Agents for the Treatment of Gout: Current Advances and Future Perspectives

Gout is characterized by hyperuricemia and the deposition of monosodium urate (MSU) crystals around joints. Despite the availability of several drugs on the market, its treatment remains challenging owing to the notable side effects, such as hepatorenal toxicity and cardiovascular complications, that are associated with most existing agents. This perspective aims to summarize the current research progress in the development of antigout agents, particularly focusing on xanthine oxidase (XO) and urate anion transporter 1 (URAT1) inhibitors from a medicinal chemistry viewpoint and their preliminary structure-activity relationships (SARs). This perspective provides valuable insights and theoretical guidance to medicinal chemists for the discovery of antigout agents with novel chemical structures, better efficiency, and lower toxicity.

Associations between obesity parameters and hyperuricemia by sex, age, and diabetes mellitus: A nationwide study in Korea

OBJECTIVE

We investigated the associations between obesity parameters and the risk of hyperuricemia among Korean adults by sex, age, and diabetes mellitus status.

METHODS

This study analyzed data from 17,753 adults from the Korea National Health and Nutrition Examination Survey (KNHANES) 2016-2018. Multivariable logistic regression analyses were conducted to examine the associations of body mass index (BMI), waist circumference (WC), and general and abdominal obesity with the risk of hyperuricemia (serum uric acid ≥7.0 mg/dL in men and ≥6.0 mg/dL in women).

RESULTS

Of all the participants, 12.7% (n = 2256) had hyperuricemia. The age-adjusted mean serum uric acid levels increased significantly with increasing BMI and WC (P for trend <0.001). The adjusted odds ratios (ORs) of hyperuricemia increased as BMI and WC increased in both sexes (P for trend <0.001). General (OR 1.98, 95% confidence interval [CI]: 1.69-2.32) and abdominal (OR 2.21, 95% CI: 1.89-2.58) obesity in men and general (OR 3.26, 95% CI: 2.60-4.09) and abdominal (OR 3.43, 95% CI: 2.69-4.37) obesity in women were associated with higher risks of hyperuricemia. These associations were prominent in women. The association between abdominal obesity and hyperuricemia persisted after additional adjustments for BMI in both sexes. Significant interactions were observed in younger adults and individuals without diabetes mellitus.

CONCLUSION

Increased BMI and WC, and general and abdominal obesity, may be important risk factors for hyperuricemia in both sexes. Women, young adults, and individuals without diabetes mellitus require particular attention to prevent obesity and hyperuricemia.

Novel urate transporter 1 (URAT1) inhibitors: a review of recent patent literature (2020-present)

INTRODUCTION

The urate transporter 1 (URAT1) is a membrane transporter located in the apical membrane of human renal proximal tubule epithelial cells, which mediates most of the reabsorption of urate. Hyperuricemia (HUA) is a common disease caused by metabolic disorders, which has been considered as the key factor of gout. Approximately 90% of patients suffer from hyperuricemia due to insufficient or poor uric acid excretion. Therefore, the drug design of URAT1 inhibitors targeting improve the renal urate excretion by reducing the reabsorption of urate anions represent a hot topic in searching for anti-gout drugs currently.

AREAS COVERED

In this review, we summarize URAT1 inhibitors patents reported since 2020 to present through the public database at https://worldwide.espacenet.com and some medicinal chemistry strategies employed to develop novel drug candidates.

EXPERT OPINION

Ligand-based drug design (LBDD) strategies have been frequently used developing new URAT1 inhibitors. Meanwhile, the discovery of dual drugs targeting both inhibition of xanthine oxidase (XOD) and URAT1 may be an emerging horizon for designing novel uric acid-lowering candidates in future. Furthermore, advanced techniques in the field of molecular biology and computer science can increase the chances to discover and/or optimize URAT1 inhibitors, contributing to the development of novel drug candidates.

New insight into the management of renal excretion and hyperuricemia: Potential therapeutic strategies with natural bioactive compounds

Hyperuricemia is the result of increased production and/or underexcretion of uric acid. Hyperuricemia has been epidemiologically associated with multiple comorbidities, including metabolic syndrome, gout with long-term systemic inflammation, chronic kidney disease, urolithiasis, cardiovascular disease, hypertension, rheumatoid arthritis, dyslipidemia, diabetes/insulin resistance and increased oxidative stress. Dysregulation of xanthine oxidoreductase (XOD), the enzyme that catalyzes uric acid biosynthesis primarily in the liver, and urate transporters that reabsorb urate in the renal proximal tubules (URAT1, GLUT9, OAT4 and OAT10) and secrete urate (ABCG2, OAT1, OAT3, NPT1, and NPT4) in the renal tubules and intestine, is a major cause of hyperuricemia, along with variations in the genes encoding these proteins. The first-line therapeutic drugs used to lower serum uric acid levels include XOD inhibitors that limit uric acid biosynthesis and uricosurics that decrease urate reabsorption in the renal proximal tubules and increase urate excretion into the urine and intestine via urate transporters. However, long-term use of high doses of these drugs induces acute kidney disease, chronic kidney disease and liver toxicity. Therefore, there is an urgent need for new nephroprotective drugs with improved safety profiles and tolerance. The current systematic review summarizes the characteristics of major urate transporters, the mechanisms underlying the pathogenesis of hyperuricemia, and the regulation of uric acid biosynthesis and transport. Most importantly, this review highlights the potential mechanisms of action of some naturally occurring bioactive compounds with antihyperuricemic and nephroprotective potential isolated from various medicinal plants.

Selectivity Enhancement for Uric Acid Detection via In Situ Preparation of Blue Emissive Carbon Dots Entrapped in Chromium Metal-Organic Frameworks

In the present work, for the first time, the in situ formation of blue emissive carbon dots (bCDs) and encapsulation into the pores of chromium-based metal-organic frameworks (Cr-MOFs) are described. The luminescent bCDs via in situ process are formed and entrapped inside the pores of Cr-MOFs to form a nanocomposite of bCDs@Cr-MOFs. The bCDs@Cr-MOFs showed a strong broad blue emission at 420 nm (excited at 310 nm), which corresponds to both, the ligand (2-aminoterephthalic acid) in the Cr-MOF and the entrapped bCDs. This is assigned for the entrapping of bCDs in the pores of the MOFs. Additionally, transmission electron microscopy (TEM) images showed two types of particles, 150 rod-like shapes for Cr-MOF and 5-10 nm spherical shapes assigned for the presence of bCDs. The bCDs alone (without Cr-MOF) showed no selectivity, and their emission was quenched by different biomolecules and ions, such as ascorbic acid, uric acid, Fe³⁺, Cu²⁺, and Hg²⁺. The selectivity of bCDs toward uric acid was increased dramatically when they were encapsulated in the Cr-MOF. The linear range for uric acid was 20-50 μM, and the LOD was measured as 1.3 μM. Spike recoveries for the detection of uric acid in serum samples were between 94 and 108%. The relative standard deviation (RSD, n = 3) at each concentration value was less than 2%. The results showed high ruggedness and robustness of the assay due to its high shelf-life stability of probe (four weeks), water stability, and long working pH range. Validation experiments showed that the established MOF-based sensing system is appropriate for uric acid detection in real samples.

