, p = 0.003). Multivariable logistic regression analysis showed that hyperuricemia was negatively associated with betel nut chewing (OR 0.75, 95% CI 0.66-0.84), older age (OR 0.84, 95% CI 0.77-0.93), and diabetes mellitus (OR 0.57, 95% CI 0.50-0.64). On the other hand, hyperuricemia was positively associated with body mass index (OR 1.75, 95% CI 1.62-1.90), drinking (OR 1.36, 95% CI 1.25-1.49), hypertension (OR 1.41, 95% CI 1.30-1.52), mixed hyperlipidemia (OR 1.84, 95% CI 1.33-2.54), chronic kidney disease (OR 3.28, 95% CI 2.94-3.65), and proteinuria (OR 1.22, 95% CI 1.08-1.38). Smoking, hypercholesterolemia, and hypertriglyceridemia had no significant association with hyperuricemia.

Conclusion

Our data suggest that betel nut chewing is negatively associated with hyperuricemia.

Effect of a novel dietary supplement on pH levels of healthy volunteers: a pilot study

OBJECTIVE

To examine the effects of a greens alkalizing dietary supplement on urinary pH levels in individuals with lower-than-average pH levels.

METHODS

The present study investigated the effects of an alkalizing formula (Reserveage Wholeganic Greens(TM)) on four individuals who had average urinary pH levels below 6.0 for three consecutive days. Following the three-day, baseline period, participants received Reserveage Wholeganic Greens(TM) for four consecutive days and were instructed to continue to measure their urine pH levels. Paired samples t-tests were used to examine pH levels before and after a four-day treatment period with Reserveage Wholeganic Greens(TM).

RESULTS

Compared to baseline, mean urine pH levels in all volunteers were significantly higher following the supplementation with Reserveage Wholeganic Greens(TM) (5.89 ± 0.20 vs 5.56 ± 0.23; P<0.01). Participants' pH levels were also significantly higher than baseline on days 5, 6, and 7 of the treatment period (P < 0.05). Noteworthy, on day 7, participants' mean pH levels were significantly higher than at the beginning of the treatment period (6.03 ± 0.15 at day 7 vs 5.65 ± 0.24 at day 4; P < 0.01).

CONCLUSION

The findings of this study suggest that supplementation with Reserveage Wholeganic Greens(TM) has an alkalizing effect on the body and can increase the urine pH levels in individuals with lower-than-average pH levels.

Effect of urine pH changed by dietary intervention on uric acid clearance mechanism of pH-dependent excretion of urinary uric acid

BACKGROUND

The finding reported in a previous paper - alkalization of urine facilitates uric acid excretion - is contradictory to what one might expect to occur: because food materials for the alkalization of urine contain fewer purine bodies than those for acidification, less uric acid in alkaline urine should have been excreted than in acid urine. To make clear what component of uric acid excretion mechanisms is responsible for this unexpected finding, we simultaneously collected data for the concentration of both creatinine and uric acid in serum as well as in urine, in order to calculate both uric acid and creatinine clearances.

METHODS

Within the framework of the Japanese government's health promotion program, we made recipes which consisted of protein-rich and less vegetable-fruit food materials for H + -load (acidic diet) and others composed of less protein and more vegetable-fruit rich food materials (alkaline diet). This is a crossover study within some limitations. Healthy female students, who had no medical problems at the regular physical examination provided by the university, were enrolled in this consecutive 5-day study for each test. From whole-day collected urine, total volume, pH, organic acid, creatinine, uric acid, titratable acid and all cations (Na+,K+,Ca2+,Mg2+,NH4+) and anions (Cl-,SO42-,PO4-) necessary for the estimation of acid-base balance were measured. In the early morning before breakfast of the 1st, 3rd and 5th experimental day, we sampled 5 mL of blood to estimate the creatinine and uric acid concentration in serum.

RESULTS AND DISCUSSION

Urine pH reached a steady state 3 days after switching from ordinary daily diets to specified regimens. The amount of acid generated ([SO42-] + organic acid - gut alkali)was linearly related with the excretion of acid (titratable acid + [NH4+] - [HCO3-]), indicating that H + in urine is generated by the metabolic degradation of food materials. Uric acid and excreted urine pH retained a linear relationship, as reported previously. Among the five factors which are associated with calculating clearances for both uric acid and creatinine, we identified a conspicuous difference between acidic and alkaline diets in the uric acid concentration in serum as well as in urine; uric acid in the serum was higher in the acidic group than in the alkaline group, while uric acid in the urine in the acidic group was lower than that in the alkaline group. These changes of uric acid in acidic urine and in serum were reflected in the reduction of its clearance. From these observations, it is considered that uric acid may be reabsorbed more actively in acidic urine than in alkaline urine.

CONCLUSION

We conclude that alkalization of urine by eating nutritionally well-designed alkaline -prone food is effective for removing uric acid from the body.

Effect of urine pH on uric acid excretion by manipulating food materials

A potential utilization of dietary intervention for reducing hyperuricemia was tested by managing food materials. Within the framework of the Japanese Government's health promotion program, we made recipes that consisted of more protein-rich and less vegetable/fruit-rich materials for the acidic diet and others composed of less protein-rich and more vegetable/fruit-rich materials for the alkaline diet. We have shown that urine alkalization facilitates uric acid excretion. In this study, it has been clarified with simultaneous measurements of both serum and urine uric acid concentration that acidic diets increase serum uric acid together with a decrease of uric acid excretion. The ratio (R) of uric acid clearance/creatinine clearance was calculated. On the third experimental day, the relative R, referring to that of the first day for the acidic diet, became smaller than that for the alkaline diet, indicating that in acidic urine, uric acid excretion is limited by more active reabsorption, compared with that in alkaline urine. Taken together, we tentatively conclude that dietary intervention may well be the safest and the most economical way for the prevention of hyperuricemia.