Management of hyperuricemia and gout in CKD

The role of gut microbiota in gout: Is gut microbiota a potential target for gout treatment

Numerous studies have demonstrated that gut microbiota is essential for the host's health because it regulates the host's metabolism, endocrine, and immune systems. In recent years, increasing evidence has shown that gut microbiota plays a role in the onset and progression of gout. Changes in the composition and metabolism of the gut microbiota, result in abnormalities of uric acid degradation, increasing uric acid generation, releasing pro-inflammatory mediators, and intestinal barrier damage in developing gout. As a result, gout therapy that targets gut microbiota has drawn significant interest. This review summarized how the gut microbiota contributes to the pathophysiology of gout and how gout affects the gut microbiota. Additionally, this study explained how gut microbiota might serve as a unique index for the diagnosis of gout and how conventional gout treatment medicines interact with it. Finally, prospective therapeutic approaches focusing on gut microbiota for the prevention and treatment of gout were highlighted, which may represent a future avenue in gout treatment.

Association between nutrient patterns and hyperuricemia: mediation analysis involving obesity indicators in the NHANES

Background

Diet has long been hypothesized to play an important role in hyperuricemia, and weight gain is a factor that is strongly associated with the rise in serum urate. We aimed to clarify the mediating role of obesity in the relationship between diet and hyperuricemia and to determine whether a weight-loss diet is an effective way to prevent hyperuricemia.

Methods

This cross-sectional study analysed representative samples of United States (n = 20,081; NHANES 2007–2016) adults. Nutrient patterns were derived with two methods: principal component analysis (PCA) and reduced rank regression (RRR) with obesity. Logistic regression and multivariable linear regression were applied to analyse the association between nutrient patterns in obesity and hyperuricemia. Mediation analyses were used to determine whether four obesity indicators, including body mass index (BMI), waist circumference (WC), visceral adiposity index (VAI) and lipid accumulation product index (LAP), mediated the relationship between nutrient patterns and hyperuricemia.

Results

PCA revealed three nutrient patterns (including “Low energy diet”, “Lower vitamin A, C, K pattern” and “Vitamin B group”), and only Vitamin B group had a total effect on hyperuricemia. RRR revealed one main nutrient pattern associated with obesity, which was characterized by High fat and low vitamin levels and was significantly associated with hyperuricemia. Mediation analysis showed that obesity mostly or even completely mediated the relationship between nutrient patterns and hyperuricemia, especially traditional obesity indicators, which played a key intermediary effect. The proportions of indirect effects for BMI and WC were as high as 53.34 and 59.69, respectively.

Conclusions

Our findings suggest that the direct effect of diet on hyperuricemia is weak, and obesity plays a critical mediating role in the relationship between diet and hyperuricemia, which confirms that a weight-loss diet such as a “Low fat and high vitamin diet” may be useful in preventing hyperuricemia.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-14357-5.

Efficacy and Safety of Acupuncture Combined with Herbal Medicine in Treating Gouty Arthritis: Meta-Analysis of Randomized Controlled Trials

Background

Gouty arthritis is a common metabolic disease caused by long-term purine metabolism and elevated serum uric acid. In recent years, the incidence of gouty arthritis has been increasing year by year. As an effective method for treating gouty arthritis, acupuncture combined with herbal medicine has been widely used in clinical practice. However, the evidence for the treatment needs to be evaluated through systematic review and meta-analysis. Methods. The Cochrane Library, PubMed, Web of Science, EMBASE, China CBM database, Clinical Trials, CNKI, China Wanfang database, and VIP information database were searched from the establishment of each database to March 2021. Randomized controlled trials (RCTs) were included in the study, and the therapeutic effects of acupuncture combined with herbal medicine versus conventional therapy, or acupuncture combined with herbal medicine versus anti-inflammatory drugs, or acupuncture combined with herbal medicine versus acupuncture/herbal medicine alone were compared in the subjects with gouty arthritis. Two authors screened all references, assessed the risk of bias, and independently extracted the data. The binary outcome was summarized using 95% confidence intervals (CIs) and risk ratios (RRs). The overall quality of the evidence was assessed with hierarchy, and meta-analysis was performed with a random-effects model.

