Serum Urate Research Articles

Causal association between uric acid levels and the risk of aortic aneurysm and aortic dissection: A two-sample Mendelian randomization study

Background and aimsIncreasing numbers of studies have sought to uncover the relationship between serum uric acid (UA) levels and the risk of aortic aneurysm (AA) or aortic dissection (AD), but the causality of the associations has not been established yet. To assess this potential relationship, we conducted a two-sample Mendelian randomization (MR) analysis. Methods and resultsWe performed two-sample Mendelian randomization (MR) analysis using independent genetic variants for UA levels from a published genome-wide association study (GWAS). Summary statistics for instrument-outcome associations from FinnGen database for AA and AD. Various sensitivity analyses were performed using different MR methods including random effects inverse variance weighting, fix effects inverse variance weighting, MR-Egger, weighted median/mode, and the contamination mixture method. Genetically predicted UA levels was associated with a higher AA risk (odds ratio (OR), 1.223; 95 % confidence interval (CI), 1.058–1.388; p = 0.017) in a simple size of 209,366 individuals. No association was found between uric acid levels and the risk of AD (OR,0.812; 95 % CI, 0.423–1.200; p = 0.293). ConclusionOur study suggests a significant and robust causal association between UA levels and risk of AA but did not support such a relationship between UA levels and AD risk, which might be interpreted with caution and further confirmed. These findings support a clinically relevant causal effect of serum urate levels on the risk of AA.

New xanthine oxidase inhibitor from white mulberry (Morus alba L.) – anti-gout prospective study

Abstract In recent years, Morus sp. (mulberry) has acquired a special importance due to its phytochemical composition and its beneficial effects on human health, including antioxidant, anticancer, antidiabetic and immuno-modulatory effects. The various parts of Morus sp., such as its fruits, leaves, twigs, and roots, are recognized as abundant sources of secondary metabolites, with the leaves containing significant amounts of glycosylated flavonols like quercetin and kaempferol, along with chlorogenic acid as the primary phenolic compound. Overall, it can be considered a multi utility plant and can be exploited as an alternative therapy in various ailments. Xanthine oxidase (XO) is the key enzyme for high serum urate levels which is the main cause of developing gout. Under the urate lowering therapy, allopurinol and febuxostat are the main XO inhibitors used to treat gout. However, mild to severe side effects of these synthetic XO inhibitors lead to finding an effective natural alternative without having any side effects. The present study was designed to find out phytochemical analysis and antigout properties of leaves of white mulberry plant. The phytochemical analysis was performed on quantitative and qualitative basis. The qualitative basis indicated the presence of alkaloids, glycosides, flavonoids, steroids, tannins, saponins and Anthraquinone. Biochemical regulation of extracts on anti-gout property using XO inhibition study. Microbial XO was isolated from the Bacillus pumilus to study the anti-gout effects of plant extracts qualitatively on xanthine – NBT plate. Additionally, image analysis studies revealed more clear aspects toward the inhibition studies by plant extracts. The XO activity observed varied from 2.89 to 13.80 μM of uric acid formed/min/ml of enzyme used. Ethanolic extract of mulberry leaves (EEML) showed higher XO inhibition than allopurinol. This is associated with its total polyphenol content, which ranged from 81.25 to 103.12 mg GAE/g of dried extract used, as reported in the case of EEML. The present study is the very first report of relating polyphenol content of EEML with the anti-gout property. EEML is a potential candidate for anti-gout property due to the presence of higher amounts of total polyphenol content and B. pumilus is the best source to extract microbial XO.

Involvement of the vagus nerve and hepatic gene expression in serum adiponectin concentrations in mice.

