Search

Objective: Caffeine, an adenosine receptor antagonist, is a potent central nervous system stimulant that also impairs insulin signaling. Recent studies have suggested that coffee consumption lowers serum urate (SU) and protects against gout by unknown mechanisms. We hypothesized that caffeine lowers SU by affecting activity of urate transporters. Methods: We examined the effect of caffeine and adenosine on basal and insulin stimulation of net 14C‐urate uptake in the human renal proximal tubule cell line PTC‐05 and on individual urate transporters expressed in Xenopus laevis oocytes. Results: We found that caffeine and adenosine efficiently inhibited both basal and insulin stimulation of net 14C‐urate uptake mediated by endogenous urate transporters in PTC‐05 cells. In oocytes expressing individual urate transporters, caffeine (>0.2 mM) more efficiently inhibited the basal urate transport activity of GLUT9 isoforms, OAT4, OAT1, OAT3, NPT1, ABCG2, and ABCC4 than did adenosine without significantly affecting URAT1 and OAT10. However, unlike adenosine, caffeine at lower concentrations (<0.2 mM) very effectively inhibited insulin activation of urate transport activity of GLUT9, OAT10, OAT1, OAT3, NPT1, ABCG2, and ABCC4 by blocking activation of Akt and extracellular signal–regulated kinase. Conclusion: We postulate that inhibition of urate transport activity of the re‐absorptive transporters GLUT9, OAT10, and OAT4 by caffeine is a key mechanism in its urate‐lowering effects. Additionally, the ability of caffeine to block insulin‐activated urate transport by GLUT9a and OAT10 suggests greater relative inhibition of these transporters in hyperinsulinemia. [ABSTRACT FROM AUTHOR]

Objective: In gout, hyperuricemia promotes urate crystal deposition, which stimulates the NLRP3 inflammasome and interleukin‐1β (IL‐1β)–mediated arthritis. Incident gout without background hyperuricemia is rarely reported. To identify hyperuricemia‐independent mechanisms driving gout incidence and progression, we characterized erosive urate crystalline inflammatory arthritis in a young female patient with normouricemia diagnosed as having sufficient and weighted classification criteria for gout according to the American College of Rheumatology (ACR)/EULAR gout classification criteria (the proband). Methods: We conducted whole‐genome sequencing, quantitative proteomics, whole‐blood RNA‐sequencing analysis using serum samples from the proband. We used a mouse model of IL‐1β–induced knee synovitis to characterize proband candidate genes, biomarkers, and pathogenic mechanisms of gout. Results: Lubricin level was attenuated in human proband serum and associated with elevated acute‐phase reactants and inflammatory whole‐blood transcripts and transcriptional pathways. The proband had predicted damaging gene variants of NLRP3 and of inter‐α trypsin inhibitor heavy chain 3, an inhibitor of lubricin‐degrading cathepsin G. Changes in the proband's serum protein interactome network supported enhanced lubricin degradation, with cathepsin G activity increased relative to its inhibitors, SERPINB6 and thrombospondin 1. Activation of Toll‐like receptor 2 (TLR‐2) suppressed levels of lubricin mRNA and lubricin release in cultured human synovial fibroblasts (P < 0.01). Lubricin blunted urate crystal precipitation and IL‐1β induction of xanthine oxidase and urate in cultured macrophages (P < 0.001). In lubricin‐deficient mice, injection of IL‐1β in knees increased xanthine oxidase–positive synovial resident M1 macrophages (P < 0.05). Conclusion: Our findings linked normouricemic erosive gout to attenuated lubricin, with impaired control of cathepsin G activity, compounded by deleterious NLRP3 variants. Lubricin suppressed monosodium urate crystallization and blunted IL‐1β–induced increases in xanthine oxidase and urate in macrophages. The collective activities of articular lubricin that could limit incident and erosive gouty arthritis independently of hyperuricemia are subject to disruption by inflammation, activated cathepsin G, and synovial fibroblast TLR‐2 signaling. [ABSTRACT FROM AUTHOR]

Gout is at least three times more prevalent in males than in females. However, concurrent with rising total gout prevalence, complex factors, including comorbidities, diet, lifestyle, and aging, have promoted higher gout prevalence in females. This narrative review focuses on summarizing recent developments in the landscape of gout in females and the mechanisms involved. New knowledge on sex hormone effects on both urate-excreting and urate-reabsorbing transporters and higher hypertension and chronic kidney disease prevalence in females compared to males may help explain why gout incidence rises robustly after menopause in females, to approach that in males. Racial and ethnic factors, risk profiles based on heritable genetic polymorphisms of urate transporters, diet, body mass index, and lifestyle factors differ according to sex. In addition, sex differences in clinical phenotypes, outcomes of gout, and non-gout illnesses include more frequent comorbidities, more pain and disability during gout flares, different perceptions of disease burden, and more frequent severe cutaneous hypersensitivity reaction to allopurinol in females. Collectively, such findings support the potential clinical benefits of tailoring gout and hyperuricemia treatment according to sex. [ABSTRACT FROM AUTHOR]

Context: Cardio-metabolic conditions in Aotearoa New Zealand (NZ) Māori and non-indigenous Polynesian (Pacific) populations have been increasing in prevalence and severity, especially over the last two decades. Objectives: To assess knowledge on genetic and non-genetic risk factors for cardio-metabolic disease in the Māori and Pacific populations residing in Aotearoa NZ by a semi-systematic review of the PubMed database. To outline possible future directions in genetic epidemiological research with Māori and Pacific communities. Results: There have been few studies to confirm that risk factors in other populations also associate with cardio-metabolic conditions in Māori and Pacific populations. Such data are important when interventions are considered. Genetic studies have been sporadic, with no genome-wide association studies done. Conclusions: Biomedical research with Māori and Pacific communities is important to reduce the prevalence and impact of the cardio-metabolic diseases, as precision medicine is implemented in other Aotearoa NZ populations using overseas findings. Genuine engagement with Māori and Pacific communities is needed to ensure positive outcomes for genetic studies, from data collection through to analysis and dissemination. Important is building trust, understanding by researchers of fundamental cultural concepts and implementing protocols that minimise risks and maximise benefits. Approaches that utilise information such as genealogical information and whole genome sequencing technologies will provide new insights into cardio-metabolic conditions—and new interventions for affected individuals and families. [ABSTRACT FROM AUTHOR]

