Pleiotropic effect of the ABCG2 gene in gout: involvement in serum urate levels and progression from hyperuricemia to gout

FABIO: TWAS fine-mapping to prioritize causal genes for binary traits

Transcriptome-wide association studies (TWAS) have emerged as a powerful tool for identifying gene-trait associations by integrating gene expression mapping studies with genome-wide association studies (GWAS). While most existing TWAS approaches focus on marginal analyses through examining one gene at a time, recent developments in TWAS fine-mapping methods enable the joint modeling of multiple genes to refine the identification of potentially causal ones. However, these fine-mapping methods have primarily focused on modeling quantitative traits and examining local genomic regions, leading to potentially suboptimal performance. Here, we present FABIO, a TWAS fine-mapping method specifically designed for binary traits that is capable of modeling all genes jointly on an entire chromosome. FABIO employs a probit model to directly link the genetically regulated expression (GReX) of genes to binary outcomes while taking into account the GReX correlation among all genes residing on a chromosome. As a result, FABIO effectively controls false discoveries while offering substantial power gains over existing TWAS fine-mapping approaches. We performed extensive simulations to evaluate the performance of FABIO and applied it for in-depth analyses of six binary disease traits in the UK Biobank. In the real datasets, FABIO significantly reduced the size of the causal gene sets by 27.9%-36.9% over existing approaches across traits. Leveraging its improved power, FABIO successfully prioritized multiple potentially causal genes associated with the diseases, including GATA3 for asthma, ABCG2 for gout, and SH2B3 for hypertension. Overall, FABIO represents an effective tool for TWAS fine-mapping of disease traits.

Causal effects of gut microbiota on gout and hyperuricemia: insights from genome-wide Mendelian randomization, RNA-sequencing, 16S rRNA sequencing, and metabolomes

BACKGROUND

This study investigated the causal relationship between gut microbiota (GM), serum metabolome, and host transcriptome in the development of gout and hyperuricemia (HUA) using genome-wide association studies (GWAS) data and HUA mouse model experiments.

METHODS

Mendelian randomization (MR) analysis of GWAS summary statistics was performed using an inverse variance weighted (IVW) approach to determine or predict the causal role of the GM on gout. The HUA mouse model was used to characterize changes in the gut microbiome, host metabolome, and host kidney transcriptome by integrating cecal 16S rRNA sequencing, untargeted serum metabolomics, and host mRNA sequencing.

RESULTS

Our analysis demonstrated causal effects of seven GM taxa on gout, including genera of Ruminococcus, Odoribacter, and Bacteroides. Thirty eight immune cell traits were associated with gout. Dysbiosis of Dubosiella, Lactobacillus, Bacteroides, Alloprevotella, and Lachnospiraceae_NK4A136_group genera were associated with changes in the serum metabolites and kidney transcriptome of the HUA model mice. The changes in the gut microbiome of the HUA model mice correlated significantly with alterations in the levels of serum metabolites such as taurodeoxycholic acid, phenylacetylglycine, vanylglycol, methyl hexadecanoic acid, carnosol, 6-aminopenicillanic acid, sphinganine, p-hydroxyphenylacetic acid, pyridoxamine, and de-o-methylsterigmatocystin, and expression of kidney genes such as CNDP2, SELENOP, TTR, CAR3, SLC12A3, SCD1, PIGR, CD74, MFSD4B5, and NAPSA.

CONCLUSION

Our study demonstrated a causal relationship between GM, immune cells, and gout. HUA development involved alterations in the vitamin B6 metabolism because of GM dysbiosis that resulted in altered pyridoxamine and pyridoxal levels, dysregulated sphingolipid metabolism, and excessive inflammation.

Association of rare and common genetic variants in MOCOS with inadequate response to allopurinol

OBJECTIVES

The minor allele of the common rs2231142 ABCG2 variant predicts inadequate response to allopurinol urate lowering therapy. We hypothesize that additional variants in genes encoding urate transporters and allopurinol-to-oxypurinol metabolic enzymes also predict allopurinol response.

METHODS

This study included a subset of participants with gout from the Long-term Allopurinol Safety Study Evaluating Outcomes in Gout Patients (LASSO), whose whole genome was sequenced (n = 563). Good responders had a 4:1 or 5:1 ratio of good [serum urate (SU) <0.36 mmol/l on allopurinol ≤300 mg/day] to poor (SU ≥0.36 mmol/l despite allopurinol >300 mg/day) responses over five to six time points, while inadequate responders had a 1:4 or 1:5 ratio of good to poor responses. Adherence to allopurinol was determined by pill counts, and for a subgroup (n = 303), by plasma oxypurinol >20μmol/l. Using the sequence kernel association test (SKAT), we estimated the combined effect of rare and common variants in urate secretory (ABCC4, ABCC5, ABCG2, SLC17A1, SLC17A3, SLC22A6, SLC22A8) and reuptake genes (SLC2A9, SLC22A11) and in allopurinol-to-oxypurinol metabolic genes (AOX1, MOCOS, XDH) on allopurinol response.