Several humoral factors, such as adiponectin and urate, have been suggested to affect metabolic syndromes. Previously, we reported a reduction in blood adiponectin concentrations after a high-fructose diet partially via the vagus nerve in rats. Although a lithogenic diet (LD), i.e., supplementation of a normal control diet (CT) with 0.6% cholesterol and 0.2% sodium cholate, reduced blood adiponectin concentrations, the involvement of the vagus nerve in this mechanism remains unclear. To estimate the involvement of the vagus nerve in the regulation of blood adiponectin concentrations using an LD, male imprinting control region mice that had been vagotomized (HVx) or only laparotomized (Sham) were administered a CT or an LD for 10weeks. Serum adiponectin concentrations in the Sham-LD, HVx-CT, and HVx-LD groups were reduced by half compared with the Sham-CT group. The hepatic mRNA levels of fibroblast growth factor 21 (Fgf21), which reportedly stimulates adiponectin secretion from white adipose tissue, were lower in the LD groups compared with the CT groups. HepG2 hepatoma cells showed that various bile acids reduced the mRNA expression of FGF21. Moreover, the LD increased serum urate concentrations and reduced hepatic expressions of the acyl-CoA oxidase 1 (Acox1) mRNA and glucokinase, suggesting insufficient regeneration of ATP from AMP. In conclusion, serum adiponectin concentration may be regulated via the vagus nerve in normal mice, whereas a reduction of hepatic Fgf21 mRNA by bile acids may also lower serum adiponectin levels. Moreover, the LD may promote hepatic AMP accumulation and subsequently increase the serum urate concentration in mice.

Emerging Urate-Lowering Drugs and Pharmacologic Treatment Strategies for Gout: A Narrative Review.

Hyperuricemia with consequent monosodium urate crystal deposition leads to gout, characterized by painful, incapacitating inflammatory arthritis flares that are also associated with increased cardiovascular event and related mortality risk. This narrative review focuses on emerging pharmacologic urate-lowering treatment (ULT) and management strategies in gout. Undertreated, gout can progress to palpable tophi and joint damage. In oral ULT clinical trials, target serum urate of < 6.0 mg/dL can be achieved in ~ 80-90% of subjects, with flare burden reduction by 1-2 years. However, real-world ULT results are far less successful, due to both singular patient nonadherence and prescriber undertreatment, particularly in primary care, where most patients are managed. Multiple dose titrations commonly needed to optimize first-line allopurinol ULT monotherapy, and substantial potential toxicities and other limitations of approved, marketed oral monotherapy ULT drugs, promote hyperuricemia undertreatment. Common gout comorbidities with associated increased mortality (e.g., moderate-severe chronic kidney disease [CKD], type 2 diabetes, hypertension, atherosclerosis, heart failure) heighten ULT treatment complexity and emphasize unmet needs for better and more rapid clinically significant outcomes, including attenuated gout flare burden. The gout drug armamentarium will be expanded by integrating sodium-glucose cotransporter-2 (SGLT2) inhibitors with uricosuric and anti-inflammatory properties as well as clinically indicated antidiabetic, nephroprotective, and/or cardioprotective effects. The broad ULT developmental pipeline is loaded with multiple uricosurics that selectively target uric acid transporter 1 (URAT1). Evolving ULT approaches include administering selected gut anaerobic purine degrading bacteria (PDB), modulating intestinal urate transport, and employing liver-targeted xanthine oxidoreductase mRNA knockdown. Last, emerging measures to decrease the immunogenicity of systemically administered recombinant uricases should simplify treatment regimens and further improve outcomes in managing the most severe gout phenotypes.

Causal Relationship between Gut Microbiota and Gout: A Two-Sample Mendelian Randomization Study.

