Association between IL-6 and the extent of coronary atherosclerosis in the veterans affairs diabetes trial (VADT)

Abstract

Aims: The aim of the present study was to investigate the association of high-sensitivity C-reactive protein (CRP), interleukin-6 (IL-6) and lipoprotein-associated phospholipase A2 (Lp-PLA2) with the extent of calcified coronary atherosclerosis in patients with type 2 diabetes mellitus (T2DM).

Materials and results: This is a cross-sectional study of 306 subjects aged 40years or older who were enrolled into the veterans affairs diabetes trial (VADT). Calcified coronary atherosclerosis was assessed using electron beam computed tomography scored by the Agatston method. Clinical parameters, traditional cardiovascular risk factors and plasma levels of CRP, IL-6 and Lp-PLA2 were measured at the time of the scan. Coronary artery calcium (CAC) scores increased stepwise across increasing categories of IL-6, but did not change across increasing categories of CRP and Lp-PLA2. After adjustment for traditional cardiovascular risk factors, IL-6 was significantly associated with CAC scores (p=0.05). The association between IL-6 and CAC was largely in those with lower (below the median) abdominal artery calcium (AAC) levels (p=0.04).

Conclusions: Despite a generally higher level of systemic inflammation in T2DM, the inflammatory marker IL-6 remained significantly associated with CAC score, particularly in those subjects with lower AAC scores.

Figure 1. Coronary artery calcium levels by tertiles of IL-6

Geometric means and 95% CI are shown for CAC levels by IL-6 tertiles for subjects with all data available (n =273). P-value= 0.11 from Kruskal-Wallis test.

Figure 2. Coronary artery calcium levels by tertiles of IL-6 according to AAC levels

Geometric means and 95% CI are shown for CAC levels by tertiles of IL-6 as defined for the entire group (see Fig. 1). Panel A: CAC values by tertiles of IL-6 in those with lower AAC (< median value of 1217). Numbers of subjects in categories I, II and III were 53, 39 and 44, respectively. P-value= 0.02 from Kruskal-Wallis test. Panel B: CAC values by tertiles of IL-6 in those with higher AAC (≥ median). Numbers of subjects in categories I, II and III were 38, 51 and 48, respectively. P-value= 0.76 from Kruskal-Wallis test.