Close association of endothelial dysfunction with insulin resistance and carotid wall thickening in hypertension

BACKGROUND: Endothelial dysfunction has been regarded as an early stage in the atherosclerotic process. Endothelial dysfunction and insulin resistance were observed in hypertensive subjects and were associated with carotid wall thickening. METHODS: We examined the determinants of endothelial dysfunction including insulin sensitivity and carotid wall thickening. A total of 41 subjects with nondiabetic essential hypertension were studied. Endothelial function of brachial artery and carotid wall thickening were assessed noninvasively using ultrasound technique. In brachial artery, we measured flow-mediated endothelium-dependent vasodilation (FMD) and glyceryl trinitrate-induced endothelium-independent vasodilation (GTN). We estimated intima-media thickness of the common carotid artery (IMT). Insulin sensitivity was measured according to the steady-state plasma glucose (SSPG) method. High SSPG levels indicated insulin resistance. RESULTS: On univariate analysis, there were significant negative correlations between FMD and SSPG (r = -0.695, P <.0001) or IMT (r = -0.449, P <.004). The FMD was negatively correlated significantly with age and with systolic and diastolic blood pressures (BP). A significant negative correlation was observed between GTN and SSPG. There was a significant positive relation between SSPG and IMT. On multiple regression analysis including systolic BP, SSPG, and age as independent variables and FMD as a dependent variable, FMD was independently related to SSPG (P <.03) and systolic BP (P <.02). If the presence of SSPG, diastolic BP, and age were entered as independent variables against FMD, FMD was independently related to SSPG (P <.002). CONCLUSIONS: One of the major determinants of endothelial function was insulin resistance. Our findings suggest that endothelial dysfunction and early structural vascular changes were related to insulin resistance.