Gout is a form of prevalent and painful inflammatory arthritis characterized by elevated serum urate (SUA) levels. The gut microbiota (GM) is believed to influence the development of gout and SUA levels. Our study aimed to explore the causal relationship between GM composition and gout, as well as SUA levels, utilizing a two-sample Mendelian Randomization (MR) approach. A total of 196 GM taxa from five levels were available for analysis. We identified five taxa associated with SUA levels and 10 taxa associated with gout. In reverse MR analysis, we discovered that gout affected the composition of five GM taxa, while SUA levels influenced the composition of 30 GM taxa. Combining existing research, our study unveiled a potential negative feedback loop between phylum Actinobacteria and SUA levels, establishing connections with gout. We also proposed two novel associations connecting GM taxa (genus Faecalibacterium and genus Prevotella9), SUA levels, and gout. These findings provide compelling evidence of causal relationships between specific GM taxa with SUA levels and gout, contributing valuable insights for the treatment of gout.

Prediction of renal and cardiometabolic outcomes in gout during urate-lowering therapy by sonography.

To assess whether the extent of monosodium urate (MSU) crystal deposition estimated by ultrasound could predict renal and cardiometabolic events during urate-lowering therapy (ULT). A prospective study on gout patients from two referral centers initiating ULT who underwent baseline ultrasound and were followed for 1 year. Ultrasound scans assessed six joints for double-contour (DC) signs and tophi. A five-point change (mL/min/1.73 m2 ) in the glomerular filtration rate at month 12 (M12) was considered significant. Outcomes of interest were renal function degraded versus improved and a composite cardiometabolic outcome (new hypertension, diabetes, atherosclerotic disease, and cardiovascular death). Homogeneity analyses and Cox regression models were performed. One hundred sixty patients were recruited. At baseline, 81.1% of patients (n = 129) showed sonographic tophi with a mean number of 1.4 joints (±1.3) with a DC sign. At M12, 18 patients (11.3%) were lost to follow-up. The serum urate (SU) target (<6.0 mg/dL) was reached in 86 patients (69.9%). Regarding renal function, 15.9% of patients showed improvement, while in 31.0% it degraded. Fourteen new cardiometabolic events occurred in 12 patients. Neither the DC sign nor tophi showed any significant impact on the outcomes of interest. Baseline SU level was higher in those with renal improvement but not with renal decline, while achieving the SU target protected against new cardiometabolic events (HR = 0.2; 95% CI: 0.05-0.81). Sonographic MSU crystal burden was unhelpful in predicting renal and cardiometabolic events during the first year of ULT. Reaching the SU target prevented cardiometabolic events, while its benefit in preserving/improving renal function is unclear.

The non-causative role of abnormal serum uric acid in intervertebral disc degeneration: A Mendelian randomization study.

Intervertebral disc degeneration (IDD) is a common musculoskeletal disorder that contributes significantly to disability and healthcare costs. Serum urate concentration has been implicated in the development of various musculoskeletal conditions. While previous observational studies have suggested an association between the two conditions, it might confound the effect of serum urate concentrations on IDD. This Mendelian randomization (MR) study aimed to investigate the causal relationship between serum urate concentration and IDD. We performed a two-sample MR analysis using summary-level data from genome-wide association studies (GWAS) of serum urate concentration (n = 13 585 994 European ancestry) and IDD (n = 16 380 337 European ancestry). Single nucleotide polymorphisms (SNPs) significantly associated with serum urate concentration (p < 5 × 10-8) were selected as instrumental variables. The associations between genetically predicted serum urate concentration and IDD were estimated using the inverse-variance weighted (IVW) method, with sensitivity analyses employing the weighted median, MR-Egger, and MR-PRESSO approaches to assess the robustness of the findings. In the primary IVW analysis, genetically predicted serum urate concentration was unrelated associated with IDD (odds ratio [OR] = 1.00, 95% confidence interval (CI): 1.00-1.00, p = 0.17)). The results remained consistent across the sensitivity analyses, and no significant directional pleiotropy was detected (MR-Egger intercept: p = 0.15). This MR study provides evidence that there is no causal relationship between serum urate concentration and IDD. It suggests previous observational associations may be confounded. Serum urate levels are unlikely to be an important contributor to IDD.

Patient factors and health outcomes associated with illness perceptions in people with gout.

