Urate-induced epigenetic modifications in myeloid cells.

OBJECTIVES: Hyperuricemia is a metabolic condition central to gout pathogenesis. Urate exposure primes human monocytes towards a higher capacity to produce and release IL-1ß. In this study, we assessed the epigenetic processes associated to urate-mediated hyper-responsiveness. METHODS: Freshly isolated human peripheral blood mononuclear cells or enriched monocytes were pre-treated with solubilized urate and stimulated with LPS with or without monosodium urate (MSU) crystals. Cytokine production was determined by ELISA. Histone epigenetic marks were assessed by sequencing immunoprecipitated chromatin. Mice were injected intraarticularly with MSU crystals and palmitate after inhibition of uricase and urate administration in the presence or absence of methylthioadenosine. DNA methylation was assessed by methylation array in whole blood of 76 participants with normouricemia or hyperuricemia. RESULTS: High concentrations of urate enhanced the inflammatory response in vitro in human cells and in vivo in mice, and broad-spectrum methylation inhibitors reversed this effect. Assessment of histone 3 lysine 4 trimethylation (H3K4me3) and histone 3 lysine 27 acetylation (H3K27ac) revealed differences in urate-primed monocytes compared to controls. Differentially methylated regions (e.g. HLA-G, IFITM3, PRKAB2) were found in people with hyperuricemia compared to normouricemia in genes relevant for inflammatory cytokine signaling. CONCLUSION: Urate alters the epigenetic landscape in selected human monocytes or whole blood of people with hyperuricemia compared to normouricemia. Both histone modifications and DNA methylation show differences depending on urate exposure. Subject to replication and validation, epigenetic changes in myeloid cells may be a therapeutic target in gout.

Maternal Smoking during Pregnancy Is Associated with Offspring Hypodontia.

Little is known about environmental risk factors for hypodontia. The objective of this study was to investigate the association between hypodontia and common environmental risk factors, such as maternal smoking and alcohol and caffeine consumption during pregnancy. Eighty-nine hypodontia cases with 1 or more missing permanent lateral incisors and/or 1 or more missing premolars were enrolled in this clinic-based case-control study. Some 253 controls with no missing teeth were frequency matched to cases by age and sex. Hypodontia was diagnosed using panoramic radiographs. Sociodemographic data were collected from both the participants and their mothers, with maternal self-reported active and passive smoking, as well as alcohol and caffeine consumption during pregnancy, assessed by a questionnaire. Odds ratios (ORs) and their 95% confidence intervals (CIs) were calculated with logistic regression to assess the strength of association between risk factors and hypodontia. OR estimates were then adjusted for possible confounders, such as maternal age at delivery, sex and gestational age of the child, and household socioeconomic background. Significant associations were found between hypodontia and maternal cigarette use during pregnancy, as well as the number of cigarettes smoked per day. The consumption of 10 or more cigarettes per day during pregnancy was associated with greater odds of having a child with hypodontia (adjusted OR, 4.18; 95% CI, 1.48-11.80; P = 0.007). Observed associations between hypodontia, second-hand smoke, and alcohol and caffeine consumption were not statistically significant. Maternal smoking during pregnancy is associated with hypodontia. Larger samples and prospective observational study designs, however, are needed to investigate this association further.

Patients with gout have short telomeres compared with healthy participants: association of telomere length with flare frequency and cardiovascular disease in gout.

AIM AND BACKGROUND: Chronic inflammation associates with increased senescence, which is a strong predictor for cardiovascular disease. We hypothesised that inflammation accelerates senescence and thereby enhances the risk of cardiovascular disease in gout. METHODS: We assessed replicative senescence by quantifying telomere length (TL) in a discovery cohort of 145 Dutch patients with gout and 273 healthy individuals and validated our results in 474 patients with gout and 293 healthy participants from New Zealand. Subsequently, we investigated the effect of cardiovascular disease on TL of all participants. Also, we measured TL of CD4+ and CD8+ T lymphocytes, B lymphocytes, monocytes, natural killer cells and plasmacytoid dendritic cells. Additionally, we assessed the potential temporal difference in TL and telomerase activity. RESULTS: TL in PBMCs of healthy donors decreased over time, reflecting normal ageing. Patients with gout demonstrated shorter telomeres (p=0.001, R2=0.01873). In fact, the extent of telomere erosion in patients with gout was higher at any age compared with healthy counterparts at any age (p<0.0001, R2=0.02847). Patients with gout with cardiovascular disease had the shortest telomeres and TL was an independent risk factor for cardiovascular disease in patients with gout (p=0.001). TL was inversely associated with the number of gouty flares (p=0.005). CONCLUSIONS: Patients with gout have shorter telomeres than healthy participants, reflecting increased cellular senescence. Telomere shortening was associated with the number of flares and with cardiovascular disease in people with gout.

