An update on the genetic architecture of hyperuricemia and gout

Role of HIF1A gene polymorphisms with serum uric acid and HIF-1α levels in monosodium urate crystal-induced arthritis

BACKGROUND

Gouty arthritis is a metabolic disease characterized by the deposition of monosodium urate crystals in the joints, which triggers the release of interleukin-1β (IL-β) by activating the NLRP3 inflammasome. Hypoxia-inducible factor-1α (HIF-1α) is a transcription factor involved in IL-β production and as a regulator of NLRP3.

OBJECTIVES

The aims were to analyze the association of HIF1A rs11549465, rs11549467, and rs2057482 variants in patients with gouty arthritis, and to evaluate the correlation between urate and HIF-1α levels according to the associated genotypes.

METHODS

Cases and controls were genotyped using TaqMan probes, and urate and HIF-1α levels were quantified. Data were analyzed using SPSS v21 software and P-values < 0.05 were considered statistically significant.

RESULTS

Urate and HIF-1α levels were higher in patients than in controls (P < 0.05). Under the three inheritance models (codominant, dominant, and recessive), the AA genotype of the rs11549467 variant was associated with gout risk (OR = 5.74, P = 0.009, OR = 3.33, P = 0.024, and OR = 9.09, P = 0.003, respectively). There were significant differences in the distribution of serum levels of both HIF-1α (P < 0.0001) and urate (P = 0.016) according to the genotypes of the rs11549467 variant.

CONCLUSION

These results suggest that the HIF1A rs11549467 variant may play a key role in the pathogenesis of gouty arthritis. Key Points • The pathogenesis of gouty arthritis involves the HIF1A gene. • In patients with gout, the AA genotype of the rs11549467 (HIF1A) variant is associated with increased serum levels of urate and HIF-1α. • HIF-1α is involved in the regulation of IL-1β and NLRP3.

Serum uric acid and pulmonary arterial hypertension: A two-sample Mendelian randomization study

BACKGROUND

Observational studies have suggested a correlation between hyperuricemia and pulmonary arterial hypertension (PAH), yet the causal relationship remains uncertain. We aimed to establish this link using Mendelian Randomization (MR) methods.

OBJECTIVES

Based on publicly accessible data, our study employs MR to determine the causal relationship between uric acid (UA) and PAH.

METHOD

MR analysis was conducted among individuals of European descent. Genetic instruments linked to UA (p-value < 5 × 10-8) were extracted from the Chronic Kidney Disease Genetic Consortium and genome-wide association study databases. PAH risk genetic associations were sourced separately. We employed four MR methods (MR-Egger, weighted median, inverse variance weighted, and weighted mode) with selected instrumental variables to assess the causal association between UA and PAH. MR-PRESSO was used to evaluate pleiotropy and outlier Single Nucleotide Polymorphisms (SNPs), while Cochran's Q test and funnel plot assessed SNP heterogeneity. Leave-one-out analysis examined SNP impacts on causal assessment.

RESULT

Two-sample MR analysis revealed a positive, causal relationship between UA levels and PAH.

CONCLUSION

Our MR analysis provides robust evidence of a causal link between serum UA and PAH, suggesting UA's potential as a biomarker and therapeutic target for PAH.

The impact of chrysanthemi indici flos-enriched flavonoid part on the model of hyperuricemia based on inhibiting synthesis and promoting excretion of uric acid

ETHNOPHARMACOLOGICAL RELEVANCE

In recent years, in addition to hypertension, hyperglycemia, and hyperlipidemia, the prevalence of hyperuricemia (HUA) has increased considerably. Being the fourth major health risk factor, HUA can affect the kidneys and cardiovascular system. Chrysanthemi Indici Flos is a flavonoid-containing traditional Chinese patent medicine that exhibits a uric acid (UA)-lowering effect. However, the mechanisms underlying Chrysanthemi Indici Flos-enriched flavonoid part (CYM.E) mediated alleviation of HUA remain unelucidated.

AIM OF THE STUDY

This study aimed to elucidate the efficacy of CYM.E in preventing and treating HUA and its specific effects on UA-related transport proteins, to explore possible mechanism.

METHODS

The buddleoside content in CYM.E was determined through high-performance liquid chromatography. HUA was induced in mice models using adenine and potassium oxonate. Subsequently, mice were administered 10 mg/kg allopurinol, and 30, 60, and 90 mg/kg CYM.E to evaluate the effects of CYM.E on the of HUA mice model. Herein, plasma uric acid (UA), creatinine (CR), blood urea nitrogen (BUN), total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-c), and low-density lipoprotein cholesterol (LDL-c) contents, along with serum alanine aminotransferase (ALT), and aspartate aminotransferase (AST) activities were measured. Additionally, xanthine oxidase (XOD) and adenosine deaminase (ADA) activities in the liver were determined. The histomorphologies of the liver and kidney tissues were examined through hematoxylin and eosin staining. The messenger RNA (mRNA) expression of facilitated glucose transporter 9 (GLUT9), organic anion transporter (OAT)1, OAT3, and adenosine triphosphate binding cassette subfamily G2 (ABCG2) in the kidney was assessed by real-time quantitative polymerase chain reaction. Furthermore, the expression of urate transporter 1 (URAT1), GLUT9, OAT1, and OAT3 in the kidney, OAT4, and ABCG2 proteins was determined by immunohistochemistry and western blotting.

RESULTS

The buddleoside content in CYM.E was approximately 32.77%. CYM.E improved body weight and autonomous activity in HUA mice. Additionally, it reduced plasma UA, BUN, and CR levels and serum ALT and AST activities, thus improving hepatic and renal functions, which further reduced the plasma UA content. CYM.E reduced histopathological damage to the kidneys. Furthermore, it lowered plasma TC, TG, and LDL-c levels, thereby improving lipid metabolism disorder. CYM.E administration inhibited hepatic XOD and ADA activities and reduced the mRNA expression of renal GLUT9. CYM.E inhibited the protein expression of renal URAT1, GLUT9, and OAT4, and increased the mRNA and protein expression of renal OAT1, OAT3, and ABCG2. Altogether, these results show that CYM.E could inhibit the production and promote reabsorption of UA and its excretion.

Mechanism of macrophages in gout: Recent progress and perspective

Gout represents an autoinflammatory disorder instigated by monosodium urate crystals. Its primary manifestation involves the recruitment of diverse immune cell populations, including neutrophils and macrophages. Macrophages assume a pivotal role in the initiation of acute gouty inflammation and subsequent inflammatory cascades. However, recent investigations have revealed that the impact of macrophages on gout is nuanced, extending beyond a solely detrimental influence. Macrophages, characterized by different subtypes, exhibit distinct functionalities that either contribute to the progression or regression of gout. A strategy aimed at modulating macrophage polarization, rather than merely inhibiting inflammation, holds promise for enhancing the efficacy of acute gout treatment. This review centres on elucidating potential mechanisms underlying macrophage polarization in the onset and resolution of gouty inflammation, offering novel insights into the immune equilibrium of macrophages in the context of gout.

A combination of red and processed meat intake and polygenic risk score influences the incidence of hyperuricemia in middle-aged Korean adults

BACKGROUND/OBJECTIVES

The high consumption of purine-rich meat is associated with hyperuricemia. However, there is limited evidence linking the consumption of red and processed meat to the genetic risk of hyperuricemia. We investigated the relationship between various combinations of red and processed meat consumption and the polygenic risk scores (PRSs) and the incidence of hyperuricemia in middle-aged Koreans.

SUBJECTS/METHODS

We analyzed the data from 44,053 participants aged ≥40 years sourced from the Health Examinees (HEXA) cohort of the Korean Genome and Epidemiology Study (KoGES). Information regarding red and processed meat intake was obtained using a semiquantitative food frequency questionnaire (SQ-FFQ). We identified 69 independent single-nucleotide polymorphisms (SNPs) at uric acid-related loci using genome-wide association studies (GWASs) and clumping analyses. The individual PRS, which is the weighted sum of the effect size of each allele at the SNP, was calculated. We used multivariable Cox proportional hazards models adjusted for covariates to determine the relationship between red and processed meat intake and the PRS in the incidence of hyperuricemia.

RESULTS

During an average follow-up period of 5 years, 2,556 patients with hyperuricemia were identified. For both men and women, the group with the highest red and processed meat intake and the highest PRS was positively associated with the development of hyperuricemia when compared with the group with the lowest red and processed meat intake and the lowest PRS (hazard ratio [HR], 2.72; 95% confidence interval [CI], 2.10-3.53; P < 0.0001; HR, 3.28; 95% CI, 2.45-4.40; P < 0.0001).

