U-shaped relationship between insulin level and coronary artery calcification (CAC)

Recent studies have suggested that hyperinsulinemia is associated with high cardiovascular risk. The purpose of this study was to assess the relationship between the serum insulin level and coronary artery calcification (CAC).

We performed a cross-sectional study of 582 consecutive and nondiabetic participants with clinical suspicion of coronary heart disease, and assessed the CAC score determined by multislice computed tomography. A standard 75-g oral glucose tolerance test was performed and venous blood was collected at 0, 30, 60 and 120 min for the measurement of plasma glucose and serum insulin. Statistical analyses were conducted for 4 subgroups according to fasting insulin and insulin area under the concentration time curve (InsAUC).

Mean log (CAC+1) and InsAUC were 1.6 and 109.1 µIU/mL, respectively. Unadjusted analysis demonstrated that the fasting insulin quartiles (p=0.0256) and InsAUC quartiles (p<0.0001) were significantly associated with log (CAC+1), and the lowest fasting insulin quartiles (p<0.0001) and the lowest InsAUC quartile (p=0.0006) had lower glucose AUC. Analysis of covariance demonstrated that the lowest InsAUC quartile had the highest log (CAC+1), and the highest InsAUC quartile had a higher log (CAC+1) than the second and third InsAUC quartiles, adjusted for several coronary risk factors (p<0.0001).

The lowest InsAUC quartile was related to CAC, although the lowest InsAUC quartile maintained glucose homeostasis, in this study population. Not only hyperinsulinemia but also a low insulin level are independently associated with CAC.