RESULTS

There was an association of rare and common variants in the allopurinol-to-oxypurinol gene group (PSKAT-C = 0.019), and in MOCOS, encoding molybdenum cofactor sulfurase, with allopurinol response (PSKAT-C = 0.011). Evidence for genetic association with allopurinol response in the allopurinol-to-oxypurinol gene group (PSKAT-C = 0.002) and MOCOS (PSKAT-C < 0.001) was stronger when adherence to allopurinol therapy was confirmed by plasma oxypurinol.

CONCLUSION

We provide evidence for common and rare genetic variation in MOCOS associating with allopurinol response.

Imperata cylindrica polysaccharide ameliorates intestinal dysbiosis and damage in hyperuricemic nephropathy

In this study, a combination of adenine and potassium oxonate was utilized to establish a hyperuricemic nephropathy (HN) mouse model, aiming to elucidate the effect through which Imperata Cylindrica polysaccharide (ICPC-a) ameliorates HN. In HN mice, an elevation in the abundance of Erysipelatoclostridium, Enterococcus, Prevotella, and Escherichia-Shigella was observed, whereas Lactobacillus and Bifidobacterium declined. Additionally, the systemic reductions in the levels of acetate, propionate, and butyrate, along with a significant increase in indole content, were noted. HN mice demonstrated intestinal barrier impairment, as evidenced by diminished mRNA expression of ZO-1, Occludin, and Claudin-1 and increased Mmp-9 levels. The pro-inflammatory factors IL-6, IL-17, TNF-α, IFN-γ, and COX-2 were overexpressed. Subsequent gavage intervention with ICPC-a markedly mitigated the inflammatory response and ameliorated colon tissue damage. ICPC-a effectively regulated the abundance of gut microbiota and their metabolites, including short-chain fatty acids (SCFAs), bile acids (BAs), and indole, promoting the correction of metabolic and gut microbiota imbalances in HN mice. These findings underscored the capacity of ICPC-a as a prebiotic to modulate gut microbiota and microbial metabolites, thereby exerting a multi-pathway and multi-targeted therapeutic effect on HN.

A systematic review of single nucleotide polymorphisms affecting allopurinol pharmacokinetics and serum uric acid level

Aim: To summarize the effects of single nucleotide polymorphisms (SNPs) on the pharmacokinetics of allopurinol to control uric acid levels.Methods: A comprehensive search was conducted in PubMed, Web of Science and Scopus databases from inception to January 2024, includes 17 articles focusing on SNPs and pharmacokinetics of allopurinol and oxypurinol.Results: A total of 11 SNPs showed a significant association with pharmacokinetics of allopurinol and oxypurinol, as well as their potential clinical implications.Conclusion: SNPs in ATP-binding cassette super-family G member 2 (ABCG2), solute carrier family 2 member 9 (SLC2A9), solute carrier family 17 member 1 (SLC17A1), solute carrier family 22 member 12 (SLC22A12), solute carrier family 22 member 13 (SLC22A13) and PDZ domain containing 1 (PDZK1) genes were associated with allopurinol clearance, while SNPs in aldehyde oxidase 1 (AOX1) genes involved in metabolism of allopurinol. SNPs in gremlin 2, DAN family BMP antagonist (GREM2) gene impacted uric acid control, but the specific mechanism governing the expression of GREM2 remains unknown. Our study indicated that the identified SNPs show contradictory effects, reflecting inconsistencies and differences observed across various studies.

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.

Diversity and scale: Genetic architecture of 2068 traits in the VA Million Veteran Program

One of the justifiable criticisms of human genetic studies is the underrepresentation of participants from diverse populations. Lack of inclusion must be addressed at-scale to identify causal disease factors and understand the genetic causes of health disparities. We present genome-wide associations for 2068 traits from 635,969 participants in the Department of Veterans Affairs Million Veteran Program, a longitudinal study of diverse United States Veterans. Systematic analysis revealed 13,672 genomic risk loci; 1608 were only significant after including non-European populations. Fine-mapping identified causal variants at 6318 signals across 613 traits. One-third (n = 2069) were identified in participants from non-European populations. This reveals a broadly similar genetic architecture across populations, highlights genetic insights gained from underrepresented groups, and presents an extensive atlas of genetic associations.