CONCLUSION

Individuals at a high genetic risk for uric acid levels should moderate their consumption of red and processed meat to prevent hyperuricemia.

Hyperuricemia and its related diseases: mechanisms and advances in therapy

Hyperuricemia, characterized by elevated levels of serum uric acid (SUA), is linked to a spectrum of commodities such as gout, cardiovascular diseases, renal disorders, metabolic syndrome, and diabetes, etc. Significantly impairing the quality of life for those affected, the prevalence of hyperuricemia is an upward trend globally, especially in most developed countries. UA possesses a multifaceted role, such as antioxidant, pro-oxidative, pro-inflammatory, nitric oxide modulating, anti-aging, and immune effects, which are significant in both physiological and pathological contexts. The equilibrium of circulating urate levels hinges on the interplay between production and excretion, a delicate balance orchestrated by urate transporter functions across various epithelial tissues and cell types. While existing research has identified hyperuricemia involvement in numerous biological processes and signaling pathways, the precise mechanisms connecting elevated UA levels to disease etiology remain to be fully elucidated. In addition, the influence of genetic susceptibilities and environmental determinants on hyperuricemia calls for a detailed and nuanced examination. This review compiles data from global epidemiological studies and clinical practices, exploring the physiological processes and the genetic foundations of urate transporters in depth. Furthermore, we uncover the complex mechanisms by which the UA induced inflammation influences metabolic processes in individuals with hyperuricemia and the association with its relative disease, offering a foundation for innovative therapeutic approaches and advanced pharmacological strategies.

Study on the effects of intestinal flora on gouty arthritis

Gouty arthritis (GA), a metabolic and immunologic disease, primarily affects joints. Dysbiosis of intestinal flora is an important cause of GA. The metabolic disorders of intestinal flora leading to GA and immune disorders might play an important role in patients with hyperuricemia and established GA. However, the exact mechanisms, through which the dysbiosis of intestinal flora causes the development of GA, are not fully understood yet. Moreover, several therapies commonly used to treat GA might alter the intestinal flora, suggesting that modulation of the intestinal flora might help prevent or treat GA. Therefore, a better understanding of the changes in the intestinal flora of GA patients might facilitate the discovery of new diagnostic and therapeutic approaches. The current review article discusses the effects of intestinal flora dysbiosis on the pathogenesis of GA and the cross-regulatory effects between gut flora and drugs for treating GA. This article also highlights the modulatory effects of gut flora by traditional Chinese medicine (TCM) to lower uric acid levels and relieve joint pain as well as provides a summary and outlook, which might help guide future research efforts.

Anti-hyperuricemia bioactive peptides: a review on obtaining, activity, and mechanism of action

Hyperuricemia, a disorder of uric acid metabolism, serves as a significant risk factor for conditions such as hypertension, diabetes mellitus, renal failure, and various metabolic syndromes. The main contributors to hyperuricemia include overproduction of uric acid in the liver or impaired excretion in the kidneys. Despite traditional clinical drugs being employed for its treatment, significant health concerns persist. Recently, there has been growing interest in utilizing protein peptides sourced from diverse food origins to mitigate hyperuricemia. This article provides a comprehensive review of bioactive peptides with anti-hyperuricemia properties derived from animals, plants, and their products. We specifically outline the methods for preparing these peptides from food proteins and elucidate their efficacy and mechanisms in combating hyperuricemia, supported by in vitro and in vivo evidence. Uric acid-lowering peptides offer promising prospects due to their safer profile, enhanced efficacy, and improved bioavailability. Therefore, this review underscores significant advancements and contributions in identifying peptides capable of metabolizing purine and/or uric acid, thereby alleviating hyperuricemia. Moreover, it offers a theoretical foundation for the development of functional foods incorporating uric acid-lowering peptides.

Single-cell and genome-wide Mendelian randomization identifies causative genes for gout

BACKGROUND

Gout is a prevalent manifestation of metabolic osteoarthritis induced by elevated blood uric acid levels. The purpose of this study was to investigate the mechanisms of gene expression regulation in gout disease and elucidate its pathogenesis.

METHODS

The study integrated gout genome-wide association study (GWAS) data, single-cell transcriptomics (scRNA-seq), expression quantitative trait loci (eQTL), and methylation quantitative trait loci (mQTL) data for analysis, and utilized two-sample Mendelian randomization study to comprehend the causal relationship between proteins and gout.

RESULTS

We identified 17 association signals for gout at unique genetic loci, including four genes related by protein-protein interaction network (PPI) analysis: TRIM46, THBS3, MTX1, and KRTCAP2. Additionally, we discerned 22 methylation sites in relation to gout. The study also found that genes such as TRIM46, MAP3K11, KRTCAP2, and TM7SF2 could potentially elevate the risk of gout. Through a Mendelian randomization (MR) analysis, we identified three proteins causally associated with gout: ADH1B, BMP1, and HIST1H3A.

CONCLUSION

According to our findings, gout is linked with the expression and function of particular genes and proteins. These genes and proteins have the potential to function as novel diagnostic and therapeutic targets for gout. These discoveries shed new light on the pathological mechanisms of gout and clear the way for future research on this condition.

Association Between Family History in Patients with Primary Gout and Left Ventricular Diastolic Function: A Cross-Sectional Study

Objective

This study aimed to employ echocardiography for measuring the markers of left ventricular (LV) diastolic function to investigate the effects of family history of gout on the LV diastolic function in patients with primary gout.

Methods

Two hundred and eighty-four patients with primary gout who visited the Department of Rheumatology and Immunology of the First Affiliated Hospital of Chengdu Medical College from September 2020 to July 2022 were selected and their family history of gout, general information, and laboratory markers were recorded. Parameters of LV diastolic function were measured via echocardiography. The correlation between family history and LV diastolic function markers was analyzed using univariate and multivariate regression and the receiver operating characteristic (ROC) curve analyses.

Results

LV diastolic function parameters, peak early mitral diastolic velocity (E)/peak late mitral diastolic velocity (A), and early septal mitral annulus diastolic motion velocity (Sepe'), early lateral mitral annulus diastolic motion velocity (Late') and their mean (e'), were significantly lower in patients with familial primary gout, while left atrial volume index (LAVI) and E/e' were markedly elevated in patients with sporadic primary gout. In patients with family history, the proportion of grade ≥2 LV diastolic insufficiency was distinctly higher than that in patients without family history (41.6% vs 12.3%). Even after adjusting for confounding variables, LAVI, E/A, Sepe', Late', e', E/e' were obviously associated with family history of gout. The area under ROC of family history combined with SUA level for identifying grade ≥2 LV diastolic insufficiency in patients with primary gout was 0.872 (P<0.05).

Conclusion

Family history of gout was closely related to echocardiographic LV diastolic function parameters in patients with gout, what is more, family history of gout combined with SUA level was found to be a valuable indicator for discriminating grade ≥2 LV diastolic insufficiency in patients with primary gout.

Pathogenesis of gout: Exploring more therapeutic target

Gout is a chronic metabolic and immune disease, and its specific pathogenesis is still unclear. When the serum uric acid exceeds its saturation in the blood or tissue fluid, it is converted to monosodium urate crystals, which lead to acute arthritis of varying degrees, urinary stones, or irreversible peripheral joint damage, and in severe cases, impairment of vital organ function. Gout flare is a clinically significant state of acute inflammation in gout. The current treatment is mostly anti-inflammatory analgesics, which have numerous side effects with limited treatment methods. Gout pathogenesis involves many aspects. Therefore, exploring gout pathogenesis from multiple perspectives is conducive to identifying more therapeutic targets and providing safer and more effective alternative treatment options for patients with gout flare. Thus, this article is of great significance for further exploring the pathogenesis of gout. The author summarizes the pathogenesis of gout from four aspects: signaling pathways, inflammatory factors, intestinal flora, and programmed cell death, focusing on exploring more new therapeutic targets.

