Aminotransferases are associated with insulin resistance and atherosclerosis in rheumatoid arthritis

BACKGROUND: Serum aminotransferase concentrations are reportedly strongly associated with insulin resistance, an established cardiovascular risk factor that is not routinely assessed in clinical practice. We therefore explored the possibility that serum aminotransferase concentrations are as closely related to large artery disease as insulin resistance in rheumatoid arthritis (RA). METHODS: Carotid artery plaque (ultrasonography), insulin resistance and liver enzymes (prior to methotrexate (MTX) were determined in 77 consecutive patients with RA (43 with and 34 without MTX). RESULTS: Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were associated with insulin resistance in univariate analysis (R = 0.54, p < 0.0001 and R = 0.36, p = 0.001, respectively) and after adjustment for age, gender and waist circumference (partial R = 0.43, p = 0.0001 and partial R = 0.37, p = 0.001, respectively). ALT and AST concentrations were higher in patients with plaque as compared to in those without plaque (ALT (u/l): 27 [22-32] versus 20 [18-23], p = 0.02; AST (u/l): 25 [21-28] versus 20 [19-22], p = 0.02). The odds ratios [95% CI] for plaque were 1.92 [1.14–3.24] (p = 0.01), 1.93 [1.17–3.16] (p = 0.009) and 1.82 [1.13–2.93] (p = 0.01) for 1 SD increase in ALT (~10 u/l) and AST (~6 u/l) concentrations and in logarithmically transformed homeostasis model assessment of insulin resistance (HOMA-IR) (~0.2 uU.mmol/ml.l), respectively. After adjustment for the potentially confounding characteristics of age, sex, hypertension and hypothyroidism in logistic regression models, ALT (p = 0.049) and AST concentrations (p = 0.027) remained associated with plaque whereas the HOMA-IR did not (p = 0.08). AST concentrations (p = 0.049) were associated with plaque independent of insulin resistance whereas the HOMA-IR (p = 0.1) was not associated with plaque independent of AST concentrations. CONCLUSION: Within currently recommended reference ranges, serum aminotransferase concentrations may be strongly associated with insulin resistance and atherosclerosis in patients with RA. The measurement of aminotransferase concentrations could be a useful tool in cardiovascular risk stratification in patients with RA.