Background: The gene PPARGC1A, in particular the Gly482Ser variant (rs8192678), had been proposed to be subject to natural selection, particularly in recent progenitors of extant Polynesian populations. Reasons include high levels of population differentiation and increased frequencies of the derived type 2 diabetes (T2D) risk 482Ser allele, and association with body mass index (BMI) in a small Tongan population. However, no direct statistical tests for selection have been applied. Methods: Using a range of Polynesian populations (Tongan, Māori, Samoan) we re-examined evidence for association between Gly482Ser with T2D and BMI as well as gout. Using also Asian, European, and African 1000 Genome Project samples a range of statistical tests for selection (FST, integrated haplotype score (iHS), cross population extended haplotype homozygosity (XP-EHH), Tajima's D and Fay and Wu's H) were conducted on the PPARGC1A locus. Results: No statistically significant evidence for association between Gly482Ser and any of BMI, T2D or gout was found. Population differentiation (FST) was smallest between Asian and Pacific populations (New Zealand Māori ≤ 0. 35, Samoan ≤ 0.20). When compared to European (New Zealand Māori ≤ 0.40, Samoan ≤ 0.25) or African populations (New Zealand Māori ≤ 0.80, Samoan ≤ 0.66) this differentiation was larger. We did not find any strong evidence for departure from neutral evolution at this locus when applying any of the other statistical tests for selection. However, using the same analytical methods, we found evidence for selection in specific populations at previously identified loci, indicating that lack of selection was the most likely explanation for the lack of evidence of selection in PPARGC1A. Conclusion: We conclude that there is no compelling evidence for selection at this locus, and that this gene should not be considered a candidate thrifty gene locus in Pacific populations. High levels of population differentiation at this locus and the reported absence of the derived 482Ser allele in some Melanesian populations, can alternatively be explained by multiple out-of-Africa migrations by ancestral progenitors, and subsequent genetic drift during colonisation of Polynesia. Intermediate 482Ser allele frequencies in extant Western Polynesian populations could therefore be due to recent admixture with Melanesian progenitors. [ABSTRACT FROM AUTHOR]

Gout is a chronic disease of deposition of monosodium urate crystals, which form in the presence of increased urate concentrations. Although environmental factors contribute to hyperuricaemia, renal and gut excretion of urate is central to regulation of serum urate, and genetic factors are important. Activation of the NLRP3 inflammasome and release of interleukin 1β have key roles in initiation of acute gout flares. A "treat to target serum urate" approach is essential for effective gout management; long-term lowering of serum urate to less than 360 μmol/L leads to crystal dissolution and ultimately to suppression of flares. An allopurinol dose-escalation strategy is frequently effective for achieving treatment targets, and several new urate-lowering drugs are also available. Worldwide, rates of initiation and continuation of urate-lowering therapy are very low, and, consequently, achievement of serum urate targets is infrequent. Strategies to improve quality of gout care are needed. [ABSTRACT FROM AUTHOR]

Introduction Rheumatic fever (RF) incidence among New Zealand (NZ) individuals of Polynesian (Māori and Pacific) ancestry remains among the highest in the world. Polymorphisms in the IL-6, IL1RN, and CTLA4 genes have been associated with RF, and their products are modulated by new medications. Confirmation of these previous associations could help guide clinical approaches. We aimed to test IL-6, IL-1RA (IL1RN), and CTLA4 functional SNPs in 204 rheumatic heart disease (RHD) patients and 116 controls of Māori and Pacific ancestry. Material and method Self-reported ancestry of the eight great-grandparents defined ancestry of participants. Severity of carditis was classified according to the 2012 World Heart Federation guideline for the echocardiographic diagnosis of RHD. The IL-6 promoter rs1800797, IL1RN rs447713 and CTLA4 rs3087243 SNPs were genotyped by Taqman. Correlations were assessed by logistic regression analysis adjusting for gender and ancestry. Results The IL-6 rs1800797 variant was significantly associated with RHD with carriers of the GG genotype 6.09 (CI 1.23; 30.23) times more likely to develop RHD than the carriers of the AA genotype (P = 0.027). No significant associations with RHD were found for the IL1RN rs447713 and CTLA4 rs3087243 SNPs. Patients carrying the G allele (GG plus AG genotype) for the IL1RN rs447713 SNP had 2.36 times (CI 1.00; 5.56) more severe carditis than those without this allele (the AA genotype) (P = 0.049). Conclusion The IL-6 promoter rs1800797 (−597G/A) SNP may influence susceptibility to RHD of people of Māori and Pacific ancestry living in NZ. The IL1RN rs447713 SNP may influence the severity of carditis in this population. [ABSTRACT FROM AUTHOR]

A commentary is presented on a study which identified a locus containing the gene PPARGC1B as a risk factor for gout. Topics covered include the testing of single nucleotide variants from five genes for their association with gout, expression of PPARGC1B and the impact of the PPARGC1B R265Q amino acid change on NOD-like receptor family pyrin domain containing 3 (NLRP3) activation.

The extent of contribution from common gene copy number (CN) variants in human disease is currently unresolved. Part of the reason for this is the technical difficulty in directly measuring CN variation (CNV) using molecular methods, and the lack of single nucleotide polymorphisms (SNPs) that can tag complex CNV that has arisen multiple times on different SNP haplotypes. One CNV locus implicated in human disease is FCGR. Here we aimed to use next-generation sequencing (NGS) data from the 1000 Genomes Project to assign CN at FCGR3A and FCGR3B and to comprehensively assess the ability of SNPs to tag specific CN variants. A read-depth algorithm was developed (CNVrd) and validated on a subset of HapMap samples using CN assignments that had previously been determined using molecular and microarray methods. At 7 out of 9 other complex loci there was >90% concordance with microarray data. However, given that some prior knowledge of CN is required, the generalizability of CNVrd is limited and should be applied to other complex CNV loci with caution. Subsequently, CN was assigned et FCGR3B using CNVrd in a total of 952 samples from the 1000 Genomes Project, using three classes and SNPs that correlated with duplication were identified. The best tag SNP was observed in the Mexican-American sample set for duplication at FCGR3B. This SNP (rs117435514, r2 = 0.79) also tagged similar duplication in Chinese and Japanese (r2 = 0.35–0.60), but not in Caucasian or African. No tag SNP for duplication at FCGR3A or deletion at FCGR3B was identified in any population. We conclude that it is possible to tag CNV at the FCGR locus, but CN and SNPs have to be characterized and correlated on a population-specific basis. [ABSTRACT FROM AUTHOR]

Objectives. To describe the national demographics, comorbidities and mortality of admissions associated with gout in New Zealand (NZ) from 1999 to 2009 and compare this with English gout admission data from the same period.Methods. The characteristics of all admissions due to or complicated by gout in NZ from 1999 to 2009 were analysed. These findings were then compared with the wider NZ population and the English National Health Service (NHS) gout admission rates from 1999 to 2009.Results. There were 10 241 admissions due to gout (group A) and 34 318 admissions complicated by gout (group B) in NZ from 1999 to 2009. There were 32 741 admissions due to gout in England over the same period. Gout admissions rose at 5.5% per year in NZ and at 7.2% per year in England over the study period. NZ gout patients admitted to hospital were more likely to be Māori or a Pacific Islander and had 3–7 comorbidities. Multiple admissions were common with 1479 NZ gout patients admitted more than once. Comorbidities varied between the NZ groups A and B: hypertension (19–39%), renal disease (16–27%) and diabetes mellitus (20–27%) were common. Heart failure (27.6%) and cardiovascular disease (39.1%) were common in those who had gout complicating their hospital admission. This group also had poorer survival compared with those admitted primarily for gout.Conclusion. This is the first study to describe the epidemiology of admissions associated with gout across an entire country. Admissions are rising in both countries studied and those admitted in NZ have a high rate of comorbidity and re-admission. [ABSTRACT FROM PUBLISHER]

