Jingru Zhou

Effects of multiple genetic loci on the pathogenesis from serum urate to gout

Gout is a common arthritis resulting from increased serum urate, and many loci have been identified that are associated with serum urate and gout. However, their influence on the progression from elevated serum urate levels to gout is unclear. This study aims to explore systematically the effects of genetic variants on the pathogenesis in approximately 5,000 Chinese individuals. Six genes (PDZK1, GCKR, TRIM46, HNF4G, SLC17A1, LRRC16A) were determined to be associated with serum urate (PFDR < 0.05) in the Chinese population for the first time. ABCG2 and a novel gene, SLC17A4, contributed to the development of gout from hyperuricemia (OR = 1.56, PFDR = 3.68E-09; OR = 1.27, PFDR = 0.013, respectively). Also, HNF4G is a novel gene associated with susceptibility to gout (OR = 1.28, PFDR = 1.08E-03). In addition, A1CF and TRIM46 were identified as associated with gout in the Chinese population for the first time (PFDR < 0.05). The present study systematically determined genetic effects on the progression from elevated serum urate to gout and suggests that urate-associated genes functioning as urate transporters may play a specific role in the pathogenesis of gout. Furthermore, two novel gout-associated genes (HNF4G and SLC17A4) were identified.

Common Variants in LRP2 and COMT Genes Affect the Susceptibility of Gout in a Chinese Population

Gout is a common inflammation disease resulting from an increase in serum uric acid. Nearly 70% of uric acid is excreted via the kidneys. To date, evidence for an association between genetic loci and gout is absent, equivocal or not replicated. Our study aims to test variants in two genes abundantly expressed in the kidney, LRP2 and COMT, for their association with uric acid and gout. In total, 1318 Chinese individuals were genotyped for rs2544390 in LRP2 and rs4680 in COMT. These LRP2 and COMT gene polymorphisms showed no significant effect on uric acid (P = 0.204 and 0.188, separately); however, rs2544390 in LRP2 did influence uric acid levels in individuals with BMI ≥ 25 (P = 0.009). In addition, the allele frequency distributions of the two loci showed a significant difference between gout patients and healthy controls. A missense variation in rs4680 (G > A) decreased the risk of gout (OR = 0.77, P = 0.015), whereas the T allele of rs2544390 was associated with gout pathogenesis risk (OR = 1.26, P = 0.020). The present study provides the first evidence for an association between COMT and gout. Rs2544390 in LRP2 only influenced uric acid levels in individuals with BMI ≥ 25, which might explain the discrepant results among previous studies. In addition, we are the first to identify the association between LRP2 and gout in a Chinese population and to confirm this association in Asians.

Copy number variants of ABCF1, IL17REL, and FCGR3A are associated with the risk of gout

