Nocturnal blood pressure but not insulin resistance influences endothelial function in treated hypertensive patients

The impact of insulin sensitivity, casual blood pressure and 24-h ambulatory blood pressure on endothelial function was studied in treated hypertensive subjects. Flow-mediated dilatation of the brachial artery after reperfusion was used to determine endothelial function. Insulin sensitivity indices were obtained by using the homeostasis model assessment, after 75 g Dextrose oral glucose tolerance tests (Matsuda index) and the euglycemic hyperinsulinemic clamp (M-value) in 49 patients with arterial hypertension. The insulin sensitivity indices were compared with healthy controls matched for body weight, age and sex (n=23). Hypertensive patients under therapy were insulin resistant, had higher LDL-cholesterol levels, higher blood pressure and lower endothelial function than healthy controls. Flow-mediated dilatation showed, in the study population being treated for arterial hypertension, no relationships of all insulin sensitivity indices with flow-mediated dilatation, casual blood pressure in the morning before the tests and 24-h ambulatory blood pressure. Flow-mediated dilatation was strongly influenced by nocturnal systolic and diastolic 24-h ambulatory blood pressure (systolic: R²=0.0943, P<0.05; diastolic: R²=0.0947, P<0.05). Therefore, endothelial function in these patients is predominantly influenced by nocturnal systolic and diastolic blood pressure and not by insulin sensitivity.