Illness perceptions are views and beliefs formed in response to a health threat, and they may influence self-management behaviours and chronic disease outcomes. Despite effective medication, sub-optimal outcomes in gout are common. This study aimed to quantitatively investigate illness perceptions in gout to examine how illness perceptions relate to health outcomes. Data were obtained from a randomized controlled trial in which people with gout (n = 493) completed surveys measuring illness perceptions [Brief Illness Perception Questionnaire (B-IPQ)], gout flares, medication adherence, health-related quality of life, health-care utilization, and productivity, alongside serum urate blood tests at baseline, and at 6- and 12-month follow-ups. Multivariable linear regression identified patient factors independently associated with each B-IPQ item score. Logistic and linear regression, adjusted for age and sex, determined whether baseline B-IPQ items could predict current and future health outcomes. Younger individuals and those with severe gout were more likely to experience pessimistic illness perceptions at baseline. Optimistic illness perceptions were associated with lower odds of having had at least one flare in the preceding 6 months. Every 1-point increase in B-IPQ treatment control, indicating an increasingly optimistic view that gout is treatable, decreased the odds of a recent flare prior to baseline by 33% [odds ratio (OR): 0.67; 95% CI: 0.53, 0.85; P < 0.001] and prior to the 12-month follow-up by 15% (OR: 0.85; 95% CI: 0.76,0.96; P = 0.01). Pessimistic illness perceptions also predicted poorer medication adherence, health-related quality of life, and productivity, but not serum urate levels. Modifying pessimistic illness perceptions, including, but not limited to, patient education, may promote prudent self-management behaviours and better outcomes in gout. Australian New Zealand Clinical Trials Registry; https://www.anzctr.org.au/, ACTRN12616000455460.

Association between specific ultrasound features of joints and impaired kidney function among gout patients.

To investigate the relationship between the specific ultrasonic manifestations of lower limb joints and impaired kidney function in gouty arthritis. In this cross-sectional study, 408 patients with gouty arthritis were divided into two groups based on the status of renal function: normal group (n = 240) and renal impairment (n = 168) group. All patients underwent ultrasound examination of the bilateral knee, ankle, and first metatarsophalangeal joints to detect ultrasound features of double-contour sign (DC) and tophus. Multiple logistic regression analysis was conducted to assess the association between kidney dysfunction and ultrasound features. A number of potential clinical confounders were adjusted in the model. Univariable conditional logistic regression produces several significant risk factors of impaired kidney function which were the highest and current lever of serum urate acid, course of disease, frequency of attack, hyperlipidemia, hypertension, diabetes, coronary heart disease, presence of multiple tophus, and DC (P < 0.05). After correcting the course of disease and other risk factors, tophus was still an independent risk factor of impaired kidney function and the multivariable adjusted odds ratios (95% CI) was 1.789 (1.005-3.185, P = 0.05), however, the association was not significant in DC (OR = 1.098, 95% CI: 0.668-1.803, P = 0.71). The ultrasound feature of tophus was associated with kidney dysfunction in patients with gout, independent of clinical risk factors, which may be helpful in guiding clinical practice.

Hyperuricemia remodels the serum proteome toward a higher inflammatory state

Gout is an autoinflammatory disease triggered by a complex innate immune response to MSU crystals and inflammatory triggers. While hyperuricemia is an obligatory risk factor for the development of gout, the majority of individuals with hyperuricemia never develop gout but have an increased risk of developing cardiometabolic disorders. Current management of gout aims at MSU crystal dissolution by lowering serum urate. We apply a targeted proteomic analysis, using Olink inflammation panel, to a large group of individuals with gout, asymptomatic hyperuricemia, and normouricemic controls, and we show a urate-driven inflammatory signature. We add invivo evidence of persistent immune activation linked to urate exposure and describe immune pathways involved in the pathogenesis of gout. Our results support a pro-inflammatory effect of asymptomatic hyperuricemia and pave the way for new research into targetable mechanisms in gout and cardiometabolic complications of asymptomatic hyperuricemia.