Results

A total of 14 randomized controlled trials (1,065 participants, 540 treatment groups, and 525 control groups) with treatment courses of 5 to 21 days were included. Acupuncture combined with herbal medicine and acupuncture was compared in three trials, acupuncture combined with herbal medicine and conventional therapy was compared in 14 of them, and acupuncture combined with herbal medicine and anti-inflammatory drugs was compared in 8 of them. The clinical efficacy (clinical symptoms, serological tests, and visual analogue scale (VAS) results) was significantly improved in the acupuncture combined with herbal medicine treatment group (P=0.0005, 95% CI 0.03 to 0.13; 687 participants; 8 trials), and the efficacy in reducing uric acid was also better (P < 0.00001; 95% CI −102.89, −68.37; 100 participants; 2 trials; evidence with moderate quality). The effect of acupuncture combined with herbal medicine was better than that of acupuncture alone (RR 1.22, 95%CI 1.06 to 1.41; 139 participants; 3 trials), the effect of acupuncture combined with herbal medicine was better than that of herbal medicine alone (RR 1.31 95%CI 1.08 to 1.57, 100 participants, 2 trials, evidence with moderate quality), and the effect of acupuncture combined with herbal medicine was better than that of colchicine (P = 0.02, RR 1.14 95%CI 1.02 to 1.27, 2 trials, evidence with moderate quality). The incidence of adverse events was considerably different between the two groups, and the acupuncture combined with herbal medicine group was significantly superior to the control group in terms of adverse events (P < 0.00001; 95% CI (0.08 to 0.32)).

Conclusions

The efficacy of acupuncture combined with herbal medicine was better than conventional drug therapy in treating gouty arthritis. The study results must be interpreted with caution due to the high or unclear risk of bias of the trials included in the study. PROSPERO registration number: CRD42020202544. INPLASY registration number: 202090006.

Evaluation of the Effectiveness of Xanthine Oxidoreductase Inhibitors on Haemodialysis Patients using a Marginal Structural Model

A lower serum uric acid (UA) level has been associated with a higher mortality rate in haemodialysis patients. We investigated the long-term confounding factors of UA and mortality, and fitted a marginal structural model (MSM) based on the causal effect of xanthine oxidoreductase inhibitors (XORi). In total, 2429 patients on regular dialysis from April 2013 to March 2016 were included, and divided into quintiles by serum UA with Kaplan Meier (KM) curves and log rank analysis. Baseline characteristics were evaluated for relationships with all-cause mortality and cardiovascular disease (CVD) using the Cox hazard model. The MSM was used to control for time-dependent confounders of the XORi treatment effect. KM curves indicated that patients in the highest UA quintile had better outcomes than those in the lowest UA quintile. UA was not correlated with all-cause mortality or CVD events in the Cox model; however, the hazard ratio (HR) for mortality was 0.96 for the baseline administration of XORi. The MSM analysis for the effect of XORi treatment on all-cause mortality revealed a HR of 0.24 (95% confidence interval: 0.15-0.38) in all cohorts. These results suggest that XORi improved all-cause mortality in end-stage renal disease, irrespective of the serum UA level.

My Treatment Approach to Gout

Gout is the most common form of inflammatory arthritis in the United States. Nevertheless, gout remains misunderstood, misdiagnosed, underdiagnosed, and undertreated. Several new recommendation and guideline documents regarding the management of gout have been published in the past few years. New diagnostic modalities, such as ultrasound and dual-energy computed tomography, are now available. Newer treatment options exist, and older agents and their interactions are now better understood. This review addresses these recent diagnostic and therapeutic developments and describes our management protocol with the aim of providing the clinician with a pragmatic approach to gout management.

The 3-Year Incidence of Gout in Elderly Patients with CKD

BACKGROUND AND OBJECTIVES

The risk of gout across CKD stages is not well described.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We performed a retrospective cohort study using linked health care databases from Ontario, Canada from 2002 to 2010. The primary outcome was the 3-year cumulative incidence of gout, on the basis of diagnostic codes. We presented our results by level of kidney function (eGFR≥90 ml/min per 1.73 m2, 60-89, 45-59, 30-44, 15-29, and chronic dialysis) and by sex. Additional analyses examined the risk of gout adjusting for clinical characteristics, incidence of gout defined by the receipt of allopurinol or colchicine, and gout risk in a subpopulation stratified by the level of eGFR and albuminuria.

