Predictors of asymmetric dimethylarginine levels in patients with rheumatoid arthritis: the role of insulin resistance

OBJECTIVE: To determine whether demographic, inflammatory, and metabolic factors predict elevated asymmetric dimethylarginine (ADMA) levels in rheumatoid arthritis (RA).

METHOD: A total of 67 RA patients [mean age 56 ± 12 years, median disease duration 8 (3-15) years] were assessed. Routine biochemistry tests, lipid profile, glycaemic profile [glucose, insulin, homeostasis model assessment (HOMA), quantitative insulin sensitivity check index (QUICKI)], and inflammatory markers were measured in all patients. ADMA levels were measured by enzyme-linked immunosorbent assay (ELISA). Regression analyses were performed to identify predictors of ADMA in RA.

RESULTS: Regression analysis revealed that HOMA (β = 0.149, p = 0.003) was an independent predictor of ADMA in RA. From the drug factors, anti-hypertensive medication use was associated with lower ADMA levels (β = -0.081, p = 0.004). ADMA was not associated with RA disease-related parameters or any of the other cardiovascular risk factors that were assessed.

CONCLUSIONS: HOMA, a strong indicator of insulin resistance, seems to be the main predictor of elevated ADMA levels in RA patients; ADMA may reflect an important pathway linking abnormal insulin metabolism with endothelial dysfunction in RA.