Objectives The objectives for this study were to assess whether gout and/or rheumatoid arthritis (RA) are risk factors for coronavirus disease 2019 (COVID‐19) diagnosis and to assess whether gout and/or RA are risk factors for death from COVID‐19. Methods We used data from the UK Biobank. Multivariable‐adjusted logistic regression was employed in the following analyses: analysis A, to test for association between gout and/or RA and COVID‐19 diagnosis (n = 473,139); analysis B, to test for association between gout and/or RA and death from COVID‐19 in a case‐control cohort of people who died of or survived COVID‐19 (n = 2059); analysis C, to test for association between gout and/or RA and death from COVID‐19 in the entire UK Biobank cohort (n = 473,139). Results RA, but not gout, was associated with COVID‐19 diagnosis in analysis A. Neither RA nor gout was associated with risk of death in the group diagnosed with COVID‐19 in analysis B. However, RA was associated with risk of death related to COVID‐19 by using the UK Biobank cohort in analysis C, independent of comorbidities and other measured risk factors (odds ratio [OR] 1.9; 95% confidence interval CI 1.2–3.0). Gout was not associated with death related to COVID‐19 in the same UK Biobank analysis (OR 1.2; 95% CI 0.8–1.7). Conclusion RA is a risk factor for death from COVID‐19 by using the UK Biobank cohort. These findings require replication in larger data sets that also allow for inclusion of a wider range of factors.

Insulin and hyperinsulinemia reduce renal fractional excretion of urate (FeU) and play a key role in the genesis of hyperuricemia and gout, via uncharacterized mechanisms. To explore this association further we studied the effects of genetic variation in insulin-associated pathways on serum urate (SU) levels and the physiological effects of insulin on urate transporters. We found that urate-associated variants in the human insulin (INS), insulin receptor (INSR), and insulin receptor substrate-1 (IRS1) loci associate with the expression of the insulin-like growth factor 2, IRS1, INSR, and ZNF358 genes; additionally, we found genetic interaction between SLC2A9 and the three loci, most evident in women. We also found that insulin stimulates the expression of GLUT9 and increases [14C]-urate uptake in human proximal tubular cells (PTC-05) and HEK293T cells, transport activity that was effectively abrogated by uricosurics or inhibitors of protein tyrosine kinase (PTK), PI3 kinase, MEK/ERK, or p38 MAPK. Heterologous expression of individual urate transporters in Xenopus oocytes revealed that the [14C]-urate transport activities of GLUT9a, GLUT9b, OAT10, OAT3, OAT1, NPT1 and ABCG2 are directly activated by insulin signaling, through PI3 kinase (PI3K)/Akt, MEK/ERK and/or p38 MAPK. Given that the high-capacity urate transporter GLUT9a is the exclusive basolateral exit pathway for reabsorbed urate from the renal proximal tubule into the blood, that insulin stimulates both GLUT9 expression and urate transport activity more than other urate transporters, and that SLC2A9 shows genetic interaction with urate-associated insulin-signaling loci, we postulate that the anti-uricosuric effect of insulin is primarily due to the enhanced expression and activation of GLUT9.

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Background Metabolic syndrome and hyperinsulinemia are associated with hyperuricemia. Insulin infusion in healthy volunteers elevates serum urate (SU) by activating net urate reabsorption in the renal proximal tubule, whereas IGF-1 infusion reduces SU by mechanisms unknown. Variation within the IGF1R gene also affects SU levels.Methods Colocalization analyses of a SU genome-wide association studies signal at IGF1R and expression quantitative trait loci signals in cis using COLOC2, RT-PCR, Western blotting, and urate transport assays in transfected HEK 293T cells and in Xenopus laevis oocytes.Results Genetic association at IGF1R with SU is stronger in women and is mediated by control of IGF1R expression. Inheritance of the urate-lowering homozygous genotype at the SLC2A9 locus is associated with a differential effect of IGF1R genotype between men and women. IGF-1, through IGF-1R, stimulated urate uptake in human renal proximal tubule epithelial cells and transfected HEK 293T cells, through activation of IRS1, PI3/Akt, MEK/ERK, and p38 MAPK; urate uptake was inhibited in the presence of uricosuric drugs, specific inhibitors of protein tyrosine kinase, PI3 kinase (PI3K), ERK, and p38 MAPK. In X. laevis oocytes expressing ten individual urate transporters, IGF-1 through endogenous IGF-1R stimulated urate transport mediated by GLUT9, OAT1, OAT3, ABCG2, and ABCC4 and inhibited insulin's stimulatory action on GLUT9a and OAT3. IGF-1 significantly activated Akt and ERK. Specific inhibitors of PI3K, ERK, and PKC significantly affected IGF-1 stimulation of urate transport in oocytes. ConclusionsThe combined results of infusion, genetics, and transport experiments suggest that IGF-1 reduces SU by activating urate secretory transporters and inhibiting insulin's action.