RESULTS

Of the 282,925 adults aged ≥66 years, the mean age was 75 years and 57.9% were women. The 3-year cumulative incidence of gout was higher in older adults with a lower level of eGFR. In women, the 3-year cumulative incidence of gout was 0.6%, 0.7%, 1.3%, 2.2%, and 3.4%, and in men the values were 0.8%, 1.2%, 2.5%, 3.7%, and 4.6%, respectively. However, patients on chronic dialysis had a lower 3-year cumulative incidence of gout (women 2.0%, men 2.9%) than those with more moderate reductions in kidney function (i.e., eGFR 15-44 ml/min per 1.73 m2). The association between a greater loss of kidney function and a higher risk of diagnosed gout was also evident after adjustment for clinical characteristics and in all additional analyses.

CONCLUSIONS

Patients with a lower level of eGFR had a higher 3-year cumulative incidence of gout, with the exception of patients receiving dialysis. Results can be used for risk stratification.

Functional and Structural Characterization of Purine Nucleoside Phosphorylase from Kluyveromyces lactis and Its Potential Applications in Reducing Purine Content in Food

Consumption of foods and beverages with high purine content increases the risk of hyperuricemia, which causes gout and can lead to cardiovascular, renal, and other metabolic disorders. As patients often find dietary restrictions challenging, enzymatically lowering purine content in popular foods and beverages offers a safe and attractive strategy to control hyperuricemia. Here, we report structurally and functionally characterized purine nucleoside phosphorylase (PNP) from Kluyveromyces lactis (KlacPNP), a key enzyme involved in the purine degradation pathway. We report a 1.97 Å resolution crystal structure of homotrimeric KlacPNP with an intrinsically bound hypoxanthine in the active site. KlacPNP belongs to the nucleoside phosphorylase-I (NP-I) family, and it specifically utilizes 6-oxopurine substrates in the following order: inosine > guanosine > xanthosine, but is inactive towards adenosine. To engineer enzymes with broad substrate specificity, we created two point variants, KlacPNP^N256D and KlacPNP^N256E, by replacing the catalytically active Asn256 with Asp and Glu, respectively, based on structural and comparative sequence analysis. KlacPNP^N256D not only displayed broad substrate specificity by utilizing both 6-oxopurines and 6-aminopurines in the order adenosine > inosine > xanthosine > guanosine, but also displayed reversal of substrate specificity. In contrast, KlacPNP^N256E was highly specific to inosine and could not utilize other tested substrates. Beer consumption is associated with increased risk of developing gout, owing to its high purine content. Here, we demonstrate that KlacPNP and KlacPNP^N256D could be used to catalyze a key reaction involved in lowering beer purine content. Biochemical properties of these enzymes such as activity across a wide pH range, optimum activity at about 25°C, and stability for months at about 8°C, make them suitable candidates for food and beverage industries. Since KlacPNP^N256D has broad substrate specificity, a combination of engineered KlacPNP and other enzymes involved in purine degradation could effectively lower the purine content in foods and beverages.

Associations Between Hyperuricemia and Chronic Kidney Disease: A Review

CONTEXT

In human beings, uric acid is the poorly soluble circulating end product of the purine nucleotide metabolism. A reduction in the glomerular filtration rate (GFR) contributes to hyperuricemia, which is frequently observed in patients with chronic kidney disease (CKD).

EVIDENCE ACQUISITION

Hyperuricemia is defined as a serum uric acid level > 7.0 mg/dL in males and > 6.0 mg/dL in females, while CKD is defined as kidney damage or a GFR < 60 mL/min/1.73 m(2) for 3 months or more, irrespective of the cause. Hyperuricemia is common in CKD and may occur because of decreased excretion, increased production, or a combination of both mechanisms.

RESULTS

The causes for hyperuricemia in overproducers may be either exogenous or endogenous. CKD has become a global public health problem because of its high prevalence and the accompanying increase in the risk of end-stage renal disease, cardiovascular disease, and premature death. The most common risk factors for CKD are obesity and the metabolic syndrome, which is strongly associated with hyperuricemia probably as a consequence of insulin resistance and the effects of insulin to reduce the urinary urate excretion. For recurring bouts of hyperuricemia or gout, patients should have a blood test and joint fluid test to determine whether the medication taken is effective. Interventional studies are a useful clinical research tool in clarifying the role of hyperuricemia in CKD.

