John Highton

Role of the urate transporter SLC2A9 gene in susceptibility to gout in New Zealand Māori, Pacific Island, and Caucasian case-control sample sets.

OBJECTIVE To examine the role of genetic variation in the renal urate transporter SLC2A9 in gout in New Zealand sample sets of Māori, Pacific Island, and Caucasian ancestry and to determine if the Māori and Pacific Island samples could be useful for fine-mapping. METHODS Patients (n= 56 Māori, 69 Pacific Island, and 131 Caucasian) were recruited from rheumatology outpatient clinics and satisfied the American College of Rheumatology criteria for gout. The control samples comprised 125 Māori subjects, 41 Pacific Island subjects, and 568 Caucasian subjects without arthritis. SLC2A9 single-nucleotide polymorphisms rs16890979 (V253I), rs5028843, rs11942223, and rs12510549 were genotyped (possible etiologic variants in Caucasians). RESULTS Association of the major allele of rs16890979, rs11942223, and rs5028843 with gout was observed in all sample sets (P = 3.7 x 10(-7), 1.6 x 10(-6), and 7.6 x 10(-5) for rs11942223 in the Māori, Pacific Island, and Caucasian samples, respectively). One 4-marker haplotype (1/1/2/1; more prevalent in the Māori and Pacific Island control samples) was not observed in a single gout case. CONCLUSION Our data confirm a role of SLC2A9 in gout susceptibility in a New Zealand Caucasian sample set, with the effect on risk (odds ratio >2.0) greater than previous estimates. We also demonstrate association of SLC2A9 with gout in samples of Māori and Pacific Island ancestry and a consistent pattern of haplotype association. The presence of both alleles of rs16890979 on susceptibility and protective haplotypes in the Māori and Pacific Island sample is evidence against a role for this nonsynonymous variant as the sole etiologic agent. More extensive linkage disequilibrium in Māori and Pacific Island samples suggests that Caucasian samples may be more useful for fine-mapping.

A strong role for the ABCG2 gene in susceptibility to gout in New Zealand Pacific Island and Caucasian, but not Māori, case and control sample sets

Genetic variation in ABCG2 (rs2231142, Q141K), encoding a uric acid transporter, is associated with gout in diverse populations. The aim of this study was to examine a role for ABCG2 in gout susceptibility in New Zealand Māori, Pacific Island and Caucasian samples. Patients (n = 185, 173 and 214, for Māori, Pacific Island and Caucasian, respectively) satisfied the American College of Rheumatology gout classification criteria. The comparison samples comprised 284, 129 and 562 individuals, respectively, without gout. rs2231142 was genotyped and stratification accounted for using genomic control markers. Association of the minor allele of rs2231142 with gout was observed in the Pacific Island samples (OR = 2.80, P(STRAT) < 0.001 after accounting for effects of population structure), but not in the Māori samples (OR = 1.08, P(STRAT)= 0.70), with heterogeneity in association evident between the Māori and Pacific Island datasets (P(HET) = 0.001). A similar dichotomy in association was observed when samples were stratified into Western (Tonga, Samoa, Niue, Tokelau) versus Eastern Polynesian (Māori, Cook Island) origin (OR = 2.59, P(STRAT) < 0.001; OR = 1.12, P(STRAT)= 0.48, respectively; P(HET) = 0.005). Association with gout was observed in the Caucasian samples (OR = 2.20, P = 3.2 × 10(-8)). Unlike SLC2A9, which is a strong risk factor for gout in both Māori and Pacific Island people, ABCG2 rs2231142 has a strong effect only in people of Western Polynesian ancestry. Our results emphasize the need to account for sub-population differences when undertaking biomedical genetic research in a group defined by a geographical region and shared ancestry but characterized by migratory events that create bottlenecks and altered genetic structure in the founder populations.

A comparison of fatigue correlates in rheumatoid arthritis and osteoarthritis: disparity in associations with disability, anxiety and sleep disturbance

OBJECTIVES To investigate correlates of fatigue among individuals with RA and OA, including mood, sleep, disease activity and radiographic damage. METHODS Fatigue was assessed using the Multidimensional Assessment of Fatigue-Global Fatigue Index (MAF-GFI) in 103 patients with RA and 103 with OA. Sleep disturbance and pain were assessed using a visual analogue scale anxiety and depression using the Hospital Anxiety and Depression scale and disability using the HAQ. In the RA cohort, the disease activity score-28 joint count (DAS-28) and the Van der Heijde modified Sharp score were calculated, and in the OA cohort, the Kellgren-Lawrence score and the WOMAC score calculated. RESULTS The MAF-GFI scores were higher in the OA cohort (P = 0.02). This was not significant after controlling for disability (P = 0.59). OA participants reported greater pain, disability, depression and sleeplessness than those with RA (all P < 0.01). The strongest correlates of fatigue in the RA cohort were depression (P < 0.001) and anxiety (P < 0.001). There was no significant association with pain (P = 0.43), DAS-28 (P = 0.07), HAQ (P = 0.10) or Sharp score (P = 0.78). In OA, the correlates of fatigue were older age (P = 0.02), sleep disturbance (P = 0.03), depression (P = 0.04), disability (P = 0.04) and lower CRP (P = 0.001). CONCLUSIONS Fatigue is common and severe in both RA and OA. In RA, fatigue had no significant association with pain, disease activity, disability or erosions, but was associated with depression and anxiety. The disparity in correlates indicates that generalizing the experience of fatigue between OA and RA is not appropriate. Fatigue is an important domain in the assessment of disease impact.

