Is There Association between Uric Acid and Inflammation in Hemodialysis Patients?

Background: Elevated serum uric acid has been associated with a variety of cardiovascular disease and with inflammation, but these have been little explored in chronic kidney disease (CKD). Elevated uric acid levels are common in CKD patients and could be involved in inflammatory milieu; our aim was to analyze the association between uric acid and inflammatory markers in hemodialysis (HD) patients. Design: This was a cross-sectional study. Setting: This study was conducted from private clinic, Rio de Janeiro, Brazil. Patients: This study included 50 HD patients and 21 healthy subjects. Methods and procedures: This study included 50 HD patients [62% men, 54.3 +/- 12.6 years, 57.5 +/- 50.1 months on dialysis, and body mass index (BMI), 24.4 +/- 4.1 kg/m(2)] and 21 healthy individuals (45% men, 50.7 +/- 15.7 years and BMI, 25.5 +/- 4 kg/m(2)). Uric acid was measured using uricase-PAP method; inflammatory [tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), C-reactive protein (CRP)] and atherosclerosis markers [intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), monocyte chemoattractant protein-1 (MCP-1), plasminogen activator inhibitor-1 (PAI-1)] were measured by a multiplexed assay. Results: Patients presented high levels of TNF-alpha, IL-6, CRP, VCAM-1, ICAM-1 (5.5 +/- 2.1 pg/mL, 4.1 +/- 1.6 pg/mL, 0.32 +/- 0.30 mg/mL, 48.5 +/- 8.5 ng/mL, 20.5 +/- 15.9 ng/mL, respectively), compared with healthy individuals (2.4 +/- 1.1 pg/mL, 2.7 +/- 0.4 pg/mL, 0.11 +/- 0.12 mg/mL, 23.8 +/- 5.5 ng/mL, 7.2 +/- 1.2 ng/mL, respectively) (p < 0.04). Uric acid levels were also higher in HD patients (5.4 +/- 1.3 mg/dL) than in healthy individuals (3.9 +/- 0.9 mg/dL) (p < 0.02). There was a positive correlation between uric acid and inflammatory markers, IL-6 (r = 0.30, p = 0.01), CRP (r = 0.37, p = 0.003), TNF-alpha (r = 0.40, p = 0.001), ICAM-1 (r = 0.53, p = 0.0001), and VCAM-1 (r = 0.45, p = 0.0001). Conclusion: These original data suggest that uric acid may have a role in inflammation and atherosclerosis in HD patients. However, further prospective studies involving intervention trials should be conducted in order to search for actual causality relationship between these markers.