Association between glucokinase regulator gene polymorphisms and serum uric acid levels in Taiwanese adolescents

The glucokinase regulator gene (GCKR) is located on chromosome 2p23. It plays a crucial role in maintaining plasma glucose homeostasis and metabolic traits. Recently, genome-wide association studies have revealed a positive association between hyperuricemia and GCKR variants in adults. This study investigated this genetic association in Taiwanese adolescents. Data were collected from our previous cross-sectional study (Taipei Children Heart Study). The frequencies of various genotypes (CC, CT, and TT) or alleles (C and T) of the GCKR intronic single-nucleotide polymorphism (SNP) rs780094 and the coding SNP rs1260326 (Pro446Leu, a common 1403C-T transition) were compared between a total of 968 Taiwanese adolescents (473 boys, 495 girls) with hyperuricemia or normal uric acid levels on the basis of gender differences. Logistic and linear regression analyses explored the role of GCKR in abnormal uric acid (UA) levels. Boys had higher UA levels than girls (6.68 ± 1.29 and 5.23 ± 0.95 mg/dl, respectively, p < 0.001). The analysis of both SNPs in girls revealed that the T allele was more likely to appear in patients with hyperuricemia than the C allele. After adjusting for confounders, the odds ratio (OR) for hyperuricemia incidence in the TT genotype was 1.75 (95% confidence interval [CI] 1.02–3.00), which was higher than that in the C allele carriers in rs1260326 in the girl population. Similarly, the TT genotypes had a higher risk of hyperuricemia, with an OR of 2.29 (95% CI 1.11–4.73) for rs1260326 and 2.28 (95% CI 1.09–4.75) for rs780094, than the CC genotype in girl adolescents. The T (Leu446) allele of GCKR rs1260326 polymorphism is associated with higher UA levels in Taiwanese adolescent girls.

Enterocyte synthesizes and secrets uric acid as antioxidant to protect against oxidative stress via the involvement of Nrf pathway

The gut is an important site to excreting uric acid (UA) in addition to the kidney. The gastrointestinal tract is constantly exposed to various potentially harmful substances, triggering intestinal oxidative damage. In the present study, the hypothesis that UA is can be synthesized to function as an antioxidant in the gut is evaluated. The synthesis and secretion of UA by enterocytes were analyzed in the presence of inosine, a precursor of UA, febuxostat (Fx), an inhibitor of xanthine oxidase (XOR), and H₂O₂. The regulation of Nrf2 pathway on UA secretion and transport were evaluated in the present of agonist (TBHQ) and inhibitor (ML385) of Nrf2. The in vivo result showed that UA and its oxidation product allantoin were presented in gut contents along the gastrointestinal tract and the highest level of UA and allantoin were detected in duodenum and jejunum respectively. The genes in the de novo purine nucleotide synthesis and salvage-catabolism pathways, and UA transporters were expressed in the intestinal tract. In the in vitro cultured enterocytes and everted gut sacs, inosine stimulated UA synthesis and secretion. H₂O₂ stimulated UA synthesis and secretion and meanwhile induced oxidative damage. UA attenuated H₂O₂-induced oxidative damage by Nrf2 pathway. UA secretion and transport were reduced by blocking Nrf2 with ML385, while increased by activating Nrf2 with TBHQ. This study provides new insights into the antioxidant effects if UA on intestinal lumen. The result suggests that activation of Nrf2 pathway is involved in the transportation and secretion of UA.

Genetic assessment of hyperuricemia and gout in Asian, Native Hawaiian, and Pacific Islander subgroups of pregnant women: biospecimens repository cross-sectional study

Background

Gout, an inflammatory condition, is characterized by the precipitation of monosodium urate crystals (MSU) in or around distal joints. The latter is caused by chronic hyperuricemia (HU)—high urate levels in the blood. Genetic variations in urate transporters play a significant role in determining urate levels within the human body, rendering some racial and ethnic groups more or less susceptible to developing either HU or gout. This study aims to estimate the frequencies of HU and gout risk alleles in Asian, Native Hawaiian, and Pacific Islander subgroups, using biorepository DNA samples.

Methods

The biospecimens repository at the University of Hawai’i provided DNA samples of consented post-partum women of Japanese, Filipino, Korean, Native Hawaiian, Samoan, and Marshallese descent. The DNA was previously extracted from maternal blood and genotyped at the Genomics and Bioinformatics Shared Resource, Cancer Center (Honolulu, HI). Nine urate genes: ABCG2, SLC2A9, SLC16A9, GCKR, SLC22A11, SLC22A12, LRR16A, PDZK1, and SLC17A1, were selected due to their significant association with HU and gout risk. Hardy–Weinberg Equilibrium (HWE) for genotype frequencies was assessed, using the Chi-Square test with p < 0.006 for statistical significance. Allele frequencies in our study were then compared to EUR from the 1000 Genomes Project Database Phase III, using Chi-square or Fisher's exact test, when appropriate. Bonferroni correction for multiple comparisons was used, with p < 0.006 for statistical significance.

Results

Our study involved 1059 post-partum women 18-year-old or older who self-reported their respective race and ethnicity, including Asian, Native Hawaiian, and Pacific Islander ancestry. The Asian subgroups included Japanese, Filipino, and Korean. The Pacific Islander subgroups included Marshallese and Samoan. None of the study participants had a history of gout. We excluded the PDZK1 gene from the final analysis due to its deviation from HWE (p < 0.006) across all the population subgroups, with eight loci remaining for cross-subgroup comparisons. Compared to EUR, the genetic polymorphism frequencies were significantly different-8/8 in Japanese, 6/8 in Korean, 6/8 in Filipino, 8/8 in Samoan, 6/8 in Native Hawaiian, and 6/8 in Marshallese. HU and gout risk alleles indices were 8, 6, 5, 5, 4, and 4 in Japanese, Filipino, Korean, Samoan, Marshallese, and Native Hawaiian, respectively. The percentage of cumulative risk alleles was 100% in both Japanese and Filipino, followed by 83.5% in Korean.

Conclusions

Compared to EUR, Asian subgroups, particularly Japanese, Filipino, and Korean, had the highest percentage of the cumulative uric acid risk alleles. These results could partly explain the increased risk of developing gout among some Asian ancestral subgroups compared to EUR.