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.

Investigating the Impact of Gut Microbiota on Gout Through Mendelian Randomization

Background

The relationship between gout and gut microbiota has attracted significant attention in current research. However, due to the diverse range of gut microbiota, the specific causal effect on gout remains unclear. This study utilizes Mendelian randomization (MR) to investigate the causal relationship between gut microbiota and gout, aiming to elucidate the underlying mechanism of microbiome-mediated gout and provide valuable guidance for clinical prevention and treatment.

Materials and Methods

The largest genome-wide association study meta-analysis conducted by the MiBioGen Consortium (n=18,340) was utilized to perform a two-sample Mendelian randomization investigation on aggregate statistics of intestinal microbiota. Summary statistics for gout were utilized from the data released by EBI. Various methods, including inverse variance weighted, weighted median, weighted model, MR-Egger, and Simple-mode, were employed to assess the causal relationship between gut microbiota and gout. Reverse Mendelian randomization analysis revealed a causal association between bacteria and gout in forward Mendelian randomization analysis. Cochran's Q statistic was used to quantify instrumental variable heterogeneity.

Results

The inverse variance weighted estimation revealed that Rikenellaceae exhibited a slight protective effect on gout, while the presence of Ruminococcaceae UCG_011 is associated with a marginal increase in the risk of gout. According to the reverse Mendelian Randomization results, no significant causal relationship between gout and gut microbiota was observed. No significant heterogeneity of instrumental variables or level pleiotropy was detected.

Conclusion

Our MR analysis revealed a potential causal relationship between the development of gout and specific gut microbiota; however, the causal effect was not robust, and further research is warranted to elucidate its underlying mechanism in gout development. Considering the significant association between diet, gut microbiota, and gout, these findings undoubtedly shed light on the mechanisms of microbiota-mediated gout and provide new insights for translational research on managing and standardizing treatment for this condition.

Gut microbiota plays a significant role in gout

With the development of social economy, the incidence of gout is increasing, which is closely related to people's increasingly rich diet. Eating a diet high in purine, fat, sugar and low-fibre for a long time further aggravates gout by affecting uric acid metabolism. The renal metabolism mechanism of uric acid has been thoroughly studied. To find a new treatment method for gout, increasing studies have recently been conducted on the mechanism of intestinal excretion, metabolism and absorption of uric acid. The most important research is the relationship between intestinal microbiota and the risk of gout. Gut microbiota represent bacteria that reside in a host's gastrointestinal tract. The composition of the gut microbiota is associated with protection against pathogen colonization and disease occurrence. This review focuses on how gut microbiota affects gout through uric acid and discusses the types of bacteria that may be involved in the occurrence and progression of gout. We also describe potential therapy for gout by restoring gut microbiota homeostasis and reducing uric acid levels. We hold the perspective that changing intestinal microbiota may become a vital method for effectively preventing or treating gout.

Study on the mechanism of Orthosiphon aristatus (Blume) Miq. in the treatment of hyperuricemia by microbiome combined with metabonomics

ETHNOPHARMACOLOGICAL RELEVANCE

Growing evidence indicates that hyperuricemia is closely associated with gut microbiota dysbiosis. Orthosiphon aristatus (Blume) Miq. (O. aristatus), as a traditional Chinese medicine, has been widely used to treat hyperuricemia in China. However, the mechanism by which O. aristatus treats hyperuricemia has not been clarified.

AIM OF THE STUDY

In this study, we investigated whether the molecular mechanism underlying the anti-hyperuricemia effect of O. aristatus is related to the regulation of gut microbiota by 16S rDNA gene sequencing combined with widely targeted metabolomics.

MATERIALS AND METHODS

Hyperuricemia was induced in rats by administration of 10% fructose and 20% yeast, and the uricosuric effect was assessed by measuring the uric acid (UA) levels in serum and cecal contents. Intestinal morphology was observed by hematoxylin and eosin (HE) staining. To explore the effects of O. aristatus on the gut microbiota and its metabolites, we utilized 16S rDNA gene sequencing combined with widely targeted metabolomics. Furthermore, metabolic pathway enrichment analysis was performed on the screened differential metabolites. The real time quantitative polymerase chain reaction (RT-PCR) and western blotting (WB) were used to detect the expression of relevant proteins in the key pathway.

