Effect of fasting insulin level on circulating Th1 and Th2 cytokines in patients with systemic lupus erythematosus

Abstract

Objective It has been increasingly recognized patients with systemic lupus erythematosus (SLE) have various cytokine abnormalities. However, both Th1- and Th2-derived cytokines can participate in promoting or inhibiting autoimmune disease depending on characteristic of disease. We previously reported that SLE patients have a higher risk of insulin resistance and abnormal insulin secretion. The objective of this study was to examine effects of fasting insulin level on circulating Th1- and Th2-derived cytokines in SLE patients. Method Plasma levels of tumor necrosis factor (TNF)-α, interferon (IFN)-γ, interleukin (IL)-4, IL-6, IL-10, IL-12, and IL-18 were determined by enzyme-linked immunosorbent assay using commercial kits in a total of 70 female SLE patients. All patients were further classified into two subgroups (SLE with hyperinsulinemia, n = 21 vs. SLE controls, n = 49) based on fasting insulin level. Results There were no statistical differences in plasma levels of Th2 cytokines between two SLE subgroups, but SLE patients with hyperinsulinemia compared with SLE controls had significantly higher plasma levels of TNF-α and IL-18 according to Mann-Whitney U test. In addition, fasting insulin level correlated positively and significantly with TNF-α and IL-18 in all SLE patients based on Spearman’s correlation analysis. Conclusion Elevated fasting insulin levels played a predominant role in mediating proinflammatory cytokines including TNF-α and IL-18 in patients with SLE.