Kyle J. Diehl

Impaired fasting blood glucose is associated with increased endothelin-1 vasoconstrictor tone.

AIM/HYPOTHESIS The experimental aim of this study was to determine whether ET-1-mediated vasoconstrictor tone is elevated in adult humans with impaired fasting blood glucose concentrations, independent of other cardiovascular risk factors. METHODS Forearm blood flow (FBF: plethysmography) responses to intra-arterial infusion of selective ETA receptor blockade (BQ-123: 100 nmol/min for 60 min) and non-selective ETA/B blockade (BQ-123 + BQ-788: 50 nmol/min for 60 min) were determined in 28 middle-aged, sedentary adults (17 M/11 F): 14 with normal fasting blood glucose (age: 57 ± 2 yr; 6 F/8 M; BMI: 29.2 ± 0.9 kg/m(2); glucose: 4.9 ± 0.1 mmol/L) and 14 impaired fasting blood glucose (58 ± 1 yr; 5 F/9 M; 29.6 ± 1.1 kg/m(2); 5.8 ± 0.1 mmol/L) concentrations. RESULTS Selective ETA receptor blockade elicited a significantly greater (∼20%) increase in FBF in the impaired fasting glucose adults compared with the normoglycemia controls. ETA/B blockade resulted in a further 2-fold increase (P < 0.05) in FBF above that elicited by ETA receptor antagonism in the impaired fasting glucose but not normal fasting glucose adults. There was a positive correlation between fasting blood glucose levels and the peak vascular responses to ETA (r = 0.44; P < 0.05) and ETA/B (r = 0.62; P < 0.05) blockade. No other anthropometric, hemodynamic or metabolic variable was correlated with the blood flow responses to ET-1 receptor blockade. CONCLUSIONS/INTERPRETATION ET-1-mediated vasoconstrictor tone is elevated in adults with impaired fasting blood glucose concentrations, independent of other cardiometabolic risk factors. Enhanced ET-1 system activity may underlie endothelial vasomotor dysfunction and increased cardiovascular risk in adults with impaired fasting blood glucose concentrations.

Chronic Nebivolol Treatment Suppresses Endothelin-1–Mediated Vasoconstrictor Tone in Adults With Elevated Blood Pressure

Abstract—Endothelin-1 (ET-1) plays a major role in the pathophysiology of hypertension and its associated cardiovascular risk. We tested the hypothesis that chronic nebivolol treatment reduces ET-1–mediated vasoconstrictor tone in adult humans with elevated blood pressure (BP). Furthermore, reducing ET-1 vasoconstrictor activity contributes to the improvement in endothelial vasodilator function associated with nebivolol treatment. Forty-two middle-aged adults with elevated BP (systolic BP ≥130 mm Hg or diastolic BP ≥85 mm Hg) completed a 3-month, double-blind, randomized, placebo controlled trial: 14 received nebivolol (8 men/6 women; 5 mg per day); 14 received metoprolol succinate (9 men/5 women; 100 mg per day); and 14 received placebo (9 men/5 women). Forearm blood flow (plethysmography) responses to selective (BQ-123: 100 nmol/min; 60 minutes) and nonselective (BQ-123+BQ-788 [50 nmol/min]; 60 minutes) ET-1 receptor blockade, as well as acetylcholine (4.0, 8.0, and 16.0 &mgr;g per 100 mL of tissue per minute) in the absence and presence of nonselective ET-1 receptor blockade were determined before and after each treatment intervention. Forearm blood flow responses to BQ-123 and BQ-123+BQ-788 were similarly and significantly elevated (≈30% and 60%, respectively) from baseline in all 3 groups. Nebivolol, but not metoprolol or placebo, therapy resulted in a marked (≈25% and 45%; P<0.05) reduction in forearm blood flow response to BQ-123 and BQ-123+BQ-788. Moreover, after nebivolol therapy only, vasodilator response to acetylcholine was not significantly increased by ET-1 receptor blockade. These results demonstrate that nebivolol, but not metoprolol, treatment reduces ET-1–mediated vasoconstrictor tone in adult humans with elevated BP. In addition, nebivolol-induced reduction in ET-1–mediated vasoconstrictor tone underlies the favorable effects of this &bgr;-blocker on endothelial vasodilation. Clinical Trial Registration—URL: http://www.clinicaltrials.gov. Unique identifier: NCT01395329.