Genomic DNA pooling for whole-genome association scans in complex disease: empirical demonstration of efficacy in rheumatoid arthritis

A pragmatic approach that balances the benefit of a whole-genome association (WGA) experiment against the cost of individual genotyping is to use pooled genomic DNA samples. We aimed to determine the feasibility of this approach in a WGA scan in rheumatoid arthritis (RA) using the validated human leucocyte antigen (HLA) and PTPN22 associations as test loci. A total of 203 269 single-nucleotide polymorphisms (SNPs) on the Affymetrix 100K GeneChip and Illumina Infinium microarrays were examined. A new approach to the estimation of allele frequencies from Affymetrix hybridization intensities was developed involving weighting for quality signals from the probe quartets. SNPs were ranked by z-scores, combined from United Kingdom and New Zealand case–control cohorts. Within a 1.7 Mb HLA region, 33 of the 257 SNPs and at PTPN22, 21 of the 45 SNPs, were ranked within the top 100 associated SNPs genome wide. Within PTPN22, individual genotyping of SNP rs1343125 within MAGI3 confirmed association and provided some evidence for association independent of the PTPN22 620W variant (P=0.03). Our results emphasize the feasibility of using genomic DNA pooling for the detection of association with complex disease susceptibility alleles. The results also underscore the importance of the HLA and PTPN22 loci in RA aetiology.

Lipid peroxidation and malondialdehyde in the synovial fluid and plasma of patients with rheumatoid arthritis.

The concentration of lipid peroxides in the plasma and synovial fluid of 65 arthritic patients was determined using a new ion-pairing reverse phase HPLC technique. Patients with rheumatoid arthritis receiving only non-steroidal anti-inflammatory drugs, had a significantly higher mean concentration of lipid peroxides in synovial fluid samples (162 +/- 22.0 micrograms/l) than osteoarthritic patients (40.0 +/- 8.0 micrograms/l, p less than 0.0001). Mean concentrations in both groups correlated strongly with the level of beta-glucuronidase activity as a measure of lysosomal enzyme release (r = 0.71, p less than 0.0001). Contrary to previous reports by investigators using less specific methods, we were unable to demonstrate any increase in plasma levels of lipid peroxides in the rheumatoid patient. Treatment of rheumatoid arthritis with D-penicillamine was associated with a significant reduction of lipid peroxide levels (83.2 +/- 11.5 micrograms/ml, p less than 0.002), suggesting that this drug may function as an oxygen radical scavenger in the joint cavity. These results give further support to the concept of oxygen-free radicals playing an important role in the pathogenesis of chronic inflammatory disorders.

Association of variation in Fcgamma receptor 3B gene copy number with rheumatoid arthritis in Caucasian samples.

Objective There is increasing evidence that variation in gene copy number (CN) influences clinical phenotype. The low-affinity Fcγ receptor 3B (FCGR3B) located in the FCGR gene cluster is a CN polymorphic gene involved in the recruitment to sites of inflammation and activation of polymorphonuclear neutrophils (PMNs). Given recent evidence that low FCGR3B CN is a risk factor for systemic but not organ-specific autoimmune disease and the potential importance of PMN in the pathophysiology of rheumatoid arthritis (RA), the authors hypothesised that FCGR3B gene dosage influences susceptibility to RA. Methods FCGR3B CN was measured in 643 cases of RA and 461 controls from New Zealand (NZ), with follow-up analysis in 768 cases and 702 controls from the Netherlands and 250 cases and 211 controls from the UK. All subjects were of Caucasian ancestry. Results Significant evidence for an association between CN <2 and RA was observed in the Dutch cohort (OR 2.01 (95% CI 1.37 to 2.94), p=3×10−4) but not in the two smaller cohorts (OR 1.45 (95% CI 0.92 to 2.26), p=0.11 and OR 1.33 (95% CI 0.58 to 3.02), p=0.50 for the NZ and UK populations, respectively). The association was evident in a meta-analysis which included a previously published Caucasian sample set (OR 1.67 (95% CI 1.28 to 2.17), p=1.2×10−4). Conclusions One possible mechanism to explain the association between reduced FCGR3B CN and RA is the reduced clearance of immune complex during inflammation. However, it is not known whether the association between RA and FCGR3B CN is aetiological or acts as a proxy marker for another biologically relevant variant. More detailed examination of genetic variation within the FCGR gene cluster is required.