Can uric acid affect the immune microenvironment in bladder cancer? A single-center multi-omics study

Metabolic abnormalities are one of the important factors in bladder cancer (BCa) progression and microenvironmental disturbance. As an important product of purine metabolism, uric acid's (UA) role in BCa metabolism and immunotherapy remains unclear. In this study, we conducted a retrospective analysis of a cohort comprising 39 BCa patients treated with PD-1 and 169 patients who underwent radical cystectomy at Shanghai Tenth People's Hospital. Kaplan-Meier curves and Cox regression analysis showed that the prognosis of patients with high UA is worse (p = 0.007), and high UA is an independent risk factor for cancer specific survival in patients with BCa (p = 0.025). We established a hyperuricemia mouse model with BCa subcutaneous xenografts in vivo. The results revealed that the subcutaneous tumors of hyperuricemia mice had a greater weight and volume in comparison with the control group. Through flow cytometric analysis, the proportion of CD8+ and CD4+ T cells in these subcutaneous tumors was seen to decline significantly. We also evaluated the relationship of UA and BCa by muti-omic analysis. UA related genes were significantly increased in the CD8+ T cell of non-responders to immunotherapy by single-cell sequencing. An 11-gene UA related signature was constructed and the risk score negatively correlated with various immune cells and immune checkpoints. Finally, a nomogram was established using a UA related signature to forecast the survival rate of patients with BCa. Collectively, this study demonstrated that UA was an independent prognostic biomarker for BCa and was associated with worse immunotherapy response.

Building capacity to conduct genetic epidemiology research on hyperuricaemia and gout in an Indigenous community in Guam

Background

Gout, the most common inflammatory arthritis disease, and hyperuricaemia onset are influenced by environmental and genetic factors. We sought to investigate these factors in an Indigenous community in Guam.

Methods

In this cross-sectional study, the University of Guam led the qualitative inquiry with the native community, training (pre-screening of participants, data collection methods, and biospecimen handling), study implementation (outreach and recruitment, data collection, and DNA extraction and quantification), and qualitative and epidemiologic data analyses. Recruitment targets were based on demographic representation in current census data. The University of Otago collaborated on ethics guidance, working with Indigenous communities, and led the genetic sequencing and genetic data analysis. Participants were recruited in Guam from Fall 2019 to Spring 2022.

Results

Of the 359 participants, most self-identified as Native CHamorus (61.6%) followed by Other Micronesians (22.0%), and Filipinos (15.6%). The prevalence of metabolic conditions from highest to lowest were obesity (55.6%), hyperuricaemia (36.0%), hypertension (27.8%), gout (23.0%), diabetes (14.9%), cardiovascular disease (8.4%), kidney disease (7.3%), and liver disease (3.4%). Compared to Filipinos and Other Micronesians, significantly more CHamorus had hyperuricaemia (42.1% versus 26.8% in Filipinos and 25.3% in Other Micronesians), gout (28.5% versus 21.4% and 8.9%), diabetes (19.5% versus 8.9% and 6.3%), and hypertension (33.9% versus 19.6% and 16.5%).

Conclusions

We estimated the prevalence of metabolic conditions, especially gout and hyperuricaemia, and found statistical differences among major ethnic groups in Guam, all while obtaining the Indigenous community's feedback on the genetic study and building gout research capacity. The results of ongoing genetic sequencing will be used to understand molecular causes of gout in Guam.

Exploring quantitative traits-associated copy number deletions through reanalysis of UK10K consortium whole genome sequencing cohorts

OBJECTIVES

We performed comprehensive association analyses of common high-confidence gnomAD-reported copy number deletions (CNDs) with 60 quantitative traits from UK10K consortium WGS data.

METHODS

The study made use of data generated by the UK10K Consortium. UK10K consortium WGS data consist of TwinsUK (n = 1754, middle-aged females) and ALSPAC (n = 1867, birth to adolescence) cohorts. UK10K consortium called 18,739 CNDs (hg19) with GenomeSTRiP software. After filtering out variants with minor allele frequency < 0.05 or HWE P < 1.0 × 10- 6, 1222 (TwinsUK) and 1211 (ALSPAC) CNDs remained for association analyses with 60 normalized quantitative traits.

RESULTS

We identified 23 genome-wide significant associations at 13 loci, among which 2 associations reached experiment-wide significance. We found that two common deletions in chromosome 4, located between WDR1 and ZNF518B (23.3 kb, dbVar ID:nssv15888957, 4:10211262-10,234,569 and 9.8 kb, dbVar ID:nssv15888975, 4:10392422-10,402,191), were associated with uric acid levels (P = 5.23 × 10- 11 and 2.29 × 10- 8, respectively). We also discovered a novel deletion spanning chromosome 18 (823 bp, dbVar ID: nssv15841628, 8:74347187-74,348,010) associated with low HDL cholesterol levels (P = 4.15 × 10- 7). Additionally, we observed two red blood cell traits-associated loci with genome-wide significance, a 13.2 kb deletion in 7q22.1 (nssv15922542) and a 3.7 kb deletion in 12q24.12 (nssv15813226), both of which were located in regions previously reported to be associated with red blood cell traits. Two deletions in 11q11 (nssv15803200 and nssv15802240), where clusters of multiple olfactory receptor genes exist, and a deletion (nssv15929560) upstream to DOCK5 were associated with childhood obesity. Finally, when defining Trait-Associated copy number Deletions (TADs) as CNDs with phenotype associations at sub-threshold significance (P < 10- 3), we identified 157 (97.5%) out of 161 TADs in non-coding regions, with a mean size of 4 kb (range: 209 - 47,942 bp).

CONCLUSION

We conducted a reanalysis of the UK10K Whole Genome Sequencing cohort, which led to the identification of multiple high confidence copy number deletions associated with quantitative traits. These deletions have standard dbVar IDs and replicate previous findings, as well as reveal novel loci that require further replication studies.

Allisartan Isoproxil Promotes Uric Acid Excretion by Interacting with Intestinal Urate Transporters in Hyperuricemic Zebrafish (Danio rerio)

To evaluate the urate-lowering effect and potential drug targets of antihypertensive agent allisartan isoproxil (ALI) and its bioactive metabolite EXP3174, we developed an acute hyperuricemic zebrafish model using potassium oxonate and xanthine sodium salt. Losartan potassium served as the positive control (reference drug). In this model, ALI and losartan potassium exerted a greater urate-lowering effect than EXP3174 indicating that the latter is not the critical substance for elimination of uric acid. The quantitative real-time PCR showed that ALI upregulates the expression of intestinal urate transporters genes ABCG2, PDZK1, and SLC2A9 (p<0.01). Thus, we can suggest that this substance promotes uric acid excretion mainly by interacting with intestinal urate transporters.

Characterizations of microRNAs involved in the molecular mechanisms underlying the therapeutic effects of noni (Morinda citrifolia L.) fruit juice on hyperuricemia in mice

Background

Hyperuricemia is generally defined as the high level of serum uric acid and is well known as an important risk factor for the development of various medical disorders. However, the medicinal treatment of hyperuricemia is frequently associated with multiple side-effects.

Methods

The therapeutic effect of noni (Morinda citrifolia L.) fruit juice on hyperuricemia and the underlying molecular mechanisms were investigated in mouse model of hyperuricemia induced by potassium oxonate using biochemical and high-throughput RNA sequencing analyses.

Results

The levels of serum uric acid (UA) and xanthine oxidase (XOD) in mice treated with noni fruit juice were significantly decreased, suggesting that the noni fruit juice could alleviate hyperuricemia by inhibiting the XOD activity and reducing the level of serum UA. The contents of both serum creatinine and blood urine nitrogen of the noni fruit juice group were significantly lower than those of the model group, suggesting that noni fruit juice promoted the excretion of UA without causing deleterious effect on the renal functions in mice. The differentially expressed microRNAs involved in the pathogenesis of hyperuricemia in mice were identified by RNA sequencing with their target genes further annotated based on both Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases to explore the metabolic pathways and molecular mechanisms underlying the therapeutic effect on hyperuricemia by noni fruit juice.

Conclusion

Our study provided strong experimental evidence to support the further investigations of the potential application of noni fruit juice in the treatment of hyperuricemia.

Filling gaps in female gout: a cross-sectional study of comorbidities in 192 037 hospitalised patients

OBJECTIVE

There is room for improvement in the knowledge of female gout, often noted at risk of gender blindness. This study aims to compare the prevalence of comorbidities in women versus men hospitalised with gout in Spain.

METHODS

This is an observational, multicentre, cross-sectional study in public and private Spanish hospitals analysing the minimum basic data set from 192 037 hospitalisations in people with gout (International Classification of Diseases, Ninth Revision (ICD-9) coding) from 2005 to 2015. Age and several comorbidities (ICD-9) were compared by sex, with a subsequent stratification of comorbidities by age group. The association between each comorbidity and sex was assessed using multivariable logistic regression. A clinical decision tree algorithm was constructed to predict the sex of patients with gout based on age and comorbidities alone.

RESULTS

Women with gout (17.4% of the sample) were significantly older than men (73.9±13.7 years vs 64.0±14.4 years, p<0.001). Obesity, dyslipidaemia, chronic kidney disease, diabetes mellitus, heart failure, dementia, urinary tract infection and concurrent rheumatic disease were more common in women. Female sex was strongly associated with increasing age, heart failure, obesity, urinary tract infection and diabetes mellitus, while male sex was associated with obstructive respiratory diseases, coronary disease and peripheral vascular disease. The decision tree algorithm built showed an accuracy of 74.4%.