Acute Oral Toxicity Assessment and Anti-hyperuricemic Activity of Alocasia longiloba Extracts on Sprague-Dawley Rats

Hyperuricemia is defined as a metabolic abnormality that occurs when serum uric acid (UA) level is abnormally high in the body. We previously reported that A. longiloba possesses various important phytochemicals and in vitro xanthine oxidase activity. Despite A. longiloba ethnomedicinal benefits, its toxicity and anti-hyperuricemic effects have not been reported. The present study was carried out to ensure the safety and investigate the anti-hyperuricemic effects of A. longiloba fruit and petiole ethanolic extracts on rats. In the acute toxicity study, extracts were orally administered at a dose of 2000 mg/kg bodyweight and closely monitored for 2-week for any toxicity effects. The rats were then sacrificed and samples were collected and analyzed for hematological, biochemical, and histopathological parameters. The anti-hyperuricemic effect of A. longiloba fruit or petiole extract was investigated through determination of UA levels on potassium oxonate (PO)-induced hyperuricemic rats. Extracts or standard drug treatments were orally administrated 1-h after PO administration for 14-day. Animals were euthanized and samples were collected for further experiments. The toxicity results show, no significant changes were observed in behavioral, bodyweight changes in experimental groups compared to the control. Moreover, there were no significant changes in hematological, biochemical, and histological parameters between extracts treated and control group. In the anti-hyperuricemia study, the fruit and petiole extracts treatments significantly reduced the level of UA in serum compared to the hyperuricemic model group. This study demonstrated that the extracts of A. longiloba have anti-hyperuricemic activity and was found to be non-toxic to rats in acute toxicity test.

Facile synthesis of flower-like CePO4 with a hierarchical structure for the simultaneous electrochemical detection of dopamine, uric acid and acetaminophen

A flower-like CePO4 with a hierarchical structure was hydrothermally prepared for electrochemical sensing of dopamine, uric acid and acetaminophen.

Cut-Off Value of Serum Uric Acid for Development of Gout Disease in Patients with Multiple Co-Morbidities

Objective:

This study aimed to determine the association between hyperuricemia, comorbid diseases and risk of developing gout disease in a Turkish population in a long follow-up period.

Methods:

A total of 2000 Turkish adults were cross-sectionally analysed for serum urate levels in 2009 at the Pamukkale University Faculty of Medicine. All patients on regular follow-up at our tertiary health center (n=1322) were included in this study. Demographic features (age and gender), comorbid clinical conditions, and medication use were noted. The risk of developing gout and the determinant factors were investigated. Multivariate logistic regression analysis was performed to analyse causative effects of factors while receiver operating characteristic (ROC) curve analysis was used to identify optimal cut-off values of uric acid level for predicting the development of gout.

Results:

Among 1322 patients, the mean age was 56.9 (SD:14.68) years. 57.3% (n=758) of the patients were female. The most common co-morbid disease was chronic kidney disease (581, 43%), followed by hypertension (522, 39.4%). Gout developed in 25 patients (1.8%). Gout development risk and presence of all the above comorbidities were significantly higher in patients with serum urate ≥7mg/dl compared with <7mg/dl. Male gender and not using urate lowering drugs were the main risk factors for developing gout disease. ROC analysis of serum uric acid levels identified a cut-off value of >7 (AUC: 0.776, sensitivity 86.96%, specificity 66.74%).

Conclusion:

There is still a dilemma concerning the culprit effects of both comorbidities and hyperuricemia on the risk of developing gout disease.

Genetic Correlation Analysis and Transcriptome-wide Association Study Suggest the Overlapped Genetic Mechanism between Gout and Attention-deficit Hyperactivity Disorder

OBJECTIVES

Gout is a common inflammatory arthritis, which is caused by hyperuricemia. Limited efforts have been paid to systematically explore the relationships between gout and common psychiatric disorders.

METHODS

Genome-wide association study summary data of gout were obtained from the GeneATLAS, which contained 452,264 participants including 3,528 gout cases. Linkage disequilibrium score regression (LDSC) was first conducted to evaluate the genetic relationships between gout and 5 common psychiatric disorders. Transcriptome-wide association studies (TWAS) was then conducted to explore the potential biological mechanism underlying the observed genetic correlation between gout and attention-deficit hyperactivity disorder (ADHD). The Database for Annotation, Visualization and Integrated Discovery online functional annotation system was applied for pathway enrichment analysis and gene ontology enrichment analysis.

RESULTS

LDSC analysis observed significant genetic correlation between gout and ADHD (genetic correlation coefficients = 0.29, standard error = 0.09 and P value = 0.0015). Further TWAS of gout identified 105 genes with P value < 0.05 in muscle skeleton and 228 genes with P value < 0.05 in blood. TWAS of ADHD also detected 300 genes with P value < 0.05 in blood. Further comparing the TWAS results identified 9 common candidate genes shared by gout and ADHD, such as CD300C (P_gout = 0.0040; P_ADHD = 0.0226), KDM6B (P_gout = 0.0074; P_ADHD = 0.0460), and BST1 (P_gout = 0.0349; P_ADHD = 0.03560).

CONCLUSION

We observed genetic correlation between gout and ADHD and identified multiple candidate genes for gout and ADHD.

Towards the Use of Adsorption Methods for the Removal of Purines from Beer

Beer corresponds to a fermented alcoholic beverage composed of several components, including purine compounds. These molecules, when ingested by humans, can be catabolized into uric acid, contributing to uric acid’s level increase in serum, which may lead to hyperuricemia and gout. To assure a proper management of this disease, physicians recommend restrictive dietary measures, particularly by avoiding the consumption of beer. Therefore, it is of relevance to develop efficient methods to remove purine compounds from alcoholic beverages such as beer. In this review, we provide an introduction on fermented alcoholic beverages, with emphasis on beer, as well as its purine compounds and their role in uric acid metabolism in the human body in relation to hyperuricemia and gout development. The several reported enzymatic, biological and adsorption methods envisaging purine compounds’ removal are then reviewed. Some enzymatic and biological methods present drawbacks, which can be overcome by adsorption methods. Within adsorption methods, adsorbent materials, such as activated carbon or charcoal, have been reported and applied to beer or wort samples, showing an excellent capacity for adsorbing and removing purine compounds. Although the main topic of this review is on the removal of purine compounds from beer, other studies involving other matrices rather than beer or wort that are rich in purines are included, since they provide relevant clues on designing efficient removal processes. By ensuring the selective removal of purine compounds from this beverage, beer can be taken by hyperuricemic and gouty patients, avoiding restrictive dietary measures, while decreasing the related healthcare economic burden.