RESULTS

Our results indicated that O. aristatus intervention decreased serum UA levels and increased the UA levels in cecal contents in hyperuricemic rats. Additionally, O. aristatus improved intestinal morphology and altered the composition of the gut microbiota and its metabolites. Specifically, 16S rDNA revealed that O. aristatus treatment significantly reduced the abundance of unidentified-Ruminococcaceae and Lachnospiraceae-NK4A136-group. Meanwhile, widely targeted metabolomics showed that 17 metabolites, including lactose, 4-oxopentanoate and butyrate, were elevated, while 55 metabolites, such as flavin adenine dinucleotide and xanthine, were reduced. Metabolic pathway enrichment analysis found that O. aristatus was mainly involved in purine metabolism. Moreover, RT-PCR and WB suggested that O. aristatus could significantly up-regulate the expression of UA excretion transporter ATP-binding cassette subfamily G member 2 (ABCG2) in the intestine.

CONCLUSION

O. aristatus exerts UA-lowering effect by regulating the gut microbiota and ABCG2 expression, indicating that this herb holds great promise in the treatment of hyperuricemia.

New drug targets for the treatment of gout arthritis: what's new?

INTRODUCTION

Gout arthritis (GA) is an intermittent inflammatory disease affecting approximately 10% of the worldwide population. Symptomatic phases (acute flares) are timely spaced by asymptomatic periods. During an acute attack, redness, joint swelling, limited movement, and excruciating pain are common symptoms. However, the current available therapies are not fully effective in reducing symptoms and offer numerous side effects. Therefore, unveiling new drug targets and effector molecules are required in developing novel GA therapeutics.

AREAS COVERED

This review discusses the pathophysiological mechanisms of GA and explores potential pharmacological targets to ameliorate disease outcome. In addition, we listed promising pre-clinical studies demonstrating effector molecules with therapeutical potential. Among those, we emphasized the importance of natural products, including traditional Chinese medicine formulas and their multitarget mechanisms of action.

EXPERT OPINION

In our search, we observed that there is a massive gap between pre-clinical and clinical knowledge. Only a minority (4.4%) of clinical trials aimed to intervene by applying natural products or current hot targets described herein. In this sense, we envisage four possibilities for GA therapeutics, which include the repurposing of existing therapies, ALX/FPR2 agonism for improvement in disease outcome, the use of multitarget drugs (e.g. natural products), and targeting the neuroinflammatory component of GA.

Diversity and Scale: Genetic Architecture of 2,068 Traits in the VA Million Veteran Program

Genome-wide association studies (GWAS) have underrepresented individuals from non-European populations, impeding progress in characterizing the genetic architecture and consequences of health and disease traits. To address this, we present a population-stratified phenome-wide GWAS followed by a multi-population meta-analysis for 2,068 traits derived from electronic health records of 635,969 participants in the Million Veteran Program (MVP), a longitudinal cohort study of diverse U.S. Veterans genetically similar to the respective African (121,177), Admixed American (59,048), East Asian (6,702), and European (449,042) superpopulations defined by the 1000 Genomes Project. We identified 38,270 independent variants associating with one or more traits at experiment-wide P < 4.6 × 10 - 11 significance; fine-mapping 6,318 signals identified from 613 traits to single-variant resolution. Among these, a third (2,069) of the associations were found only among participants genetically similar to non-European reference populations, demonstrating the importance of expanding diversity in genetic studies. Our work provides a comprehensive atlas of phenome-wide genetic associations for future studies dissecting the architecture of complex traits in diverse populations.

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.

Uric acid in metabolic syndrome: Does uric acid have a definitive role?

Increased serum uric acid (SUA) levels are commonly seen in patients with metabolic syndrome and are widely accepted as risk factors for hypertension, gout, non-alcoholic fatty liver disease, chronic kidney disease (CKD), and cardiovascular diseases. Although some ambiguity for the exact role of uric acid (UA) in these diseases is still present, several pathophysiological mechanisms have been identified such as increased oxidative stress, inflammation, and apoptosis. Accumulating evidence in genomics enlightens genetic variabilities and some epigenetic changes that can contribute to hyperuricemia. Here we discuss the role of UA within metabolism and the consequences of asymptomatic hyperuricemia while providing newfound evidence for the associations between UA and gut microbiota and vitamin D. Increased SUA levels and beneficial effects of lowering SUA levels need to be elucidated more to understand its complicated function within different metabolic pathways and set optimal target levels for SUA for reducing risks for metabolic and cardiovascular diseases.

