ObjectiveTo systematically test dietary components for association with serum urate levels and to evaluate the relative contributions of estimates of diet pattern and inherited genetic variants to population variance in serum urate levels.DesignMeta-analysis of cross sectional data from the United States.Data sourcesFive cohort studies.Review methods16 760 individuals of European ancestry (8414 men and 8346 women) from the US were included in analyses. Eligible individuals were aged over 18, without kidney disease or gout, and not taking urate lowering or diuretic drugs. All participants had serum urate measurements, dietary survey data, information on potential confounders (sex, age, body mass index, average daily calorie intake, years of education, exercise levels, smoking status, and menopausal status), and genome wide genotypes. The main outcome measures were average serum urate levels and variance in serum urate levels. β values (95% confidence intervals) and Bonferroni corrected P values from multivariable linear regression analyses, along with regression partial R2 values, were used to quantitate associations.ResultsSeven foods were associated with raised serum urate levels (beer, liquor, wine, potato, poultry, soft drinks, and meat (beef, pork, or lamb)) and eight foods were associated with reduced serum urate levels (eggs, peanuts, cold cereal, skim milk, cheese, brown bread, margarine, and non-citrus fruits) in the male, female, or full cohorts. Three diet scores, constructed on the basis of healthy diet guidelines, were inversely associated with serum urate levels and a fourth, data driven diet pattern positively associated with raised serum urate levels, but each explained ≤0.3% of variance in serum urate. In comparison, 23.9% of variance in serum urate levels was explained by common, genome wide single nucleotide variation.ConclusionIn contrast with genetic contributions, diet explains very little variation in serum urate levels in the general population.

A central aspect of the pathogenesis of gout is elevated urate concentrations, which lead to the formation of monosodium urate crystals. The clinical features of gout result from an individual's immune response to these deposited crystals. Genome-wide association studies (GWAS) have confirmed the importance of urate excretion in the control of serum urate levels and the risk of gout and have identified the kidneys, the gut and the liver as sites of urate regulation. The genetic contribution to the progression from hyperuricaemia to gout remains relatively poorly understood, although genes encoding proteins that are involved in the NLRP3 (NOD-, LRR- and pyrin domain-containing 3) inflammasome pathway play a part. Genome-wide and targeted sequencing is beginning to identify uncommon population-specific variants that are associated with urate levels and gout. Mendelian randomization studies using urate-associated genetic variants as unconfounded surrogates for lifelong urate exposure have not supported claims that urate is causal for metabolic conditions that are comorbidities of hyperuricaemia and gout. Genetic studies have also identified genetic variants that predict responsiveness to therapies (for example, urate-lowering drugs) for treatment of hyperuricaemia. Future research should focus on large GWAS (that include asymptomatic hyperuricaemic individuals) and on increasing the use of whole-genome sequencing data to identify uncommon genetic variants with increased penetrance that might provide opportunities for clinical translation.

Our results in New Zealand Polynesian adults replicate, with very similar effect sizes, the association of the A allele of rs373863828 with higher BMI but lower odds of type 2 diabetes among Samoan adults living in Samoa and American Samoa.

ObjectivesGenome-wide meta-analyses of clinically defined gout were performed to identify subtype-specific susceptibility loci. Evaluation using selection pressure analysis with these loci was also conducted to investigate genetic risks characteristic of the Japanese population over the last 2000–3000 years.MethodsTwo genome-wide association studies (GWASs) of 3053 clinically defined gout cases and 4554 controls from Japanese males were performed using the Japonica Array and Illumina Array platforms. About 7.2 million single-nucleotide polymorphisms were meta-analysed after imputation. Patients were then divided into four clinical subtypes (the renal underexcretion type, renal overload type, combined type and normal type), and meta-analyses were conducted in the same manner. Selection pressure analyses using singleton density score were also performed on each subtype.ResultsIn addition to the eight loci we reported previously, two novel loci, PIBF1 and ACSM2B, were identified at a genome-wide significance level (p<5.0×10–8) from a GWAS meta-analysis of all gout patients, and other two novel intergenic loci, CD2-PTGFRN and SLC28A3-NTRK2, from normal type gout patients. Subtype-dependent patterns of Manhattan plots were observed with subtype GWASs of gout patients, indicating that these subtype-specific loci suggest differences in pathophysiology along patients’ gout subtypes. Selection pressure analysis revealed significant enrichment of selection pressure on ABCG2 in addition to ALDH2 loci for all subtypes except for normal type gout.ConclusionsOur findings on subtype GWAS meta-analyses and selection pressure analysis of gout will assist elucidation of the subtype-dependent molecular targets and evolutionary involvement among genotype, phenotype and subtype-specific tailor-made medicine/prevention of gout and hyperuricaemia.