Abstract: Gout results from elevated urate concentrations in the blood (hyperuricaemia). When super-saturation of urate is reached, monosodium urate crystals form within the joint. In some individuals, these crystals elicit a painful self-limiting inflammatory response that is characteristic of acute gouty arthritis. The most important cause of hyperuricaemia is reduced excretion of uric acid in the urine. Uric acid excretion is coordinated by a suite of urate transport molecules expressed in the renal collecting tubules, and is a key physiological checkpoint in gout. Other checkpoints in gout are hepatic production of urate, monosodium urate crystal formation, and initiation of the acute inflammatory response. Genome-wide association scans for genes regulating serum urate concentrations have identified two major regulators of hyperuricaemia– the renal urate transporters SLC2A9 and ABCG2. The risk variants at each gene approximately double the risk for gout in people of Caucasian ancestry, with SLC2A9 also resulting in higher risk for gout in people of Polynesian ancestry, a diverse population characterized by a high prevalence of gout. Ongoing genetic association studies are identifying and confirming other genes controlling serum urate concentrations; although genome-wide association studies in gout per se await recruitment of suitable case sample sets. [ABSTRACT FROM AUTHOR]

Abstract: Gout results from elevated urate concentrations in the blood (hyperuricaemia). When super-saturation of urate is reached, monosodium urate crystals form within the joint. In some individuals, these crystals elicit a painful self-limiting inflammatory response that is characteristic of acute gouty arthritis. The most important cause of hyperuricaemia is reduced excretion of uric acid in the urine. Uric acid excretion is coordinated by a suite of urate transport molecules expressed in the renal collecting tubules, and is a key physiological checkpoint in gout. Other checkpoints in gout are hepatic production of urate, monosodium urate crystal formation, and initiation of the acute inflammatory response. Genome-wide association scans for genes regulating serum urate concentrations have identified two major regulators of hyperuricaemia– the renal urate transporters SLC2A9 and ABCG2. The risk variants at each gene approximately double the risk for gout in people of Caucasian ancestry, with SLC2A9 also resulting in higher risk for gout in people of Polynesian ancestry, a diverse population characterized by a high prevalence of gout. Ongoing genetic association studies are identifying and confirming other genes controlling serum urate concentrations; although genome-wide association studies in gout per se await recruitment of suitable case sample sets. [Copyright &y& Elsevier]

Abstract: The ‘A1’ genetic variant of β-casein in milk has been linked to type 1 diabetes (T1D). The keystone piece of supporting evidence is an ecological study positively correlating the incidence of T1D with amount of A1 β-casein consumption per capita. Of relevance, A1 β-casein consumption is also positively correlated with latitude, itself implicated in T1D through vitamin D deficiency. Ecological and biological evidence convincingly implicate vitamin D deficiency in T1D. Latitude is a confounder of the ecological data that underpin the hypothesis that A1 β-casein in cow''s milk is a causative factor in T1D. [Copyright &y& Elsevier]

The past few years have seen the identification of PTPN22 and the confirmation of CTLA-4 as common autoimmune disease genes. Together with MHC and INS, these developments have increased the collection of confirmed susceptibility loci for autoimmunity. In this article, the latest developments related to these genes and to other recently studied candidate autoimmune susceptibility loci (PDCD1, FCRL3, SUMO4, CD25, PADI4 and SLC22A4) are reviewed. Collectively, these genes strongly indicate that aberrant inhibition of the signalling cascade initiated by activation of the T-cell receptor is involved in the aetiology of autoimmune disease. However, much basic genetic, molecular and clinical research is still needed to help us fully understand the underlying mechanisms of autoimmunity and how these translate into prognosis or therapy. [Copyright &y& Elsevier]

Some immune system disorders, such as type 1 diabetes, multiple sclerosis (MS), and rheumatoid arthritis (RA), share common features: the presence of autoantibodies and self-reactive T-cells, and a genetic association with the major histocompatibility complex. We have previously published evidence, from 1,708 families, for linkage and association of a haplotype of three markers in the D18S487 region of chromosome 18q21 with type 1 diabetes. Here, the three markers were typed in an independent set of 627 families and, although there was evidence for linkage (maximum logarithm of odds score [MLS] = 1.2; P = 0.02), no association was detected. Further linkage analysis revealed suggestive evidence for linkage of chromosome 18q21 to type 1 diabetes in 882 multiplex families (MLS = 2.2; lambdas = 1.2; P = 0.001), and by meta-analysis the orthologous region (also on chromosome 18) is linked to diabetes in rodents (P = 9 x 10(-4)). By meta-analysis, both human chromosome 18q12-q21 and the rodent orthologous region show positive evidence for linkage to an autoimmune phenotype (P = 0.004 and 2 x 10(-8), respectively, empirical P = 0.01 and 2 x 10(-4), respectively). In the diabetes-linked region of chromosome 18q12-q21, a candidate gene, deleted in colorectal carcinoma (DCC), was tested for association with human autoimmunity in 3,380 families with type 1 diabetes, MS, and RA. A haplotype ("2-10") of two newly characterized microsatellite markers within DCC showed evidence for association with autoimmunity (P = 5 x 10(-6)). Collectively, these data suggest that a locus (or loci) exists on human chromosome 18q12-q21 that influences multiple autoimmune diseases and that this association might be conserved between species. [ABSTRACT FROM AUTHOR]

The choice of which population to study in the mapping of common disease genes may be critical. Isolated founder populations, such as that found in Finland, have already proved extremely useful for mapping the genes for specific rare monogenic disorders and are being used in attempts to map the genes underlying common, complex diseases. But simulation results suggest that, under the common disease-common variant hypothesis, most isolated populations will prove no more useful for linkage disequilibrium (LD) mapping of common disease genes than large outbred populations. There is very little empirical data to either support or refute this conclusion at present. Therefore, we evaluated LD between 21 common microsatellite polymorphisms on chromosome 18q21 in 2 genetic isolates (Finland and Sardinia) and compared the results with those observed in two mixed populations (United Kingdom and United States of America). Mean levels of LD were similar across all four populations. Our results provide empirical support for the expectation that genetic isolates like Finland and Sardinia will not prove significantly more valuable than general populations for LD mapping of common variants underlying complex disease. [ABSTRACT FROM AUTHOR]

The article discusses the study "A Mendelian Randomization Study of Circulating Uric Acid and Type 2 Diabetes" by I. Slujis, M. V. Holmes, Y. T. van der Schouw and colleagues, published within the issue. Topics covered include the uric acid-insulin resistance hypothesis, the use of a genetic epidemiological approach known as Mendelian randomization, and the single nucleotide polymorphisms identified from genome-wide association studies.

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 (P SKAT-C = 0.019), and in MOCOS , encoding molybdenum cofactor sulfurase, with allopurinol response (P SKAT-C = 0.011). Evidence for genetic association with allopurinol response in the allopurinol-to-oxypurinol gene group (P SKAT-C = 0.002) and MOCOS (P SKAT-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. [ABSTRACT FROM AUTHOR]

The article offers update on the curation of genetic associations with rheumatologic autoimmune diseases to improve patient outcomes. Topics discussed include monogenic autoimmune and/or autoinflammatory conditions, development of a framework for curation of HLA disease associations, development of a methodology for curation of complex, multigenic diseases, and curation of disease-associated somatic variants.

