Usefulness of insulin resistance estimation and the metabolic syndrome in predicting coronary atherosclerosis in type 2 diabetes mellitus

Metabolic syndrome (MS) definitions predict cardiovascular events beyond traditional risk factors in patients with type 2 diabetes mellitus (DM) as well as subjects without DM. It has been shown that apolipoprotein B (apoB) and nonhigh-density lipoprotein cholesterol are associated with coronary artery calcification in DM. However, the relative value of MS, apoB lipoproteins, and estimates of insulin resistance is unknown in predicting atherosclerosis in DM. Cross-sectional analyses of white subjects in 2 community-based studies were performed (n = 611 patients with DM, n = 803 subjects without DM) using multivariate analysis of traditional risk factors and then adding MS, apoB, and homeostasis model assessment of insulin resistance (HOMA-IR). Incremental value was tested using likelihood ratio testing. Beyond traditional risk, HOMA-IR (tobit regression ratio 1.86, p = 0.002), apoB (tobit regression ratio 1.55, p = 0.001), and MS (tobit regression ratio 2.37, p = 0.007) were independently associated with coronary artery calcification in DM. In nested models, HOMA-IR added value to apoB (tobit regression ratio 1.72, p = 0.008), MS (tobit regression ratio 1.72, p = 0.011), and apoB and MS (tobit regression ratio 1.64, p = 0.021). ApoB showed a similar pattern when added to HOMA-IR (tobit regression ratio 1.51, p = 0.004), MS (tobit regression ratio 1.46, p = 0.005), and HOMA-IR and MS (tobit regression ratio 1.48, p = 0.006). MS added to apoB (tobit regression ratio 1.99, p = 0.032) but not HOMA-IR (tobit regression ratio 1.54, p = 0.221) or apoB and HOMA-IR (tobit regression ratio 1.32, p = 0.434). In conclusion, insulin resistance estimates add value to MS and apoB in predicting coronary artery calcification scores in DM and warrant further evaluation in clinic for identification of patients with DM at higher risk for atherosclerotic cardiovascular disease.