Circadian variation of blood pressure is correlated to vascular endothelial function in nondiabetic essential hypertensives

Background: Hypertension is associated with altered endothelial nitric oxide (NO) release. Abnormal endothelium-dependent vascular relaxation in patients with primary hypertension has been described and is associated with abnormalities of the NO system. Little is known about the relationship between the circadian rhythm of blood pressure (BP) and endothelial function in patients with essential hypertension. Methods: Non-diabetic patients with either treated or untreated essential hypertension were evaluated if their office systolic BP (SBP) ≥ 140 mmHg or diastolic BP (DBP) ≥ 90 mmHg. Serial studies including serum biochemistry, 24-hour ambulatory BP monitoring (ABPM), and brachial artery ultrasound were conducted. Results: Thirty-nine patients were enrolled into the study. They were subclassified by their nocturnal DBP fall (25 dippers, with nocturnal DBP fall ≥ 10%; and 14 non-dippers, with nocturnal DBP fall < 10%). The baseline characteristics and serum biomarkers including adiponectin, asymmetric dimethylargine, oxidized low-density lipoprotein, monocyte chemoattractant protein-1, high-sensitivity C-reactive protein, insulin, and nitrate and nitrite were similar between the dippers and the non-dippers. The flow-mediated dilation (FMD) was greater in the dippers than in the non-dippers (6.1 ± 3.1% vs. 4.1 ± 2.6%, P = 0.040) while the nitroglycerin-mediated dilation was similar between the two groups (14.3 ± 5.5% vs. 13.7 ± 6.0%, P = 0.746). In all patients, sleep DBP (r = -0.379, p = 0.017), nocturnal change of SBP (r = 0.344, p = 0.032) and DBP (r = 0.420, p = 0.008), and the use of calcium channel blockers (r = -0.394, p = 0.013) were correlated to FMD. However, only nocturnal change of DBP was an independent predictor for FMD (β = 0.175, p = 0.008). Conclusion: In non-diabetic hypertensive patients, the dippers had better endothelial function than the non-dippers. Nocturnal change of DBP was the major predictor for endothelial function.