CONCLUSIONS

A nationwide analysis of inpatients with gout in 2005-2015 confirms a different comorbidity profile between men and women. A different approach to female gout is needed to reduce gender blindness.

A review on gout: Looking back and looking ahead

Gout is a metabolic disease caused by the deposition of monosodium urate (MSU) crystals inside joints, which leads to inflammation and tissue damage. Increased concentration of serum urate is an essential step in the development of gout. Serum urate is regulated by urate transporters in the kidney and intestine, especially GLUT9 (SLC2A9), URAT1 (SLC22A12) and ABCG. Activation of NLRP3 inflammasome bodies and subsequent release of IL-1β by monosodium urate crystals induce the crescendo of acute gouty arthritis, while neutrophil extracellular traps (NETs) are considered to drive the self-resolving of gout within a few days. If untreated, acute gout may eventually develop into chronic tophaceous gout characterized by tophi, chronic gouty synovitis, and structural joint damage, leading the crushing burden of treatment. Although the research on the pathological mechanism of gout has been gradually deepened in recent years, many clinical manifestations of gout are still unable to be fully elucidated. Here, we reviewed the molecular pathological mechanism behind various clinical manifestations of gout, with a view to making contributions to further understanding and treatment.

Relationship between rs4349859 and rs116488202 polymorphisms close to MHC-I region and serum urate levels in patients with gout

BACKGROUND

Gout is the most common inflammatory rheumatic disease and elevated levels of serum urate (SU) are the main cause for its development. Major histocompatibility complex class 1 (MHC-1) plays an important role in the development of multiple inflammatory diseases; however, there is little evidence of its involvement in gout. The present study focused on evaluating the association of the rs4349859 and rs116488202 single nucleotide polymorphisms (SNPs) close to the MHC-1 region in patients with gout.

METHODS AND RESULTS

One hundred and seventy-six individuals of Mexican origin were included, of which 81 were patients with primary gout and 95 were healthy controls. The rs4349859 and rs116488202 SNPs were genotyped using TaqMan probes by allelic discrimination by real-time PCR. Serum concentrations of biochemical parameters were measured with enzymatic methods. Descriptive statistics were applied and P-values < 0.05 were considered significant. It was observed that the rs4349859 and rs116488202 SNPs showed significant association with the risk of gout (OR = 146, 95%CI = 44.8-480.2, P < 0.01; OR = 2885, 95%CI = 265-31398, P < 0.01, respectively). Our results also showed significantly higher serum SU levels in gout patients with respect to controls (P < 0.01) in the carriers of the GA genotype compared with the GG genotype of the rs4349859 variant, and in the carriers of the CT genotype compared with the CC genotype of the rs116488202 variant.

CONCLUSION

The study revealed that rs4349859 and rs116488202 SNPs close to MHC-I region confers strong susceptibility to gout in Mexican population, and the heterozygous genotypes of both were associated with higher levels of SU.

Genetic contributions to female gout and hyperuricaemia using genome-wide association study and polygenic risk score analyses

OBJECTIVES

To identify genetic variants and polygenic risk score (PRS) relating to female gout and asymptomatic hyperuricaemia (AH) in a genome-wide association study (GWAS).

METHODS

Gout, AH and normouricemia controls were included from Taiwan biobank and China Medical University Hospital. All participants were divided into discovery and replication cohorts for GWAS. PRS was estimated according to whether the variant exhibited a protective effect on the phenotypes or not. Each cohort was separated into two groups by the age of 50 years old.

RESULTS

A total of 59 472 females were enrolled, and gout and AH occupied 1.60% and 19.59%, respectively. Six variants located in genes SLC2A9, C5orf22, CNTNAP2 and GLRX5 were significantly predictors of female gout in those aged ≥50. For those aged <50 years old, only the variant rs147750368 (SPANXN1) on chromosome X was found. Most variants located in genes SLC2A9, ZNF518B, PKD2 and ABCG2 were found to be significantly related to AH in both age groups. The PRS could explain ∼0.59% to 0.89% of variance of gout in variants with protective effects, which showed 6.2 times of mean PRS in the risk variants, but only 1.2 times in the AH phenotype. Moreover, the PRS also revealed a dose-response trend between AH rates and quartile scores.

CONCLUSION

The variants in gene SLC2A9 are the major genetic factors for females associated with gout in those aged ≥50. PRS can provide a more robust prediction of the gout/AH under a homogeneous selection of variants that show effects on the traits.

Global status and trends in gout research from 2012 to 2021: a bibliometric and visual analysis

BACKGROUND

Gout is the most common inflammatory arthritis with an increasing prevalence and incidence across the globe. We aimed to provide a comprehensive and systematic knowledge map of gout research to determine its current status and trends over the past decade.

METHODS

Publications on gout research were obtained from the Web of Science Core Collection (WOSCC) database. Bibliometric R, VOSviewer, and Citespace were employed to analyze the eligible literature.

RESULTS

A total of 5535 publications concerning gout research between 2012 and 2021 were included. Most publications and citations both numerically came from China. The strongest international cooperation belonged to the USA. The University of Auckland was the most productive institution with a leading place in research collaboration. The prime funding agency was the National Natural Science Foundation of China. Most papers were published in Clinical Rheumatology. Annals of the Rheumatic Diseases achieved the highest number of citations, H-index and IF, which showed the most excellent comprehensive strength. The individual author with the most paper authorship was Dalbeth Nicola with 241 publications and 46 H-index. Keywords and co-citation analysis discovered that pathological mechanism remains the future hotspot in gout research. It may involve gout connection with gut microbiota, NLRP3 inflammasome, xanthine oxidase, and urate-transporter ABCG2. In addition, besides metabolic diseases, the relationship between gout and heart failure may need more attention.

CONCLUSION

This study clarified the current status and research frontier in gout over the past decade, which would provide valuable research references for later researchers. Key Points •We disclosed the current status and frontier directions of gout over the past 10 years worldwide. •We identified future hotspots of gout research, including gout connection with gut microbiota, NLRP3 inflammasome, xanthine oxidase, and urate-transporter ABCG2. •We discovered that the relationship between gout and heart status would be the research frontier.

Polygenic risk score trend and new variants on chromosome 1 are associated with male gout in genome-wide association study

Background

Gout is a highly hereditary disease, but not all those carrying well-known risk variants have developing gout attack even in hyperuricemia status. We performed a genome-wide association study (GWAS) and polygenic risk score (PRS) analysis to illustrate the new genetic architectures of gout and asymptomatic hyperuricemia (AH).

Methods

GWAS was performed to identify variants associated with gout/AH compared with normouricemia. The participants were males, enrolled from the Taiwan Biobank and China Medical University, and divided into discovery (n=39,594) and replication (n=891) cohorts for GWAS. For PRS analysis, the discovery cohort was grouped as base (n=21,814) and target (n=17,780) cohorts, and the score was estimated by grouping the polymorphisms into protective or not for the phenotypes in the base cohort.

Results

The genes ABCG2 and SLC2A9 were found as the major genetic factors governing gouty and AH, and even in those carrying the rs2231142 (ABCG2) wild-genotype. Surprisingly, variants on chromosome 1, such as rs7546668 (DNAJC16), rs10927807 (AGMAT), rs9286836 (NUDT17), rs4971100 (TRIM46), rs4072037 (MUC1), and rs2974935 (MTX1), showed significant associations with gout in both discovery and replication cohorts (all p-values < 1e−8). Concerning the PRS, the rates of gout and AH increased with increased quartile PRS in those SNPs having risk effects on the phenotypes; on the contrary, gout/AH rates decreased with increased quartile PRS in those protective SNPs.

Conclusions

We found new variants on chromosome 1 significantly relating to gout, and PRS predicts the risk of developing gout/AH more robustly based on the SNPs’ effect types on the trait.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02917-4.

The interplay between HLA-B and NLRP3 polymorphisms may be associated with the genetic susceptibility of gout

BACKGROUND

HLA and NLRP3 play an important role in the development of various autoimmune and autoinflammatory diseases. Gout is an autoinflammatory disease associated with multiple genetic and environmental factors. The objective of the present study was to evaluate the interaction and association between genetic polymorphisms of HLA-B and the NLRP3 gene in Mexican patients with gout.

