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Applied Physiology, Nutrition, and... Jul 2015High-fat diets are associated with an increased risk of cardiovascular disease. A potential underlying mechanism for the increased cardiovascular risk is endothelial...
High-fat diets are associated with an increased risk of cardiovascular disease. A potential underlying mechanism for the increased cardiovascular risk is endothelial dysfunction. Nitric oxide (NO)-mediated endothelium-dependent vasodilation is critical in the regulation of vascular tone and overall vascular health. The aim of this study was to determine the influence of dietary fat intake on endothelium-dependent vasodilation. Forty-four middle-aged and older sedentary, healthy adults were studied: 24 consumed a lower fat diet (LFD; 29% ± 1% calories from fat) and 20 consumed a high-fat diet (HFD; 41% ± 1% calories from fat). Four-day diet records were used to assess fat intake, and classifications were based on American Heart Association guidelines (<35% of total calories from fat). Forearm blood flow (FBF) responses to acetylcholine, in the absence and presence of the endothelial NO synthase inhibitor N(G)-monomethyl-l-arginine (L-NMMA), as well as responses to sodium nitroprusside were determined by plethysmography. The FBF response to acetylcholine was lower (∼15%; P < 0.05) in the HFD group (4.5 ± 0.2 to 12.1 ± 0.8 mL/100 mL tissue/min) than in the LFD group (4.6 ± 0.2 to 14.4 ± 0.6 mL/100 mL tissue/min). L-NMMA significantly reduced the FBF response to acetylcholine in the LFD group (∼25%) but not in the HFD group. There were no differences between groups in the vasodilator response to sodium nitroprusside. These data indicate that a high-fat diet is associated with endothelium-dependent vasodilator dysfunction due, in part, to diminished NO bioavailability. Impaired NO-mediated endothelium-dependent vasodilation may contribute to the increased cardiovascular risk with high dietary fat intake.
Topics: Acetylcholine; Adult; Aged; Analysis of Variance; Diet, High-Fat; Dietary Fats; Endothelium, Vascular; Feeding Behavior; Female; Humans; Male; Middle Aged; Nitric Oxide Synthase Type III; Nitroprusside; Plethysmography; Risk Factors; Vasodilation; omega-N-Methylarginine
PubMed: 26058441
DOI: 10.1139/apnm-2015-0006 -
PloS One 2015Glucagon levels are often moderately elevated in diabetes. It is known that glucagon leads to a decrease in hepatic glutathione (GSH) synthesis that in turn is...
Glucagon levels are often moderately elevated in diabetes. It is known that glucagon leads to a decrease in hepatic glutathione (GSH) synthesis that in turn is associated with decreased postprandial insulin sensitivity. Given that cAMP pathway controls GSH levels we tested whether insulin sensitivity decreases after intraportal (ipv) administration of a cAMP analog (DBcAMP), and investigated whether glucagon promotes insulin resistance through decreasing hepatic GSH levels.Insulin sensitivity was determined in fed male Sprague-Dawley rats using a modified euglycemic hyperinsulinemic clamp in the postprandial state upon ipv administration of DBcAMP as well as glucagon infusion. Glucagon effects on insulin sensitivity was assessed in the presence or absence of postprandial insulin sensitivity inhibition by administration of L-NMMA. Hepatic GSH and NO content and plasma levels of NO were measured after acute ipv glucagon infusion. Insulin sensitivity was assessed in the fed state and after ipv glucagon infusion in the presence of GSH-E. We founf that DBcAMP and glucagon produce a decrease of insulin sensitivity, in a dose-dependent manner. Glucagon-induced decrease of postprandial insulin sensitivity correlated with decreased hepatic GSH content and was restored by administration of GSH-E. Furthermore, inhibition of postprandial decrease of insulin sensitivity L-NMMA was not overcome by glucagon, but glucagon did not affect hepatic and plasma levels of NO. These results show that glucagon decreases postprandial insulin sensitivity through reducing hepatic GSH levels, an effect that is mimicked by increasing cAMP hepatic levels and requires physiological NO levels. These observations support the hypothesis that glucagon acts via adenylate cyclase to decrease hepatic GSH levels and induce insulin resistance. We suggest that the glucagon-cAMP-GSH axis is a potential therapeutic target to address insulin resistance in pathological conditions.