ABCG2 loss-of-function polymorphism predicts poor response to allopurinol in patients with gout.

Many patients fail to achieve the recommended serum urate (SU) target (<6 mgdl-1) with allopurinol. The aim of our study was to examine the association of ABCG2 with SU target in response to standard doses of allopurinol using a cohort with confirmed adherence. Good response was defined as SU<6 mgdl-1 on allopurinol ⩽300 mgd-1 and poor response as SU⩾6 mgdl-1 despite allopurinol >300 mgd-1. Adherence was confirmed by oxypurinol concentrations. ABCG2 genotyping was performed using pre-designed single nucleotide polymorphism (SNP) TaqMan assays. Of 264 patients, 120 were good responders, 68 were poor responders and 76 were either non-adherent or could not be classified. The minor allele of ABCG2 SNP rs2231142 conferred a significantly increased risk of poor response to allopurinol (odds ratio=2.71 (1.70-4.48), P=6.0 × 10-5). This association remained significant after adjustment for age, sex, body mass index, ethnicity, estimated glomerular filtration rate, diuretic use and SU off urate-lowering therapy. ABCG2 rs2231142 predicts poor response to allopurinol, as defined by SU⩾6 mgdl-1 despite allopurinol >300 mgd-1.

Uric acid and bone mineral density in postmenopausal osteoporotic women: the link lies within the fat.

The association between serum uric acid (SUA) levels and bone mineral density (BMD) is controversial. Fat accumulation is linked to SUA and BMD, thus possibly explaining the mixed results. We found that adiposity drives part of the association between SUA and BMD in women with postmenopausal osteoporosis. INTRODUCTION: Both positive and negative associations between SUA and BMD have been reported. SUA levels and BMD increase with higher body weight and other indices of adiposity; hence, the association between SUA and BMD might be a consequence of the confounding effect of adiposity. We investigated in this cross-sectional study whether the association between SUA and BMD is independent of measures of fat accumulation and other potential confounders. METHODS: SUA levels, femur BMD, markers of bone metabolism, body mass index (BMI), fat mass (FM), waist circumference (WC), and abdominal visceral fat area were measured in 180 treatment-naive postmenopausal osteoporotic women (mean age 66.3 ± 8.5 years, age range 48-81 years). RESULTS: Women with higher SUA levels (third tertile) had significantly higher femur BMD and lower cross-linked C-terminal telopeptide of type I collagen (CTX) and bone alkaline phosphatase (bALP) levels. SUA levels were positively associated with all indices of adiposity. In multivariable analysis with femur BMD as dependent variable, the association between logarithmic (LG)-transformed SUA levels and BMD (beta = 0.42, p < 0.001) was lessened progressively by the different indices of adiposity, like LG-BMI (beta = 0.22, p = 0.007), LG-WC (beta = 0.21, p = 0.01), LG-FM (beta = 0.18, p = 0.01), and LG-abdominal visceral fat area (beta = 0.12, p = 0.05). The association between SUA levels and markers of bone metabolism was dependent on the effect of confounders. CONCLUSION: In postmenopausal osteoporotic women, the strong univariable association between SUA levels and femur BMD is partly explained by the confounding effect of indices of adiposity.

Self-reported oral behaviour habits in hyperdivergent and normodivergent facial types.