Objective: Initiating urate‐lowering therapy (ULT) in gout can precipitate arthritis flares. There have been limited comparisons of flare risk during the initiation and escalation of allopurinol and febuxostat, administered as a treat‐to‐target strategy with optimal anti‐inflammatory prophylaxis. Methods: This was a post‐hoc analysis of a 72‐week randomized, double‐blind, placebo‐controlled, noninferiority trial comparing the efficacy of allopurinol and febuxostat. For this analysis, the occurrence of flares was examined during weeks 0 to 24 when ULT was initiated and titrated to a serum urate (sUA) goal of less than 6 mg/dl (<5 mg/dl if tophi). Flares were assessed at regular intervals through structured participant interviews. Predictors of flare, including treatment assignment, were examined using multivariable Cox proportional hazards regression. Results: Study participants (n = 940) were predominantly male (98.4%) and had a mean age of 62.1 years with approximately equal proportions receiving allopurinol or febuxostat. Mean baseline sUA was 8.5 mg/dl and all participants received anti‐inflammatory prophylaxis (90% colchicine). In a multivariable model, there were no significant associations of ULT treatment (hazard ratio [HR] 1.17; febuxostat vs allopurinol), ULT‐dose escalation (HR 1.18 vs no escalation), prophylaxis type, or individual comorbidity with flare and no evidence of ULT‐dose escalation interaction. Factors independently associated with flare risk during ULT initiation/escalation included younger age, higher baseline sUA, and absence of tophi. Conclusion: These results demonstrate that gout flare risk during the initiation and titration of allopurinol is similar to febuxostat when these agents are administered according to a treat‐to‐target strategy using gradual ULT‐dose titration and best practice gout flare prophylaxis. [ABSTRACT FROM AUTHOR]

15th Anniversary this year: the ECN workshop is set up in Paris, down town. Every year ECN workshop offers a unique opportunity for clinicians and researchers interested in crystals, inflammation, crystal-induced diseases including gout, to present their latest results and discuss novel concepts. Twenty nine out of 52 accepted abstracts are reported here. [ABSTRACT FROM AUTHOR]

Describes the cloning and characterization of a gene, pvdS, which is required for expression of pyoverdine synthesis genes in Pseudomonas aeruginosa. Isolation of plasmid clone pOT306; Contents of pOT306; Sequence analysis of the activating gene; Role of pvdS in pyoverdine synthesis; Regulation of expression of pvdS by iron.

Studies the similarity of Pseudomonas aeruginosa's pyoverdine biosynthetic gene pvdD to peptide synthetases. Identification of pvdD; Thioesterase active-site within pvdD; Similarity of pvdD to pbsC.

The pathogenesis of gout involves a series of steps beginning with hyperuricaemia, followed by the deposition of monosodium urate crystal in articular structures and culminating in an innate immune response, mediated by the NLRP3 inflammasome, to the deposited crystals. Large genome-wide association studies (GWAS) of serum urate levels initially identified the genetic variants with the strongest effects, mapping mainly to genes that encode urate transporters in the kidney and gut. Other GWAS highlighted the importance of uncommon genetic variants. More recently, genetic and epigenetic genome-wide studies have revealed new pathways in the inflammatory process of gout, including genetic associations with epigenomic modifiers. Epigenome-wide association studies are also implicating epigenomic remodelling in gout, which perhaps regulates the responsiveness of the innate immune system to monosodium urate crystals. Notably, genes implicated in gout GWAS do not include those encoding components of the NLRP3 inflammasome itself, but instead include genes encoding molecules involved in its regulation. Knowledge of the molecular mechanisms underlying gout has advanced through the translation of genetic associations into specific molecular mechanisms. Notable examples include ABCG2, HNF4A, PDZK1, MAF and IL37. Current genetic studies are dominated by participants of European ancestry; however, studies focusing on other population groups are discovering informative population-specific variants associated with gout. Genetic, epigenetic and transcriptomic studies in hyperuricaemia and gout have, in the past 6 years, provided important insights into the underlying molecular mechanisms, revealing new inflammatory pathways and epigenetic factors and expanding research beyond European populations. Key points: Genome-wide association studies (GWAS) of serum urate levels show that common genetic variants within loci encoding urate transporters and ancillary molecules confer the strongest genetic effects on the risk of hyperuricaemia and gout. Exome-wide analyses of urate levels show that uncommon protein-coding variants in established hyperuricaemia risk genes exert strong effects, emphasizing the valuable translational insights gained from identifying uncommon risk variants. Epigenome-wide analyses of urate levels highlight DNA methylation of SLC2A9 and of genes encoding molecules involved in amino acid transport and metabolism as key factors in the epigenetic regulation of urate homeostasis. Genome-wide association studies of gout highlight the importance of epigenomic pathways, suggesting that epigenetic reprogramming of innate immune cells by soluble urate increases their responsiveness to monosodium urate crystals. Genome-wide association studies of gout are yet to be conducted in under-represented populations; however, the identification of population-specific genetic variants is providing new insights into the pathogenesis of gout. The translation of genetic signals into mechanistic knowledge requires experimental studies, which are gradually being conducted in loci such as ABCG2, PDZK1, MAF and HNF4A. [ABSTRACT FROM AUTHOR]

Objective: Hyperuricemia can be stratified into four subtypes according to renal uric acid handling. The aim of this study was to comprehensively describe the biologic characteristics (including genetic background) of clinically defined hyperuricemia subtypes in two large geographically independent gout cohorts. Methods: Hyperuricemia subtype was defined as renal uric acid overload (ROL), renal uric acid underexcretion (RUE), combined, or renal normal. Twenty single nucleotide polymorphisms (SNPs) previously identified as gout risk loci or associated with serum urate (SU) concentration in the East Asian population were genotyped. Weighted polygenic risk scores were calculated to assess the cumulative effect of genetic risks on the subtypes. Results: Of the 4,873 participants, 8.8% had an ROL subtype, 60.9% RUE subtype, 23.1% combined subtype, and 7.2% normal subtype. The ROL subtype was independently associated with older age at onset, lower SU, tophi, and diabetes mellitus; RUE was associated with lower body mass index (BMI) and non–diabetes mellitus; the combined subtype was associated with younger age at onset, higher BMI, SU, estimated glomerular filtration rate (eGFR), and smoking; and the normal subtype was independently associated with older age at onset, lower SU, and eGFR. Thirteen SNPs were associated with gout with 6 shared loci and subtype‐dependent risk loci patterns. High polygenic risk scores were associated with ROL subtype (odds ratio [OR] = 9.63, 95% confidence interval [95% CI] 4.53–15.12), RUE subtype (OR = 2.18, 95% CI 1.57–3.03), and combined subtype (OR = 6.32, 95% CI 4.22–9.48) compared with low polygenic risk scores. Conclusion: Hyperuricemia subtypes classified according to renal uric acid handling have subtype‐specific clinical and genetic features, suggesting subtype‐unique pathophysiologic mechanisms. [ABSTRACT FROM AUTHOR]