Topics: Adenylyl Cyclases; Animals; Blood Glucose; Bucladesine; Cyclic AMP; Dose-Response Relationship, Drug; Glucagon; Glucose Clamp Technique; Glutathione; Injections, Intravenous; Insulin; Insulin Resistance; Liver; Male; Nitric Oxide; Portal Vein; Postprandial Period; Rats; Rats, Sprague-Dawley; omega-N-Methylarginine
PubMed: 25961284
DOI: 10.1371/journal.pone.0127221 -
The Journal of Physiology Jun 2015During exercise there is a balance between vasoactive factors that facilitate increases in blood flow and oxygen delivery to the active tissue and the sympathetic...
KEY POINTS
During exercise there is a balance between vasoactive factors that facilitate increases in blood flow and oxygen delivery to the active tissue and the sympathetic nervous system, which acts to limit muscle blood flow for the purpose of blood pressure regulation. Functional sympatholysis describes the ability of contracting skeletal muscle to blunt the stimulus for vasoconstriction, yet the underlying signalling of this response in humans is not well understood. We tested the hypothesis that activation of inwardly rectifying potassium channels and the sodium-potassium ATPase pump, two potential vasodilator pathways within blood vessels, contributes to the ability to blunt α1 -adrenergic vasoconstriction. Our results show preserved blunting of α1 -adrenergic vasconstriction despite blockade of these vasoactive factors. Understanding this complex phenomenon is important as it is impaired in a variety of clinical populations.
ABSTRACT
Sympathetic vasoconstriction in contracting skeletal muscle is blunted relative to that which occurs in resting tissue; however, the mechanisms underlying this 'functional sympatholysis' remain unclear in humans. We tested the hypothesis that α1 -adrenergic vasoconstriction is augmented during exercise following inhibition of inwardly rectifying potassium (KIR ) channels and Na(+) /K(+) -ATPase (BaCl2 + ouabain). In young healthy humans, we measured forearm blood flow (Doppler ultrasound) and calculated forearm vascular conductance (FVC) at rest, during steady-state stimulus conditions (pre-phenylephrine), and after 2 min of phenylephrine (PE; an α1 -adrenoceptor agonist) infusion via brachial artery catheter in response to two different stimuli: moderate (15% maximal voluntary contraction) rhythmic handgrip exercise or adenosine infusion. In Protocol 1 (n = 11 subjects) a total of six trials were performed in three conditions: control (saline), combined enzymatic inhibition of nitric oxide (NO) and prostaglandin (PG) synthesis (l-NMMA + ketorolac) and combined inhibition of NO, PGs, KIR channels and Na(+) /K(+) -ATPase (l-NMMA + ketorolac + BaCl2 + ouabain). In Protocol 2 (n = 6) a total of four trials were performed in two conditions: control (saline), and combined KIR channel and Na(+) /K(+) -ATPase inhibition. All trials occurred after local β-adrenoceptor blockade (propranolol). PE-mediated vasoconstriction was calculated (%ΔFVC) in each condition. Contrary to our hypothesis, despite attenuated exercise hyperaemia of ∼30%, inhibition of KIR channels and Na(+) /K(+) -ATPase, combined with inhibition of NO and PGs (Protocol 1) or alone (Protocol 2) did not enhance α1 -mediated vasoconstriction during exercise (Protocol 1: -27 ± 3%; P = 0.2 vs. control, P = 0.4 vs. l-NMMA + ketorolac; Protocol 2: -21 ± 7%; P = 0.9 vs. control). Thus, contracting human skeletal muscle maintains the ability to blunt α1 -adrenergic vasoconstriction during combined KIR channel and Na(+) /K(+) -ATPase inhibition.
Topics: Adenosine; Adult; Barium Compounds; Brachial Artery; Chlorides; Exercise; Female; Forearm; Hand Strength; Humans; Ketorolac; Male; Muscle Contraction; Muscle, Skeletal; Ouabain; Potassium Channels, Inwardly Rectifying; Propranolol; Receptors, Adrenergic, alpha-1; Regional Blood Flow; Sodium-Potassium-Exchanging ATPase; Vasoconstriction; Young Adult; omega-N-Methylarginine
PubMed: 25893955
DOI: 10.1113/JP270461 -
PloS One 2015Activation of different pattern recognition receptors causes distinct profiles of innate immune responses, which in turn dictate the adaptive immune response. We found...
