Examining the Association of Rare Allelic Variants in Urate Transporters SLC22A11, SLC22A13, and SLC17A1 with Hyperuricemia and Gout.

Genetic variations in urate transporters play a significant role in determining human urate levels and have been implicated in developing hyperuricemia or gout. Polymorphism in the key urate transporters, such as ABCG2, URAT1, or GLUT9 was well-documented in the literature. Therefore in this study, our objective was to determine the frequency and effect of rare nonsynonymous allelic variants of SLC22A11, SLC22A13, and SLC17A1 on urate transport. In a cohort of 150 Czech patients with primary hyperuricemia and gout, we examined all coding regions and exon-intron boundaries of SLC22A11, SLC22A13, and SLC17A1 using PCR amplification and Sanger sequencing. For comparison, we used a control group consisting of 115 normouricemic subjects. To examine the effects of the rare allelic nonsynonymous variants on the expression, intracellular processing, and urate transporter protein function, we performed a functional characterization using the HEK293A cell line, immunoblotting, fluorescent microscopy, and site directed mutagenesis for preparing variants in vitro. Variants p.V202M (rs201209258), p.R343L (rs75933978), and p.P519L (rs144573306) were identified in the SLC22A11 gene (OAT4 transporter); variants p.R16H (rs72542450), and p.R102H (rs113229654) in the SLC22A13 gene (OAT10 transporter); and the p.W75C variant in the SLC17A1 gene (NPT1 transporter). All variants minimally affected protein levels and cytoplasmic/plasma membrane localization. The functional in vitro assay revealed that contrary to the native proteins, variants p.P519L in OAT4 (p ≤ 0.05), p.R16H in OAT10 (p ≤ 0.05), and p.W75C in the NPT1 transporter (p ≤ 0.01) significantly limited urate transport activity. Our findings contribute to a better understanding of (1) the risk of urate transporter-related hyperuricemia/gout and (2) uric acid handling in the kidneys.

Brain age estimation at tract group level and its association with daily life measures, cardiac risk factors and genetic variants.

Brain age can be estimated using different Magnetic Resonance Imaging (MRI) modalities including diffusion MRI. Recent studies demonstrated that white matter (WM) tracts that share the same function might experience similar alterations. Therefore, in this work, we sought to investigate such issue focusing on five WM bundles holding that feature that is Association, Brainstem, Commissural, Limbic and Projection fibers, respectively. For each tract group, we estimated brain age for 15,335 healthy participants from United Kingdom Biobank relying on diffusion MRI data derived endophenotypes, Bayesian ridge regression modeling and 10 fold-cross validation. Furthermore, we estimated brain age for an Ensemble model that gathers all the considered WM bundles. Association analysis was subsequently performed between the estimated brain age delta as resulting from the six models, that is for each tract group as well as for the Ensemble model, and 38 daily life style measures, 14 cardiac risk factors and cardiovascular magnetic resonance imaging features and genetic variants. The Ensemble model that used all tracts from all fiber groups (FG) performed better than other models to estimate brain age. Limbic tracts based model reached the highest accuracy with a Mean Absolute Error (MAE) of 5.08, followed by the Commissural ([Formula: see text]), Association ([Formula: see text]), and Projection ([Formula: see text]) ones. The Brainstem tracts based model was the less accurate achieving a MAE of 5.86. Accordingly, our study suggests that the Limbic tracts experience less brain aging or allows for more accurate estimates compared to other tract groups. Moreover, the results suggest that Limbic tract leads to the largest number of significant associations with daily lifestyle factors than the other tract groups. Lastly, two SNPs were significantly (p value [Formula: see text]) associated with brain age delta in the Projection fibers. Those SNPs are mapped to HIST1H1A and SLC17A3 genes.

SLC17A3 rs9379800 and Ischemic Stroke Susceptibility at the Northern Region of Malaysia.