The relationship between facial morphology and jaw function remains controversial. The purpose of this study was to investigate differences in self-reported oral behaviour habits between individuals with normodivergent and hyperdivergent facial types. Some 80 cases and controls were individually matched on age, sex ethnicity and treatment stage. The participants were recruited from an orthodontic clinic, and included both adolescents and adults. Habitual oral activity was assessed using the Oral Behaviour Checklist (OBC) based on their experiences in the past 4 weeks. Univariate and bivariate analyses were performed. The sample had a mean age of 17·2 years (SD = 4·6; range = 12-49 years), and was predominantly female (65·0%) and of New Zealand European origin (91·3%). The prevalence of reporting one or more frequently performed habitual muscular behaviour in either study group was over 85% (P > 0·05). There was no difference in total OBC score between the hyperdivergent (25·6; SD: 9·0) and normodivergent group (25·3; SD: 9·9). Moreover, there was no difference in the prevalence of either nocturnal or daytime oral behaviours between the two groups. While this study did not include any objective measures of functional or habitual activity, we found no differences in self-reported oral behaviour habits between normodivergent and hyperdivergent individuals. The findings do not support an association between vertical facial form and habitual muscular activity.

Twenty-eight loci that influence serum urate levels: analysis of association with gout.

OBJECTIVES: Twenty-eight genetic loci are associated with serum urate levels in Europeans. Evidence for association with gout at most loci is absent, equivocal or not replicated. Our aim was to test the loci for association with gout meeting the American College of Rheumatology gout classification criteria in New Zealand European and Polynesian case-control sample sets. METHODS: 648 European cases and 1550 controls, and 888 Polynesian (Ma¯ori and Pacific) cases and 1095 controls were genotyped. Association with gout was tested by logistic regression adjusting for age and sex. Power was adequate (>0.7) to detect effects of OR>1.3. RESULTS: We focused on 24 loci without previous consistent evidence for association with gout. In Europeans, we detected association at seven loci, one of which was the first report of association with gout (IGF1R). In Polynesian, association was detected at three loci. Meta-analysis revealed association at eight loci-two had not previously been associated with gout (PDZK1 and MAF). In participants with higher Polynesian ancestry, there was association in an opposing direction to Europeans at PRKAG2 and HLF (HLF is the first report of association with gout). There was obvious inconsistency of gout association at four loci (GCKR, INHBC, SLC22A11, SLC16A9) that display very similar effects on urate levels. CONCLUSIONS: We provide the first evidence for association with gout at four loci (IGF1R, PDZK1, MAF, HLF). Understanding why there is lack of correlation between urate and gout effect sizes will be important in understanding the aetiology of gout.

A genome-wide association study of rheumatoid arthritis without antibodies against citrullinated peptides.

INTRODUCTION: Rheumatoid arthritis (RA) patients can be classified based on presence or absence of anticitrullinated peptide antibodies (ACPA) in their serum. This heterogeneity among patients may reflect important biological differences underlying the disease process. To date, the majority of genetic studies have focused on the ACPA-positive group. Therefore, our goal was to analyse the genetic risk factors that contribute to ACPA-negative RA. METHODS: We performed a large-scale genome-wide association study (GWAS) in three Caucasian European cohorts comprising 1148 ACPA-negative RA patients and 6008 controls. All patients were screened using the Illumina Human Cyto-12 chip, and controls were genotyped using different genome-wide platforms. Population-independent analyses were carried out by means of logistic regression. Meta-analysis with previously published data was performed as follow-up for selected signals (reaching a total of 1922 ACPA-negative RA patients and 7087 controls). Imputation of classical HLA alleles, amino acid residues and single nucleotide polymorphisms was undertaken. RESULTS: The combined analysis of the studied cohorts resulted in identification of a peak of association in the HLA-region and several suggestive non-HLA associations. Meta-analysis with previous reports confirmed the association of the HLA region with this subset and an observed association in the CLYBL locus remained suggestive. The imputation and deep interrogation of the HLA region led to identification of a two amino acid model (HLA-B at position 9 and HLA-DRB1 at position 11) that accounted for the observed genome-wide associations in this region. CONCLUSIONS: Our study shed light on the influence of the HLA region in ACPA-negative RA and identified a suggestive risk locus for this condition.