METHODS AND RESULTS

Eighty-one patients with gout were included and compared with 95 healthy subjects. The polymorphisms rs4349859, rs116488202, rs2734583 and rs3099844 (within the HLA-B region) and rs3806268 and rs10754558 of the NLRP3 gene were genotyped using TaqMan probes in a Rotor-Gene device. The interactions were determined using the multifactorial dimensionality reduction (MDR) method, while the associations were determined through logistic regression models. The MDR analysis revealed significant interactions between the rs116488202 and rs10754558 polymorphisms with an entropy value of 4.31% (p < 0.0001). Significant risk associations were observed with rs4349859 and rs116488202 polymorphisms (p < 0.01); however, no significant associations were observed with the polymorphisms of the NLRP3 gene.

CONCLUSIONS

The results suggest that HLA-B polymorphisms and their interaction with NLRP3 may contribute to the genetic susceptibility of gout.

Differences of Uric Acid Transporters Carrying Extracellular Vesicles in the Urine from Uric Acid and Calcium Stone Formers and Non-Stone Formers

Background: Low urine pH and volume are established risk factors for uric acid (UA) stone disease (UASD). Renal tubular epithelial cells exposed to an acidic pH and/or UA crystals can shed extracellular vesicles (EVs) into the tubular fluid, and these EVs may be a pathogenic biomarker of UASD. Methods: Urinary EVs bearing UA transporters (SLC2A9, SLC17A3, SLC22A12, SLC5A8, ABCG2, and ZNF365) were quantified in urine from UA stone formers (UASFs), calcium stone formers (CSFs), and age-/sex-matched non-stone formers (NSFs) using a standardized and published method of digital flow cytometry. Results: Urinary pH was lower (p < 0.05) and serum and urinary UA were greater (p < 0.05) in UASFs compared with NSFs. Urinary EVs carrying SLC17A3 and SLC5A8 were lower (p < 0.05) in UASFs compared with NSFs. Urinary EVs bearing SLC2A9, SLC22A12, SLC5A8, ABCG2, and ZNF365 were lower (p < 0.05) in CSFs than UASFs, while excretion of SLC17A3-bearing EVs did not differ between groups. Conclusion: EVs bearing specific UA transporters might contribute to the pathogenesis of UASD and represent non-invasive pathogenic biomarkers for calcium and UA stone risk.

Environmental factors and risk of gout

Gout is a chronic disease with inflammatory arthritis caused by monosodium urate (MSU) crystals deposition, an elevated serum urate level (hyperuricaemia) is the critical factor leading to MSU crystals deposition and promoting the progression of gout. The onset and development of gout is generally the result of multiple factors, such as diet, heredity and environmental factors. Although genetics and diet are thought to play as major factors, a growing body of research evidence has highlighted that environmental factors also play a significant role in the onset and exacerbation of gout. Recent studies have shown that air pollutants such as particulate matter, sulfur dioxide (SO₂) and carbon monoxide (CO) may increase the risk of hospitalizations for gout, and that the changes in temperature and humidity may affect uric acid (UA) levels. There is also seasonal trend in gout. It has been demonstrated that environmental factors may induce or accelerate the production and release of pro-inflammatory mediators, causing an unbalance oxidative stress and systemic inflammation, and then participating in the overall process or a certain link of gout. Moreover, several environmental factors have shown the ability to induce the production urate and regulate the innate immune pathways, involving in the pathogenesis of gout. Nevertheless, the role of environmental factors in the etiology of gout remains unclear. In this review, we summarized the recent literatures and aimed to discuss the relationship between environmental factors (such as microclimate, season, ambient/indoor air pollution and extreme weather) and gout. We further discussed the inflammatory mechanisms of environmental factors and gout and the comprehensive effects of environmental factors on gout. We also made a prospect of the management and treatment of gout, with special consideration to environmental factors associated with gout.

Susceptibility genes of hyperuricemia and gout

Gout is a chronic metabolic disease that seriously affects human health. It is also a major challenge facing the world, which has brought a heavy burden to patients and society. Hyperuricemia (HUA) is the most important risk factor for gout. In recent years, with the improvement of living standards and the change of dietary habits, the incidence of gout in the world has increased dramatically, and gradually tends to be younger. An increasing number of studies have shown that gene mutations may play an important role in the development of HUA and gout. Therefore, we reviewed the existing literature and summarized the susceptibility genes and research status of HUA and gout, in order to provide reference for the early diagnosis, individualized treatment and the development of new targeted drugs of HUA and gout.

Weak Association Between Genetic Markers of Hyperuricemia and Cardiorenal Outcomes: Insights From the STANISLAS Study Cohort With a 20-Year Follow-Up

Background Hyperuricemia is associated with poor cardiovascular outcomes, although it is uncertain whether this relationship is causal in nature. This study aimed to: (1) assess the heritability of serum uric acid (SUA) levels, (2) conduct a genome-wide association study on SUA levels, and (3) investigate the association between certain single-nucleotide polymorphisms and target organ damage. Methods and Results The STANISLAS (Suivi Temporaire Annuel Non-Invasif de la Santé des Lorrains Assurés Sociaux) study cohort is a single-center longitudinal cohort recruited between 1993 and 1995 (visit 1), with a last visit (visit 4 [V4]) performed ≈20 years apart. Serum lipid profile, SUA, urinary albumin/creatinine ratio, estimated glomerular filtration rate, 24-hour ambulatory blood pressure monitoring, transthoracic echocardiography, pulse wave velocity, and genotyping for each participant were assessed at V4. A total of 1573 participants were included at V4, among whom 1417 had available SUA data at visit 1. Genome-wide association study results highlighted multiple single-nucleotide polymorphisms on the SLC2A9 gene linked to SUA levels. Carriers of the most associated mutated SLC2A9 allele (rs16890979) had significantly lower SUA levels. Although SUA level at V4 was highly associated with diabetes, prediabetes, higher body mass index, CRP (C-reactive protein) levels, estimated glomerular filtration rate variation (visit 1-V4), carotid intima-media thickness, and pulse wave velocity, rs16890979 was only associated with higher carotid intima-media thickness. Conclusions Our findings demonstrate that rs16890979, a genetic determinant of SUA levels located on the SLC2A9 gene, is associated with carotid intima-media thickness despite significant associations between SUA levels and several clinical outcomes, thereby lending support to the hypothesis of a link between SUA and cardiovascular disease.

The Role of the Intestine in the Development of Hyperuricemia

Gout is a common inflammatory arthritis caused by the deposition of sodium urate crystals in the joints. Hyperuricemia is the fundamental factor of gout. The onset of hyperuricemia is related to purine metabolism disorders or uric acid excretion disorders. Current studies have shown that the intestine is an important potential organ for the excretion of uric acid outside the kidneys. The excretion of uric acid of gut is mainly achieved through the action of uric acid transporters and the catabolism of intestinal flora, which plays an important role in the body’s uric acid balance. Here we reviewed the effects of intestinal uric acid transporters and intestinal flora on uric acid excretion, and provide new ideas for the treatment of hyperuricemia and gout.

The chemistry, processing, and preclinical anti-hyperuricemia potential of tea: a comprehensive review

Hyperuricemia is an abnormal purine metabolic disease that occurs when there is an excess of uric acid in the blood, associated with cardiovascular diseases, hypertension, gout, and renal disease. Dietary intervention is one of the most promising strategies for preventing hyperuricemia and controlling uric acid concentrations. Tea (Camellia sinensis) is known as one of the most common beverages and the source of dietary polyphenols. However, the effect of tea on hyperuricemia is unclear. Recent evidence shows that a lower risk of hyperuricemia is associated with tea intake. To better understand the anti-hyperuricemia effect of tea, this review first briefly describes the pathogenesis of hyperuricemia and the processing techniques of different types of tea. Next, the epidemiological and experimental studies of tea and its bioactive compounds on hyperuricemia in recent years were reviewed. Particular attention was paid to the anti-hyperuricemia mechanisms targeting the hepatic uric acid synthase, renal uric acid transporters, and intestinal microbiota. Additionally, the desirable intake of tea for preventing hyperuricemia is provided. Understanding the anti-hyperuricemia effect and mechanisms of tea can better utilize it as a preventive dietary strategy.HighlightsHigh purine diet, excessive alcohol/fructose consumption, and less exercise/sleep are the induction factors of hyperuricemia.Tea and tea compounds showed alleviated effects for hyperuricemia, especially polyphenols.Tea (containing caffeine or not) is not associated with a higher risk of hyperuricemia.Xanthine oxidase inhibition (reduce uric acid production), Nrf2 activation, and urate transporters regulation (increase uric acid excretion) are the potential molecular targets of anti-hyperuricemic effect of tea.About 5 g tea intake per day may be beneficial for hyperuricemia prevention.

