Endothelial Dysfunction and Subclincal Atherosclerosis in Insulin Resistance Syndrome
Insulin resistance syndrome, which constitutes obesity, hypertension, impaired glucose tolerance, and low high density lipoprotein is closely associated with cardiovascular events. Impairment of endothelial function precedes and exacerbates atherosclerosis. Accordingly, the aim of this study was to investigate a possible link among endothelial dysfunction, subclinical atherosclerosis, and insulin resistance syndrome. First, to examine the association between functional changes of large artery and insulin resistance syndrome, flow-mediated vasodilation (FMD) of the brachial artery was examined by high resolution ultrasonography, as a non-invasive measure of endothelial function in subjects without cardiovascular diseases (n=75). Coronary risk factors, including factors constituting insulin resistance syndrome were evaluated as well. Univariate and multivariate analyses revealed that FMD was inversely correlated with body mass index (BMI; r=-.26, p<0.03), mean arterial pressure (r=-.27, p<0.03), HbA1C (r=-.39, p<0.01), triglyceride (r=-.37, p<0.01), and the number of risk factors (r=-.47, p<0.001). Second, to examine the association between structural changes of large artery and insulin resistance syndrome in apparently healthy subjects (n=545), duplex scanning of the carotid arteries was performed to measure the intima-media thickness (IMT), an index of subclinical atherosclerosis. Age-adjusted-IMT was positively correlated with BMI (r=.14, p<0.002), mean arterial pressure (r=.27, p<0.001), HbA1C (r=.40, p<0.001), triglyceride (r=.12, p<0.005), HOMA, an index of insulin resistance, (r=.17, p<0.007), and the number of risk factors (r=.37, p<0.001). Finally, FMD was inversely correlated with IMT (r=-.28, p<0.03). Thus, the factors constituting insulin resistant syndrome were closely associated with both functional and structural changes of arteries in apparently healthy subjects. Our results suggest that insulin resistance may play a key role in the early process of atherosclerosis.