69Serum urate is the end-product of purine metabolism. Elevated serum urate is causal of 70 gout and a predictor of renal disease, cardiovascular disease and other metabolic 71 conditions. Genome-wide association studies (GWAS) have reported dozens of loci 72 associated with serum urate control, however there has been little progress in 73 understanding the molecular basis of the associated loci. Here we employed trans-74 ancestral meta-analysis using data from European and East Asian populations to 75 identify ten new loci for serum urate levels. Genome-wide colocalization with cis-76 expression quantitative trait loci (eQTL) identified a further five new loci. By cis-and 77 trans-eQTL colocalization analysis we identified 24 and 20 genes respectively where 78 the causal eQTL variant has a high likelihood that it is shared with the serum urate-79 associated locus. One new locus identified was SLC22A9 that encodes organic anion 80 transporter 7 (OAT7). We demonstrate that OAT7 is a very weak urate-butyrate 81 exchanger. Newly implicated genes identified in the eQTL analysis include those 82 encoding proteins that make up the dystrophin complex, a scaffold for signaling 83 proteins and transporters at the cell membrane; MLXIP that, with the previously 84 identified MLXIPL, is a transcription factor that may regulate serum urate via the 85 pentose-phosphate pathway; and MRPS7 and IDH2 that encode proteins necessary for 86 mitochondrial function. Trans-ancestral functional fine-mapping identified six loci 87 (RREB1, INHBC, HLF, UBE2Q2, SFMBT1, HNF4G) with colocalized eQTL that 88 contained putative causal SNPs (posterior probability of causality > 0.8). This 89 systematic analysis of serum urate GWAS loci has identified candidate causal genes at 90 19 loci and a network of previously unidentified genes likely involved in control of 91 serum urate levels, further illuminating the molecular mechanisms of urate control. 92 93 Author Summary 94 High serum urate is a prerequisite for gout and a risk factor for metabolic disease. 95Previous GWAS have identified numerous loci that are associated with serum urate 96 control, however, only a small handful of these loci have known molecular 97 consequences. The majority of loci are within the non-coding regions of the genome 98 and therefore it is difficult to ascertain how these variants might influence serum urate 99 levels without tangible links to gene expression and / or protein function. We have 100 applied a novel bioinformatic pipeline where we combined population-specific GWAS 101 4 data with gene expression and genome connectivity information to identify putative 102 causal genes for serum urate associated loci. Overall, we identified 15 novel serum 103 urate loci and show that these loci along with previously identified loci are linked to 104 the expression of 44 genes. We show that some of the variants within these loci have 105 strong predicted regulatory function which can be further tested in functional analyses. 106 This study expands on previous GWAS by ident...

Background: The ABCG2 Q141K (rs2231142) and rs10011796 variants associate with hyperuricaemia (HU). The effect size of ABCG2 rs2231142 on urate is~60% that of SLC2A9, yet the effect size on gout is greater. We tested the hypothesis that ABCG2 plays a role in the progression from HU to gout by testing for association of ABCG2 rs2231142 and rs10011796 with gout using HU controls. Methods: We analysed 1699 European gout cases and 14,350 normouricemic (NU) and HU controls, and 912 New Zealand (NZ) Polynesian (divided into Eastern and Western Polynesian) gout cases and 696 controls. Association testing was performed using logistic and linear regression with multivariate adjusting for confounding variables. Results: In Europeans and Polynesians, the ABCG2 141K (T) allele was associated with gout using HU controls (OR = 1.85, P = 3.8E − 21 and OR meta = 1.85, P = 1.3E − 03 , respectively). There was evidence for an effect of 141K in determining HU in European (OR = 1.56, P = 1.7E − 18 ) but not in Polynesian (OR meta = 1.49, P = 0.057). For SLC2A9 rs11942223, the T allele associated with gout in the presence of HU in European (OR = 1.37, P = 4.7E − 06 ), however significantly weaker than ABCG2 rs2231142 141K (P Het = 0.0023). In Western Polynesian and European, there was epistatic interaction between ABCG2 rs2231142 and rs10011796. Combining the presence of the 141K allele with the rs10011796 CC-genotype increased gout risk, in the presence of HU, 21.5-fold in Western Polynesian (P = 0.009) and 2.6-fold in European (P = 9.9E − 06 ). The 141K allele of ABCG2 associated with increased gout flare frequency in Polynesian (P meta = 2.5E − 03 ). Conclusion: These data are consistent with a role for ABCG2 141K in gout in the presence of established HU.

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.

BackgroundFerritin positively associates with serum urate and an interventional study suggests that iron has a role in triggering gout flares. The objective of this study was to further explore the relationship between iron/ferritin and urate/gout.MethodsEuropean (100 cases, 60 controls) and Polynesian (100 cases, 60 controls) New Zealand (NZ) males and 189 US male cases and 60 male controls participated. The 10,727 participants without gout were from the Jackson Heart (JHS; African American = 1260) and NHANES III (European = 5112; African American = 4355) studies. Regression analyses were adjusted for age, sex, body mass index and C-reactive protein. To test for a causal relationship between ferritin and urate, bidirectional two-sample Mendelian randomization analysis was performed.ResultsSerum ferritin positively associated with gout in NZ Polynesian (OR (per 10 ng ml− 1 increase) = 1.03, p = 1.8E–03) and US (OR = 1.11, p = 7.4E–06) data sets but not in NZ European (OR = 1.00, p = 0.84) data sets. Ferritin positively associated with urate in NZ Polynesian (β (mg dl− 1) = 0.014, p = 2.5E–04), JHS (β = 0.009, p = 3.2E–05) and NHANES III (European β = 0.007, p = 5.1E–11; African American β = 0.011, p = 2.1E–16) data sets but not in NZ European (β = 0.009, p = 0.31) or US (β = 0.041, p = 0.15) gout data sets. Ferritin positively associated with the frequency of gout flares in two of the gout data sets. By Mendelian randomization analysis a one standard deviation unit increase in iron and ferritin was, respectively, associated with 0.11 (p = 8E–04) and 0.19 mg dl− 1 (p = 2E–04) increases in serum urate. There was no evidence for a causal effect of urate on iron/ferritin.ConclusionsThese data replicate the association of ferritin with serum urate. Increased ferritin levels associated with gout and flare frequency. There was evidence of a causal effect of iron and ferritin on urate.Electronic supplementary materialThe online version of this article (10.1186/s13075-018-1668-y) contains supplementary material, which is available to authorized users.