La prévalence de la goutte augmente, mais les études analysant ses caractéristiques cliniques dans de grands échantillons sont insuffisantes. Cette étude s'attache à clarifier les changements dans les manifestations cliniques de la goutte en Chine au cours des dix dernières années et à analyser les caractéristiques cliniques et les facteurs de risque de la goutte précoce. Les manifestations cliniques de la goutte ont été comparées chez 9754 patients reçus pour la première fois dans notre établissement entre 2008 et 2012 (premier groupe) ou entre 2013 et 2018 (dernier groupe). La goutte apparue ≤ 30 ans a été définie comme goutte précoce et > 30 ans, comme goutte tardive. Les caractéristiques cliniques et les facteurs de risque ont été comparés entre les groupes. La goutte est apparue 4,14 ans plus tôt dans le dernier groupe (2013-2018, 5979 patients) et le pourcentage de goutte précoce (3827 patients) y était plus élevé. La durée de la maladie était significativement plus courte (5,72 ± 0,09 contre 6,01 ± 0,11, p < 0,05) et la proportion de patients présentant des tophi était plus faible dans le dernier groupe (20,0 % contre 22,0 %, p <0,05). Le dernier groupe comptait davantage de patients obèses (37,7 % contre 32,6 %, p < 0,001) et l'uricémie y était significativement plus élevée (485,5 ± 1,5 μmol/l contre 465,0 ± 1,9 μmol/l). Comme la goutte survenait à un âge plus jeune, nous avons appliqué une régression logistique multivariée et déterminé que des antécédents familiaux positifs, le sexe masculin, l'obésité, une uricémie élevée et la consommation de sodas sucrés étaient des facteurs prédictifs indépendants de goutte précoce. Les manifestations de la goutte en Chine ont évolué au cours des dix dernières années, avec notamment une tendance à une apparition plus précoce. [ABSTRACT FROM AUTHOR]

The article discusses whether Rheumatoid Arthritis (RA) a Causal Factor in Cardiovascular Disease (CVD). Presents a study that addresses the question of whether the pathogenesis of RA is causally related to CVD. The investigators found that genetic liability (the totality of the effect of genetic factors on the development of RA) is associated with an increased risk of coronary artery disease and intracerebral hemorrhage.

Aims: Dose escalation at the initiation of allopurinol therapy can be protracted and resource intensive. Tools to predict the allopurinol doses required to achieve target serum urate concentrations would facilitate the implementation of more efficient dose‐escalation strategies. The aim of this research was to develop and externally evaluate allopurinol dosing tools, one for use when the pre‐urate‐lowering therapy serum urate is known (Easy‐Allo1) and one for when it is not known (Easy‐Allo2). Methods: A revised population pharmacokinetic‐pharmacodynamic model was developed using data from 653 people with gout. Maintenance doses to achieve the serum urate target of <0.36 mmol L−1 in >80% of individuals were simulated and evaluated against external data. The predicted and observed allopurinol doses were compared using the mean prediction error (MPE) and root mean square error (RMSE). The proportion of Easy‐Allo predicted doses within 100 mg of the observed was quantified. Results: Allopurinol doses were predicted by total body weight, baseline urate, ethnicity and creatinine clearance. Easy‐Allo1 produced unbiased and suitably precise dose predictions (MPE 2 mg day−1 95% confidence interval [CI] −13‐17, RMSE 91%, 90% within 100 mg of the observed dose). Easy‐Allo2 was positively biased by about 70 mg day−1 and slightly less precise (MPE 70 mg day−1 95% CI 52‐88, RMSE 131%, 71% within 100 mg of the observed dose). Conclusions: The Easy‐Allo tools provide a guide to the allopurinol maintenance dose requirement to achieve the serum urate target of <0.36 mmol L−1 and will aid in the development of novel dose‐escalation strategies for allopurinol therapy. [ABSTRACT FROM AUTHOR]

The 14th annual international European Crystal Network was held in Paris on 2 and 3 March 2023. This in-person meeting was attended by 93 participants. Over 40 research abstract submissions were received from investigators, ranging from early career investigators to senior researchers, for plenary oral and poster presentations. Here, we present the accepted, lightly edited abstracts from the presenters consenting to have their work published. We thank and congratulate the presenters for their work and contributions to the meeting. [ABSTRACT FROM AUTHOR]

Gout is a common autoinflammatory joint diseases characterized by deposition of monosodium urate (MSU) crystals which trigger an innate immune response mediated by inflammatory cytokines. IGF1R is one of the loci associated with both urate levels and gout susceptibility in GWAS to date, and IGF-1-IGF-1R signaling is implicated in urate control. We investigate the role of IGF-1/IGF1R signaling in the context of gouty inflammation. Also, we test the gout and urate-associated IGF1R rs6598541 polymorphism for association with the inflammatory capacity of mononuclear cells. For this, freshly isolated human peripheral blood mononuclear cells (PBMCs) were exposed to recombinant IGF-1 or anti-IGF1R neutralizing antibody in the presence or absence of solubilized urate, stimulated with LPS/MSU crystals. Also, the association of rs6598541 with IGF1R and protein expression and with ex vivo cytokine production levels after stimulation with gout specific stimuli was tested. Urate exposure was not associated with IGF1R expression in vitro or in vivo. Modulation of IGF1R did not alter urate-induced inflammation. Developing urate-induced trained immunity in vitro was not influenced in cells challenged with IGF-1 recombinant protein. Moreover, the IGF1R rs6598541 SNP was not associated with cytokine production. Our results indicate that urate-induced inflammatory priming is not regulated by IGF-1/IGF1R signaling in vitro. IGF1R rs6598541 status was not asociated with IGF1R expression or cytokine production in primary human PBMCs. This study suggests that the role of IGF1R in gout is tissue-specific and may be more relevant in the control of urate levels rather than in inflammatory signaling in gout. [ABSTRACT FROM AUTHOR]

Objective: The objective of this study was to discover differential metabolites and pathways underlying infrequent gout flares (InGF) and frequent gout flares (FrGF) using metabolomics and to establish a predictive model by machine learning (ML) algorithms. Methods: Serum samples from a discovery cohort of 163 patients with InGF and 239 patients with FrGF were analyzed by mass spectrometry–based untargeted metabolomics to profile differential metabolites and explore dysregulated metabolic pathways using pathway enrichment analysis and network propagation–based algorithms. ML algorithms were performed to establish a predictive model based on selected metabolites, which was further optimized by a quantitative targeted metabolomics method and validated in an independent validation cohort with 97 participants with InGF and 139 participants with FrGF. Results: A total of 439 differential metabolites between InGF and FrGF groups were identified. Top dysregulated pathways included carbohydrates, amino acids, bile acids, and nucleotide metabolism. Subnetworks with maximum disturbances in the global metabolic networks featured cross‐talk between purine metabolism and caffeine metabolism, as well as interactions among pathways involving primary bile acid biosynthesis, taurine and hypotaurine metabolism, alanine, aspartate, and glutamate metabolism, suggesting epigenetic modifications and gut microbiome in metabolic alterations underlying InGF and FrGF. Potential metabolite biomarkers were identified using ML‐based multivariable selection and further validated by targeted metabolomics. Area under receiver operating characteristics curve for differentiating InGF and FrGF achieved 0.88 and 0.67 for the discovery and validation cohorts, respectively. Conclusion: Systematic metabolic alterations underlie InGF and FrGF, and distinct profiles are associated with differences in gout flare frequencies. Predictive modeling based on selected metabolites from metabolomics can differentiate InGF and FrGF. [ABSTRACT FROM AUTHOR]