Fat storage syndrome in Pacific peoples: a combination of environment and genetics?

Pacific people (especially Micronesian and Polynesian) have some of the highest rates of obesity and diabetes in the world that largely developed since the introduction of western culture and diet. Recent studies suggest that much of the risk relates to the excessive intake of sugar (sucrose) and carbohydrates, leading to a type of fat storage syndrome (metabolic syndrome). Here we discuss some of the environmental. genetic and epigenetic reasons why this group might be especially prone to developing obesity and diabetes compared to other ethnic groups. Indirect evidence suggests that the higher endogenous uric acid levels in the Polynesian-Micronesian population may represent a predisposing factor for the development of obesity and diabetes in the context of Western diets and lifestyles. Pacific people may be an ideal group to study the role of "thrifty genes" in the pathogenesis of the current obesity epidemic.

An 'end-game' for sugar sweetened beverages?

OBJECTIVE: The epidemic of unhealthy weight is now in its third decade. The multitude of initiatives designed to address this issue (globally) have predominantly been ineffective as the prevalence of unhealthy weight has continued to rise. Public health professionals have proposed an 'endgame' for tobacco smoking in New Zealand by 2025, which has received widespread support. Similarly, here, to control the prevalence of unhealthy weight, we consider whether a similar approach to tobacco is justified to restrict the intake of sweetened beverages. APPROACH: This paper reviews the evidence relating sugar sweetened beverages to unhealthy weight and adverse health effects. Current initiatives aimed at reducing sugar sweetened beverage consumption both internationally and in New Zealand are reviewed. FINDINGS: Epidemiological evidence consistently links sugar-sweetened drink intake with unhealthy weight and other risk factors for cardiovascular disease, such as diabetes, gout, and raised blood pressure. Food disappearance data suggests that sugar intake continues to increase in New Zealand, and that a subtle addiction to sugar may underlie this trend. A number of successful initiatives to reduce sugary drink intake are described. IMPLICATION/CONCLUSION: We argue that an 'endgame' to the consumption of sugar-sweetened beverages be supported as a means to address the issue of unhealthy weight at a population level. Finally, a preliminary draft endgame plan is presented for consideration, dialogue and debate.

Sugar-sweetened beverages, urate, gout and genetic interaction.

The clinical manifestations of gout occur as a result of immune responses to monosodium urate crystals. Elevated serum levels of urate (hyperuricemia) are a prerequisite for the development of gout with reduced fractional renal excretion of uric acid (FEUA) an important cause. In New Zealand, Mãori and Pacific Island people have inherently raised urate levels with one consequence a higher prevalence of more severe gout. One characteristic metabolic effect of fructose, present in sugar-sweetened beverages (SSB), is raised urate from hepatic processing of fructose. Here we discuss, and place in a biological context evidence, linking consumption of SSB with hyperuricemia and gout, including the first review of recent ecological and clinical studies of the impact of fructose and SSB exposure in Pacific Island people. Both increased serum urate and increased FEUA are observed in clinical studies examining the effects of an acute fructose load. In contrast, chronic exposure to increased fructose in the diet also leads to increased serum urate concentrations, but reduced FEUA. Epidemiological studies have consistently associated SSB consumption with increased serum urate levels and increased risk of gout. Non-additive interaction of SSB consumption with a genetic variant of a uric acid transporter in serum urate levels and gout risk emphasizes the causality of SSB in gout. Taken together these data demonstrate the hyperuricemic effect of SSB and fructose, with biochemical pathways reasonably well understood. The evidence that dietary fructose increases urate is strong. The evidence summarized here is of sufficient weight to recommend reduction of SSB consumption, particularly in Pacific Island and Mãori people, to reduce the burden of gout.

Analysis of the DISC1 translocation partner (11q14.3) in genetic risk of schizophrenia.

