Relationship of plasma interleukin-18 concentrations to traditional and non-traditional cardiovascular risk factors in patients with systemic lupus erythematosus

Objectives. Systemic lupus erythematosus (SLE) is associated with premature atherosclerosis. Recent studies indicated that the concentrations of circulating interleukin (IL)-18, a novel proinflammatory T helper-1 cytokine, in SLE patients were significantly higher than those in healthy control subjects. The objective of this study was to examine the relationship between IL-18 and cardiovascular risk factors in patients with SLE. Methods. Both traditional and non-traditional cardiovascular risk factors including body mass index (BMI), systolic blood pressure, diastolic blood pressure (DBP), fasting insulin and glucose, plasma lipid profile, plasma homocysteine, thiobarbituric acid-reactive substances, titres of autoantibodies against oxidized low-density lipoprotein, and brachial-ankle pulse wave velocity (baPWV) were determined in a total of 72 female SLE patients. All patients were further classified into subgroups based on tertiles of plasma IL-18 concentrations. Results. Plasma concentrations of IL-18 were significantly higher in SLE patients than age-matched healthy controls. SLE patients with IL-18 concentration in the top tertile compared with the bottom tertile had significantly higher plasma levels of insulin, triglyceride, homocysteine and values of homeostasis model assessment insulin resistance (HOMA IR) and HOMA beta-cell. In addition, plasma concentrations of IL-18 correlated positively and significantly with BMI, insulin, HOMA IR, HOMA beta-cell, triglyceride, homocysteine, DBP and baPWV in all SLE patients. Conclusions. This is the first report showing the relationship between IL-18 and cardiovascular risk factors in SLE. In patients with SLE, the synergistic effects of hyperinsulinaemia, insulin resistance, hyperhomocysteinaemia, and vascular stiffness most likely contribute to the elevation of plasma IL-18 concentrations.