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

Aims: This study aimed to develop and evaluate an allopurinol adherence tool based on steady‐state oxypurinol plasma concentrations, allopurinol's active metabolite. Methods: Plasma oxypurinol concentrations were simulated stochastically from an oxypurinol pharmacokinetic model for allopurinol doses of 100‐800 mg daily, accounting for differences in renal function, diuretic use and ethnicity. For each scenario, the 20th percentile for peak and trough concentrations defined the adherence threshold, below which imperfect adherence was assumed. Predictive performance was evaluated using both simulated low adherence and against data from 146 individuals with paired oxypurinol plasma concentrations and adherence measures. Sensitivity and specificity (S&S), negative and positive predictive values (NPV, PPV) and receiver operating characteristic (ROC) area under the curve (AUC) were determined. The predictive performance of the tool was evaluated using adherence data from an external study (CKD‐FIX). Results: The allopurinol adherence tool produced S&S values for trough thresholds of 89‐98% and 76‐84%, respectively, and 90%‐98% and 76‐83% for peak thresholds. PPV and NPV were 79‐84% and 88‐94%, respectively, for trough and 80‐85% and 89‐98%, respectively, for peak concentrations. The ROC AUC values ranged from 0.84 to 0.88 and from 0.86 to 0.89 for trough and peak concentrations, respectively. S&S values for the external evaluation were found to be 75.8% and 86.5%, respectively, producing an ROC AUC of 0.8113. Conclusion: A tool to identify people with gout who require additional support to maintain adherence using plasma oxypurinol concentrations was developed and evaluated. The predictive performance of the tool is suitable for adherence screening in clinical trials and may have utility in some clinical practice settings. [ABSTRACT FROM AUTHOR]

Objective: To examine whether the cross‐sectional gene–diet interaction for prevalent hyperuricemia among women translates prospectively to risk of incident female gout. Methods: We analyzed the interaction between genetic predisposition and adherence to a healthy dietary pattern (i.e., Dietary Approaches to Stop Hypertension [DASH] score) on risk of incident female gout in 18,244 women from Nurses' Health Study (NHS; discovery) and 136,786 women from 3 additional prospective female cohorts from the US and UK (replication). Genetic risk score (GRS) was calculated from 114 urate‐associated loci. Results: In the NHS and replication cohorts, association between diet and gout risk was larger and stronger among women with higher genetic risk. In all cohorts combined, compared to women with an unhealthy DASH score (less than the mean score), multivariable relative risk (RR) for incident gout among women with a healthy DASH score (greater than/equal to the mean score) was 0.67 (95% confidence interval [95% CI] 0.60–0.76) among higher GRS (greater than/equal to the mean score) and 0.91 (0.78–1.05) among lower GRS (P for multiplicative interaction = 0.001); multivariable RR for higher versus lower GRS was 2.03 (95% CI 1.80–2.29) and 1.50 (95% CI 1.31–1.71) among unhealthy and healthy DASH score groups, respectively. Additive interaction was also significant, in both the discovery and replication cohorts (P < 0.001), with 51% of the excess risk attributable to the additive gene–diet interaction in all cohorts combined. Conclusion: The deleterious effect of genetic predisposition on risk of incident female gout was more pronounced among women with unhealthy diets, with nearly half the excess risk attributable to this gene–diet interaction. These data elucidate the important synergy of genetics and diet for female gout development. [ABSTRACT FROM AUTHOR]

Over the last decade, there have been major advances in the understanding of the genetic basis of hyperuricaemia and gout as well as of the pharmacogenetics of urate-lowering therapy. Key findings include the reporting of 28 urate-associated loci, the discovery that ABCG2 plays a central role on extra-renal uric acid excretion, the identification of genes associated with development of gout in the context of hyperuricaemia, recognition that ABCG2 variants influence allopurinol response, and the impact of HLA-B*5801 testing in reducing the prevalence of allopurinol hypersensitivity in high-risk populations. These advances, together with the reducing cost of whole genome sequencing, mean that integrated personalised medicine approaches may soon be possible in clinical practice. Genetic data may inform assessment of disease prognosis in individuals with hyperuricaemia or established gout, personalised lifestyle advice, selection and dosing of urate-lowering therapy, and prevention of serious medication adverse effects. In this article, we summarise the discoveries from genome-wide association studies and discuss the potential for translation of these findings into clinical practice. [ABSTRACT FROM AUTHOR]

Objective Oxylipins modulate inflammation via complex pathways. The oxylipin profile in gout remains unexplored. In this study, we systemically profiled oxylipins in young men and identified new oxylipin biomarkers for clinical use in differentiating gout from hyperuricaemia. Material and methods Oxylipin profiling was performed in 90 men (30 very early onset gout, 30 asymptomatic hyperuricaemia [HU] and 30 normouricaemia [NU], all aged <20 years) divided into discovery and validation sample sets. The dataset was analysed based on orthogonal projection to latent structure-discriminant analysis. Correlation network and pathway enrichment were conducted to reveal potential oxylipin-involved pathways of gout. Candidate oxylipins were further evaluated and optimized in the validation cohort, and differential oxylipin biomarkers combined with or without serum urate were applied to construct diagnostic models. Results In discovery stage, 21 differential oxylipins in the gout vs HU comparisons and 14 differential oxylipins in the gout vs NU comparisons were discovered. Correlation network analysis was performed and 14(S)-HDHA (14 S -hydroxy-4 Z ,7 Z ,10 Z ,12 E ,16 Z ,19 Z -docosahexaenoic acid) was identified as a hub metabolite in both comparisons. Seven down-regulated oxylipins in the gout vs HU group and five down-regulated oxylipins in the gout vs NU group were validated. Diagnostic models were constructed with the above oxylipins, with 14(S)-HDHA alone having an area under the curve of 1 (95% CI, 1, 1) in both comparisons. Conclusions Young men with very early onset gout have distinct oxylipin spectrums, especially those derived from arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid. Differential oxylipins could serve as candidate serum biomarkers in differentiating gout from hyperuricaemia. [ABSTRACT FROM AUTHOR]

The genetic determinants of the allopurinol dose‐concentration relationship have not been extensively studied. We aimed to clarify what factors, including genetic variation in urate transporters, influence oxypurinol pharmacokinetics (PKs). A population PK model for oxypurinol was developed with NONMEM (version 7.3). The influence of urate transporter genetic variants for ABCG2 (rs2231142 and rs10011796), SLC2A9/GLUT9 (rs11942223), SLC17A1/NPT1 (rs1183201), SLC22A12/URAT1 (rs3825018), SLC22A11/OAT4 (rs17300741), and ABCC4/MRP4 (rs4148500), as well as other participant factors on oxypurinol PKs was assessed. Data from 325 people with gout were available. The presence of the T allele for ABCG2 (rs2231142) and SLC17A1/NPT1 (rs1183201) was associated with a 24% and 22% increase in oxypurinol clearance, respectively, in univariate analysis. This effect was not significant in the multivariate analysis. In the final model, oxypurinol PKs were predicted by creatinine clearance, diuretic use, ethnicity, and body weight. We have found that genetic variability in the transporters examined does not appear to influence oxypurinol PKs. [ABSTRACT FROM AUTHOR]

Aims The primary aim of this research was to predict the allopurinol maintenance doses required to achieve the target plasma urate of ≤0.36 mmol l−1. Methods A population analysis was conducted in nonmem using oxypurinol and urate plasma concentrations from 133 gout patients. Maintenance dose predictions to achieve the recommended plasma urate target were generated. Results The urate response was best described by a direct effects model. Renal function, diuretic use and body size were found to be significant covariates. Dose requirements increased approximately 2-fold over a 3-fold range of total body weight and were 1.25-2 fold higher in those taking diuretics. Renal function had only a modest impact on dose requirements. Conclusions Contrary to current guidelines, the model predicted that allopurinol dose requirements were determined primarily by differences in body size and diuretic use. A revised guide to the likely allopurinol doses to achieve the target plasma urate concentration is proposed. [ABSTRACT FROM AUTHOR]

