The correlation of insulin resistance with serum tumor necrosis factor-alpha levels in patients with rheumatoid arthritis

The aim of this study was to assess the acute insulin response and insulin sensitivity in patients with rheumatoid arthritis. We also examined the correlation of serum tumor necrosis factor-alpha (TNF-alpha) levels with insulin resistance and impaired acute insulin response. Thirty-six subjects (22 women and 14 men, aged 51.5 +/- 17.1 year (range 21-80), BMI 27.1 +/- 5.0 kg/m(2)) with rheumatoid arthritis and 20 healthy control subjects were studied. After a 12-hour overnight fast, all subjects underwent a diagnostic protocol including serum insulin level, and a homeostasis model that assessed insulin resistance (HOMA-IR) estimated insulin sensitivity, acute insulin response (AIR) derived from intravenous glucose tolerance test data and serum TNF-alpha level. The fasting insulin levels, HOMA scores and serum TNF-alpha levels were significantly higher in patients with rheumatoid artritis than in control subjects (14.7 +/- 6.7 versus 8.7 +/- 1.9 mu IU/mL, P < 0.001 and 3.3 +/- 1.5 versus 1.9 +/- 0.5, P < 0.001 and 368.4 +/- 649.2 versus 3.6 +/- 5.0 pg/mL, P < 0.001, respectively). Acute insulin responses were lower in patients with rheumatoid arthritis than in control subjects (35.8 +/- 17 versus 85.2 +/- 17.9, P < 0.001). Fasting insulin, HOMA-IR, TNF-alpha, and AIR were positively correlated. Insulin resistance seems to be the main metabolic abnormality that alters glucose metabolism and decreases the sensitivity of peripheral tissues to insulin in patients with rheumatoid arthritis.