Effects of genetic and nongenetic factors on hyperuricemia in Chinese patients with coronary artery disease

Aim: The relationship between hyperuricemia and polymorphisms of transporter genes in coronary artery disease (CAD) patients in China remains unclear. Materials & methods: A total of 258 hyperuricemia patients with CAD and 242 control patients with CAD were recruited in this case-control study. Twenty-four SNPs in genes of ABCG2, PDZK1, URAT1, OAT4, GLUT9, ABCC4, NPT1 and NPT4 were genotyped using direct sequencing in all subjects. Results: The mutation of ABCG2 rs2231142 locus increases the risk of hyperuricemia, and there is a gene dose effect in the influence of mutant heterozygotes and homozygotes. rs3825017 in URAT1 and rs62293298 in GLUT9 were also confirmed to be associated with hyperuricemia. Conclusion: Age, weight, creatinine clearance rate, diuretics and SNPs on ABCG2, URAT1 and GLUT9 were all risk factors of hyperuricemia.

The impact of an URAT1 polymorphism on the losartan treatment of hypertension and hyperuricemia

BACKGROUND

This study was designed to evaluate the impact of polymorphisms in the urate transporter 1 (URAT1) gene on the uricosuric action of losartan therapy in hypertensive patients suffering from hyperuricemia.

METHODS

A MassARRAY approach was used to detect single nucleotide polymorphism (SNP) loci in the URAT1 and CYP2C9 genes (16 and 2 loci, respectively) in 111 patients with hypertension and hyperuricemia taking losartan and in 121 healthy controls. In addition, we compared serum urate (SUA) levels and other key clinical biochemistry indices between these two patient groups.

RESULTS

We detected significant differences between the two patient groups with respect to age, SUA, urea, creatine, triglycerides, high-density lipoprotein, low-density lipoprotein, and fasting plasma glucose (all p < 0.05). In addition, we found that hypertensive patients with hyperuricemia were more likely to exhibit the rs3825016(C/T) (36.9% vs 21.5%, p = 0.03), and we determined that a 2-week treatment course with losartan was associated with significant decreases in SUA values (p < 0.001).

CONCLUSION

Our findings indicate that the URAT1 rs3825016 polymorphism may influence the uricosuric action of losartan.

A review on the fruit components affecting uric acid level and their underlying mechanisms

Uric acid (UA) is produced in the liver and excreted through the kidneys and intestines. If UA is overproduced or its excretion reduces, the concentration of UA increases, leading to hyperuricemia and gout. The high concentration of UA is also related to cardiovascular disease, hypertension, obesity, and other diseases. Fruits are healthy foods. However, fruits contain fructose and small amounts of purine, and the product of their metabolism is UA. Therefore, theoretically, eating fruits will increase the concentration of serum UA. Fruit components are numerous, and their effects on serum UA are complex. According to the current research, fructose, purine, polyphenols, vitamin C, dietary fiber, and minerals present in fruits influence serum UA concentrations. In addition to the UA synthesized by fructose and purine metabolism, the mechanisms by which other components affect the concentration of serum UA can be summarized as follows: (a) inhibiting xanthine oxidase; (b) reducing reabsorption of UA; and (c) improving the excretion of UA. In this review, we comprehensively discussed the fruit components that affect serum UA concentrations, and explained their mechanisms for the first time, which references for patients with hyperuricemia to take fruits. PRACTICAL APPLICATIONS: With the rising prevalence, hyperuricemia and gout have become public health problems that endanger our daily life. The key to the treatment of hyperuricemia is to control the level of serum UA within the normal range. Fruits are healthy foods. However, fruit components are numerous, and their effects on serum UA are complex. According to the current research, fructose, purine, polyphenols, vitamin C, dietary fiber, and minerals present in fruits influence serum UA concentrations. In this review, we comprehensively discussed the fruit components that affect serum UA concentrations. We also explained their mechanisms, which references for patients with hyperuricemia to take fruits.

Function of Uric Acid Transporters and Their Inhibitors in Hyperuricaemia

Disorders of uric acid metabolism may be associated with pathological processes in many diseases, including diabetes mellitus, cardiovascular disease, and kidney disease. These diseases can further promote uric acid accumulation in the body, leading to a vicious cycle. Preliminary studies have proven many mechanisms such as oxidative stress, lipid metabolism disorders, and rennin angiotensin axis involving in the progression of hyperuricaemia-related diseases. However, there is still lack of effective clinical treatment for hyperuricaemia. According to previous research results, NPT1, NPT4, OAT1, OAT2, OAT3, OAT4, URAT1, GLUT9, ABCG2, PDZK1, these urate transports are closely related to serum uric acid level. Targeting at urate transporters and urate-lowering drugs can enhance our understanding of hyperuricaemia and hyperuricaemia-related diseases. This review may put forward essential references or cross references to be contributed to further elucidate traditional and novel urate-lowering drugs benefits as well as provides theoretical support for the scientific research on hyperuricemia and related diseases.

Genetics of hyperuricemia and gout: Insights from recent genome-wide association studies and Mendelian randomization studies

Gout is the most common form of inflammatory arthritis in adults. Elevation serum uric acid (SUA) concentration is known to be the key to gout pathogenesis. Since the first genome-wide association study (GWAS) for SUA was performed in 2007, the number of gene loci known to be associated with hyperuricemia and gout has grown rapidly. GWASs and Mendelian randomization studies have also reported numerous novel results regarding the genetics of hyperuricemia and gout since 2018. We concisely review recent advances in scholarship on the effects of genetics on hyperuricemia and gout risk. We also review data from genetic association studies in Taiwan and perform GWASs of SUA levels among Taiwan Biobank participants.

Uric acid and cardiometabolic diseases

Hyperuricemia, which has been considered as a cause of gout and nephrolithiasis has recently been suggested to be associated with hypertension, coronary heart disease, heart failure, atrial fibrillation, insulin resistance, and nonalcoholic fatty liver disease. Several clinical and experimental studies have supported uric acid (UA) as an independent risk factor for predicting disease development along with the traditional risk factors. The mechanism by which UA causes cardiometabolic disease has not been fully elucidated to date; however, it has been explained by several hypotheses such as oxidative stress, reduced nitric oxide bioavailability, inflammation, endothelial dysfunction, and so on. Although evidence of the preventive and therapeutic effects of UA lowering therapy on cardiometabolic diseases is still insufficient, it is expected to be considered as a new treatment strategy for such diseases through additional, carefully designed, large-scale clinical studies.

Polygenic analysis of the effect of common and low-frequency genetic variants on serum uric acid levels in Korean individuals

Increased serum uric acid (SUA) levels cause gout and are associated with multiple diseases, including chronic kidney disease. Previous genome-wide association studies (GWAS) have identified more than 180 loci that contribute to SUA levels. Here, we investigated genetic determinants of SUA level in the Korean population. We conducted a GWAS for SUA in 6,881 Korean individuals, calculated polygenic risk scores (PRSs) for common variants, and validated the association of low-frequency variants and PRS with SUA levels in 3,194 individuals. We identified two low-frequency and six common independent variants associated with SUA. Despite the overall similar effect sizes of variants in Korean and European populations, the proportion of variance for SUA levels explained by the variants was greater in the Korean population. A rare, nonsense variant SLC22A12 p.W258X showed the most significant association with reduced SUA levels, and PRSs of common variants associated with SUA levels were significant in multiple Korean cohorts. Interestingly, an East Asian-specific missense variant (rs671) in ALDH2 displayed a significant association on chromosome 12 with the SUA level. Further genetic epidemiological studies on SUA are needed in ethnically diverse cohorts to investigate rare or low-frequency variants and determine the influence of genetic and environmental factors on SUA.