Genetic Association Between SLC22A12 Variants and Susceptibility to Hyperuricemia: A Meta-Analysis

Aims: Gout is a form of inflammatory arthritis characterized by the deposition of monosodium urate crystals. An important risk factor for gout is hyperuricemia. The relationship between SLC22A12 gene variants and the susceptibility to hyperuricemia has been reported, but these findings have been inconsistent. Thus, we aimed to assess the relationship between SLC22A12 gene variants and hyperuricemia susceptibility through a meta-analysis. Methods: The meta-analysis was performed by searching PubMed, Embase, Web of Science, and Chinese National Knowledge Infrastructure (CNKI) databases. The relationship between hyperuricemia risk and the SLC22A12 rs11602903, rs524023, rs3825018, rs3825016, rs11231825, rs7932775, rs893006, and rs475688 variants was assessed by odds ratios and 95% confidence intervals. Results: In total, 20 eligible publications with 4817 cases and 6819 controls were included in the meta-analysis. Hyperuricemia risk was significantly associated with the SLC22A12 alleles rs3825018, rs7932775, and rs475688 under both the dominant and recessive models and with rs3825016 under the allelic and dominant models. Conclusions: Under the allelic model SLC22A12 rs3825018 and rs3825016 were risk factors for hyperuricemia and gout as was rs7932775 under dominant and recessive models, while the SLC22A12 rs475688 was protective against hyperuricemia under both dominant and recessive models.

Traditional Chinese Herbal Medicine Plays a Role in the Liver, Kidney, and Intestine to Ameliorate Hyperuricemia according to Experimental Studies

In the last few decades, hyperuricemia has drawn increasing attention owing to its global prevalence. Observational surveys have manifested that there is a relation between hyperuricemia and increased risks of hypertension, chronic kidney disease, cardiovascular events, metabolic disorders, end stage renal disease, and mortality. As alternatives, Traditional Chinese medicinal herbs have demonstrated concrete effects in mitigating hyperuricemia in different experiments. Researchers have made efforts to investigate the role of herbal medicine in attenuating hyperuricemia. This review focuses on traditional Chinese herbal medicines that have been reported to ameliorate hyperuricemia in experimental studies.

Nut intake and hyperuricemia risk in young adults

OBJECTIVE

The relationship between dietary nut intake and hyperuricemia risk remains unclear. The aim of this study was to investigate the relationship between different nut intake and hyperuricemia risk with a cross-sectional study.

DESIGN

A semi-quantitative FFQ was adopted to collect dietary information. Biochemical and anthropometric parameters were measured by standard methods. Multivariate-adjusted logistic regression models were implemented to analyse the relationship between individual nut intake and hyperuricemia risk.

SETTING

Qingdao University in Shandong Province, China.

PARTICIPANTS

During 2018-2019, a total of 14 056 undergraduates (6862 males and 7194 females) aged 15-25 years participated in the study.

RESULTS

After adjusting for multiple confounding factors, compared with the lowest quartile, the highest quartile intakes of pine nut (95 % CI (0·51, 0·98)) was significantly associated with 29 % reduction in hyperuricemia risk, the highest quartile intake of walnut (OR = 0·78; 95 % CI (0·58, 1·05)) was marginally negatively associated with hyperuricemia risk.

CONCLUSIONS

The present study showed that the relationships between intakes of different nuts and hyperuricemia risk were different. Increased dietary intakes of walnut and pine nut are negatively associated with the hyperuricemia.

Calcitriol Treatment Attenuates Uric Acid-Induced Kidney Injury via Super Oxide Dismutase-1 (SOD-1) Upregulation and Fibrosis Reduction

Background

Hyperuricemia induces nephropathy through the mediation of oxidative stress, tubular injury, inflammation, and fibrosis. The high uric acid level is associated with the reduction of vitamin D levels. However, the reno-protective effects of this vitamin in hyperuricemia condition remain unknown. This study aimed to elucidate calcitriol treatment in a uric acid-induced hyperuricemia mice model.

Methods

: Uric acid (125 mg/kg body weight [BW]) was administered intraperitoneally for 7 (UA7) and 14 (UA14) days. Calcitriol (0.5 g/kg BW) was intraperitoneally injected for the following seven days, after 14 days of uric acid induction (UA14VD7 group). The control group received NaCl 0.9%, by the same route. Serum creatinine was measured using calorimetric method, and uric acid levels were assessed using enzymatic calorimetric assay. Tubular injury and fibrosis were assessed using PAS and Sirius red staining. RT-PCR and real-time reverse transcription PCR were carried out for the analyses of SOD-1, Collagen-1, and TGF-1 mRNA expression in the kidney. Immunostaining of super oxide dismutase type 1 (SOD-1) was performed to detect its expression in the kidney.

Results

Uric acid and creatinine levels markedly increased in UA14 groups, followed by an exacerbation of tubular injury. RT-PCR revealed the upregulation of Collagen-1 and TGF-1, along with the downregulation of SOD-1. Calcitriol treatment attenuated the injury with reducing uric acid and creatinine levels, as well as tubular injury. This was associated with lower Collagen-1 and TGF-1 mRNA expression compared to the UA7 and UA14 groups. SOD-1 was upregulated in epithelial cells in the UA14VD7 group.

Conclusion

Calcitriol treatment after uric acid induction may attenuate kidney injury through upregulation of SOD-1 and downregulation of Collagen-1 and TGF-1 gene expression.

Characterization of a Compound Heterozygous SLC2A9 Mutation That Causes Hypouricemia

Renal hypouricemia is a rare genetic disorder. Hypouricemia can present as renal stones or exercise-induced acute renal failure, but most cases are asymptomatic. Our previous study showed that two recessive variants of SLC22A12 (p.Trp258*, pArg90His) were identified in 90% of the hypouricemia patients from two independent cohorts: the Korean genome and epidemiology study (KoGES) and the Korean Cancer Prevention Study (KCPS-II). In this work, we investigate the genetic causes of hypouricemia in the rest of the 10% of unsolved cases. We found a novel non-synonymous mutation of SLC2A9 (voltage-sensitive uric acid transporter) in the whole-exome sequencing (WES) results. Molecular dynamics prediction suggests that the novel mutation p.Met126Val in SLCA9b (p.Met155Val in SLC2A9a) hinders uric acid transport through a defect of the outward open geometry. Molecular analysis using Xenopus oocytes confirmed that the p.Met126Val mutation significantly reduced uric acid transport but does not affect the SLC2A9 protein expression level. Our results will shed light on a better understanding of SLC2A9-mediated uric acid transport and the development of a uric acid-lowering agent.

Serum Uric Acid: A Murderer or Bystander for Cardiac-related Mortality?

In this issue of The Journal of Rheumatology, Colantonio, et al ¹ conducted a case-cohort study from the REGARDS study to evaluate whether the association between serum uric acid (SUA) and sudden cardiac death, and between SUA and incident coronary heart disease (CHD) events, is confounded by SLC2A9 single-nucleotide polymorphisms (SNPs). Incident CHD events were the composites of nonfatal myocardial infarction (MI) or CHD deaths.

Genomic dissection of 43 serum urate-associated loci provides multiple insights into molecular mechanisms of urate control

High serum urate is a prerequisite for gout and associated with metabolic disease. Genome-wide association studies (GWAS) have reported dozens of loci associated with serum urate control; however, there has been little progress in understanding the molecular basis of the associated loci. Here, we employed trans-ancestral meta-analysis using data from European and East Asian populations to identify 10 new loci for serum urate levels. Genome-wide colocalization with cis-expression quantitative trait loci (eQTL) identified a further five new candidate loci. By cis- and trans-eQTL colocalization analysis, we identified 34 and 20 genes, respectively, where the causal eQTL variant has a high likelihood that it is shared with the serum urate-associated locus. One new locus identified was SLC22A9 that encodes organic anion transporter 7 (OAT7). We demonstrate that OAT7 is a very weak urate-butyrate exchanger. Newly implicated genes identified in the eQTL analysis include those encoding proteins that make up the dystrophin complex, a scaffold for signaling proteins and transporters at the cell membrane; MLXIP that, with the previously identified MLXIPL, is a transcription factor that may regulate serum urate via the pentose-phosphate pathway and MRPS7 and IDH2 that encode proteins necessary for mitochondrial function. Functional fine mapping identified six loci (RREB1, INHBC, HLF, UBE2Q2, SFMBT1 and HNF4G) with colocalized eQTL containing putative causal SNPs. This systematic analysis of serum urate GWAS loci identified candidate causal genes at 24 loci and a network of previously unidentified genes likely involved in control of serum urate levels, further illuminating the molecular mechanisms of urate control.