Hyperuricemia (serum urate >6.8mg/dl) is associated with several cardiometabolic and renal diseases, such as gout and chronic kidney disease. Previous studies have examined the shared genetic basis of chronic kidney disease and hyperuricemia in humans either using singlevariant tests or estimating whole-genome genetic correlations between the traits. Individual variants typically explain a small fraction of the genetic correlation between traits, thus the ability to map pleiotropic loci is lacking power for available sample sizes. Alternatively, wholegenome estimates of genetic correlation indicate a moderate correlation between these traits. While useful to explain the comorbidity of these traits, whole-genome genetic correlation estimates do not shed light on what regions may be implicated in the shared genetic basis of traits. Therefore, to fill the gap between these two approaches, we used local Bayesian multitrait models to estimate the genetic covariance between a marker for chronic kidney disease (estimated glomerular filtration rate) and serum urate in specific genomic regions. We identified 134 overlapping linkage disequilibrium windows with statistically significant covariance estimates, 49 of which had positive directionalities, and 85 negative directionalities, the latter being consistent with that of the overall genetic covariance. The 134 significant windows condensed to 64 genetically distinct shared loci which validate 17 previously identified shared loci with consistent directionality and revealed 22 novel pleiotropic genes. Finally, to examine potential biological mechanisms for these shared loci, we have identified a subset of the genomic windows that are associated with gene expression using colocalization analyses. The regions identified by our local Bayesian multitrait model approach may help explain the association between chronic kidney disease and hyperuricemia. [ABSTRACT FROM AUTHOR]

Background: Copy number variation (CNV) is a common feature of eukaryotic genomes, and a growing body of evidence suggests that genes affected by CNV are enriched in processes that are associated with environmental responses. Here we use next generation sequence (NGS) data to detect copy-number variable regions (CNVRs) within the Malus x domestica genome, as well as to examine their distribution and impact. Methods: CNVRs were detected using NGS data derived from 30 accessions of M. x domestica analyzed using the read-depth method, as implemented in the CNVrd2 software. To improve the reliability of our results, we developed a quality control and analysis procedure that involved checking for organelle DNA, not repeat masking, and the determination of CNVR identity using a permutation testing procedure. Results: Overall, we identified 876 CNVRs, which spanned 3.5 % of the apple genome. To verify that detected CNVRs were not artifacts, we analyzed the B- allele-frequencies (BAF) within a single nucleotide polymorphism (SNP) array dataset derived from a screening of 185 individual apple accessions and found the CNVRs were enriched for SNPs having aberrant BAFs (P < 1e-13, Fisher's Exact test). Putative CNVRs overlapped 845 gene models and were enriched for resistance (R) gene models (P < 1e-22, Fisher's exact test). Of note was a cluster of resistance gene models on chromosome 2 near a region containing multiple major gene loci conferring resistance to apple scab. Conclusion: We present the first analysis and catalogue of CNVRs in the M. x domestica genome. The enrichment of the CNVRs with R gene models and their overlap with gene loci of agricultural significance draw attention to a form of unexplored genetic variation in apple. This research will underpin further investigation of the role that CNV plays within the apple genome. [ABSTRACT FROM AUTHOR]

In observational studies, serum urate positively associates with cardiometabolic and kidney diseases. We analyzed data from a randomised placebo-controlled trial to determine whether moderate hyperuricemia induced by inosine affects cardiometabolic and kidney function markers. One hundred and twenty post-menopausal women were recruited into a 6-month randomised, double-blind, placebo-controlled trial of inosine for bone health. Change from baseline in the following pre-specified endpoints was analyzed: body mass index; blood pressure; lipid profile; C-reactive protein; fasting glucose; insulin; HbA1c; serum creatinine; and estimated glomerular filtration rate (eGFR). Despite increases in serum urate levels (+ 0.17 mmol/L at week 6, P < 0.0001), no significant between-group differences were observed in cardiometabolic markers, with the exception of lower fasting glucose concentrations with inosine at week 19. In the inosine group, change in serum urate correlated with change in serum creatinine (r = 0.41, P = 0.0012). However, there was no between-group difference in serum creatinine values. Over the entire study period, there was no significant difference in eGFR (ANCOVA P = 0.13). Reduction in eGFR was greater in the inosine group at Week 13 (mean difference − 4.6 mL/min/1.73 m2, false detection rate P = 0.025), with no between-group difference in eGFR at other time points. These data indicate that increased serum urate does not negatively influence body mass index, blood pressure, lipid profile, or glycaemic control. Serum urate changes associated with inosine intake correlate with changes in serum creatinine, but this does not lead to clinically important reduction in kidney function over 6 months. Clinical trial registration number: Australia and New Zealand Clinical Trials Registry (ACTRN12617000940370), registered 30/06/2017. [ABSTRACT FROM AUTHOR]

Pacific Island populations, particularly those of Polynesian descent, have a high prevalence of hyperuricaemia and gout. This is due to an inherently higher urate level among these populations with a demonstrated genetic predisposition. While an excess of urate can cause pathology, urate is also important for human health. It has been implicated as an antioxidant, has a neuroprotective role and is involved in innate immune responses. This paper provides a brief review of urate levels worldwide, with a particular focus on island Southeast Asia and the Pacific. We then present possible evolutionary explanations for the elevated serum urate levels among Pacific populations in the context of the physiological importance of urate and of the settlement history of the region. Finally, we propose that ancestry may play a significant role in hyperuricaemia in these populations and that exposure to malaria prior to population expansion into the wider Pacific may have driven genetic selection for variants contributing to high serum urate. [ABSTRACT FROM AUTHOR]

Short-chain enoyl-coA hydratase (SCEH) deficiency due to biallelic pathogenic ECHS1 variants was first reported in 2014 in association with Leigh syndrome (LS) and increased S-(2-carboxypropyl)cysteine excretion. It is potentially treatable with a valine-restricted, high-energy diet and emergency regimen. Recently, Simon et al. described four Samoan children harbouring a hypomorphic allele (c.489G > A, p.Pro163=) associated with reduced levels of normally-spliced mRNA. This synonymous variant, missed on standard genomic testing, is prevalent in the Samoan population (allele frequency 0.17). Patients with LS and one ECHS1 variant were identified in NZ and Australian genomic and clinical databases. ECHS1 sequence data were interrogated for the c.489G > A variant and clinical data were reviewed. Thirteen patients from 10 families were identified; all had Pacific ancestry including Samoan, Māori, Cook Island Māori, and Tokelauan. All developed bilateral globus pallidi lesions, excluding one pre-symptomatic infant. Symptom onset was in early childhood, and was triggered by illness or starvation in 9/13. Four of 13 had exercise-induced dyskinesia, 9/13 optic atrophy and 6/13 nystagmus. Urine S-(2-carboxypropyl)cysteine-carnitine and other SCEH-related metabolites were normal or mildly increased. Functional studies demonstrated skipping of exon four and markedly reduced ECHS1 protein. These data provide further support for the pathogenicity of this ECHS1 variant which is also prevalent in Māori, Cook Island Māori, and Tongan populations (allele frequency 0.14–0.24). It highlights the need to search for a second variant in apparent heterozygotes with an appropriate phenotype, and has implications for genetic counselling in family members who are heterozygous for the more severe ECHS1 alleles. Short-chain enoyl-CoA hydratase deficiency is a frequent cause of Leigh-like disease in Māori and wider-Pacific populations, due to the high carrier frequency of a hypomorphic ECHS1 variant c.489G > A, p.[Pro163=, Phe139Valfs*65] that may be overlooked by standard genomic testing. [ABSTRACT FROM AUTHOR]