Supramolecular Electrochemical Sensor for Dopamine Detection Based on Self-Assembled Mixed Surfactants on Gold Nanoparticles Deposited Graphene Oxide

A new supramolecular electrochemical sensor for highly sensitive detection of dopamine (DA) was fabricated based on supramolecular assemblies of mixed two surfactants, tetra-butylammonium bromide (TBABr) and sodium dodecyl sulphate (SDS), on the electrodeposition of gold nanoparticles on graphene oxide modified on glassy carbon electrode (AuNPs/GO/GCE). Self-assembled mixed surfactants (TBABr/SDS) were added into the solution to increase the sensitivity for the detection of DA. All electrodes were characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The supramolecular electrochemical sensor (TBABr/SDS⋅⋅⋅AuNPs/GO/GCE) showed excellent electrocatalytic activity toward the oxidation of DA. Under the optimum conditions, the concentration of DA was obtained in the range from 0.02 µM to 1.00 µM, with a detection limit of 0.01 µM (3s/b). The results displayed that TBABr/SDS⋅⋅⋅AuNPs/GO/GCE exhibited excellent performance, good sensitivity, and reproducibility. In addition, the proposed supramolecular electrochemical sensor was successfully applied to determine DA in human serum samples with satisfactory recoveries (97.26% to 104.21%).

Genetic association of polymorphism rs2230054 in CXCR2 gene with gout in Chinese Han male population

Neutrophils are crucial in the process of gout flare and remission. The signal transduction pathway of chemokine plays a vital role in the chemotaxis and activation of neutrophils. CXCR2 gene knocked out can avoid the acute neutrophilic inflammation stimulated by monosodium urate (MSU) crystals in mice. To investigate the relationship among CXCR1 rs2234671, CXCR2 rs1126579, and rs2230054 polymorphisms with gout arthritis flare in the Chinese Han male population, a case-control study was carried out in 412 gout patients and 508 gout-free individuals. TaqMan probes fluorescence real-time polymerase chain reaction (PCR) was used to genotype CXCR1 rs2234671, CXCR2 rs1126579, and rs2230054 SNPs. There was a clear link between CXCR2 rs2230054 T included genotypic and T allelic frequencies and gout cases (c² = 9.286, p = 0.002 by genotype, c² = 8.639, p = 0.003 by allele), while no significant differences were observed between the gouty arthritis group and the control group in CXCR1 rs2234671 and CXCR2 rs1126579 genotypic and allelic frequencies. Multivariate logistic regression analysis showed that the T genotype included in rs2230054 can decrease the risk of gouty arthritis (adjusted OR = 0.47; 95% CI: 0.31-0.74) compared with the CC genotype. Our study might suggest that rs2230054 in CXCR2 is associated with susceptibility to gout in Chinese males.

Unraveling the genetic causes in large pedigrees with gout by whole‑exome sequencing

Gout is a common type of inflammatory arthritis that is clinically and genetically heterogeneous. The genetic aetiology remains unclear, and mainly relies on previous genome-wide association studies focused on sporadic cases. The present study aimed to identify the genetic basis of gout in three families using whole-exome sequencing (WES). WES was performed in the probands, and family members were involved in the co-segregation analysis. In total, three deleterious rare or novel missense mutations were identified in ATP-binding cassette super-family G member 2 (ABCG2), protein kinase CGMP-dependent 2 (PRKG2) and adrenoceptor β3 (ADRB3) genes in three different families. In addition, certain gout-associated candidate genes were revealed to be shared among the co-expression and protein-protein interaction (PPI) networks of ABCG2, PRKG2 and ADRB3. Furthermore, the disease ontology analysis of the genes present in the co-expression network exhibited significant (P<0.05) enrichment in hyperuricemia, gout, cardiovascular system disease and metabolic disease. In addition, genes involved in the PPI network were significantly enriched in the purine nucleoside monophosphate biosynthetic process, urate transport and biological processes associated with glycose metabolism. Collectively, to the best of our knowledge, the present study was the first to use WES to identify three candidate rare or novel deleterious mutations in three families with gout. The present results provided novel insights that may improve the current understanding of the molecular genetic basis underlying gout. Importantly, the present results may facilitate the improvement of clinical diagnosis and the development of novel personalized therapies.

Whole-Exome Sequencing Reveals a Rare Missense Variant in SLC16A9 in a Pedigree with Early-Onset Gout

Gout is a common inflammatory arthritis triggered by monosodium urate deposition after longstanding hyperuricemia. In the general community, the disease is largely polygenic in genetic architecture, with many polymorphisms having been identified in gout or urate-associated traits. In a small proportion of cases, rare high penetrant mutations associated with monogenic segregation of the disease in families have been demonstrated to be disease causative. In this study, we recruited a two-generation pedigree with early-onset gout. To elucidate the genetic predisposition, whole-exome sequencing (WES) was performed. After comprehensive variant analyses and cosegregation testing, we identified a missense variant (c.277C>A, p.L93M) in SLC16A9, an extremely rare variant in genetic databases. Moreover, in silico assessments showed strong pathogenicity. This variant cosegregated with the disease phenotype perfectly in the family and is located in a highly conserved functional domain. A few studies supported our results of the association between SLC16A9 and gout and serum urate levels. In conclusion, we provide the first evidence for the association of rare missense in SLC16A9 with early-onset gout. These findings not only expand our current understanding of gout but also may have further implications for the treatment and prevention of gout.

The causal role of elevated uric acid and waist circumference on the risk of metabolic syndrome components

BACKGROUND/OBJECTIVES

Hyperuricemia has been found to cluster with multiple components of metabolic syndrome (MetS). It is unclear whether hyperuricemia is a downstream result of MetS or may play an upstream role in MetS development. Using the Mendelian randomization (MR) method, we examined the causal relationship between elevated uric acid and the various components of MetS with waist circumference as a positive control.

SUBJECTS/METHODS

Data from 10k participants of Taiwan Biobank was used to carry out MR analysis with uric acid risk score (wGRS) and waist circumference wGRS as instrumental variables and components of MetS as the outcomes.

RESULTS

We found that genetically increased serum uric acid corresponds to a significant increment of triglyceride (β = 0.065, p < 0.0001), systolic blood pressure (β = 1.047, p = 0.0005), diastolic blood pressure (β = 0.857, p < 0.0001), and mean arterial pressure (β = 0.920, p < 0.0001), but a significant reduction of high-density lipoprotein cholesterol (β = -0.020, p = 0.0014). Uric acid wGRS was not associated with fasting serum glucose, HbA1C, waist circumference, or BMI. On the other hand, waist circumference was causally associated with all the components of MetS including uric acid.