Gout is of particularly high prevalence in the Māori and Pacific (Polynesian) populations of Aotearoa New Zealand (NZ). Here, we investigated the contribution of common population-specific CNV to gout in the Aotearoa NZ Polynesian population. Microarray-generated genome-wide genotype data from Aotearoa NZ Polynesian individuals with (n = 1196) and without (n = 1249) gout were analyzed. Comparator population groups were 552 individuals of European ancestry and 1962 of Han Chinese ancestry. Levels of circulating MHC Class I Polypeptide-related sequence A (MICA) were measured by ELISA. Fifty-four CNV regions (CNVRs) appearing in at least 10 individuals were detected, of which seven common CNVRs were specific to or amplified in Polynesian people. A burden test of these seven revealed associations of insertion/deletion with gout (OR = 1.80 [1.01; 3.22], P = 0.046). Individually testing of the seven CNVRs for association with gout revealed nominal association of CNVR1 with gout in Western Polynesian (Chr6: 31.36–31.45 Mb, OR = 1.72 [1.03; 2.92], P = 0.04), CNVR6 in the meta-analyzed Polynesian sample sets (Chr1: 196.75–196.92 Mb, OR = 1.86 [1.16; 3.00], P = 0.01) and CNVR9 in Western Polynesian (Chr1: 189.35–189.54 Mb, OR = 2.75 [1.15; 7.13], P = 0.03). Analysis of European gout genetic association data demonstrated a signal of association at the CNVR1 locus that was an expression QTL for MICA. The most common CNVR (CNVR1) includes deletion of the MICA gene, encoding an immunomodulatory protein. Expression of MICA was reduced in the serum of individuals with the deletion. In summary, we provide evidence for the association of CNVR1 containing MICA with gout in Polynesian peoples, implicating class I MHC-mediated antigen presentation in gout.

Gout is a chronic disease of monosodium urate crystal deposition in the setting of hyperuricemia that typically presents with recurrent flares of acute inflammatory arthritis that occur due to innate immune response to deposited crystals. The molecular mechanism of the progression from hyperuricemia to clinical gout is poorly understood. Here we provide insights into this progression from a genetic study of 2.6 million people, including 120,282 people with gout. We detected 376 loci and 410 genetically independent signals (148 new loci in urate and gout). We identified 1,768 candidate genes with subsequent pathway analysis revealing urate metabolism, type 2 diabetes, and chromatin modification and structure as top pathways in gout. Genes located within or statistically linked to significant GWAS loci were prioitized for their potential to control the progression from hyperuricemia to gout. This identified strong candidate immune genes involved in epigenetic remodelling, cell osmolarity, and regulation of NLRP3-inflammasome activity. The genetic association signal at XDH, encoding the urate-producing enzyme xanthine oxidoreductase (XOR), co-localizes with genetic control of XDH expression, but only in the prostate. We demonstrate XOR activity and urate production in the mouse prostate, and use single-cell RNA sequence data to propose a model of urate reuptake, synthesis, and secretion by the prostate. The gout-associated loci were over-represented for genes implicated in clonal hematopoeiesis of indeterminate potential (CHIP) and Mendelian randomization analysis provided evidence for a causal role of CHIP in gout. In concert with implication of epigenomic regulators, this provides support for epigenomic remodelling as causal in gout. We provide new insights into the molecular pathogenesis of gout and identify an array of candidate genes for a role in the inflammatory process of gout.

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