The Disrupted-in-Schizophrenia 1 (DISC1) locus on human chromosome 1 was identified as a consequence of its involvement in a balanced translocation (1;11)(q42.1;q14.3) segregating with major psychiatric disorders in a Scottish family. Recently a comprehensive meta-analysis of genome-wide association scan data found no evidence that common variants of DISC1 (1q42.1) are associated with schizophrenia. Our aim was to test for association of variants in the 11q14.3 translocation region with schizophrenia. The 11q14.3 region was examined by meta-analysis of genome-wide scan data made available by the Genetic Association Information Network (GAIN) and other investigators (non-GAIN) through dbGap. P-values were adjusted for multiple testing using the false discovery rate (FDR) approach. There were no single-nucleotide polymorphisms (SNPs) significant (P < 0.05) after correction for multiple testing in the combined schizophrenia dataset. However, one SNP (rs2509382) was significantly associated in the male-only analysis with P(FDR) = 0.024. Whilst the relevance of the (1;11)(q42.1;q14.3) translocation to psychiatric disorders is currently specific to the Scottish family, genetic material in the chromosome 11 region may contain risk variants for psychiatric disorders in the wider population. The association found in this region does warrant follow-up analysis in further sample sets.

Evidence that deletion at FCGR3B is a risk factor for systemic sclerosis.

There is increasing evidence that gene copy number (CN) variation influences clinical phenotype. The low-affinity Fc receptor 3B (FCGR3B) located in the FCGR gene cluster is a CN polymorphic gene involved in the recruitment of polymorphonuclear neutrophils to sites of inflammation and their activation. Given the genetic overlap between systemic lupus erythematosus and systemic sclerosis (SSc) and the strong evidence for FCGR3B CN in the pathology of SLE, we hypothesised that FCGR3B gene dosage influences susceptibility to SSc. We obtained FCGR3B deletion status in 777 European Caucasian cases and 1000 controls. There was an inverse relationship between FCGR3B CN and disease susceptibility. CN of ≤ 1 was a significant risk factor for SSc (OR=1.55 (1.13-2.14), P=0.007) relative to CN ≥ 2. Although requiring replication, these results suggest that impaired immune complex clearance arising from FCGR3B deficiency contributes to the pathology of SSc, and FCGR3B CN variation is a common risk factor for systemic autoimmunity.

Systematic review of the prevalence of gout and hyperuricaemia in Australia.

AIMS: Gout is a growing health problem worldwide especially in affluent countries, such as Australia. Gout and hyperuricaemia are associated with the metabolic syndrome, diabetes mellitus, obesity and hypertension. More importantly, Australia has a growing prevalence of these important health problems. The aim of this study was to systematically review published information regarding the prevalence of gout and hyperuricaemia in Australia. METHODS: A systematic search was undertaken of the MEDLINE, EMBASE and Web of Science databases, as well as relevant websites for journal articles and reports relating to the prevalence of hyperuricaemia and gout in Australia. RESULTS: Twenty-five journal articles and five reports were included in the review. Data collected in a standardised way show gout increased in prevalence from 0.5% population prevalence to 1.7% population prevalence from 1968 to 1995/1996. There has been a significant rise in the prevalence of gout in the Australian Aboriginal population from 0% in 1965 to 9.7% in men and 2.9% in women in 2002. Consistent with the rise in gout prevalence, serum uric acid in blood donors has increased from 1959 to 1980 (17% in 30- to 40-year-old men). CONCLUSIONS: The rate of gout and hyperuricaemia in Australia is high in relation to comparable countries and is increasing. The prevalence of gout in elderly male Australians is second only to New Zealand, which has the highest reported rate in the world. Further research on Aboriginal and Torres Strait Islander gout and hyperuricaemia is required as a result of the lack of contemporary data.

Clinical and genetic risk factors for perianal Crohn's disease in a population-based cohort.