CONCLUSIONS

Our MR investigation shows that uric acid increment may augment the risk of MetS through increasing blood pressure and triglyceride levels and lowering HDL-C value but not through accumulating fat or hyperglycemia. High waist circumference may be a causal agent for all the components of MetS including hyperuricemia.

Novel urate transporter 1 (URAT1) inhibitors: a review of recent patent literature (2016-2019)

Introduction: Human urate transporter 1 (URAT1), which is an influx transporter protein, is located at the apical surface of renal tubular cells and presumed to be the major transporter responsible for the reabsorption of urate from blood. About 90% of patients develop hyperuricemia due to insufficient urate excretion; thus, it is important to develop URAT1 inhibitors that could enhance renal urate excretion by blocking the reabsorption of urate anion. Areas covered: In this review, the authors addressed the patent applications (2016-2019) about URAT1 inhibitors and some medicinal chemistry strategies employed in these patents. Expert opinion: Substituent decorating, bioisosterism, and scaffold hopping are three common medicinal chemistry strategies used in the discovery of URAT1 inhibitors. Meanwhile, the introduction of sulfonyl group into small molecules has become one of the important strategies for structural optimization of URAT1 inhibitors. Furthermore, developing drug candidates targeting both URAT1 and xanthine oxidase (XOD) has attracted lots of interest and attention.

Contribution of SLC22A12 on hypouricemia and its clinical significance for screening purposes

Differentiating between inherited renal hypouricemia and transient hypouricemic status is challenging. Here, we aimed to describe the genetic background of hypouricemia patients using whole-exome sequencing (WES) and assess the feasibility for genetic diagnosis using two founder variants in primary screening. We selected all cases (N = 31) with extreme hypouricemia (<1.3 mg/dl) from a Korean urban cohort of 179,381 subjects without underlying conditions. WES and corresponding downstream analyses were performed for the discovery of rare causal variants for hypouricemia. Two known recessive variants within SLC22A12 (p.Trp258*, pArg90His) were identified in 24 out of 31 subjects (77.4%). In an independent cohort, we identified 50 individuals with hypouricemia and genotyped the p.Trp258* and p.Arg90His variants; 47 of the 50 (94%) hypouricemia cases were explained by only two mutations. Four novel coding variants in SLC22A12, p.Asn136Lys, p.Thr225Lys, p.Arg284Gln, and p.Glu429Lys, were additionally identified. In silico studies predict these as pathogenic variants. This is the first study to show the value of genetic diagnostic screening for hypouricemia in the clinical setting. Screening of just two ethnic-specific variants (p.Trp258* and p.Arg90His) identified 87.7% (71/81) of Korean patients with monogenic hypouricemia. Early genetic identification of constitutive hypouricemia may prevent acute kidney injury by avoidance of dehydration and excessive exercise.

Causal effect of alcohol consumption on hyperuricemia using a Mendelian randomization design

AIM

We used a Mendelian randomization analysis to assess the causal effect of alcohol consumption on hyperuricemia in Koreans.

METHODS

The Korean Cancer Prevention Study-II (KCPS-II) Biobank cohort consisted of 156 701 healthy Korean aged 20 years or older. Clinical data including serum uric acid, alcohol consumption, and other related confounding variables were collected at baseline. The 27 single nucleotide polymorphisms (SNP) including rs671 in aldehyde dehydrogenase 2 (ALDH2) were obtained from a genome-wide association study of alcohol consumption in the KCPS-II Biobank among 11 678 men and women in 2017. Both unweighted and weighted genetic risk score (wGRS) were calculated using 10 SNPs selected based on linkage disequilibrium.

RESULTS

As strong instrumental variables, both rs671 and wGRS were associated with an increased amount of alcohol drinking in men and women. Alcohol consumption was also positively associated with hyperuricemia risk in men (P < .001) and women (P = .014). Both rs671 major G allele and wGRS were not associated with hyperuricemia. In Mendelian randomization analysis, the causal relationship between any alcohol consumption and hyperuricemia was found only in men, albeit non-significant after correction for multiple testing. The associations did not change after excluding heavy drinkers or the elderly.

CONCLUSIONS

These results provide evidence that alcohol consumption is causally associated with risk of hyperuricemia in Korean men and support its role as a risk determinant.

Risk Factors of Gout in MDR-TB Patients in Eritrea: A Case-Control Study

Though the incidence of gout in general population is less than 5% (globally), a study conducted in Eritrea among patients with multidrug resistant tuberculosis (MDR-TB) revealed a higher incidence (25%). Other similar studies conducted elsewhere, however, did not report gout as an adverse effect. It is unknown why a higher incidence of gout is being reported in Eritrea compared to similar studies from other countries. The objective of this study is therefore to explore risk factors for the increased risk of incident gout among MDR-TB patients in Eritrea. A case-control study was conducted in Merhano MDR-TB National Referral Hospital in Eritrea. All MDR-TB patients diagnosed with gout between June 2011 and June 2018 were considered as cases. Controls matched by age, sex, and cumulative drug exposure time were selected from the same study population (1:1 ratio). A total of 84 MDR-TB patients, 42 cases and 42 controls, were included in this study. No patient from the control group has comorbidities, while six patients from the case group have diabetes (χ2 = 6.46, df=1, p=0.026). Patients having tachycardia (OR=3.26, 95% CI=1.28, 8.27), alopecia (OR=3.11, 95% CI=1.00, 9.67), and gastrointestinal upset (OR=3.17, 95% CI=1.26, 7.96) as adverse effects and being on prolonged use of propranolol (OR=3.26, 95% CI=1.28, 8.27) were found to be more likely to develop incident gout compared to their controls. In conclusion, MDR-TB patients with diabetes mellitus, tachycardia, alopecia, and gastrointestinal upset and on prolonged use of propranolol tablet had increased risk of incident gout.

The prevalence of hyperuricemia and its correlates in Ganzi Tibetan Autonomous Prefecture, Sichuan Province, China

Background

Hyperuricemia is a common and serious public health problem. There has been no broad epidemiological survey of hyperuricemia in China, especially in Tibetan area. This study was therefore investigated the prevalence of hyperuricemia and its correlated factors among people aged 18–85 years in Ganzi Tibetan Autonomous Prefecture, Sichuan Province, China.

Methods

We carried out a cross-sectional study among 3093 participants in Ganzi Tibetan Autonomous Prefecture using questionnaires in face-to-face interviews, anthropometric measurements and biochemical tests. We included 1416 subjects with complete data including serum uric acid and medical history to analyze the prevalence of hyperuricemia and correlated factors. Hyperuricemia was defined as a fasting serum uric acid level higher than 420 μmol/L in men and 360 μmol/L in women.