Gut microbiota remodeling: A promising therapeutic strategy to confront hyperuricemia and gout

The incidence of hyperuricemia (HUA) and gout continuously increases and has become a major public health problem. The gut microbiota, which colonizes the human intestine, has a mutually beneficial and symbiotic relationship with the host and plays a vital role in the host's metabolism and immune regulation. Structural changes or imbalance in the gut microbiota could cause metabolic disorders and participate in the synthesis of purine-metabolizing enzymes and the release of inflammatory cytokines, which is closely related to the occurrence and development of the metabolic immune disease HUA and gout. The gut microbiota as an entry point to explore the pathogenesis of HUA and gout has become a new research hotspot. This review summarizes the characteristics of the gut microbiota in patients with HUA and gout. Meanwhile, the influence of different dietary structures on the gut microbiota, the effect of the gut microbiota on purine and uric acid metabolism, and the internal relationship between the gut microbiota and metabolic endotoxemia/inflammatory factors are explored. Moreover, the intervention effects of probiotics, prebiotics, and fecal microbial transplantation on HUA and gout are also systematically reviewed to provide a gut flora solution for the prevention and treatment of related diseases.

A glance into the future of gout

Gout is characterized by monosodium urate (MSU) crystal deposits in and within joints. These deposits result from persistent hyperuricaemia and most typically lead to recurrent acute inflammatory episodes (gout flares). Even though some aspects of gout are well characterized, uncertainties remain; this upcoming decade should provide further insights into many of these uncertainties. Synovial fluid analysis allows for the identification of MSU crystals and unequivocal diagnosis. Non-invasive methods for diagnosis are being explored, such as Raman spectroscopy and imaging modalities. Both ultrasound and dual-energy computed tomography (DECT) allow the detection of MSU crystals; this not only provides a mean of diagnosis, but also has furthered gout knowledge defining the presence of a preclinical deposition in asymptomatic hyperuricaemia. Scientific consensus establishes the beginning of gout as the beginning of symptoms (usually the first flare), but the concept is currently under review. For effective long-term gout management, the main goal is to promote crystal dissolution treatment by reducing serum urate below 6 mg/dL (or 5 mg/dL if faster crystal dissolution is required). Current urate-lowering therapies' (ULTs) options are limited, with allopurinol and febuxostat being widely available, and probenecid, benzbromarone, and pegloticase available in some regions. New xanthine oxidase inhibitors and, especially, uricosurics inhibiting urate transporter URAT1 are under development; it is probable that the new decade will see a welcomed increase in the gout therapeutic armamentarium. Cardiovascular and renal comorbidities are common in gout patients. Studies determining whether optimal treatment of gout will positively impact these comorbidities are currently lacking, but will hopefully be forthcoming. Overall, the single change that will most impact gout management is greater uptake of international rheumatology society recommendations. Innovative strategies, such as nurse-led interventions based on these recommendations have recently demonstrated treatment success for people with gout.

Examining an Association of Single Nucleotide Polymorphisms with Hyperuricemia in Chinese Flight Attendants

Background

Both genetic and environmental factors strongly affect serum uric acid (SUA) concentrations. The incidence of hyperuricemia tends to be younger in the Chinese population. In particular, we have found a high prevalence of hyperuricemia among Chinese flight attendants, aged from 20 to 40, in our survey. This study aims to evaluate whether there is an association between gene polymorphisms and hyperuricemia among Chinese flight attendants.

Methods

A total of 532 flight attendants with high and normal serum uric acid levels were recruited. Allele-specific polymerase chain reaction (AS-PCR) was performed using blood samples of enrolled subjects.

Results

Previous studies have reported single nucleotide polymorphisms (SNPs) that are tightly associated with uric acid levels. Among them, six SNPs that are strongly associated with SUA or gout in Asians, for instance ABCG2 (rs2231142, rs72552713 and rs2231137), GCKR (rs780094), SLC2A9 (rs1014290) and SLC17A1 (rs1183201), were selected for AS-PCR analyses. We found that SNPs such as ABCG2 rs2231142, GCKR rs780094 and SLC2A9 rs1014290 are strongly associated with hyperuricemia in male flight attendants, and SLC2A9 rs1014290 among female flight attendants.

Conclusion

Our study provides evidences of an association between SNPs and hyperuricemia in the Chinese flight attendants, and highlights the significance of improving diagnostics and prevention of disease development in uric acid metabolism disorders and gout using these SNPs.