OBJECTIVES: The relationships of Paired Like Homeodomain 2 (PITX2), Ninjurin 2 (NINJ2), TWIST-Related Protein 1 (TWIST1), Ras Interacting Protein 1 (Rasip1), Solute Carrier Family 17 Member 3 (SLC17A3), Methylmalonyl Co-A Mutase (MUT) and Fer3 Like BHLH Transcription Factor (FERD3L) polymorphisms and gene expression with ischemic stroke have yet to be determined in Malaysia. Hence, this study aimed to explore the associations of single nucleotide polymorphisms (SNPs) and gene expression with ischemic stroke risk among population who resided at the Northern region of Malaysia. MATERIALS AND METHODS: Study subjects including 216 ischemic stroke patients and 203 healthy controls were recruited upon obtaining ethical clearance. SNP genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism assays. Gene expression levels were quantified by real-time polymerase chain reaction assays. Statistical and genetic analyses were conducted with SPSS version 22.2, PLINK version 1.07 and multifactor dimensionality reduction software. RESULTS: Study subjects with G allele, CG or GG genotypes of SLC17A3 rs9379800 demonstrated increased risk of ischemic stroke with the odds ratios ranging from 1.76-fold to 3.14-fold (p<0.05). When stratified study subjects according to the ethnicity, SLC17A3 rs9379800 G allele and CG genotype contributed to 2.14- and 2.96-fold of ischemic stroke risk among Malay population significantly, in the multivariate analysis (p<0.05). However, no significant associations were observed for PITX2, NINJ2, TWIST1, Rasip1, and MUT polymorphisms with ischemic stroke risk in the multivariate analysis for the pooled cases and controls as well as when stratified them according to the ethnicity. Lower mRNA expression levels of Rasip1, SLC17A3, MUT and FERD3L were observed among cases (p<0.05). After FDR adjustment, the mRNA level of SLC17A3 remained significantly associated with ischemic stroke among Malay population (q=0.034). CONCLUSION: In conclusion, this study suggests that SLC17A3 rs9379800 polymorphism and its gene expression contribute to significant ischemic stroke risk among Malaysian population, particularly the Malay who resided at the Northern Region of the country. Our findings can provide useful information for the future diagnosis, management and treatment of ischemic stroke patients.

Comparison of DNA methylation profiles from saliva in Coeliac disease and non-coeliac disease individuals.

BACKGROUND: Coeliac disease (CD) is a autoimmune disease characterised by mucosal inflammation in the small intestine in response to dietary gluten. Genetic factors play a key role with CD individuals carrying either the HLA-DQ2 or HLA-DQ8 haplotype, however these haplotypes are present in half the general population making them necessary but insufficient to cause CD. Epigenetic modifications, including DNA methylation that can change in response to environmental exposure could help to explain how interactions between genes and environmental factors combine to trigger disease development. Identifying changes in DNA methylation profiles in individuals with CD could help discover novel genomic regions involved in the onset and development of CD. METHODS: The Illumina InfiniumMethylation450 Beadchip array (HM450) was used to compare DNA methylation profiles in saliva, in CD and non-CD affected individuals. CD individuals who had been diagnosed at least 2 years previously; were on a GFD; and who were currently asymptomatic; were compared to age and sex-matched non-CD affected healthy controls. Bisulphite pyrosequencing was used to validate regions found to be differentially methylated. These regions were also validated in a second larger cohort of CD and non-CD affected individuals. RESULTS: Methylation differences within the HLA region at HLA-DQB1 were identified on HM450 but could not be confirmed with pyrosequencing. Significant methylation differences near the SLC17A3 gene were confirmed on pyrosequencing in the initial pilot cohort. Interestingly pyrosequencing sequencing of these same sites within a second cohort of CD and non-CD affected controls produced significant methylation differences in the opposite direction. CONCLUSION: Altered DNA methylation profiles appear to be present in saliva in CD individuals. Further work to confirm whether these differences are truly associated with CD is needed.

Evolutionary history of disease-susceptibility loci identified in longitudinal exome-wide association studies.