Results

The overall crude prevalence of hyperuricemia was 37.2%, and was greater in men than women (41% vs 34.4%, P = 0.011). The age-adjusted prevalence was 33.0%. Characteristics linked to hyperuricemia were farmers-herdsmen (OR: 1.749, 95% CI: 1.022–2.992), low to moderate education level (low OR:1.57, 95% CI: 1.102–2.237; moderate OR: 1.86, 95% CI: 1.167–2.963), current drinking (OR: 1.795, 95% CI: 1.193–2.702), hypertension (OR: 1.48, 95% CI: 1.091–2.006), higher body mass index (1 unit increase) (OR: 1.116, 95% CI: 1.077–1.156) and higher serum creatinine (1 unit increase) (OR: 1.046, 95% CI: 1.034–1.059). Serum uric acid was positively related to triglycerides and total cholesterol and negatively related to high density lipoprotein cholesterol in all subjects. Hyperuricemia was a risk factor for high triglyceride ((OR: 2.13, 95% CI: 1.156–3.9266) and high total cholesterol (OR: 2.313, 95% CI: 1.364–3.923) in men and for high low-density lipoprotein cholesterol (OR: 2.696, 95% CI: 1.386–5.245) in women.

Conclusion

There is a high prevalence of hyperuricemia in Ganzi Tibetan Autonomous Prefecture. The government needs to prevent and manage hyperuricemia in this area.

Ruthenium and manganese metalloporphyrins modified screen-printed electrodes for bio-relevant electroactive targets

Ruthenium(II) 5-(4[Formula: see text]-sulfanylmethylphenyl)-10,15,20-triphenylporphyrin (Ru-TPP-SH) and manganese(III) 5-(4[Formula: see text]-sulfanylmethylphenyl)-10,15,20-triphenylporphyrin (Mn-TPP-SH) were synthesized, spectroscopically characterized and drop casted to modify screen-printed electrodes (SPEs). The modified SPEs were then tested against the redox target [Fe(CN)6][Formula: see text] in comparison with the bare SPE and SPE modified with the free porphyrin. The best performing one, [Formula: see text]. Mn-TPP-SH was used for the electrochemical detection of 1,4–benzoquinone, serotonin, caffeic and ascorbic acids, the latter also in association with uric acid, showing good electrocatalytic properties. The tunability of the metal-TPP-SH through the choice of the coordinating metal, the drop casting conditions and possible further functionalization make this type of porphyrin a good candidate for further developments of porphyrin-modified SPEs.

The association between thyroid disorders and incident gout: population-based case-control study

Context

Thyroid hormones influence kidney function and thereby might alter serum urate levels, a major risk factor for gouty arthritis.

Objective

To assess the risk of developing incident gout in association with hypothyroidism or hyperthyroidism.

Design

Retrospective population-based case–control analysis.

Setting

UK-based Clinical Practice Research Datalink, a primary care research database.

Patients

We identified adult patients with a diagnosis of incident gout between 1990 and 2014. We matched one control to each gout case in terms of age, sex, general practice, calendar time, and years of active history in the database.

Main outcome measure

We used conditional logistic regression to calculate odds ratios (ORs) with 95% confidence intervals (CIs) for developing gout in association with hypo- or hyperthyroidism and adjusted for potential confounders.

Results

The study population encompassed 68,159 incident gout cases, of whom 78.8% were male, and the same number of matched controls. There was no increased risk of gout in patients with hypothyroidism: adjusted OR of gout of 1.12 (95% CI 1.05–1.20) compared with no hypothyroidism. Current short-term treatment of thyroid hormone replacement therapy was associated with an adjusted OR of gout of 1.54 (95% CI 1.24–1.92), compared with no treatment. Neither hyperthyroidism nor current treatment with thyroid suppression therapy was associated with gout (adjusted OR, 1.08 [95% CI 0.95–1.22] and 0.82 [95% CI 0.57–1.17], respectively).

Conclusion

This large observational study does not provide evidence that hypothyroidism or hyperthyroidism, irrespective of treatment, is associated with a clinically relevant increased risk of developing incident gout. There may be an exception among patients with newly diagnosed and treated hypothyroidism.

The Role of miRNAs in Common Inflammatory Arthropathies: Osteoarthritis and Gouty Arthritis

MicroRNAs (miRNAs) are small, non-coding RNA species that are highly evolutionarily conserved, from higher invertebrates to man. Up to 1000 miRNAs have been identified in human cells thus far, where they are key regulators of the expression of numerous targets at the post-transcriptional level. They are implicated in various processes, including cell differentiation, metabolism, and inflammation. An expanding list of miRNAs is known to be involved in the pathogenesis of common, non-autoimmune inflammatory diseases. Interestingly, osteoarthritis (OA) is now being conceptualized as a metabolic disease, as there is a correlation among hyperuricemia and metabolic syndrome (MetS). Experimental evidence suggests that metabolic deregulation is a commonality between these different pathological entities, and that miRNAs are key players in the modulation of metabolic routes. In light of these findings, this review discusses the role of miRNAs in OA and gouty arthritis, as well as the possible therapeutic targetability of miRNAs in these diseases.

Natural Products Improving Hyperuricemia with Hepatorenal Dual Effects

This review aims to put forth an overview of natural products reducing uric acid level with hepatorenal dual effects. The prevalence of hyperuricemia increased rapidly in recent years and has closely interdependent relationship with other metabolic disorders. Current therapeutically used drugs including a few uricostatic and uricosuric chemical drugs are proved efficient to control serum uric acid level. However, their side effects as well as contraindication in some cases with liver, kidney injury, or other conditions frequently limit their clinic application. More attention thus has been paid to natural products as an alternative means in treating hyperuricemia. Many natural products have been proved efficient in downregulating uric acid level, among which some can improve hyperuricemia with hepatorenal dual effects. It means these natural products can regulate both the production and the excretion of uric acid by targeting the key metabolic enzymes mainly in liver or uric acid transporters in kidneys. Thus, these natural products could have stronger efficacy and broader application, which may be developed for the treatment of hyperuricemia in clinic.

Comparison of the effect of high fruit and soybean products diet and standard diet interventions on serum uric acid in asymptomatic hyperuricemia adults: an open randomized controlled trial

The aim of this study was to compare the effect of high fruit and soybean products diet and standard diet interventions on serum uric acid (SUA) in asymptomatic hyperuricemia adults. A total of 187 Chinese adults (20-59 years old) with asymptomatic hyperuricemia participated in this randomized trial and were assigned to receive the standard diet recommended by guideline (group 1) and high fruit and soybean products diet (group 2) for 3 months. The outcome of SUA was assessed before and at the end of the intervention period. After 3 months, the SUA in group 1 and group 2 was significant reduced, whereas the SUA was not significantly changed in-between groups. These data suggest that over a 3-month period, although the high fruit and soybean products diet and standard diet interventions yield no different effects on SUA, the high fruit and soybean products dietary intervention could be an effective alternative to a standard diet for achieving clinically important reductions in SUA for asymptomatic hyperuricemia patients.