Gout is usually characterized by recurrent flares of acute inflammatory arthritis and the crystallization of urate in tissues and joints (Dong et al., 2017). The formation of monosodium urate crystals (MSU) is due to the elevated uric acid levels in the blood (Yang et al., 2016). But only 10% of individuals with hyperuricemia develop gout, suggesting that certain people are at a higher risk of developing MSU crystals (Merriman and Dalbeth, 2011) or initiating of the acute inflammatory response than others. This phenomenon is likely explained by the complex pathogenic process of inflammation and innate immunity in the development of gout since theMSU crystal-mediated inflammatory pathways have been reported to associate with many immunological processes (Behrens et al., 2008). Theabove results suggest that inflammationand immunity-related factors can regulate the development of gout, particularly the progression from hyperuricemia to gout. Recent genome-wide association studies (GWAS) identified some single nucleotide polymorphisms (SNPs) that were associated with the risk of gout (Kottgen et al., 2013). However, the common SNPs only explained part of the heritability of gout, and copy number variants (CNVs), an important source of genetic diversity in humans, have been shown to play a critical role in the genetic susceptibility to multiple rheumatic diseases (Zhang et al., 2009). Therefore, CNVs might be a new source for the genetic variants associated with the pathogenesis of gout. However, CNV studies on gout have not been reported, making it necessary to explore the pathogenesis of gout through the copy number variants in the inflammationand immunity-related genes. In this study, we aimed to identify the gout-associated CNVs in a Chinese population using a three-step approach. The entire analysis strategy, from genome-wide CNV discovery to gout-associated CNV identification to CNV validation, was illustrated in Fig. S1. Using this strategy, we provided the first evidence that CNVs could influence the pathogenesis of gout, and identified three novel genes, ABCF1, IL17REL and FCGR3A, which are associated with the risk of gout. Based on a genome-wide analysis of CNVs, a total of 1,901 CNVs were identified in 22 patients with inflammationand immunity-related rheumatic disorders (inclunding gout, ankylosing spondylitis, systemic lupus erythematosus, and systemic sclerosis) compared to the controls by using Agilent SurePrint G3 Human 1 × 1 M comparative genomic hybridization (CGH) microarray. After they were filtered according to their frequency (>5% and ≤50%), genome location (in gene region), gene function (related with inflammation and immunity), reliability (at least five consecutive probes) and previous studies for these CNVs, 48 gene regions with CNVs were selected (Table S1). To identify candidate gout-associated CNVs, the above pre-selected CNVs were further tested in 46 gout patients and 47 healthy Chinese individuals using the NimbleGen CGH Arrays (12 × 270 K), which is a high-density CGH assay, designed and made by Roche. Five CNVs appeared in more than 5% of the subjects, and located at a chromosome region that contained exons for inflammationand immunity-related genes (ABCF1, IL17REL, FCGR3A, DPCR1, and DEFA10P), and were identified to be candidate CNVs associated with gout. To validate the significance of the CNVs, the above five candidate CNVs (Table S2) were tested in an additional 1,274 Chinese individuals (576 gout patients and 698 control subjects, Tables S3 and S4) using AccuCopy (Du et al., 2012). The distributions of three CNVs in ABCF1, IL17REL, and FCGR3A were significantly different between the gout patients and the controls according to Fisher’s exact test, with P values of 0.018, 0.021 and 0.022, respectively (Tables S5 and S6). After correcting for multiple comparisons, the distributions of these CNVs were still significantly different (all P = 0.037) (Table S5). In addition, to avoid the heterogeneity of gender and age, deviance analysis for the logistic regression model adjusted for gender and age also showed that the CNVs in IL17REL and FCGR3A were significantly different between gout patients and control subjects (P = 0.002 and 0.038, respectively). The other two CNVs in the DPCR1 and DEFA10P genes were not associated with the risk of gout in the Chinese population (P = 0.328 and 0.221, respectively). The ABCF1 gene encodes a superfamily member of the ATP-binding cassette (ABC) transporters. The ABC

Common UCP2 variants contribute to serum urate concentrations and the risk of hyperuricemia

Elevated serum urate, which is regulated at multiple levels including genetic variants, is a risk factor for gout and other metabolic diseases. This study aimed to investigate the association between UCP2 variants and serum urate as well as hyperuricemia in a Chinese population. In total, 4332 individuals were genotyped for two common UCP2 variants, −866G/A and Ala55Val. These loci were not associated either serum urate level or with a risk of hyperuricemia in the total group of subjects. However, in females, −866G/A and Ala55Val were associated with a lower serum urate (P = 0.006 and 0.014, seperately) and played a protective role against hyperuricemia (OR = 0.80, P = 0.018; OR = 0.79, P = 0.016). These associations were not observed in the males. After further stratification, the two loci were associated with serum urate in overweight, but not underweight females. The haplotype A-T (−866G/A-Ala55Val) was a protective factor for hyperuricemia in the female subgroup (OR = 0.80, P = 0.017). This present study identified a novel gene, UCP2, that influences the serum urate concentration and the risk of hyperuricemia, and the degree of association varies with gender and BMI levels.

PKD2 influence uric acid levels and gout risk by interacting with ABCG2

Background Uric acid is the final product of purine metabolism and elevated serum urate levels can cause gout. Conflicting results were reported for the effect of PKD2 on serum urate levels and gout risk. Therefore, our study attempted to state the important role of PKD2 in influencing the pathogenesis of gout. Method SNPs in PKD2 (rs2725215 and rs2728121) and ABCG2 (rs2231137 and rs1481012) were tested in approximately 5,000 Chinese individuals. Results Two epistatic interactions between loci in PKD2 (rs2728121) and ABCG2 (rs1481012 and rs2231137) showed distinct contributions to uric acid levels with P int values of 0.018 and 0.004, respectively, and the associations varies by gender and BMI. The SNP pair of rs2728121 and rs1481012 justly played roles in uric acid in females (P int = 0.006), while the other pair did in males (P int = 0.017). Regarding BMI, the former SNP pair merely contributed in overweigh subjects (P int = 0.022) and the latter one did in both normal and overweigh individuals (P int = 0.013 and 0.047, respectively). Furthermore, the latter SNP pair was also associated with gout pathology (P int = 0.001), especially in males (P int = 0.001). Finally, functional analysis showed potential epistatic interactions in those genes region and PKD2 mRNA expression had a positive correlation with ABCG2’s (r = 0.743, P = 5.83e-06). Conclusion Our study for the first time identified that epistatic interactions between PKD2 and ABCG2 influenced serum urate concentrations and gout risk, and PKD2 might affect the pathogenesis from elevated serum urate to hyperuricemia to gout by modifying ABCG2.