OBJECTIVES: Perianal Crohn's disease (CD) affects around one-quarter of CD patients and represents a distinct disease phenotype. The objective of this study was to investigate a large population-based cohort of inflammatory bowel disease (IBD) patients to identify clinical and genetic risk factors for perianal CD. METHODS: Data were collected in the Canterbury IBD database, estimated to include 91% of all patients with IBD in Canterbury, New Zealand. Genotyping was performed for selected loci previously demonstrated to be associated with CD. Patients with perianal disease were then compared with both CD patients without perianal disease and healthy controls to assess the presence of potential phenotypic, environmental, and genetic risk factors. RESULTS: Of the 715 CD patients in the database, 190 (26.5%) had perianal disease. In all, 507 patients with genotype data available were analyzed. Perianal disease was associated with younger age at diagnosis (P < 0.0001), complicated intestinal disease (P < 0.0001), and ileal disease location (P = 0.002). There was no association with gender, ethnicity, smoking, or breast feeding. Genotype analysis revealed an association with the neutrophil cytosolic factor 4 (NCF4) gene compared with both non-perianal CD patients (odds ratio (OR): 1.47; 95% confidence interval (CI): 1.08-1.99) and healthy controls (OR: 1.47; 95% CI: 1.10-1.95). There was no association identified with other genes, including IBD5 (OR: 0.91; 95% CI: 0.69-1.20), tumor necrosis factor α (OR: 1.04; 95% CI: 0.56-1.85), and IRGM (immunity-related guanosine triphosphatase protein type M) (OR: 1.21; 95% CI: 0.80-1.82). CONCLUSIONS: This study suggests that younger age at diagnosis, complicated disease behavior, and ileal disease location are risk factors for perianal CD. In addition, this paper represents the first report of an association of the NCF4 gene with perianal disease.

IL-23R rs11209026 polymorphism modulates IL-17A expression in patients with rheumatoid arthritis.

The interleukin (IL)-17/IL-23 axis is an important pro-inflammatory pathway in rheumatoid arthritis (RA). IL-23 maintains CD4(+) T-helper 17 (Th(17)) cells, whereas IL-12 negates IL-17A production by promoting Th(1)-cell differentiation. We sought evidence for any effect of polymorphisms within the interleukin-23 receptor (IL-23R), IL-12 or IL-21 genes on serum cytokine concentrations in 81 patients with RA. Serum cytokines were measured using bead-based multiplex assays. Targeted cytokines were detected in up to 66% of samples. A subgroup of 48 patients had detectable serum IL-17A. Within this subgroup, patients, homozygous for the IL-23R rs11209026 major allele had significantly higher serum IL-17A concentrations compared with patients with the minor allele (394.51 ± 529.72 pg ml(-1) vs 176.11 ± 277.32 pg ml(-1); P = 0.017). There was no significant difference in any of the cytokine concentrations examined in patients positive for the minor allele vs homozygosity for the major allele of IL-12B rs3213337, IL-12Bpro rs17860508 and IL-21 rs6822844. Our results suggest the IL-23R Arg381Gln substitution may influence serum IL-17A concentrations. In patients with the 381Gln allele higher IL-23 concentrations may be needed to produce similar IL-17A concentrations to those in patients with the 381Arg allele. This suggests altered IL-23R function in patients with the minor allele and warrants further functional studies.

Evidence that glioma-associated oncogene homolog 1 is not a universal risk gene for inflammatory bowel disease in Caucasians.

The transcription factor glioma-associated oncogene homolog 1 (GLI1) has a central function in gastrointestinal tract development and homeostasis. A non-synonymous single-nucleotide polymorphism (SNP) (rs2228226; Q1100E) in GLI1, which impairs GLI1 function in vitro, has been proposed as a risk factor for inflammatory bowel disease (IBD). In this study, we assessed the cumulative evidence for association of GLI1 with IBD. New genotype data for rs2228226 from New Zealand (907 controls, 990 IBD patients) and Belgian Caucasian case-control data sets (312 controls, 1214 IBD patients) were combined with data from the National Institute of Diabetes and Digestive and Kidney Diseases and three previously studied Caucasian case-control data sets. Meta-analysis of rs2228226 did not detect any association with ulcerative colitis (UC) (P=0.09, odds ratio (OR)=1.07, 95% confidence interval (CI)=0.92-1.24), Crohn's disease (CD) (P=0.29, OR=1.06, 95% CI=0.93-1.21) or overall IBD (P=0.15, OR=1.05, 95% CI=0.92-1.19). Our analyses of rs2228226 suggest that GLI1 is not a significant risk factor for IBD in Caucasians.