BACKGROUND: Our longitudinal exome-wide association studies previously detected various genetic determinants of complex disorders using ~26,000 single-nucleotide polymorphisms (SNPs) that passed quality control and longitudinal medical examination data (mean follow-up period, 5 years) in 4884-6022 Japanese subjects. We found that allele frequencies of several identified SNPs were remarkably different among four ethnic groups. Elucidating the evolutionary history of disease-susceptibility loci may help us uncover the pathogenesis of the related complex disorders. METHODS: In the present study, we conducted evolutionary analyses such as extended haplotype homozygosity, focusing on genomic regions containing disease-susceptibility loci and based on genotyping data of our previous studies and datasets from the 1000 Genomes Project. RESULTS: Our evolutionary analyses suggest that derived alleles of rs78338345 of GGA3, rs7656604 at 4q13.3, rs34902660 of SLC17A3, and six SNPs closely located at 12q24.1 associated with type 2 diabetes mellitus, obesity, dyslipidemia, and three complex disorders (hypertension, hyperuricemia, and dyslipidemia), respectively, rapidly expanded after the human dispersion from Africa (Out-of-Africa). Allele frequencies of GGA3 and six SNPs at 12q24.1 appeared to have remarkably changed in East Asians, whereas the derived alleles of rs34902660 of SLC17A3 and rs7656604 at 4q13.3 might have spread across Japanese and non-Africans, respectively, although we cannot completely exclude the possibility that allele frequencies of disease-associated loci may be affected by demographic events. CONCLUSION: Our findings indicate that derived allele frequencies of nine disease-associated SNPs (rs78338345 of GGA3, rs7656604 at 4q13.3, rs34902660 of SLC17A3, and six SNPs at 12q24.1) identified in the longitudinal exome-wide association studies largely increased in non-Africans after Out-of-Africa.

Identification of six novel susceptibility loci for dyslipidemia using longitudinal exome-wide association studies in a Japanese population.

Recent genome-wide association studies have identified various dyslipidemia-related genetic variants. However, most studies were conducted in a cross-sectional manner. We thus performed longitudinal exome-wide association studies of dyslipidemia in a Japanese population. We used ~244,000 genetic variants and clinical data of 6022 Japanese individuals who had undergone annual health checkups for several years. After quality control, the association of dyslipidemia-related phenotypes with 24,691 single nucleotide polymorphisms (SNPs) was tested using the generalized estimating equation model. In total, 82 SNPs were significantly (P < 2.03 × 10-6) associated with dyslipidemia phenotypes. Of these SNPs, four (rs74416240 of TCHP, rs925368 of GIT2, rs7969300 of ATXN2, and rs12231744 of NAA25) and two (rs34902660 of SLC17A3 and rs1042127 of CDSN) were identified as novel genetic determinants of hypo-HDL- and hyper-LDL-cholesterolemia, respectively. A replication study using the cross-sectional data of 8310 Japanese individuals showed the association of the six identified SNPs with dyslipidemia-related traits.

Genome-wide analyses identify a role for SLC17A4 and AADAT in thyroid hormone regulation.

Thyroid dysfunction is an important public health problem, which affects 10% of the general population and increases the risk of cardiovascular morbidity and mortality. Many aspects of thyroid hormone regulation have only partly been elucidated, including its transport, metabolism, and genetic determinants. Here we report a large meta-analysis of genome-wide association studies for thyroid function and dysfunction, testing 8 million genetic variants in up to 72,167 individuals. One-hundred-and-nine independent genetic variants are associated with these traits. A genetic risk score, calculated to assess their combined effects on clinical end points, shows significant associations with increased risk of both overt (Graves' disease) and subclinical thyroid disease, as well as clinical complications. By functional follow-up on selected signals, we identify a novel thyroid hormone transporter (SLC17A4) and a metabolizing enzyme (AADAT). Together, these results provide new knowledge about thyroid hormone physiology and disease, opening new possibilities for therapeutic targets.