Apigenin ameliorates hyperuricemic nephropathy by inhibiting URAT1 and GLUT9 and relieving renal fibrosis via the Wnt/β-catenin pathway

BACKGROUND

Hyperuricemia (HUA) is characterized by abnormal serum uric acid (UA) levels and demonstrated to be involved in renal injury leading to hyperuricemic nephropathy (HN). Apigenin (API), a flavonoid naturally present in tea, berries, fruits, and vegetables, exhibits various biological functions, such as antioxidant and anti-inflammatory activity.

PURPOSE

To investigate the effect of API treatment in HN and to reveal its underlying mechanisms.

METHODS

The mice with HN were induced by potassium oxonate intraperitoneally and orally administered for two weeks. The effects of API on renal function, inflammation, fibrosis, and uric acid (UA) metabolism in mice with HN were evaluated. The effects of API on urate transporters were further examined in vitro.

RESULTS

The mice with HN exhibited abnormal renal urate excretion and renal dysfunction accompanied by increased renal inflammation and fibrosis. In contrast, API reduced the levels of serum UA, serum creatinine (CRE), blood urea nitrogen (BUN) and renal inflammatory factors in mice with HN. Besides, API ameliorated the renal fibrosis via Wnt/β-catenin pathway suppression. Furthermore, API potently promoted urinary UA excretion and inhibited renal urate transporter 1 (URAT1) and glucose transporter 9 (GLUT9) in mice with HN. In vitro, API competitively inhibited URAT1 and GLUT9 in a dose-dependent manner, with IC₅₀ values of 0.64 ± 0.14 μM and 2.63 ± 0.69 μM, respectively.

CONCLUSIONS

API could effectively attenuate HN through co-inhibiting UA reabsorption and Wnt/β-catenin pathway, and thus it might be a potential therapy to HN.

The biology of urate

Urate is the end-product of the purine metabolism in humans. The dominant source of urate is endogenous purines and the remainder comes through diet. Approximately two thirds of urate is eliminated via the kidney with the rest excreted in the feces. While the transporter BCRP, encoded by ABCG2, has been found to play a role in both the gut and kidney, SLC22A12 and SLC2A9 encoding URAT1 and GLUT9, respectively, are the two transporters best characterized. Only 8-12% of the filtered urate is excreted by the kidney. Renal elimination of urate depends substantially on specific transporters, including URAT1, GLUT9 and BCRP. Studies that have assessed the biologic effects of urate have produced highly variable results. Although there is a suggestion that urate may have anti-oxidant properties in some circumstances, the majority of evidence indicates that urate is pro-inflammatory. Hyperuricemia can result in the formation of monosodium urate (MSU) crystals that may be recognized as danger signals by the immune system. This immune response results in the activation of the NLRP3 inflammasome and ultimately in the production and release of interleukin-1β, and IL-18, that mediate both inflammation, pyroptotic cell death, and necroinflammation. It has also been demonstrated that soluble urate mediates effects on the kidney to induce hypertension and can induce long term epigenetic reprogramming in myeloid cells to induce "trained immunity." Together, these sequelae of urate are thought to mediate most of the physiological effects of hyperuricemia and gout, illustrating this biologically active molecule is more than just an "end-product" of purine metabolism.

Regulation of crystal induced inflammation: current understandings and clinical implications

Introduction: Accumulation of abnormal crystals in the body, derived from endogenous or exogenous materials can drive a wide spectrum of inflammatory disease states. It is well established that intra-articular deposition of monosodium urate (MSU) and calcium pyrophoshate (CPP) crystals contributes to joint destruction through pro-inflammatory processes.Areas covered: This review will focus on current understanding and recent novelty about the mechanisms and the clinical implications of the inflammation induced by MSU and CPP crystals.Expert opinion: Advances in molecular biology reveal that at the base of the inflammatory cascade, stimulated by MSU or CPP crystals, there are many complex cellular mechanisms mainly involving the NLRP3 inflammasome, the hallmark of autoinflammatory syndromes. The extensive studies carried out through in vitro and in vivo models along with a better clinical definition of the disease has led to an optimized use of existing drugs and the introduction of novel therapeutic strategies. In particular, the identification of IL-1 as the most important target in gout and pseudogout has made it possible to expand the pharmacological indications of anti-IL-1 biological drugs, opening new therapeutic perspectives for patients.

Genetic correlations between traits associated with hyperuricemia, gout, and comorbidities

Hypertension, obesity, chronic kidney disease and type 2 diabetes are comorbidities that have very high prevalence among persons with hyperuricemia (serum urate > 6.8 mg/dL) and gout. Here we use multivariate genetic models to test the hypothesis that the co-association of traits representing hyperuricemia and its comorbidities is genetically based. Using Bayesian whole-genome regression models, we estimated the genetic marker-based variance and the covariance between serum urate, serum creatinine, systolic blood pressure (SBP), blood glucose and body mass index (BMI) from two independent family-based studies: The Framingham Heart Study-FHS and the Hypertension Genetic Epidemiology Network study-HyperGEN. The main genetic findings that replicated in both FHS and HyperGEN, were (1) creatinine was genetically correlated only with urate and (2) BMI was genetically correlated with urate, SBP, and glucose. The environmental covariance among the traits was generally highest for trait pairs involving BMI. The genetic overlap of traits representing the comorbidities of hyperuricemia and gout appears to cluster in two separate axes of genetic covariance. Because creatinine is genetically correlated with urate but not with metabolic traits, this suggests there is one genetic module of shared loci associated with hyperuricemia and chronic kidney disease. Another module of shared loci may account for the association of hyperuricemia and metabolic syndrome. This study provides a clear quantitative genetic basis for the clustering of comorbidities with hyperuricemia.

Molecular Pathophysiology of Uric Acid Homeostasis

Uric acid, the end product of purine metabolism, plays a key role in the pathogenesis of gout and other disease processes. The circulating serum uric acid concentration is governed by the relative balance of hepatic production, intestinal secretion, and renal tubular reabsorption and secretion. An elegant synergy between genome-wide association studies and transport physiology has led to the identification and characterization of the major transporters involved with urate reabsorption and secretion, in both kidney and intestine. This development, combined with continued analysis of population-level genetic data, has yielded an increasingly refined mechanistic understanding of uric acid homeostasis as well as greater understanding of the genetic and acquired influences on serum uric acid concentration. The continued delineation of novel and established regulatory pathways that regulate uric acid homeostasis promises to lead to a more complete understanding of uric acid-associated diseases and to identify new targets for treatment.

Association of urinary cotinine-verified smoking status with hyperuricemia: Analysis of population-based nationally representative data

INTRODUCTION

Smoking status based solely on self-reporting is unreliable and might be inaccurate, particularly among women. This study investigated the association between urinary cotinine-verified smoking status and hyperuricemia in a nationwide Korean population.

METHODS

This study included 5329 participants aged ≥19 years with information on smoking status, urine cotinine levels and serum uric acid. We determined smoking status according to self-reports and urinary cotinine levels. Multivariate linear regression analysis was used to measure the association between smoking exposure and serum uric acid levels. The effects of smoking on hyperuricemia were evaluated by multivariate logistic regression analysis.

RESULTS

Biochemically verified active and passive smokers comprised 22% (38.7% of men and 8.8% of women) and 12.3% (11.9% of men and 12.6% of women) of the study population, respectively. While reclassification rate of active smokers was 1.4% in men, 31.8% of cotinine-verified female active smokers were self-reported never smokers. Higher uric acid levels were observed with increased tobacco exposure among women (p-trend=0.007) but not among men. After adjusting for confounders, the risk of hyperuricemia increased with tobacco exposure only in women (p-trend=0.016).

CONCLUSIONS

Cotinine-verified smoking status was associated with increased serum uric acid and hyperuricemia in a dose-response manner only in women. This study might provide evidence to support the importance of smoking cessation in women with gout and further studies are necessary to elucidate the underlying mechanism of the observed association.

The ABCG2/BCRP transporter and its variants - from structure to pathology

The ABCG2 protein has a key role in the transport of a wide range of structurally dissimilar endo- and xenobiotics in the human body, especially in the tissue barriers and the metabolizing or secreting organs. The human ABCG2 gene harbors a high number of polymorphisms and mutations, which may significantly modulate its expression and function. Recent high-resolution structural data, complemented with molecular dynamic simulations, may significantly help to understand intramolecular movements and substrate handling, as well as the effects of mutations on the membrane transporter function of ABCG2. As reviewed here, structural alterations may result not only in direct alterations in drug binding and transporter activity, but also in improper folding or problems in the carefully regulated process of trafficking, including vesicular transport, endocytosis, recycling, and degradation. Here, we also review the clinical importance of altered ABCG2 expression and function in general drug metabolism, cancer multidrug resistance, and impaired uric acid excretion, leading to gout.

