Background — Forearm endothelial dysfunction, characterized by an impaired vasodilating response to acetylcholine (ACh), may be associated with several cardiovascular risk factors, including essential hypertension. Although the prognostic value of coronary endothelial dysfunction has been demonstrated, that of forearm endothelial dysfunction is still unknown. Methods and Results — Endothelium-dependent and -independent vasodilation was investigated in 225 never-treated hypertensive patients (age, 35 to 54 years) by intra-arterial infusion of increasing doses of ACh and sodium nitroprusside. Patients were divided into tertiles on the basis of their increase in ACh-stimulated forearm blood flow (FBF) from basal: group 1, from 30% to 184%; group 2, from 185% to 333%; and group 3, from 339% to 760% increase from basal. During a mean follow-up of 31.5 of months (range, 4 to 84 months), there were 29 major adverse events at the cardiac (n=19), cerebrovascular (n=9), or peripheral vascular (n=1) level. Events included myocardial infarction, angina, coronary revascularization procedures, stroke, transient cerebral ischemic attack, and aortoiliac occlusive disease. Event rate per 100 patient-years was 8.17, 4.34, and 2.02 in the first, second, and third tertiles of peak percent increase in FBF during ACh infusion. The excess risk associated with an FBF increase in the first tertile was significant (relative risk, 2.084; 95% CI, 1.25 to 3.48; P =0.0049) after controlling for individual risk markers, including 24-hour ambulatory blood pressure. Conclusions — Our data suggest that forearm endothelial dysfunction is a marker of future cardiovascular events in patients with essential hypertension.

Endothelial dysfunction has been reported in obese subjects, but its mechanism has not been elucidated. We have therefore investigated 1) the possible relationship among BMI, waist-to-hip ratio (WHR), and endothelium-dependent vasodilation and 2) whether oxidative stress participates in endothelial dysfunction. We recruited 76 healthy subjects (50 men and 26 women aged 21-45 years) and measured their BMI (kg/m²), WHR, and insulin resistance (IR) estimated by the homeostasis model assessment (HOMA). Endothelium-dependent and -independent vasodilation were assessed by increasing doses of acetylcholine (ACh) (7.5, 15, and 30 μg · ml^-1 · min^-1) and sodium nitroprusside (SNP) (0.8, 1.6, and 3.2 μg · ml^-1 · min^-1) during saline and vitamin C coinfusion (24 mg/min). The effects of cyclooxygenase activity were evaluated by a dose-response curve to intrabrachial coinfusion of ACh and indomethacin (500 μg/min). Three different groups have been identified according to their BMI: group A (BMI <25), consisting of 10 men and 5 women; group B (BMI between 25 and 29), consisting of 16 men and 8 women; and group C (BMI ≥30), consisting of 24 men and 13 women. Obese subjects had significantly lower forearm blood flow (FBF) during ACh infusions (means ± SD): 19.8 ± 2.8, 10.8 ± 2.7, and 6.5 ± 1.8 ml · 100 ml^-1 tissue · min^-1 (P < 0.0001) for groups A, B, and C, respectively. SNP caused comparable increments in FBF in all groups. Regression analysis revealed a significant negative correlation between BMI (r = -0.676, P < 0.0001), WHR (r = -0.631, P < 0.0001), fasting insulin (r = -0.695, P < 0.0001), HOMA-IR (r = -0.633, P < 0.0001), and percent peak increase in FBF during ACh infusion. In obese subjects, both vitamin C and indomethacin increased the impaired vasodilating response to ACh, whereas the SNP effect was unchanged. In conclusion, in obese subjects, ACh-stimulated vasodilation is blunted, and the increase in FBF is inversely related to BMI, WHR, fasting insulin, and HOMA-IR. The effects of both vitamin C and indomethacin on impaired ACh-stimulated vasodilation support the hypothesis that oxidative stress contributes to endothelial dysfunction in human obesity.