Genetic variants in two pathways influence serum urate levels and gout risk: a systematic pathway analysis.

The aims of this study were to identify candidate pathways associated with serum urate and to explore the genetic effect of those pathways on the risk of gout. Pathway analysis of the loci identified in genome-wide association studies (GWASs) showed that the ion transmembrane transporter activity pathway (GO: 0015075) and the secondary active transmembrane transporter activity pathway (GO: 0015291) were both associated with serum urate concentrations, with PFDR values of 0.004 and 0.007, respectively. In a Chinese population of 4,332 individuals, the two pathways were also found to be associated with serum urate (PFDR = 1.88E-05 and 3.44E-04, separately). In addition, these two pathways were further associated with the pathogenesis of gout (PFDR = 1.08E-08 and 2.66E-03, respectively) in the Chinese population and a novel gout-associated gene, SLC17A2, was identified (OR = 0.83, PFDR = 0.017). The mRNA expression of candidate genes also showed significant differences among different groups at pathway level. The present study identified two transmembrane transporter activity pathways (GO: 0015075 and GO: 0015291) were associations with serum urate concentrations and the risk of gout. SLC17A2 was identified as a novel gene that influenced the risk of gout.

A genetic association study of carotid intima-media thickness (CIMT) and plaque in Mexican Americans and European Americans with rheumatoid arthritis.

BACKGROUND AND AIMS: Little is known about specific genetic determinants of carotid-intima-media thickness (CIMT) and carotid plaque in subjects with rheumatoid arthritis (RA). We have used the Metabochip array to fine map and replicate loci that influence variation in these phenotypes in Mexican Americans (MAs) and European Americans (EAs). METHODS: CIMT and plaque were measured using ultrasound from 700 MA and 415 EA patients with RA and we conducted association analyses with the Metabochip single nucleotide polymorphism (SNP) data using PLINK. RESULTS: In MAs, 12 SNPs from 11 chromosomes and 6 SNPs from 6 chromosomes showed suggestive associations (p < 1 × 10-4) with CIMT and plaque, respectively. The strongest association was observed between CIMT and rs17526722 (SLC17A2 gene) (ß ± SE = -0.84 ± 0.18, p = 3.80 × 10-6). In EAs, 9 SNPs from 7 chromosomes and 7 SNPs from 7 chromosomes showed suggestive associations with CIMT and plaque, respectively. The top association for CIMT was observed with rs1867148 (PPCDC gene, ß ± SE = -0.28 ± 0.06, p = 5.11 × 10-6). We also observed strong association between plaque and two novel loci: rs496916 from COL4A1 gene (OR = 0.51, p = 3.15 × 10-6) in MAs and rs515291 from SLCA13 gene (OR = 0.50, p = 3.09 × 10-5) in EAs. CONCLUSIONS: We identified novel associations between CIMT and variants in SLC17A2 and PPCDC genes, and between plaque and variants from COL4A1 and SLCA13 that may pinpoint new candidate risk loci for subclinical atherosclerosis associated with RA.

Mendelian randomization analysis indicates serum urate has a causal effect on renal function in Chinese women.

PURPOSE: High levels of serum uric acid can predict the progression of stage I and II chronic kidney disease (CKD), but whether serum urate is an independent risk factor or has causal impact on serum creatinine (SCr) and renal function remains unclear. METHODS: Mendelian randomization was used to determine whether serum uric acid had a causal effect on renal function, represented by estimated glomerular filtration rate (eGFR), with potential confounding factors, in 3734 subjects from the Taizhou Longitudinal Study. In the two-stage least squares method of Mendelian randomization, serum uric acid level was selected as the exposure, genetic risk score of uric acid transporters was selected as the instrumental variable, and SCr and eGFR were selected as the outcomes. RESULTS: The result of the analysis showed that increased serum uric acid was not a causal effect on renal function, but it was a causal effect on reducing estimated glomerular filtration rate in both the female population and the subjects who were under 65 years old. We also found that increased serum uric acid levels led to impaired renal function only in the subjects with normal eGFR values. In addition, the serum uric acid was a risk factor for renal function in the subjects with relatively high levels of fasting glucose or who were currently smokers. CONCLUSIONS: Although serum urate is not an independent risk factor for renal dysfunction, it has a causal effect on renal dysfunction in either female or individuals of under 65, or normal eGFR, or high level of fasting glucose, or current smokers.