The Stiff Joint: Comparative Evaluation of Monotherapy and Combination Therapy With Urate Lowering Agents in Managing Acute Gout.

Gout, an extremely painful form of arthritis, is triggered by the innate immune system's response to the accumulation of monosodium urate crystals in specific joints and surrounding tissues. This condition is characterized by recurring episodes of excruciating arthritis flares, interspersed with periods of disease quiescence. Over time, gout can result in disability, tophi formation, and severe pain. The treatment of gout is centered around two main objectives: alleviating inflammation and pain during acute gout attacksand long-term management to reduce serum urate levels and mitigate the risk of future attacks. Addressing inflammation and pain during acute attacks is often complicated by various factors, including underlying health conditions commonly associated with gout, such as hypertension, chronic kidney disease, cardiovascular disease, and diabetes mellitus. Moreover, gout patients are frequently older and have multiple coexisting health issues, necessitating complex medication regimens. Given the rising prevalence of gout and its associated comorbidities, there's a growing demand for improved treatment options. While existing treatments effectively manage gout in some patients, a significant portion, particularly those with comorbidities, face contraindications to these treatments and require alternative approaches. Innovative medications are required to enhance gout treatment, especially for individuals with concurrent health conditions. These considerations underscore the importance of reviewing both monotherapy and combination therapy approaches for acute gout treatment.

The Tophus Impact Questionnaire (TIQ-20): responsiveness to change during urate-lowering therapy.

In 2015, the 20-item Tophus Impact Questionnaire (TIQ-20) was developed as a tophus-specific patient-reported outcome measure. The aim of this study was to determine whether TIQ-20 scores change during urate-lowering therapy. We analysed data from a 2-year clinical trial of allopurinol dose escalation using a treat-to-target serum urate approach. For participants with tophaceous gout, the longest diameter of up to three index tophi was measured, using Vernier calipers, and the TIQ-20 was recorded at study visits. Participants at the one site were invited to participate in a dual-energy CT (DECT) substudy. Participants were included in this analysis if they had tophaceous gout and TIQ-20 scores available at baseline, Year 1 and Year 2 (n = 58, 39 with DECT data). Data were analysed using a mixed-model approach to repeated measures. Improvements were observed in all tophus measures over the 2-year period. The mean (s.d.) TIQ-20 scores reduced over 2 years from 3.59 (1.77) to 2.46 (1.73), P < 0.0001, and the mean (95% CI) TIQ-20 change over the 2 years was -1.13 (-1.54, -0.71). The effect size (Cohen's d) for the change in the sum of the index tophi diameter over 2 years was 0.68, for the DECT urate volume was 0.50, and for the TIQ-20 was 0.71. For people with tophaceous gout treated with allopurinol using a treat-to-target serum urate approach, improvements in TIQ-20 occurred, as did improvements in physical and imaging tophus measures. These findings demonstrate that the TIQ-20 is a responsive patient-reported instrument of tophus impact.

Mechanisms and rationale for uricase use in patients with gout.

Xanthine oxidase inhibitors such as allopurinol and febuxostat have been the mainstay urate-lowering therapy (ULT) for treating hyperuricaemia in patients with gout. However, not all patients receiving oral ULT achieve the target serum urate level, in part because some patients cannot tolerate, or have actual or misconceived contraindications to, their use, mainly due to comorbidities. ULT dosage is also limited by formularies and clinical inertia. This failure to sufficiently lower serum urate levels can lead to difficult-to-treat or uncontrolled gout, usually due to poorly managed and/or under-treated gout. In species other than humans, uricase (urate oxidase) converts urate to allantoin, which is more soluble in urine than uric acid. Exogenic uricases are an exciting therapeutic option for patients with gout. They can be viewed as enzyme replacement therapy. Uricases are being used to treat uncontrolled gout, and can achieve rapid reduction of hyperuricaemia, dramatic resolution of tophi, decreased chronic joint pain and improved quality of life. Availability, cost and uricase immunogenicity have limited their use. Uricases could become a leading choice in severe and difficult-to-treat gout as induction and/or debulking therapy (that is, for lowering of the urate pool) to be followed by chronic oral ULT. This Review summarizes the evidence regarding available uricases and those in the pipeline, their debulking effect and their outcomes related to gout and beyond.