CREBRF missense variant rs373863828 has both direct and indirect effects on type 2 diabetes and fasting glucose in Polynesian peoples living in Samoa and Aotearoa New Zealand

INTRODUCTION

The minor allele of a missense variant, rs373863828, in CREBRF is associated with higher body mass index (BMI), lower fasting glucose, and lower odds of type 2 diabetes. rs373863828 is common in Pacific Island populations (minor allele frequency (MAF) 0.096-0.259) but rare in non-Pacific Island populations (MAF <0.001). We examined the cross-sectional associations between BMI and rs373863828 in type 2 diabetes and fasting glucose with a large sample of adults of Polynesian ancestries from Samoa, American Samoa, and Aotearoa New Zealand, and estimated the direct and indirect (via BMI) effects of rs373863828 on type 2 diabetes and fasting glucose.

RESEARCH DESIGN AND METHODS

We regressed type 2 diabetes and fasting glucose on BMI and rs373863828 stratified by obesity, regressed type 2 diabetes and fasting glucose on BMI stratified by rs373863828 genotype, and assessed the effects of rs373863828 on type 2 diabetes and fasting glucose with path analysis. The regression analyses were completed separately in four samples that were recruited during different time periods between 1990 and 2010 and then the results were meta-analyzed. All samples were pooled for the path analysis.

RESULTS

Association of BMI with type 2 diabetes and fasting glucose may be greater in those without obesity (OR=7.77, p=0.015 and β=0.213, p=9.53×10^-5, respectively) than in those with obesity (OR=5.01, p=1.12×10^-9 and β=0.162, p=5.63×10^-6, respectively). We did not observe evidence of differences in the association of BMI with type 2 diabetes or fasting glucose by genotype. In the path analysis, the minor allele has direct negative (lower odds of type 2 diabetes and fasting glucose) and indirect positive (higher odds of type 2 diabetes and fasting glucose) effects on type 2 diabetes risk and fasting glucose, with the indirect effects mediated through a direct positive effect of rs373863828 on BMI.

CONCLUSIONS

There may be a stronger effect of BMI on fasting glucose in Polynesian individuals without obesity than in those with obesity. Carrying the rs373863828 minor allele does not decouple higher BMI from higher odds of type 2 diabetes.

Multidrug efflux transporter ABCG2: expression and regulation

The adenosine triphosphate (ATP)-binding cassette efflux transporter G2 (ABCG2) was originally discovered in a multidrug-resistant breast cancer cell line. Studies in the past have expanded the understanding of its role in physiology, disease pathology and drug resistance. With a widely distributed expression across different cell types, ABCG2 plays a central role in ATP-dependent efflux of a vast range of endogenous and exogenous molecules, thereby maintaining cellular homeostasis and providing tissue protection against xenobiotic insults. However, ABCG2 expression is subjected to alterations under various pathophysiological conditions such as inflammation, infection, tissue injury, disease pathology and in response to xenobiotics and endobiotics. These changes may interfere with the bioavailability of therapeutic substrate drugs conferring drug resistance and in certain cases worsen the pathophysiological state aggravating its severity. Considering the crucial role of ABCG2 in normal physiology, therapeutic interventions directly targeting the transporter function may produce serious side effects. Therefore, modulation of transporter regulation instead of inhibiting the transporter itself will allow subtle changes in ABCG2 activity. This requires a thorough comprehension of diverse factors and complex signaling pathways (Kinases, Wnt/β-catenin, Sonic hedgehog) operating at multiple regulatory levels dictating ABCG2 expression and activity. This review features a background on the physiological role of transporter, factors that modulate ABCG2 levels and highlights various signaling pathways, molecular mechanisms and genetic polymorphisms in ABCG2 regulation. This understanding will aid in identifying potential molecular targets for therapeutic interventions to overcome ABCG2-mediated multidrug resistance (MDR) and to manage ABCG2-related pathophysiology.

Purine metabolites and complex diseases: role of genes and nutrients

PURPOSE OF REVIEW

Purines have several important physiological functions as part of nucleic acids and as intracellular and extracellular signaling molecules. Purine metabolites, particularly uric acid, have been implicated in congenital and complex diseases. However, their role in complex diseases is not clear and they have both beneficial and detrimental effects on disease pathogenesis. In addition, the relationship between purines and complex diseases is affected by genetic and nutritional factors. This review presents latest findings about the relationship between purines and complex diseases and the effect of genes and nutrients on this relationship.

RECENT FINDINGS

Evidence from recent studies show strong role of purines in complex diseases. Although they are causal in only few diseases, our knowledge about their role in other diseases is still evolving. Of all the purines, uric acid is the most studied. Uric acid acts as an antioxidant as well as a prooxidant under different conditions, thus, its role in disease also varies. Other purines, adenosine and inosine have been less studied, but they have neuroprotective properties which are valuable in neurodegenerative diseases.