Transcriptomic analysis and plasma metabolomics in Aldh16a1-null mice reveals a potential role of ALDH16A1 in renal function.

ALDH16A1 is a novel member of the ALDH superfamily that is enzymatically-inactive and highly expressed in the kidney. Recent studies identified an association between a rare missense single nucleotide variant (SNV) in the ALDH16A1 gene and elevated serum uric acid levels and gout. The present study explores the mechanisms by which ALDH16A1 influences uric acid homeostasis in the kidney. We generated and validated a mouse line with global disruption of the Aldh16a1 gene through gene targeting and performed RNA-seq analyses in the kidney of wild-type (WT) and Aldh16a1 knockout (KO) mice, along with plasma metabolomics. We found that ALDH16A1 is expressed in proximal and distal convoluted tubule cells in the cortex of the kidney and in zone 3 hepatocytes. RNA-seq and gene ontology enrichment analyses showed that cellular lipid and lipid metabolic processes are up-regulated. Three transporters localized in the apical membrane of the proximal convoluted tubule of the kidney known to influence urate/uric acid homeostasis were found to be up-regulated (Abcc4, Slc16a9) or down-regulated (Slc17a3). An initial metabolomics analysis in plasma revealed an altered lipid profile in KO mice that is in agreement with our RNA-seq analysis. This is the first study demonstrating a functional role of ALDH16A1 in the kidney.

GWAS of clinically defined gout and subtypes identifies multiple susceptibility loci that include urate transporter genes.

OBJECTIVE: A genome-wide association study (GWAS) of gout and its subtypes was performed to identify novel gout loci, including those that are subtype-specific. METHODS: Putative causal association signals from a GWAS of 945 clinically defined gout cases and 1213 controls from Japanese males were replicated with 1396 cases and 1268 controls using a custom chip of 1961 single nucleotide polymorphisms (SNPs). We also first conducted GWASs of gout subtypes. Replication with Caucasian and New Zealand Polynesian samples was done to further validate the loci identified in this study. RESULTS: In addition to the five loci we reported previously, further susceptibility loci were identified at a genome-wide significance level (p<5.0×10-8): urate transporter genes (SLC22A12 and SLC17A1) and HIST1H2BF-HIST1H4E for all gout cases, and NIPAL1 and FAM35A for the renal underexcretion gout subtype. While NIPAL1 encodes a magnesium transporter, functional analysis did not detect urate transport via NIPAL1, suggesting an indirect association with urate handling. Localisation analysis in the human kidney revealed expression of NIPAL1 and FAM35A mainly in the distal tubules, which suggests the involvement of the distal nephron in urate handling in humans. Clinically ascertained male patients with gout and controls of Caucasian and Polynesian ancestries were also genotyped, and FAM35A was associated with gout in all cases. A meta-analysis of the three populations revealed FAM35A to be associated with gout at a genome-wide level of significance (p meta =3.58×10-8). CONCLUSIONS: Our findings including novel gout risk loci provide further understanding of the molecular pathogenesis of gout and lead to a novel concept for the therapeutic target of gout/hyperuricaemia.

Expression of a human NPT1/SLC17A1 missense variant which increases urate export.