Purpose: The aims of this study were to develop a population pharmacokinetic model for allopurinol and oxypurinol and to explore the influence of patient characteristics on allopurinol and oxypurinol pharmacokinetics. Methods: Data from 92 patients with gout and 12 healthy volunteers were available for analysis. A parent-metabolite model with a two-compartment model for allopurinol and a one-compartment model for oxypurinol was fitted to the data using non-linear mixed effects modelling. Results: Renal function, fat-free mass (FFM) and diuretic use were found to predict differences in the pharmacokinetics of oxypurinol. The population estimates for allopurinol clearance, inter-compartmental clearance, central and peripheral volume were 50, 142 L/h/70 kg FFM, 11.4, 91 L/70 kg FFM, respectively, with a between-subject variability of 33 % (coefficient of variance, CV) for allopurinol clearance. Oxypurinol clearance and volume of distribution were estimated to be 0.78 L/h per 6 L/h creatinine clearance/70 kg FFM and 41 L/70 kg FFM in the final model, with a between-subject variability of 28 and 15 % (CV), respectively. Conclusions: The pharmacokinetic model provides a means of predicting the allopurinol dose required to achieve target oxypurinol plasma concentrations for patients with different magnitudes of renal function, different body mass and with or without concomitant diuretic use. The model provides a basis for the rational dosing of allopurinol in clinical practice. [ABSTRACT FROM AUTHOR]

Objective: The prevalence of gout is increasing but studies of its clinical features in large samples are lacking. This study aimed to clarify changes in the clinical manifestations of gout in China over the last decade and investigate the clinical features and risk factors of early-onset gout.Methods: Clinical manifestations were compared between 9754 gout patients who first presented at our clinic with gout in 2008-2012 (earlier group) or 2013-2018 (later group). Gout onset≤30 years old was defined as early-onset and>30 years as late-onset. Clinical features and risk factors were compared between the groups.Results: The gout-onset age was 4.14 years younger and the percentage of early-onset gout (3827 patients) was higher in the later 2013-2018 group (5979 patients). The disease duration was significantly shorter (5.72±0.09 vs. 6.01±0.11 years P < 0,05) and the ratio of patients with tophi was correspondingly lower in the later group (22.0% vs. 20.0%, P < 0,05). More patients were obese (32.6% vs. 37.7%, P<0.001) and serum urate levels (465.0±1.9μmol/L vs. 485.5±1.5μmol/L) were significantly higher in the later group. As the age of gout-onset became younger, we did the multivariate logistic regression and identified a positive family history, male sex, obesity, elevated serum urate, and sugar-sweetened soft drinks as independent predictors of early-onset gout.Conclusion: The manifestations of gout in China have changed over the last decade, associated with a trend towards younger onset. [ABSTRACT FROM AUTHOR]

Comparative mapping between the human and rodent genomes is one approach for positional cloning of complex disease loci. The human type 1 diabetes susceptibility locus IDDM6 has orthology with distal rodent chromosome 18, to which Iddm3 has been mapped in rat. Previously, we mapped Idd21 to mouse chromosome 18. Here, the primary aim was to determine whether Idd21 mapped to distal mouse chromosome 18. We constructed novel congenic strains from the consomic NOD-Chr 18(ABH) strain and mapped two loci (Idd21.1 and Idd21.2) to the distal 29.3-Mb portion of mouse chromosome 18, orthologous to IDDM6 (human) and Iddm3 (rat). Idd21.3 was mapped to proximal mouse chromosome 18 (0-21.9 Mb). Although Idd21.1 did not influence beta-islet inflammation, splenocytes from pre-diabetic Idd21.1-congenic mice were less efficient at transferring diabetes to immunodeficient NOD-scid mice. This suggests that Idd21.1 may act by reducing the pathogenicity of islet-infiltrating immune cells. For the first time, the presence of a non-major histocompatibility complex autoimmune diabetes locus colocalizing in three species has been demonstrated; IDDM6 (human), Iddm3 (rat), and now Idd21.1-21.2 in mouse. Further genetic localization of Idd21.1 and Idd21.2 could expedite characterization of the human IDDM6 region. [ABSTRACT FROM AUTHOR]

Elevated serum urate is the most important causal risk factor for developing gout. However, in longitudinal cohort studies, a small proportion of people with normal urate levels develop gout and the majority of those with high urate levels do not. These observations may be due to subsequent variations in serum urate over time. Our analysis examined whether single or repeat testing of serum urate more accurately predicts incident gout over time. Individual participant data from three publicly-available cohorts were included. Data from paired serum urate measures 3–5 years apart, followed by an assessment of gout incidence 5–6 years from the second urate measure were used to calculate the predictive ability of four measures of serum urate on incident gout: the first measure, the second measure, the average of the two measures, and the highest of the two measures. Participants with prevalent gout prior to the second measure were excluded. Receiver operator characteristic (ROC) curves and area under the curve (AUC) statistics were computed to compare the four measures. A total of 16,017 participants were included across the three cohorts, with a mean follow-up from the first serum urate test of 9.3 years (range 8.9–10.1 years). Overall, there was a small increase in the mean serum urate between the first and second measures (322 μmol/L (5.42 mg/dL) vs. 340 μmol/L (5.71 mg/dL), P<0.001) which were a mean of 3.5 years apart, but the first and second measures were highly correlated (r = 0.81, P<0.001). No differences were observed in the predictive ability of incident gout between the four measures of serum urate measurement with ROC curve AUC statistics ranging between 0.81 (95% confidence intervals: 0.78–0.84) and 0.84 (95% confidence intervals: 0.81–0.87). These data show that repeat serum urate testing is not superior to a single measure of serum urate for prediction of incident gout over approximately one decade. [ABSTRACT FROM AUTHOR]

Background: Historically, geneticists have relied on genotyping arrays and imputation to study human genetic variation. However, an underrepresentation of diverse populations has resulted in arrays that poorly capture global genetic variation, and a lack of reference panels. This has contributed to deepening global health disparities. Whole genome sequencing (WGS) better captures genetic variation but remains prohibitively expensive. Thus, we explored WGS at "mid-pass" 1-7x coverage. Results: Here, we developed and benchmarked methods for mid-pass sequencing. When applied to a population without an existing genomic reference panel, 4x mid-pass performed consistently well across ethnicities, with highc recall (98%) and precision (97.5%). Conclusion: Compared to array data imputed into 1000 Genomes, mid-pass performed better across all metrics and identified novel population-specific variants with potential disease relevance. We hope our work will reduce financial barriers for geneticists from underrepresented populations to characterize their genomes prior to biomedical genetic applications. [ABSTRACT FROM AUTHOR]