It has been suggested that serine (Ser) phosphorylation of insulin receptor substrate-1 (IRS-1) decreases the ability of IRS-1 to be phosphorylated on tyrosine, thereby attenuating insulin signaling. There is evidence that angiotensin II (AII) may impair insulin signaling to the IRS-1/phosphatydilinositol 3-kinase (PI 3-kinase) pathway by enhancing Ser phosphorylation. Insulin stimulates NO production by a pathway involving IRS-1/PI3-kinase/Akt/endothelial NO synthase (eNOS). We addressed the question of whether AII affects insulin signaling involved in NO production in human umbilical vein endothelial cells and tested the hypothesis that the inhibitory effect of AII on insulin signaling was caused by increased site-specific Ser phosphorylation in IRS-1. Exposure of human umbilical vein endothelial cells to AII resulted in inhibition of insulin-stimulated production of NO. This event was associated with impaired IRS-1 phosphorylation at Tyr ⁶¹² and Tyr ⁶³² , two sites essential for engaging the p85 subunit of PI3-kinase, resulting in defective activation of PI 3-kinase, Akt, and eNOS. This inhibitory effect of AII was reversed by the type 1 receptor antagonist losartan. AII increased c-Jun N-terminal kinase (JNK) and extracellular signal–regulated kinase (ERK) 1/2 activity, which was associated with a concomitant increase in IRS-1 phosphorylation at Ser ³¹² and Ser ⁶¹⁶ , respectively. Inhibition of JNK and ERK1/2 activity reversed the negative effects of AII on insulin-stimulated NO production. Our data suggest that AII, acting via the type 1 receptor, increases IRS-1 phosphorylation at Ser ³¹² and Ser ⁶¹⁶ via JNK and ERK1/2, respectively, thus impairing the vasodilator effects of insulin mediated by the IRS-1/PI 3-kinase/Akt/eNOS pathway.

Background— Chronic kidney disease is a risk factor for cardiovascular disease, increasing all-cause mortality. Some evidence suggests that endothelial dysfunction is present in the early stages of renal insufficiency, but no data exist about its possible role in the progression of renal disease. Thus, we prospectively evaluated the effect of endothelial function on estimated glomerular filtration rate (eGFR) in essential hypertension. Methods and Results— We enrolled 500 never-treated uncomplicated hypertensive subjects with serum creatinine ≤1.5 mg/dL. Endothelial function was measured by strain-gauge plethysmography during intra-arterial infusion of acetylcholine and sodium nitroprusside. eGFR was calculated by use of the Chronic Kidney Disease Epidemiology Collaboration equation. The annual rate of decline of eGFR (ΔeGFR/y) was determined as the difference between the follow-up and baseline eGFR values, with this value divided by the time interval in years. During follow-up (92.3±36.2 months), mean ΔeGFR/y was 1.49±1.65 mL · min ⁻¹ · 1.73 m ^{− 2} , with no significant differences between men and women (1.55±1.72 versus 1.43±1.58 mL · min ⁻¹ · 1.73 m ^{− 2} , respectively; P =0.455). This was correlated with acetylcholine-stimulated forearm blood flow ( r =−0.256, P <0.0001), creatinine ( r =0.141, P =0.001), systolic blood pressure ( r =−0.103, P =0.01), and eGFR ( r =0.092, P =0.020). In multivariable regression analysis, forearm blood flow and systolic blood pressure remained associated with change in eGFR. On average, eGFR changed by 0.37 mL · min ⁻¹ · 1.73 m ^{− 2} for each 100% change in forearm blood flow ( P <0.001) and by 0.1 mL · min ⁻¹ · 1.73 m ^{− 2} for each difference of 10 mm Hg in systolic blood pressure ( P =0.032). Conclusions— We demonstrated that acetylcholine-stimulated vasodilation and systolic blood pressure were associated with eGFR loss after adjustment for other cardiovascular risk factors and antihypertensive treatment.