Uric acid is independently associated with interleukin-1 beta levels in tear fluid of hyperuricemia and gout patients

ObjectivesTo explore pro-inflammatory cytokines status in the tear fluid of patients with hyperuricemia and gout and its association with uric acid level. MethodsA total of 58 control subjects, 58 hyperuricemia patients including 40 asymptomatic hyperuricemia and 18 gout participants were recruited in this study. For tear analysis, each patient's tears were collected using capillary action microcaps after stimulation. Tear uric acid levels were measured using chemiluminescence. Tear and serum interleukin-1beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) levels were measured using enzyme-linked immunosorbent assay. The correlation of serum and tear uric acid levels with IL-1 beta and TNF-alpha were determined. ResultsTear uric acid levels were significantly higher in hyperuricemia group (98.2 +/- 51.5 vs. 42.7 +/- 24.0 mu mol/L, p < .001) than in controls group. IL-1 beta concentrations were significantly higher in hyperuricemia eyes compared to control eyes (210.2 +/- 113.9 vs. 142.6 +/- 29.8 pg/mL, p < .001). Multiple linear regression analysis showed that tear uric acid levels were independently positively associated with tear IL-1 beta concentrations (B = 0.192, p < .001). However, no significant correlations were found between serum or tear uric acid and TNF-alpha level. Moreover, there were no statistically differences of tear IL-1 beta and TNF-alpha levels between the asymptomatic hyperuricemia and gout groups. ConclusionsTear uric acid levels were higher in patients with hyperuricemia and gout than in controls. There was a significant positive correlation between tear uric acid value and tear IL-1 beta level, implying an interaction between hyperuricemia and ocular inflammation responses.