The inflammatory role of silent urate crystal deposition in intercritical gout

Objective. To study subclinical inflammation in intercritical gout patients and its relation to the estimated size of monosodium urate crystal deposition and cardiovascular risk factors. Methods. We performed a secretome analysis and the quantification of cytokine and adipokine plasma levels [IL-1 beta, IL-18, IL-6, soluble IL-6 receptor (sIL-6R), TNF-alpha, C-X-C motif chemokine 5, RANTES (Regulated upon Activation, Normal T Cell Expressed and Presumably Secreted), leptin, resistin and adiponectin] to analyse subclinical inflammation in intercritical gout patients. Since it is currently not feasible to determinate the whole body deposit of monosodium urate crystals, we created an indirect clinical classification to estimate it. Then we compared cytokine levels in controls and gout patients and in patients with different crystal deposition sizes. We also studied the association between cytokine-levels and the number of cardiovascular risk factors. Results. Ninety consecutive patients attending a crystal arthritis unit were studied. IL-18, sIL-6R, RANTES, leptin and adiponectin were higher in intercritical gout patients than in controls. An association was observed between IL-18, sIL6-R and RANTES levels and the size of crystal deposition. IL-18, sIL6-R, RANTES and leptin were higher in patients with no cardiovascular risk factors compared with controls with no risk factors. Conclusion. Our results showed that the levels of some pro-inflammatory cytokines and metabolic proteins are elevated in intercritical gout patients. The levels of certain cytokines were related to the estimated size of the monosodium urate crystal deposition and to the number of cardiovascular risk factors. These cytokine changes may help to explain the increase in cardiovascular events in gout patients.