Human sodium-dependent phosphate cotransporter type 1 (NPT1/SLC17A1) is one of the urate transporters in the kidney. Our recent study revealed that a common missense variant, I269T (rs1165196), of NPT1 decreases the risk of renal underexcretion gout. Moreover, we demonstrated that human NPT1 is localized to the apical membrane of the renal proximal tubule, and that I269T is the gain-of-function variant which increases the NPT1-mediated urate export. However, the mechanism by which I269T variant increases the urate export remains to be clarified. Thus, we performed immunostaining and functional analysis of human NPT1 using the Xenopus oocyte expression system. For comparison of human NPT1 expression levels of oocyte membrane between 269I (wild type) and 269T (variant), immunostaining was performed with anti-human NPT1 antibodies. As a result, we showed that NPT1 I269T variant did not change the human NPT1 membrane expression levels, although NPT1 I269T variant increased the urate transport compared with NPT1 wild type. Combined with the previous report that I269T variant did not induce Km changes but increased the Vmax of urate transport in a proteoliposome system, our findings suggest that I269T variant increases NPT1-mediated urate export without increase of NPT1 expression levels on the membrane. Thus, I269T, a common missense variant of NPT1, might have faster conformation changes than NPT1 wild type in terms of the alternating-access model of transporters, and increases renal urate export in humans.

The homocysteine associated variant rs548987 of SLC17A3 confers susceptibility to ischemic stroke in Chinese population.

Ischemic stroke is a common cause of death due to obstructed blood supply of the brain. Despite growing numbers of research, etiology underlying ischemic stroke remains complex and elusive. Elevated plasma homocysteine has been known as a risk factor for ischemic stroke. Recently, a genome-wide association study reported association between rs548987 of SLC17A3 and homocysteine. Given existing relation between homocysteine and ischemic stroke, SLC17A3 was believed to be a promising candidate gene of ischemic stroke. Indeed, its association with ischemic stroke was previously reported in a western population. Herein, we used rs548987 as a candidate genetic variant of ischemic stroke and performed association analysis in a Chinese population with 918 ischemic stroke cases and 979 controls. Although rs548987 failed to show significant association with total ischemic stroke and large vessel disease subtype, the C allele of rs548987 showed significant association with small vessel disease subtype of ischemic stroke (OR=0.68, p=0.004). Our preliminary results suggested different genetic etiology underlying the two most common subtypes of ischemic stroke and provided additional evidence to understand contribution of homocysteine to the disease.

Genome-wide association study of serum iron phenotypes in premenopausal women of European descent.

A genome-wide association study was performed on 1130 premenopausal women to detect common variants associated with three serum iron-related phenotypes. Total iron binding capacity was strongly associated (p=10(-14)) with variants in and near the TF gene (transferrin), the serum iron transporting protein, and with variants in HFE (p=4×10(-7)), which encodes the human hemochromatosis gene. Association was also detected between percent iron saturation (p=10(-8)) and variants in the chromosome 6 region containing both HFE and SLC17A2, which encodes a phosphate transport protein. No significant associations were detected with serum iron, but variants in HFE were suggestive (p=10(-6)). Our results corroborate prior studies in older subjects and demonstrate that the association of these genetic variants with iron phenotypes can be detected in premenopausal women.

[Polymorphisms of SLC17A1 gene and their interaction with alcohol drinking among Uygur patients with hyperuricemia].

OBJECTIVE: To investigate the correlation between polymorphisms of uric acid transporter related gene SLC17A1 and hyperuricemia (HUA) among ethnic Uygur patients from Xinjiang. METHODS: A case-control study was carried out, which enrolled 1036 patients with hyperuricemia and 1031 healthy controls. Two single nucleotide polymorphisms (SNPs) of the SLC17A1 gene were determined with Sequenom MassARRAY. Crossover analysis was used to assess the effect of interaction between above SNPs and alcohol drinking on uric acid level. RESULTS: Genotypic and allelic frequencies of the SLC17A1 gene at the two loci in the two groups were compared. The CT genotype of the rs9467596 locus and TC genotype of the rs2096386 locus showed a higher risk for hyperuricemia (OR=1.334, 95%CI:1.082-1.644; OR=1.242, 95%CI:1.015-1.519, respectively). Crossover analysis also revealed that the SLC17A1 rs2096386 polymorphism has a positive interaction with alcohol drinking in a multiplication model (ORint=1.21, P<0.05, OR>1). CONCLUSION: SNP rs9467596 and rs2096386 of the SLC17A1 gene may have a correlation between hyperuricemia and alcohol drinking among Uygur patients.