Efficacy and safety of tart cherry supplementary citrate mixture on gout patients: a prospective, randomized, controlled study

BackgroundLow urine pH, which may be mediated by metabolic syndrome (MetS), is common in gout. Tart cherries are shown to improve MetS symptoms and possess anti-inflammatory properties. However, the efficacy of tart cherry supplements on urine pH has yet to be studied.ObjectivesThis study aimed to investigate the efficacy and safety of tart cherry supplementary citrate (TaCCi) mixture on urine pH, serum urate (sUA), C-reactive protein (CRP), and gout flares in gout patients initiating urate-lowering therapy (ULT), in comparison to citrate mixture and sodium bicarbonate.MethodsA prospective, randomized (1:1:1), open-label, parallel-controlled trial was conducted among 282 men with gout and fasting urine pH ≤ 6, who were initiating ULT with febuxostat (initially 20 mg daily, escalating to 40 mg daily if serum urate ≥ 360 μmol/L). Participants were randomized to groups taking either sodium bicarbonate, citrate mixture, or TaCCi mixture. All participants were followed every 4 weeks until week 12. Urine pH and sUA were co-primary outcomes, with various biochemical and clinical secondary endpoints.ResultsUrine pH increased to a similar extent in all three groups. SUA levels declined in all three groups as well, with no significant differences observed between the groups. At week 12, the TaCCi mixture group exhibited a greater reduction in the urine albumin/creatinine ratio (UACR) compared to the other two groups (p < 0.05). Participants taking TaCCi mixture or citrate mixture experienced fewer gout flares than those in the sodium bicarbonate group over the study period (p < 0.05). Additionally, the TaCCi mixture group had a lower CRP level at week 12 relative to the other two groups (p < 0.01). Adverse events were similar across all three groups.ConclusionThe TaCCi mixture had similar efficacy and safety on urine alkalization and sUA-lowering as the citrate mixture and sodium bicarbonate in patients with gout. However, the TaCCi mixture resulted in greater improvements in UACR and CRP, which suggests that tart cherry supplements may provide additional benefits for renal protection and reduce inflammation in gout, particularly when starting ULT.Trial registrationThis project was registered in ChiCTR (www.chictr.org.cn), with the registration number: ChiCTR2100050749.

The Effect of Decrease in Serum Urate for the Risk of Gout Flares During Urate-Lowering Therapy Initiation Among Chinese Male Gout Patients: A Prospective Cohort Study.

Higher baseline serum urate or higher initial urate-lowering medication dose increased risk of gout flares during urate-lowering therapy (ULT) initiation. The decrease in serum urate may play a crucial role in this process. Therefore, we aim to explore the relationship between decrease in serum urate and the risk of gout flares during ULT initiation. A 12-week prospective cohort study of Chinese male gout patients was conducted at Shandong Provincial Clinical Research Center for Immune Diseases and Gout in China. Patients were grouped by baseline serum urate (7-7.9 mg/dL, 8-8.9 mg/dL and ≥9 mg/dL). All patients received febuxostat 20 mg daily during weeks 0-4, then escalated to 40mg during weeks 4-12 if serum urate >6mg/dL. The main outcomes were the number of gout flares and the decrease in serum urate. Poisson regression was performed. A total of 282 participants were enrolled, of whom 260 completed (84, 87 and 89 in each group) from March 2021 to December 2021. A 44.2% of all participants experienced at least one gout flare. In the multivariate Poisson regression 1, Δ serum urate 0-12 weeks (IRR 1.184, 95% CI, 1.062-1.320; P=0.002), the number of gout flares before treatment 1 year (1.017, 1.010-1.024; P<0.001) and tophus (1.580, 1.023-2.440; P=0.039) were independently associated with the number of gout flares. While in the multivariate Poisson regression 2, baseline serum urate (1.256, 1.050-1.503; P=0.013) and the number of gout flares before treatment 1 year (1.014, 1.007-1.022; P<0.001) were independently associated with the number of gout flares, Δ serum urate 0-12 weeks (1.055, 0.923-1.207; P=0.433) was no longer a risk factor. ULT-induced gout flares depend on the degree of decrease in serum urate, which is affected by baseline serum urate. Higher baseline serum urate and greater decrease in serum urate lead to higher risk of gout flares.