Characterizations of the Urate Transporter, GLUT9, and Its Potent Inhibitors by Patch-Clamp Technique

Glucose transporter 9 (GLUT9), which transports urate in an electrogenic and voltage-dependent manner, plays an important role in the maintenance of normal blood uric acid/urate levels. In the present study, we established a cell model based on the single-electrode patch-clamp technique for characterization of GLUT9 and explored the inhibitory effects of benzobromarone (BM) and probenecid (PB) on urate-induced currents in mouse GLUT9a (mGLUT9a)-expressing HEK-293T cells. The results showed that uric acid, rather than glucose perfusion, led to a rapid and large outward current by mGLUT9a in dose-, voltage-, and pH-dependent manners. BM prominently and irreversibly inhibited the uric acid-induced currents through mGLUT9a, and PB weakly and reversibly inhibited mGLUT9a. We found that depletion of K⁺ in the external solution significantly strengthened the blockade of BM on mGLUT9a. In addition, an enhanced inhibitory rate of BM was detected when the pH of the external solution was changed from 7.4 to 5.5, indicating that BM functions optimally in an acidic environment. In conclusion, the combination of the established cell model with patch-clamp techniques first revealed the function properties of GLUT9 inhibitors and may provide potential benefits to the study of GLUT9 inhibitors as antihyperuricemic or antigout agents.

The haplotype of SLC2A9_rs3733591, PKD2_rs2725220 and ABCG2_rs2231142 increases the hyperuricaemia risk and alcohol, chicken and processed meat intakes and smoking interact with its risk

We determined that a genetic haplotype increased the risk of hyperuricaemia and it interacted with lifestyle factors, including nutrients in 28,445 middle-aged Koreans. ABCG2_rs2231142, PKD2_rs2725220 and SLC2A9_rs3733591 were selected from GWAS based on hyperuricaemia (≥7 mg/dL; p = 6.88E-42, 1.56E-26 and 1.01E-20, respectively). Hyperuricaemia and gout were elevated by 3.93- and 3.23-fold, respectively, by the minor alleles as compared with the major alleles of the haplotype of the selected 3 SNPs after adjusting for covariates. The haplotype significantly interacted with alcohol, chicken and processed meat intakes, and smoking status in the hyperuricaemia risk (p = 0.002-0.007). Minor alleles of the haplotype had an association with hyperuricaemia as compared with major alleles particularly in high intakes of alcohol (2g/day), chicken (6.3g/day), and processed meat (3g/day) and smokers. In conclusion, people carrying minor alleles of the haplotype of SLC2A9_rs3733591, PKD2_rs2725220 and ABCG2_rs2231142 should avoid diets high in chicken and processed meat, alcohol drinking, and cigarette smoking to protect against hyperuricaemia risk.

Efficacy of different urinary uric acid indicators in patients with chronic kidney disease

Background

Mounting studies have shown that hyperuricemia is related to kidney diseases through multiple ways. However, the application of urinary uric acid indicators in patients with reduced renal function is not clear. In this study, we aim to determine the effects of renal function on various indicators reflecting uric acid levels in patients with chronic kidney disease (CKD).

Methods

Anthropometric and biochemical examinations were performed in 625 patients with CKD recruited from Dept of Nephrology of Huadong hospital affiliated to Fudan University. Multiple regression analyses were used to study correlations of the estimated glomerular filtration rate (eGFR) with serum uric acid (SUA) and renal handling of uric acid. For further study, smooth curve plots and threshold effect analyses were applied to clarify associations between renal function and uric acid levels.

Results

The nonlinear relationships were observed between eGFR and urinary uric acid indicators. The obvious inflection points were observed in smooth curve fitting of eGFR and fractional excretion of uric acid (FEur), excretion of uric acid per volume of glomerular filtration (EurGF). In subsequent analyses where levels of eGFR< 15 mL/min/1.73m² were dichotomized (CKD5a/CKD5b), patients in the CKD5a showed higher levels of FEur and EurGF while lower levels of urinary uric acid excretion (UUA), clearance of uric acid (Cur) and glomerular filtration load of uric acid (FLur) compared with CKD5b group (all P < 0.05). And there was no significant difference of SUA levels between two groups. On the other hand, when eGFR< 109.9 ml/min/1.73 m² and 89.1 ml/min/1.73 m², the resultant curves exhibited approximately linear associations of eGFR with Cur and FLur respectively.

Conclusion

FEur and EurGF showed significantly compensatory increases with decreased renal function. And extra-renal uric acid excretion may play a compensatory role in patients with severe renal impairment to maintain SUA levels. Moreover, Cur and FLur may be more reliable indicators of classification for hyperuricemia in CKD patients.

Update on the epidemiology, genetics, and therapeutic options of hyperuricemia

Hyperuricemia may occur when there is an excess of uric acid in the blood. Hyperuricemia may result from increased production or decreased excretion of uric acid. Elevated uric acid levels are a risk factor for gout, and various risk factors, including some medications, alcohol consumption, kidney disease, high blood pressure, hypothyroidism, and pesticide exposure, as well as obesity, are associated with an elevated risk of hyperuricemia. Although the mechanisms underlying the pathogenesis of hyperuricemia are complex, previously reported studies have revealed that hyperuricemia is involved in a variety of biological processes and signaling pathways. In this review, we summarize common comorbidities related to hyperuricemia and describe an update of epidemiology, pathogenesis, and therapeutic options of hyperuricemia. This systematic review highlights the epidemiology and risk factors of hyperuricemia. Moreover, we discuss genetic studies on hyperuricemia to uncover current status and advances in the pathogenesis of hyperuricemia. Additionally, we conclude with a reflection on the underlying mechanisms of hyperuricemia and present the alternative drug strategies for the treatment of hyperuricemia to offer more effective clinical interventions.

Advances in our understanding of gout as an auto-inflammatory disease

Gout, the most common inflammatory arthritis, is the result of hyperuricemia and inflammation induced by monosodium urate (MSU) crystal deposition. However, most people with hyperuricemia will never develop gout, implying a molecular-genetic contribution to the development of gout. Recent genomic studies reveal links between certain genetic variations and gout. We highlight recent advances in our understanding of gout as an auto-inflammatory disease. We review the auto-inflammatory aspects of gout, including the inflammasome and thirteen gout-associated inflammatory-pathway genes and associated comorbidities. This information provides important insights into emerging immune-modulating targets in the management of gout, and future novel therapeutic targets in gout treatment. Cumulatively, this has important implications for treating gout as an auto-inflammatory disease, as opposed to a purely metabolic disease.

A population-specific low-frequency variant of SLC22A12 (p.W258*) explains nearby genome-wide association signals for serum uric acid concentrations among Koreans

Prolonged hyperuricemia is a cause of gout and an independent risk factor for chronic health conditions including diabetes and chronic kidney diseases. Genome-wide association studies (GWASs) for serum uric acid (SUA) concentrations have repeatedly confirmed genetic loci including those encoding uric acid transporters such as ABCG2 and SLC9A2. However, many single nucleotide polymorphisms (SNPs) found in GWASs have been common variants with small effects and unknown functions. In addition, there is still much heritability to be explained. To identify the causative genetic variants for SUA concentrations in Korean subjects, we conducted a GWAS (1902 males) and validation study (2912 males and females) and found four genetic loci reaching genome-wide significance on chromosomes 4 (ABCG2) and 11 (FRMD8, EIF1AD and SLC22A12-NRXN2). Three loci on chromosome 11 were distributed within a distance of 1.3 megabases and they were in weak or moderate linkage disequilibrium (LD) states (r² = 0.02–0.68). In a subsequent association analysis on the GWAS loci of chromosome 11 using closely positioned markers derived from whole genome sequencing data, the most significant variant to be linked with the nearby GWAS signal was rs121907892 (c.774G>A, p.W258*) of the SLC22A12 gene. This variant, and each of the three GWAS SNPs, were in LD (r² = 0.06–0.32). The strength of association of SNPs with SUA concentration (negative logarithm of P-values) and the genetic distance (r² of LD) between rs121907892 and the surrounding SNPs showed a quantitative correlation. This variant has been found only in Korean and Japanese subjects and is known to lower the SUA concentration in the general population. Thus, this low-frequency variant, rs121907892, known to regulate SUA concentrations in previous studies, is responsible for the nearby GWAS signals.