Genetic variants of SLC17A1 are associated with cholesterol homeostasis and hyperhomocysteinaemia in Japanese men.

Hyperuricaemia is an undisputed and highly predictive biomarker for cardiovascular risk. SLC17A1, expressed in the liver and kidneys, harbours potent candidate single nucleotide polymorphisms that decrease uric acid levels. Therefore, we examined SLC17A1 polymorphisms (rs1165196, rs1179086, and rs3757131), which might suppress cardiovascular risk factors and that are involved in liver functioning, via a large-scale pooled analysis of the Japanese general population in a cross-sectional study. Using data from the Japan Multi-Institutional Collaborative Cohort Study, we identified 1842 participants of both sexes, 35-69-years-old, having the requisite data, and analysed their SLC17A1 genotypes. In men, logistic regression analyses revealed that minor alleles in SLC17A1 polymorphisms (rs1165196 and rs3757131) were associated with a low-/high-density lipoprotein cholesterol ratio >2.0 (rs1165196: odds ratio [OR], 0.703; 95% confidence interval [CI], 0.536-0.922; rs3757131: OR, 0.658; 95% CI, 0.500-0.866), and with homocysteine levels of >10.0 nmol/mL (rs1165196: OR, 0.544; 95% CI, 0.374-0.792; rs3757131: OR, 0.509; 95% CI, 0.347-0.746). Therefore, these polymorphisms had dominant negative effects on cholesterol homeostasis and hyperhomocysteinaemia, in men, independent of alcohol consumption, physical activity, or daily energy and nutrition intake. Thus, genetic variants of SLC17A1 are potential biomarkers for altered cholesterol homeostasis and hyperhomocysteinaemia in Japanese men.

Polymorphisms in GCKR, SLC17A1 and SLC22A12 were associated with phenotype gout in Han Chinese males: a case-control study.

BACKGROUND: Gout is a common arthritic disease resulting from elevated serum uric acid (SUA) level. A large meta-analysis including 28,141 individuals identified nine single nucleotide polymorphisms (SNPs) associated with altered SUA level in a Caucasian population. However, raised SUA level alone is not sufficient for the development of gout arthritis and most of these SNPs have not been studied in a Han Chinese population. Here, we performed a case-control association analysis to investigate the relationship between these SUA correlated SNPs and gout arthritis in Han Chinese. METHODS: A total of 622 ascertained gout p9atients and 917 healthy controls were genotyped. Genome-wide significant SNPs, rs12129861, rs780094, rs734553, rs742132, rs1183201, rs12356193, rs17300741 and rs505802 in the previous SUA study, were selected for our analysis. RESULTS: No deviation from the Hardy-Weinberg equilibrium was observed either in the case or control cohorts (corrected p > 0.05). Three SNPs, rs780094 (located in GCKR, corrected p = 1.78E(-4), OR = 0.723), rs1183201 (located in SLC17A1, corrected p = 1.39E(-7), OR = 0.572) and rs505802 (located in SLC22A12, corrected p = 0.007, OR = 0.747), were significantly associated with gout on allelic level independent of potential cofounding traits. While the remaining SNPs were not replicated. We also found significant associations of uric acid concentrations with these three SNPs (rs780094 in GCKR, corrected p = 3.94E(-5); rs1183201 in SLC17A1, corrected p = 0.005; rs505802 in SLC22A12, corrected p = 0.003) and of triglycerides with rs780094 (located in GCKR, corrected p = 2.96E(-4)). Unfortunately, SNP-SNP interactions for these three significant SNPs were not detected (rs780094 vs rs1183201, p = 0.402; rs780094 vs rs505802, p = 0.434; rs1183201 vs rs505802, p = 0.143). CONCLUSIONS: Three SUA correlated SNPs in Caucasian population, rs780094 in GCKR, rs1183201 in SLC17A1 and rs505802 in SLC22A12 were confirmed to be associated with gout arthritis and uric acid concentrations in Han Chinese males. Considering genetic differences among populations and complicated pathogenesis of gout arthritis, more validating tests in independent populations and relevant functional experiments are suggested in future.