SUMMARY

Purines are molecules with great potential in disease pathogenesis as either metabolic markers or therapeutic targets. More studies need to be conducted to understand their relevance for complex diseases.

Variants in urate transporters, ADH1B, GCKR and MEPE genes associate with transition from asymptomatic hyperuricaemia to gout: results of the first gout versus asymptomatic hyperuricaemia GWAS in Caucasians using data from the UK Biobank

OBJECTIVES

To perform a genome-wide association study (GWAS) of gout cases versus asymptomatic hyperuricaemia (AH) controls, and gout cases versus normouricaemia controls, and to generate a polygenic risk score (PRS) to determine gout-case versus AH-control status.

METHODS

Gout cases and AH controls (serum urate (SU) ≥6.0 mg/dL) from the UK Biobank were divided into discovery (4934 cases, 56 948 controls) and replication (2115 cases, 24 406 controls) cohorts. GWAS was conducted and PRS generated using summary statistics in discovery cohort as the base dataset and the replication cohort as the target dataset. The predictive ability of the model was evaluated. GWAS were performed to identify variants associated with gout compared with normouricaemic controls using SU <6.0 mg/dL and <7.0 mg/dL thresholds, respectively.

RESULTS

Thirteen independent single nucleotide polymorphisms (SNPs) in ABCG2, SLC2A9, SLC22A11, GCKR, MEPE, PPM1K-DT, LOC105377323 and ADH1B reached genome-wide significance and replicated as predictors of AH to gout transition. Twelve of 13 associations were novel for this transition, and rs1229984 (ADH1B) was identified as GWAS locus for gout for the first time. The best PRS model was generated from association data of 17 SNPs; and had predictive ability of 58.5% that increased to 69.2% on including demographic factors. Two novel SNPs rs760077(MTX1) and rs3800307(PRSS16) achieved GWAS significance for association with gout compared with normouricaemic controls using both SU thresholds.

CONCLUSION

The association of urate transporters with gout supports the central role of hyperuricaemia in its pathogenesis. Larger GWAS are required to identify if variants in inflammatory pathways contribute to progression from AH to gout.

The Epidemiology and Genetics of Hyperuricemia and Gout across Major Racial Groups: A Literature Review and Population Genetics Secondary Database Analysis

Gout is an inflammatory condition caused by elevated serum urate (SU), a condition known as hyperuricemia (HU). Genetic variations, including single nucleotide polymorphisms (SNPs), can alter the function of urate transporters, leading to differential HU and gout prevalence across different populations. In the United States (U.S.), gout prevalence differentially affects certain racial groups. The objective of this proposed analysis is to compare the frequency of urate-related genetic risk alleles between Europeans (EUR) and the following major racial groups: Africans in Southwest U.S. (ASW), Han-Chinese (CHS), Japanese (JPT), and Mexican (MXL) from the 1000 Genomes Project. The Ensembl genome browser of the 1000 Genomes Project was used to conduct cross-population allele frequency comparisons of 11 SNPs across 11 genes, physiologically involved and significantly associated with SU levels and gout risk. Gene/SNP pairs included: ABCG2 (rs2231142), SLC2A9 (rs734553), SLC17A1 (rs1183201), SLC16A9 (rs1171614), GCKR (rs1260326), SLC22A11 (rs2078267), SLC22A12 (rs505802), INHBC (rs3741414), RREB1 (rs675209), PDZK1 (rs12129861), and NRXN2 (rs478607). Allele frequencies were compared to EUR using Chi-Square or Fisher’s Exact test, when appropriate. Bonferroni correction for multiple comparisons was used, with p < 0.0045 for statistical significance. Risk alleles were defined as the allele that is associated with baseline or higher HU and gout risks. The cumulative HU or gout risk allele index of the 11 SNPs was estimated for each population. The prevalence of HU and gout in U.S. and non-US populations was evaluated using published epidemiological data and literature review. Compared with EUR, the SNP frequencies of 7/11 in ASW, 9/11 in MXL, 9/11 JPT, and 11/11 CHS were significantly different. HU or gout risk allele indices were 5, 6, 9, and 11 in ASW, MXL, CHS, and JPT, respectively. Out of the 11 SNPs, the percentage of risk alleles in CHS and JPT was 100%. Compared to non-US populations, the prevalence of HU and gout appear to be higher in western world countries. Compared with EUR, CHS and JPT populations had the highest HU or gout risk allele frequencies, followed by MXL and ASW. These results suggest that individuals of Asian descent are at higher HU and gout risk, which may partly explain the nearly three-fold higher gout prevalence among Asians versus Caucasians in ambulatory care settings. Furthermore, gout remains a disease of developed countries with a marked global rising.