Impaired endogenous fibrinolytic capacity in prehypertensive men

Prehypertension (blood pressure (BP) 120–139/80–89 mm Hg) is associated with an increased risk for future atherothrombotic events. Although the mechanisms underlying this elevated risk are not completely understood, one possibility is that prehypertension is associated with impaired endothelial fibrinolytic capacity. We tested the hypothesis that vascular endothelial release of tissue-type plasminogen activator (t-PA) is impaired in prehypertensive men. Net endothelial release of t-PA was determined, in vivo, in response to intrabrachial infusions of bradykinin (12.5, 25, 50 ng per 100 ml tissue per min) and sodium nitroprusside at (1.0, 2.0, 4.0 μg per 100 ml tissue per min) in 42 middle-age and older men: 16 normotensive (BP range: 100–119/57–79 mm Hg); 16 prehypertensive (BP range: 120–139/76–89 mm Hg); and 10 hypertensive (BP range: 140–150/74–100 mm Hg). Net release of t-PA antigen was ~25% lower (P<0.05) in the prehypertensive (−0.9±0.8 to 42.4±5.3 ng per 100 ml tissue per min) compared with the normotensive (0.5±1.0 to 53.9±6.5 ng per 100 ml tissue per min) men. There was no significant difference in t-PA release between the hypertensive (−1.8±1.6 to 40.8±6.6 ng per 100 ml tissue per min) and prehypertensive groups. Sodium nitroprusside did not significantly alter the t-PA release in any group. These data indicate that endothelial t-PA release is diminished in prehypertensive men. Further, the level of impairment in t-PA release seen with clinical hypertension is already apparent in the prehypertensive state. Impaired endothelial fibrinolytic function may underlie the increased atherothrombotic risk associated with BP in the prehypertensive range.

Effects of endothelin-1 on endothelial progenitor cell function

Abstract Background: Circulating endothelial progenitor cells (EPCs) contribute to vascular endothelial repair. Endothelin (ET)-1 is associated with endothelial damage and atherogenesis. The experimental aim of this study was to determine, in vitro, the effects of ET-1 on the ability of EPCs to form colonies, migrate, release angiogenic growth factors and resist apoptosis. Methods: Peripheral blood samples were collected from 10 healthy adult humans. Cells with phenotypic EPC characteristics were isolated and EPC colony-forming capacity (CFU assay), migratory activity (Boyden chamber), release of angiogenic growth factors (enzyme immunoassay) and apoptosis (TUNEL assay) were determined in the absence and presence of ET-1 (100 pmol). Results: EPC colony-forming units (42±12 vs. 39±11), migratory capacity (910±146 vs. 936±148 AU) and release of vascular endothelial growth factor (202.8±68.1 vs. 204.8±69.8 pg/mL) and granulocyte-colony stimulating factor (1294.4±378.3 vs. 1136.1±310.3 pg/mL) were not significantly affected by ET-1. EPCs treated with ET-1 demonstrated a 20% increase (p<0.05) in cellular apoptosis. The proapoptotic effect of ET-1 was abolished with ET receptor blockade as well as with apocynin, a nicotinamide adenine dinucleotide phosphate (NADPH) inhibitor. Conclusions: These results indicate that ET-1 does not affect EPC colony formation, migratory capacity or angiogenic growth factor release, but does increase EPC susceptibility to apoptosis through an NADPH-dependent mechanism. Increased EPC apoptosis may contribute to the proatherogenic effects of ET-1.

Influence of Overweight and Obesity on Circulating Inflammation-Related Microrna

BACKGROUND Increased cardiovascular disease risk and prevalence associated with overweight and obesity is due, in part, to heightened inflammatory burden. The mechanisms underlying adiposity-related amplification of inflammation are not fully understood. Alterations in regulators of inflammatory processes such as microRNAs (miRs), however, are thought to play a pivotal role. OBJECTIVE The aim of this study was to determine the influence of overweight and obesity, independent of other cardiovascular risk factors, on circulating expression of miR-34a, miR-126, miR-146a, miR-150 and miR-181b. METHODS Forty-five sedentary, middle-aged (47-64 years) adults were studied: 15 were normal weight (8M/7F; BMI: 23.3 ± 0.3 kg/m2); 15 were overweight (8M/7F; 28.2 ± 0.3 kg/m2); and 15 were obese (7M/8F; 32.3 ± 0.5 kg/m2). All subjects were non-smokers, normotensive and free of overt cardiometabolic disease. Circulating levels of the following inflammation-related miRs: miR-34a, miR-126, miR-146a, miR-150 and miR-181b were determined in plasma using standard RT-PCR techniques. miR expression was normalized to exogenous C. elegans miR-39 and reported as relative expression (AU). RESULTS Circulating miR-34a was ~200% higher (P< 0.05) in the obese as compared with normal weight and overweight groups. Whereas, miR-126, miR-146a and miR-150 were significantly lower (~65%) in both the obese and overweight groups than the normal weight group. There were no significant group differences in circulating expression of miR-181b. miR-34a was positively related (r = 0.43; P< 0.05); whereas, miR-126 (r = -0.48), miR-146a (r = -0.33) and miR-150 (r = -0.43) levels were significantly inversely related to BMI. CONCLUSION Overweight and obesity, independent of other cardiometabolic risk factors, negatively influences circulating inflammation-related miRs. Dysregulation of circulating miRs may contribute mechanistically to the heightened inflammatory state associated with overweight and obesity.