Is colchicine prophylaxis required with start-low go-slow allopurinol dose escalation in gout? A non-inferiority randomised double-blind placebo-controlled trial

ObjectivesTo determine whether placebo is non-inferior to low-dose colchicine for reducing gout flares during the first 6 months of allopurinol using the ‘start-low go-slow’ dose approach.MethodsA 12-month double-blind, placebo-controlled non-inferiority...

Glutathione-Mediated Neuroprotective Effect of Purine Derivatives.

Numerous basic studies have reported on the neuroprotective properties of several purine derivatives such as caffeine and uric acid (UA). Epidemiological studies have also shown the inverse association of appropriate caffeine intake or serum urate levels with neurodegenerative diseases such as Alzheimer disease (AD) and Parkinson's disease (PD). The well-established neuroprotective mechanisms of caffeine and UA involve adenosine A2A receptor antagonism and antioxidant activity, respectively. Our recent study found that another purine derivative, paraxanthine, has neuroprotective effects similar to those of caffeine and UA. These purine derivatives can promote neuronal cysteine uptake through excitatory amino acid carrier protein 1 (EAAC1) to increase neuronal glutathione (GSH) levels in the brain. This review summarizes the GSH-mediated neuroprotective effects of purine derivatives. Considering the fact that GSH depletion is a manifestation in the brains of AD and PD patients, administration of purine derivatives may be a new therapeutic approach to prevent or delay the onset of these neurodegenerative diseases.

Lactiplantibacillus plantarum enables blood urate control in mice through degradation of nucleosides in gastrointestinal tract

BackgroundLactobacillus species in gut microbiota shows great promise in alleviation of metabolic diseases. However, little is known about the molecular mechanism of how Lactobacillus interacts with metabolites in circulation. Here, using high nucleoside intake to induce hyperuricemia in mice, we investigated the improvement in systemic urate metabolism by oral administration of L. plantarum via different host pathways.ResultsGene expression analysis demonstrated that L. plantarum inhibited the activity of xanthine oxidase and purine nucleoside phosphorylase in liver to suppress urate synthesis. The gut microbiota composition did not dramatically change by oral administration of L. plantarum over 14 days, indicated by no significant difference in α and β diversities. However, multi-omic network analysis revealed that increase of L. plantarum and decrease of L. johnsonii contributed to a decrease in serum urate levels. Besides, genomic analysis and recombinant protein expression showed that three ribonucleoside hydrolases, RihA–C, in L. plantarum rapidly and cooperatively catalyzed the hydrolysis of nucleosides into nucleobases. Furthermore, the absorption of nucleobase by intestinal epithelial cells was less than that of nucleoside, which resulted in a reduction of urate generation, evidenced by the phenomenon that mice fed with nucleobase diet generated less serum urate than those fed with nucleoside diet over a period of 9-day gavage.ConclusionCollectively, our work provides substantial evidence identifying the specific role of L. plantarum in improvement of urate circulation. We highlight the importance of the enzymes RihA–C existing in L. plantarum for the urate metabolism in hyperuricemia mice induced by a high-nucleoside diet. Although the direct connection between nucleobase transport and host urate levels has not been identified, the lack of nucleobase transporter in intestinal epithelial cells might be important to decrease its absorption and metabolization for urate production, leading to the decrease of serum urate in host. These findings provide important insights into urate metabolism regulation.BbgstkDZoHsJm_QsUh-oZNVideo