Sugar-sweetened beverage consumption: a risk factor for prevalent gout with SLC2A9 genotype-specific effects on serum urate and risk of gout

Objective Consumption of high fructose corn syrup (HFCS)-sweetened beverages increases serum urate and risk of incident gout. Genetic variants in SLC2A9, that exchanges uric acid for glucose and fructose, associate with gout. We tested association between sugar (sucrose)-sweetened beverage (SSB) consumption and prevalent gout. We also tested the hypothesis that SLC2A9 genotype and SSB consumption interact to determine gout risk. Methods Participants were 1634 New Zealand (NZ) European Caucasian, Ma¯ori and Pacific Island people and 7075 European Caucasians from the Atherosclerosis Risk in Communities (ARIC) study. NZ samples were genotyped for rs11942223 and ARIC for rs6449173. Effect estimates were multivariate adjusted. Results SSB consumption increased gout risk. The OR for four drinks/day relative to zero was 6.89 (p=0.045), 5.19 (p=0.010) and 2.84 (p=0.043) for European Caucasian, Ma¯ori and Pacific Islanders, respectively. With each extra daily SSB serving, carriage of the gout-protective allele of SLC2A9 associated with a 15% increase in risk (p=0.078), compared with a 12% increase in non-carriers (p=0.002). The interaction term was significant in pooled (pInteraction=0.01) but not meta-analysed (pInteraction=0.99) data. In ARIC, with each extra daily serving, a greater increase in serum urate protective allele carriers (0.005 (p=8.7×10−5) compared with 0.002 (p=0.016) mmol/L) supported the gout data (pInteraction=0.062). Conclusions Association of SSB consumption with prevalent gout supports reduction of SSB in management. The interaction data suggest that SLC2A9-mediated renal uric acid excretion is physiologically influenced by intake of simple sugars derived from SSB, with SSB exposure negating the gout risk discrimination of SLC2A9.

Pathogenic mechanisms in the rheumatoid nodule: Comparison of proinflammatory cytokine production and cell adhesion molecule expression in rheumatoid nodules and synovial membranes from the same patient

OBJECTIVE To investigate the production of proinflammatory cytokines and expression of cell adhesion molecules in the rheumatoid nodule. METHODS Cytokine content (tumor necrosis factor alpha [TNFalpha], interleukin-1beta [IL-1beta], and IL-1 receptor antagonist [IL-1Ra]), at the messenger RNA (mRNA) and protein levels, and cell adhesion molecule expression were studied in 16 rheumatoid nodules and 6 synovial membranes. RESULTS Macrophages in the rheumatoid nodules contained TNFalpha, IL-1beta, and IL-1Ra mRNA and protein, particularly in perivascular cells of the stroma and in the palisading layer. All cell adhesion molecules studied were expressed in both the rheumatoid nodules and synovial membranes, with increased expression of E-selectin in the rheumatoid nodule compared with the synovial membrane, and with the absence of vascular cell adhesion molecule 1 expression on cells of the palisading layer in the rheumatoid nodule. CONCLUSION The presence of similar proinflammatory cytokines and cell adhesion molecules in the rheumatoid nodule and synovial membrane suggests that similar pathogenic processes result in the chronic inflammation and tissue destruction in these lesions.

Probiotic Therapy for the Treatment of Spondyloarthritis: A Randomized Controlled Trial

Objective. To investigate the effect of an orally administered probiotic on disease activity, fatigue, quality of life, and intestinal symptoms in patients with active spondyloarthritis. Methods. Patients with active spondyloarthritis [defined as Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) ≥ 3, Bath Ankylosing Spondylitis Functional Index (BASFI) ≥ 3, Maastricht Ankylosing Spondylitis Enthesitis Score (MASES) ≥ 2, or peripheral joint count ≥ 2] were randomized to oral probiotic or placebo for 12 weeks. Patients and assessors were blinded to treatment allocation. The primary outcome measure was 10% improvement in the BASFI. Additional outcome measures were improvements in the ASsessments in Ankylosing Spondylitis (ASAS)-endorsed core domains: pain, spinal mobility, patient global, peripheral joint and entheseal scores, stiffness, C-reactive protein, and fatigue. The ASAS20 criteria, a composite measure of response, were also applied. Quality of life and bowel symptoms were quantified using the Ankylosing Spondylitis Quality of Life Questionnaire (ASQoL) and Dudley Inflammatory Bowel Symptom Questionnaire (DISQ). Results. Sixty-three patients were randomized to oral probiotic (n = 32) or placebo (n = 31). All patients completed the trial. No significant difference was noted between groups in any of the core domains. The mean BASFI fell from 3.5 ± 2.0 to 2.9 ± 1.9 in the probiotic group and from 3.6 ± 1.9 to 3.1 ± 2.2 in the placebo group (p = 0.839). The mean BASDAI fell from 4.2 ± 2.2 to 3.2 ± 2.1 in the probiotic group and 4.5 ± 2.0 to 3.9 ± 2.2 in the placebo group (p = 0.182). No significant adverse events were recorded in the probiotic-treated group. Conclusion. In this randomized controlled trial, the probiotic combination administered did not demonstrate significant benefit over placebo, despite a theoretical rationale for this therapy.

Hospital admissions associated with gout and their comorbidities in New Zealand and England 1999–2009

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.