Association between hypertension and circulating vascular-related microRNAs

AbstractmicroRNAs (miRNAs) have a key role in regulating inflammation, vascular health and in turn, cardiovascular disease. Specifically, altered circulating expression of miR-17, miR-21, miR-34a, miR-92a, miR-126, miR-145, miR-146a, and miR-150 has been linked with the pathogenesis and progression of cardiovascular disease. The aim of this study was to determine whether the circulating profile of these vascular-related miRNAs is disrupted with hypertension. Thirty sedentary, middle-aged adults were studied: 15 normotensive (10M/5F; age: 56 ± 1 year; BP: 113/71 ± 2/1 mmHg) and 15 hypertensive (10M/5F; 56 ± 2 year; 140/87 ± 2/2 mmHg). All subjects were non-obese and free of other cardiometabolic disorders. Circulating miRNAs were determined in plasma using standard RT-PCR techniques with miRNA primers of interest. Expression was normalized to exogenous C. elegans miR-39 and reported as relative expression in arbitrary units (AU). Circulating expression of miR-34a (9.18 ± 0.94 vs 5.33 ± 0.91 AU) was higher (~170%; P < 0.01) whereas the expression of miR-21 (1.32 ± 0.25 vs 2.50 ± 0.29 AU), miR-126 (0.85 ± 0.10 vs 1.74 ± 0.27 AU) and miR-146a (1.50 ± 0.20 vs 3.10 ± 0.50 AU) were markedly lower (~50%, ~55%, and ~55% respectively; P < 0.05) in the hypertensive vs normotensive groups. Moreover, circulating levels of miR-34a, miR-21, and miR-126 were significantly related to systolic blood pressure (r = 0.48, r = −0.38; r = −0.48); whereas, miR-146a was significantly related to both systolic (r = −0.58) and diastolic (r = −0.55) blood pressure. There were no significant group differences in circulating miR-17, miR-92a, miR-145, and miR-150. In summary, these results suggest that hypertension, independent of other cardiometabolic risk factors, adversely affects the circulating profile of a subset of vascular-related miRNAs that have been link to CVD risk and development.

Nebivolol, But Not Metoprolol, Treatment Improves Endothelial Fibrinolytic Capacity in Adults With Elevated Blood Pressure

Background Vascular endothelial fibrinolytic function is impaired in adults with prehypertension and hypertension and plays a mechanistic role in the development of atherothrombotic events. The influence of β‐blockers on endothelial fibrinolysis is unknown. This study compared the effects of chronic nebivolol and metoprolol treatment on endothelial tissue‐type plasminogen activator (t‐PA) release in adults with elevated blood pressure (BP). Methods and Results Forty‐four middle‐aged adults (36% women) with elevated BP completed a 3‐month, double‐blind, randomized, placebo‐controlled trial comparing nebivolol (5 mg/d), metoprolol succinate (100 mg/d), and placebo. Net endothelial t‐PA release was determined in vivo in response to intrabrachial infusions of bradykinin and sodium nitroprusside before and after each intervention. In a subset, the dose‐response curves to bradykinin and sodium nitroprusside were repeated with a coinfusion of the antioxidant vitamin C. At baseline, resting BP and endothelial t‐PA release were comparable between the 3 groups. BP decreased to a similar extent (≈10 mm Hg) in the nebivolol‐ and metoprolol‐treated groups. There was a substantial increase (≈30%; P<0.05) in the capacity of the endothelium to release t‐PA following chronic treatment with nebivolol but not metoprolol or placebo. Mitigating oxidant stress with vitamin C coinfusion potentiated t‐PA release (90%; P<0.05) at baseline in all groups. However, after the intervention, t‐PA release was unchanged by vitamin C coinfusion in the nebivolol group only. Conclusions Nebivolol but not metoprolol improves endothelial t‐PA release in adults with elevated BP. This may be an important vascular benefit of nebivolol. Clinical Trial Registration URL: http://www.clinicaltrials.gov. Unique identifier: NCT01595516.