CONCLUSIONS

Although many evidence-based studies have suggested that uric acid itself may harm patients with CKD by increasing inflammation and CKD progression, the issue is still a matter of controversy. Special attention should be paid to specific contraindications to certain drugs and the possibility of infectious arthritis.

Successful treatment of refractory gout using combined therapy consisting of febuxostat and allopurinol in a patient with chronic renal failure

Gouty arthritis is a metabolic disorder associated with hyperuricemia. Despite the development of novel pharmacotherapies, some hyperuricemia patients are drug refractory and develop gout. A 74-year-old man with frequent gouty attacks and chronic renal failure presented with asymmetrical polyarthritis affecting multiple joints. The diagnosis of gout was confirmed based on the presence of monosodium urate crystals in the patient's right wrist. The administration of systemic corticosteroids relieved the joint inflammation and pain; however, the urate level increased to 28 mg/dL and the gout attacks recurred. Combined allopurinol, febuxostat, and benzbromarone therapy reduced the urate level to <6 mg/dL, and the attacks gradually declined. This is the first report of two xanthine oxidase inhibitors being used to treat refractory gout.

Uric acid as a target of therapy in CKD

The prevalence of chronic kidney disease (CKD) has increased and will continue to increase in the United States and worldwide. This is alarming considering that CKD is an irreversible condition and patients who progress to chronic kidney failure have reduced quality of life and high mortality rates. As such, it is imperative to identify modifiable risk factors to develop strategies to slow CKD progression. One such factor is hyperuricemia. Recent observational studies have associated hyperuricemia with kidney disease. In addition, hyperuricemia is largely prevalent in patients with CKD. Data from experimental studies have shown several potential mechanisms by which hyperuricemia may contribute to the development and progression of CKD. In this article, we offer a critical review of the experimental evidence linking hyperuricemia to CKD, highlight gaps in our knowledge on the topic as it stands today, and review the observational and interventional studies that have examined the potential nephroprotective effect of decreasing uric acid levels in patients with CKD. Although uric acid also may be linked to cardiovascular disease and mortality in patients with CKD, this review focuses only on uric acid as a potential therapeutic target to prevent kidney disease onset and progression.

Use of diuretics and the risk of gouty arthritis: a systematic review

OBJECTIVE

To systematically review the literature investigating the relationship between use of diuretics and the risk of gouty arthritis.

METHODS

PubMed (1950-October 2009), Embase (1974-October 2009), and the Cochrane Library (up to October 2009) were searched using keywords and MeSH terms diuretics, adverse effects, and gout. For this review, the technique of "best evidence synthesis" was used. Studies reporting frequency, absolute or relative risks, odds ratio, or rate ratio of gouty arthritis in diuretic users compared with nonusers were selected and evaluated. Studies had to be published in English. Checklists from the Dutch Cochrane Centre were used to assess the quality of randomized controlled trials (RCTs), cohort, and case-control studies.

RESULTS

Two RCTs, 6 cohort studies, and 5 case-control studies met the inclusion criteria. The overall quality of the studies was moderate. In a RCT the rate ratio of gout for use of bendrofluazide vs placebo was 11.8 (95% CI 5.2-27.0). The other RCT found a rate ratio of 6.3 (95% CI 0.8-51) for use of hydrochlorothiazide plus triamterene vs placebo. Three cohort studies and 4 case-control studies found higher risks of gouty arthritis in users compared with nonusers of diuretics.

CONCLUSIONS

There is a trend toward a higher risk for acute gouty arthritis attacks in patients on loop and thiazide diuretics, but the magnitude and independence is not consistent. Therefore, stopping these useful drugs in patients who develop gouty arthritis is not supported by the results of this review.

Dietary intake and the risk of hyperuricemia, gout and chronic kidney disease in elderly Taiwanese men

INTRODUCTION

This study was conducted to examine the relationship between dietary intake and the risk of chronic kidney disease (CKD), treated hyperuricemia (or gout) without CKD, and untreated hyperuricemia without CKD in elderly men.

METHODS

The study population comprised 752 men aged 65 or older who had been included in the Elderly Nutrition and Health Survey (1999-2000) (Elderly NAHSIT).