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.

Treatment of osteomyelitis defects by a vancomycin-loaded gelatin/β-tricalcium phosphate composite scaffold

Objective In the present study, we aimed to assess whether gelatin/β-tricalcium phosphate (β-TCP) composite porous scaffolds could be used as a local controlled release system for vancomycin. We also investigated the efficiency of the scaffolds in eliminating infections and repairing osteomyelitis defects in rabbits. Methods The gelatin scaffolds containing differing amounts of of β-TCP (0%, 10%, 30% and 50%) were prepared for controlled release of vancomycin and were labelled G-TCP0, G-TCP1, G-TCP3 and G-TCP5, respectively. The Kirby-Bauer method was used to examine the release profile. Chronic osteomyelitis models of rabbits were established. After thorough debridement, the osteomyelitis defects were implanted with the scaffolds. Radiographs and histological examinations were carried out to investigate the efficiency of eliminating infections and repairing bone defects. Results The prepared gelatin/β-TCP scaffolds exhibited a homogeneously interconnected 3D porous structure. The G-TCP0 scaffold exhibited the longest duration of vancomycin release with a release duration of eight weeks. With the increase of β-TCP contents, the release duration of the β-TCP-containing composite scaffolds was decreased. The complete release of vancomycin from the G-TCP5 scaffold was achieved within three weeks. In the treatment of osteomyelitis defects in rabbits, the G-TCP3 scaffold showed the most efficacious performance in eliminating infections and repairing bone defects. Conclusions The composite scaffolds could achieve local therapeutic drug levels over an extended duration. The G-TCP3 scaffold possessed the optimal porosity, interconnection and controlled release performance. Therefore, this scaffold could potentially be used in the treatment of chronic osteomyelitis defects. Cite this article: J. Zhou, X. G. Zhou, J. W. Wang, H. Zhou, J. Dong. Treatment of osteomyelitis defects by a vancomycin-loaded gelatin/β-tricalcium phosphate composite scaffold. Bone Joint Res 2018;7:46–57. DOI: 10.1302/2046-3758.71.BJR-2017-0129.R2.

Elevated serum urate is a potential factor in reduction of total bilirubin: a Mendelian randomization study

Aim A Mendelian randomization study (MRS) can be linked to a “natural” randomized controlled trial in order to avoid potential bias of observational epidemiology. We aimed to study the possible association between serum urate (SU) and total bilirubin (TBIL) using MRS. Materials and Methods An observational epidemiological study using ordinary least squares (OLS) regression and MRS using two-stage least square (TLS) regression was conducted to assess the effect of SU on TBIL. The comparison between the OLS regression and the TLS regression was analyzed by the Durbin-Hausman test. If the p value is significant, it suggests that the OLS regression cannot evaluate the relationship between exposure and outcome, and the TLS regression is precise; while if the p value is not significant, there would be no significant difference between the two regressions. Results A total of 3,753 subjects were analyzed. In OLS regression, there was no significant association between SU and TBIL in all subjects and subgroup analysis (all p > 0.05). However, MRS revealed a negative correlation between SU and TBIL after adjustment for confounders (beta = –0.021, p = 0.010). Further analysis was conducted in different SU subgroups, and results show that elevated SU was associated with a significant reduction in TBIL after adjustment for hyperuricemic subjects (beta = –0.053, p = 0.027). In addition, the results using the Durbin-Hausman test further confirmed a negative effect of SU on TBIL (p = 0.002 and 0.010, respectively). Conclusions This research shows for the first time that elevated SU was a potential causal factor in the reduction of TBIL and it provides strong evidence to resolve the controversial association between SU and TBIL.