Noriega L, Tovar A, Alegría-Torres JA. Polymorphisms of the genes ABCG2, SLC22A12 and XDH and their relation with hyperuricemia and hypercholesterolemia in Mexican young adults

Background: Hyperuricemia is a pathological condition associated with risk factors of cardiovascular disease. In this study, three genetic polymorphisms were genotyped as predisposing factors of hyperuricemia. Methods: A total of 860 Mexicans (129 cases and 731 controls) between 18 and 25 years of age were genotyped for the ABCG2 (Q191K),  SLC22A12 (517G>A), and  XDH (518T>C) polymorphisms, as predisposing factors of hyperuricemia. Biochemical parameters were measured by spectrophotometry, while genetic polymorphisms were analyzed by real-time PCR. An analysis of the risk of hyperuricemia in relation to the variables studied was carried out using a logistic regression. Results: Male sex, being overweight or obese, having hypercholesterolemia or having hypertriglyceridemia were factors associated with hyperuricemia ( p ≤ 0.05). The ABCG2 polymorphism was associated with hyperuricemia (OR = 2.43, 95% CI: 1.41-4.17, p = 0.001) and hypercholesterolemia (OR = 4.89, 95% CI: 1.54-15.48, p = 0.003), employing a dominant model, but only in male participants. Conclusions: The ABCG2 (Q191K) polymorphism increases the risk of hyperuricemia and hypercholesterolemia in young Mexican males.

Polymorphisms of the genes ABCG2, SLC22A12 and XDH and their relation with hyperuricemia and hypercholesterolemia in Mexican young adults

Background: Hyperuricemia is a pathological condition associated with risk factors of cardiovascular disease. In this study, three genetic polymorphisms were genotyped as predisposing factors of hyperuricemia. Methods: A total of 860 Mexicans between 18 and 25 years of age were genotyped for the ABCG2 (rs2231142), SLC22A12 (rs476037), and XDH (rs1042039) polymorphisms, as predisposing factors of hyperuricemia. Biochemical parameters were measured by spectrophotometry, while genetic polymorphisms were analyzed by real-time PCR. An analysis of the risk of hyperuricemia in relation to the variables studied was carried out using a logistic regression. Results: Male sex, being overweight or obese, having hypercholesterolemia or having hypertriglyceridemia were factors associated with hyperuricemia ( p ≤ 0.05). The ABCG2 polymorphism was associated with hyperuricemia (OR = 2.43, 95% CI: 1.41-4.17, p = 0.001) and hypercholesterolemia (OR = 4.89, 95% CI: 1.54-15.48, p = 0.003), employing a dominant model, but only in male participants. Conclusions: The ABCG2 (rs2231142) polymorphism increases the risk of hyperuricemia and hypercholesterolemia in young Mexican males.

Trans-ancestral dissection of urate- and gout-associated major loci SLC2A9 and ABCG2 reveals primate-specific regulatory effects

Gout is a complex inflammatory arthritis affecting ~20% of people with an elevated serum urate level (hyperuricemia). Gout and hyperuricemia are essentially specific to humans and other higher primates, with varied prevalence across ancestral groups. SLC2A9 and ABCG2 are major loci associated with both urate and gout in multiple ancestral groups. However, fine mapping has been challenging due to extensive linkage disequilibrium underlying the associated regions. We used trans-ancestral fine mapping integrated with primate-specific genomic information to address this challenge. Trans-ancestral meta-analyses of GWAS cohorts of either European (EUR) or East Asian (EAS) ancestry resulted in single-variant resolution mappings for SLC2A9 (rs3775948 for urate and rs4697701 for gout) and ABCG2 (rs2622621 for gout). Tests of colocalization of variants in both urate and gout suggested existence of a shared candidate causal variant for SLC2A9 only in EUR and for ABCG2 only in EAS. The fine-mapped gout variant rs4697701 was within an ancient enhancer, whereas rs2622621 was within a primate-specific transposable element, both supported by functional evidence from the Roadmap Epigenomics project in human primary tissues relevant to urate and gout. Additional primate-specific elements were found near both loci and those adjacent to SLC2A9 overlapped with known statistical epistatic interactions associated with urate as well as multiple super-enhancers identified in urate-relevant tissues. We conclude that by leveraging ancestral differences trans-ancestral fine mapping has identified ancestral and functional variants for SLC2A9 or ABCG2 with primate-specific regulatory effects on urate and gout.

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.