RESULTS

Statistical analysis using a polychotomous logistic regression model revealed that compared with the individuals in the normouricemic group, the individuals in the other groups exhibited a significant association between a higher prevalence of CKD and the following factors: advanced age, drug use for hypertension, egg and shellfish consumption and consumption of poultry with the skin and meat with fat. The significant risk factors for the patients who did not have CKD and were undergoing treatment for hyperuricemia were as follows: BMI ≥ 25 kg/m(2); drug use for hypertension; intake of poultry with skin; increased daily consumption of shellfish, fried food, sugar and juice.

CONCLUSIONS

Men who use anti-hypertensive drugs and who consume fewer soy products and more shellfish may be at a higher risk of developing hyperuricemia or CKD.

Renal co-morbidity in patients with rheumatic diseases

Renal co-morbidity is common in patients with rheumatic disease based on regular assessment of serum and urine parameters of renal function. When patients present with both arthritis and renal abnormalities the following questions have to be addressed. Is kidney disease a complication of rheumatic disease or its management, or are they both manifestations of a single systemic autoimmune disease? Is rheumatic disease a complication of kidney disease and its management? How do rheumatic disease and kidney disease affect each other even when they are unrelated? The present review provides an overview of how to address these questions in daily practice.

New and improved strategies for the treatment of gout

The Western world appears to be in the midst of the third great gout epidemic of all time. In this century, gout is increasing in prevalence despite an increased understanding of its risk factors and pathophysiology, and the availability of reasonably effective treatment. The main cultural factors responsible for this appear to be diet, obesity, ethanol use and medications. Excess fructose consumption is a newly recognized modifiable risk factor. The debate has been renewed concerning hyperuricemia as an independent risk factor for renal insufficiency and cardiovascular disease. Prevention is still rooted in lifestyle choices. Existing treatments have proven to be unsatisfactory in many patients with comorbidities. New treatments are available today and on the horizon for tomorrow, which offer a better quality of life for gout sufferers. These include febuxostat, a nonpurine inhibitor of xanthine oxidase with a potentially better combination of efficacy and safety than allopurinol, and investigational inhibitors of URAT-1, an anion exchanger in the proximal tubule that is critical for uric acid homeostasis. New abortive treatments include interleukin-1 antagonists that can cut short the acute attack in 1 to 2 days in persons who cannot take nonsteroidal anti-inflammatory drugs, colchicine or corticosteroids. Lastly, newer formulations of uricase have the ability to dissolve destructive tophi over weeks or months in patients who cannot use currently available hypouricemic agents. Diagnostically, ultrasound and magnetic resonance imaging offer advanced ways to diagnose gout noninvasively, and just as importantly, a way to follow the progress of tophus dissolution. The close association of hyperuricemia with metabolic syndrome, hypertension and renal insufficiency ensures that nephrologists will see increasing numbers of gout-afflicted patients.

Phytochemicals from Acacia confusa heartwood extracts reduce serum uric acid levels in oxonate-induced mice: their potential use as xanthine oxidase inhibitors

In this study, the antihyperuricemic effect of Acacia confusa heartwood extracts and their phytochemicals on potassium oxonate (PO)-induced acute hyperuricemia was investigated for the first time. All treatments at the same dosage (100 mmol/kg) were administered to the abdominal cavity of PO-induced hyperuricemic mice, and serum uric acid level was measured at 3 h after administration. In experimental mice, serum uric acid level was significantly suppressed by the administration of A. confusa heartwood extracts and their major phytochemicals, (-)-2,3-cis-3,4-cis-3,3',4,4',7,8-hexahydroxyflavan, (-)-2,3-cis-3,4-cis-4'-methoxy-3,3',4,7,8-pentahydroxyflavan, melanoxetin, transilitin, and okanin, relative to the PO group. The direct inhibitory effect of these five compounds on xanthine oxidase (XOD) activity was examined using isothermal titration calorimetry (ITC). Among them, melanoxetin showed a more remarkable inhibitory effect on XOD activity than allopurinol, a clinical drug used for XOD inhibitor. To further understand the stereochemistry between XOD and melanoxetin (or allopurinol), structure-based molecular modeling was performed. Melanoxetin undergoes extended interactions in the hydrophobic region via the 3',4'-dihydroxyphenyl moiety, thus accounting for its higher binding affinity to XOD than allopurinol. These results indicate that A. confusa heartwood extracts and their major phytochemicals exhibit strong XOD inhibitory effects, which reduce serum uric acid levels while inhibiting uric acid generation in purine metabolism.