Wide expression of type I Na+-phosphate cotransporter 3 (NPT3/SLC17A2), a membrane potential-driven organic anion transporter.

Membrane potential (Δψ)-driven and Cl(-)-dependent organic anion transport is a primary function of the solute carrier family 17 (SLC17) transporter family. Although the transport substrates and physiological relevance of the major members are well understood, SLC17A2 protein known to be Na(+)-phosphate cotransporter 3 (NPT3) is far less well characterized. In the present study, we investigated the transport properties and expression patterns of mouse SLC17A2 protein (mNPT3). Proteoliposomes containing the purified mNPT3 protein took up radiolabeled p-aminohippuric acid (PAH) in a Δψ- and Cl(-)-dependent manner. The mNPT3-mediated PAH uptake was inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDs) and Evans blue, common inhibitors of SLC17 family members. The PAH uptake was also inhibited by various anionic compounds, such as hydrophilic nonsteroidal anti-inflammatory drugs (NSAIDs) and urate. Consistent with these observations, the proteoliposome took up radiolabeled urate in a Δψ- and Cl(-)-dependent manner. Immunohistochemistry with specific antibodies against mNPT3 combined with RT-PCR revealed that mNPT3 is present in various tissues, including the hepatic bile duct, luminal membranes of the renal urinary tubules, maternal side of syncytiotrophoblast in the placenta, apical membrane of follicle cells in the thyroid, bronchiole epithelial cells in the lungs, and astrocytes around blood vessels in the cerebrum. These results suggested that mNPT3 is a polyspecific organic anion transporter that is involved in circulation of urate throughout the body.

NPT1/SLC17A1 is a renal urate exporter in humans and its common gain-of-function variant decreases the risk of renal underexcretion gout.

OBJECTIVE: Serum uric acid (SUA) levels in humans are mainly regulated by urate transporters. Recent genome-wide association studies suggested that common variants of the human sodium-dependent phosphate cotransporter type 1 gene (NPT1/SLC17A1) influence SUA. NPT1 has been reported to mediate urate transport, but its physiologic role in regulating SUA in humans remains unclear. Furthermore, the findings of replication studies of the relationship between NPT1 variants and gout have been inconsistent. The aims of this study were to investigate the effect of NPT1 on gout and to determine its physiologic role. METHODS: Five hundred forty-five male Japanese patients with gout and 1,115 male Japanese control subjects were genotyped for rs1165196 (I269T), a common missense variant in NPT1. Analyses of the association between rs1165196 and gout were then conducted, focusing especially on renal underexcretion (RUE) gout. Immunohistochemical analysis and functional analysis using Xenopus oocytes were also performed. RESULTS: Single-nucleotide polymorphism rs1165196 significantly decreased the risk of RUE gout (odds ratio 0.73, P = 0.031) but did not confer a risk for all gout (P = 0.123). The immunohistochemical analysis revealed that human NPT1 is localized to the apical membrane of the renal proximal tubule. The functional analysis using Xenopus oocyte expression systems showed that rs1165196 increases NPT1-mediated urate export. CONCLUSION: This study showed that NPT1 is a urate exporter located in the renal proximal tubule in humans, and that its common gain-of-function variant, rs1165196, causes RUE gout, a major subtype of gout. These findings enable us to deepen our understanding of the physiologic role of NPT1 as a renal urate exporter as well as its pathophysiologic role in gout.