Discovery of URAT1 SNPs and association between serum uric acid levels and URAT1

OBJECTIVES

Human urate transporter 1 (URAT1) is a member of the organic anion transporter family (SLC22A12) that primarily regulates the renal tubular reabsorption of uric acid. This case-control study was designed to analyse whether hURAT1 might also be a candidate gene for hyperuricaemia or hypouricaemia.

SETTING

We recruited 68 healthy volunteers and divided them into two groups: a normal uric acid group and a hyperuricaemia group. We analysed the sequence of the URAT1 gene and found five significant single nucleotide polymorphisms (SNPs). We then selected 900 male subjects from the 262,200 enrolled in the Korean Cancer Prevention Study-II (KCPS-II) cohort for further genetic analysis.

PARTICIPANTS

DNA samples from 36 individuals with normal uric acid (<4.5 mg/dL) and 32 individuals with hyperuricaemia (>8.5 mg/dL) were sequenced. Five significant SNPs (rs7929627, rs75786299, rs3825017, rs11602903 and rs121907892) were identified. We then chose 900 subjects from the KCPS-II cohort consisting of 450 subjects with normal uric acid (UA <4.1 mg/dL) and 450 subjects with hyperuricaemia (UA >8.7 mg/dL). The groups were matched by age, body mass index, metabolic syndrome and use of anti-hypertensive medication.

PRIMARY OUTCOME MEASURES

We compared the OR of the incidence of hyperuricaemia by URAT1 genotype.

RESULTS

The strongest association with hyperuricaemia was observed for rs75786299 (IVS3+11A/G) with an OR of 32.05. rs7929627 (IVS7-103A/G) and rs3825017 (N82N) showed an association with hyperuricaemia with ORs of 2.56 and 2.29, respectively. rs11602903 (788A/T) and rs121907892 (W258X) were negatively correlated with hyperuricaemia with ORs of 0.350 and 0.447, respectively. Individuals carrying the GATAG haplotype (n=32)-a relatively common variant consisting of rs7929627, rs75786299 and rs3825017-showed the highest risk for hyperuricaemia with an OR of 92.23 (p=9.55×10(-3)).

CONCLUSIONS

These results indicate that five newly described SNPs in the hURAT1 gene are significantly associated with uric acid level (4-2008-0318 and 4-2011-0277).

Uric Acid-Induced Adipocyte Dysfunction Is Attenuated by HO-1 Upregulation: Potential Role of Antioxidant Therapy to Target Obesity

Increased uric acid levels have been implicated in the pathogenesis of metabolic syndrome. To examine the mechanisms by which this occurs, we hypothesized that an increase in heme oxygenase 1, a potent antioxidant gene, will decrease uric acid levels and adipocyte dysfunction via suppression of ROS and xanthine oxidase (XO) levels. We examined the effect of uric acid on adipogenesis in human mesenchymal stem cells (MSCs) in the presence and absence of cobalt protoporphyrin (CoPP), an HO-1 inducer, and tin mesoporphyrin (SnMP), an HO activity inhibitor. Uric acid increased adipogenesis by increasing NADPH oxidase expression and elevation in the adipogenesis markers C/EBPα, PPARγ, and Mest, while decreasing small lipid droplets and Wnt10b levels. We treated MSCs with fructose, a fuel source that increases uric acid levels. Our results showed that fructose increased XO expression as compared to the control and concomitant treatment with CoPP significantly decreased XO expression and uric acid levels. These beneficial effects of CoPP were reversed by SnMP, supporting a role for HO activity in mediating these effects. These findings demonstrate that increased levels of HO-1 appear crucial in modulating the phenotype of adipocytes exposed to uric acid and in downregulating XO and NADPH oxidase levels.

Genome-wide association analysis identifies three new risk loci for gout arthritis in Han Chinese

Gout is one of the most common types of inflammatory arthritis, caused by the deposition of monosodium urate crystals in and around the joints. Previous genome-wide association studies (GWASs) have identified many genetic loci associated with raised serum urate concentrations. However, hyperuricemia alone is not sufficient for the development of gout arthritis. Here we conduct a multistage GWAS in Han Chinese using 4,275 male gout patients and 6,272 normal male controls (1,255 cases and 1,848 controls were genome-wide genotyped), with an additional 1,644 hyperuricemic controls. We discover three new risk loci, 17q23.2 (rs11653176, P=1.36 × 10⁻¹³, BCAS3), 9p24.2 (rs12236871, P=1.48 × 10⁻¹⁰, RFX3) and 11p15.5 (rs179785, P=1.28 × 10⁻⁸, KCNQ1), which contain inflammatory candidate genes. Our results suggest that these loci are most likely related to the progression from hyperuricemia to inflammatory gout, which will provide new insights into the pathogenesis of gout arthritis.

Raised serum urate levels are a risk factor for gout, a common form of inflammatory arthritis. Here Li et al. conduct a multistage genome-wide association study in a Han Chinese population and identify three novel loci likely associated with the progression from hyperuricemia to gout.

An update on the genetic architecture of hyperuricemia and gout

Genome-wide association studies that scan the genome for common genetic variants associated with phenotype have greatly advanced medical knowledge. Hyperuricemia is no exception, with 28 loci identified. However, genetic control of pathways determining gout in the presence of hyperuricemia is still poorly understood. Two important pathways determining hyperuricemia have been confirmed (renal and gut excretion of uric acid with glycolysis now firmly implicated). Major urate loci are SLC2A9 and ABCG2. Recent studies show that SLC2A9 is involved in renal and gut excretion of uric acid and is implicated in antioxidant defense. Although etiological variants at SLC2A9 are yet to be identified, it is clear that considerable genetic complexity exists at the SLC2A9 locus, with multiple statistically independent genetic variants and local epistatic interactions. The positions of implicated genetic variants within or near chromatin regions involved in transcriptional control suggest that this mechanism (rather than structural changes in SLC2A9) is important in regulating the activity of SLC2A9. ABCG2 is involved primarily in extra-renal uric acid under-excretion with the etiological variant influencing expression. At the other 26 loci, probable causal genes can be identified at three (PDZK1, SLC22A11, and INHBB) with strong candidates at a further 10 loci. Confirmation of the causal gene will require a combination of re-sequencing, trans-ancestral mapping, and correlation of genetic association data with expression data. As expected, the urate loci associate with gout, although inconsistent effect sizes for gout require investigation. Finally, there has been no genome-wide association study using clinically ascertained cases to investigate the causes of gout in the presence of hyperuricemia. In such a study, use of asymptomatic hyperurcemic controls would be expected to increase the ability to detect genetic associations with gout.