The Impact of Uric Acid on Human Health: Beyond Gout and Kidney Stones

AbstractIn most primates, including humans, uric acid (UA) is the end product of purine metabolism due to the loss of hepatic uricase activity during evolution. This loss resulted in higher serum urate concentrations (3.5–7.5 mg/dL) than normally observed in other mammals (0.05–2 mg/dL). About 70% of the daily urate burden is eliminated via the kidneys and the remainder via the intestines, where gut bacteria break it down. Urate is freely filtered through the glomerular capillaries, and most of the filtered urate is reabsorbed so that only an amount equivalent to about 10% of the filtered load is excreted in the urine. Virtually all of the renal urate reabsorption takes place in proximal convoluted tubules. Many transport proteins connected with urate have been identified. However, the best studied are URAT1 and GLUT9, which function in concert to translocate urate from the proximal tubule lumen to the peritubular fluid, the first in the apical membrane and the second in the basolateral membrane. Genetic mutations, as well as drugs that alter the function of these transporters, can affect urate homeostasis resulting in abnormal serum levels, which may, in turn, be involved in the pathogenesis of chronic metabolic and inflammatory diseases, including most features of the metabolic syndrome, hypertension, cardiovascular disease, and chronic kidney disease. Several mechanisms are thought to provide the link between urate and these disorders, including reactive oxygen species (oxidative stress) and both acute and chronic inflammation. This mini-review summarizes the basic human biology of UA and its association with and potential involvement in developing chronic diseases beyond gout and nephrolithiasis.

Prediagnostic Glycoprotein Acetyl Levels and Incident and Recurrent Flare Risk Accounting for Serum Urate Levels: A Population-Based, Prospective Study and Mendelian Randomization Analysis.

To prospectively investigate population-based metabolomics for incident gout and reproduce the findings for recurrent flares, accounting for serum urate. We conducted a prediagnostic metabolome-wide analysis among 105,615 UK Biobank participants with nuclear magnetic resonance metabolomic profiling data (168 total metabolites) from baseline blood samples collected 2006-2010 in those without history of gout. We calculated hazard ratios (HRs) for incident gout, adjusted for gout risk factors, excluding and including serum urate levels, overall and according to fasting duration before sample collection. Potential causal effects were tested with 2-sample Mendelian randomization. Poisson regression was used to calculate rate ratios (RRs) for the association with recurrent flares among incident gout cases. Correcting for multiple testing, 88 metabolites were associated with risk of incident gout (N=1,303 cases) before serum urate adjustment, including glutamine and glycine (inversely), and lipids, branched-chain amino acids, and most prominently, glycoprotein acetyls (GlycA; P = 9.17 × 10-32 ). Only GlycA remained associated with incident gout following urate adjustment (HR 1.52 [95% confidence interval (95% CI) 1.22-1.88] between extreme quintiles); the HR increased progressively with fasting duration before sample collection, reaching 4.01 (95% CI 1.36-11.82) for ≥8 hours of fasting. Corresponding HRs per SD change in GlycA levels were 1.10 (95% CI 1.04-1.17) overall and 1.54 (95% CI 1.21-1.96) for ≥8 hours of fasting. GlycA levels were also associated with recurrent gout flares among incident gout cases (RR 1.90 [95% CI 1.27-2.85] between extreme quintiles) with larger associations with fasting. Mendelian randomization corroborated a potential causal role for GlycA on gout risk. This prospective, population-based study implicates GlycA, a stable long-term biomarker reflecting neutrophil overactivity, in incident and recurrent gout flares (central manifestation from neutrophilic synovitis) beyond serum urate.