Activation of different pattern recognition receptors causes distinct profiles of innate immune responses, which in turn dictate the adaptive immune response. We found that mice had higher CD4+ T cell expansion to an immunogen, ovalbumin, when coadministered with CpG than with CL097 in vivo. To account for this differential adjuvanticity, we assessed the activities of CpG and CL097 on antigen-specific CD4+ T cell expansion in vitro using an OT-II CD4+ T cell/bone marrow-derived dendritic cell (DC) co-culture system. Unexpectedly, ovalbumin-stimulated expansion of OT-II CD4+ T cells in vitro was potently suppressed by both TLR agonists, with CL097 being stronger than CpG. The suppression was synergistically reversed by co-inhibition of cyclooxygenases 1 and 2, and inducible nitric oxide (NO) synthase. In addition, stimulation of OT-II CD4+ T cell/DC cultures with CL097 induced higher levels of CD4+ T cell death than stimulation with CpG, and this CD4+ T cell turnover was reversed by NO and PGE2 inhibition. Consistently, the co-cultures stimulated with CL097 produced higher levels of prostaglandin E2 (PGE2) and NO than stimulation with CpG. CL097 induced higher PGE2 production in DC cultures and higher IFN-γ in the OT-II CD4+ T cell/DC cultures, accounting for the high levels of PGE2 and NO. This study demonstrates that the adjuvant activities of immunostimulatory molecules may be determined by differential induction of negative regulators, including NO and PGE2 suppressing clonal expansion and promoting cell death of CD4+ T cells.
Topics: Animals; CD4-Positive T-Lymphocytes; Cell Death; Dendritic Cells; Dinoprostone; Imidazoles; Indomethacin; Interleukin-2; Lymphocyte Activation; Mice; Nitric Oxide; Oligodeoxyribonucleotides; Ovalbumin; Quinolines; Toll-Like Receptor 7; Toll-Like Receptor 9; omega-N-Methylarginine
PubMed: 25875128
DOI: 10.1371/journal.pone.0123165 -
American Journal of Physiology. Heart... Jun 2015Endothelial cell release of nitric oxide (NO) is a defining characteristic of nondiseased arteries, and abnormal endothelial NO release is both a marker of early...
Endothelial cell release of nitric oxide (NO) is a defining characteristic of nondiseased arteries, and abnormal endothelial NO release is both a marker of early atherosclerosis and a predictor of its progression and future events. Healthy coronaries respond to endothelial-dependent stressors with vasodilatation and increased coronary blood flow (CBF), but those with endothelial dysfunction respond with paradoxical vasoconstriction and reduced CBF. Recently, coronary MRI and isometric handgrip exercise (IHE) were reported to noninvasively quantify coronary endothelial function (CEF). However, it is not known whether the coronary response to IHE is actually mediated by NO and/or whether it is reproducible over weeks. To determine the contribution of NO, we studied the coronary response to IHE before and during infusion of N(G)-monomethyl-l-arginine (l-NMMA, 0.3 mg·kg(-1)·min(-1)), a NO-synthase inhibitor, in healthy volunteers. For reproducibility, we performed two MRI-IHE studies ~8 wk apart in healthy subjects and patients with coronary artery disease (CAD). Changes from rest to IHE in coronary cross-sectional area (%CSA) and diastolic CBF (%CBF) were quantified. l-NMMA completely blocked normal coronary vasodilation during IHE [%CSA, 12.9 ± 2.5 (mean ± SE, placebo) vs. -0.3 ± 1.6% (l-NMMA); P < 0.001] and significantly blunted the increase in flow [%CBF, 47.7 ± 6.4 (placebo) vs. 10.6 ± 4.6% (l-NMMA); P < 0.001]. MRI-IHE measures obtained weeks apart strongly correlated for CSA (P < 0.0001) and CBF (P < 0.01). In conclusion, the normal human coronary vasoactive response to IHE is primarily mediated by NO. This noninvasive, reproducible MRI-IHE exam of NO-mediated CEF promises to be useful for studying CAD pathogenesis in low-risk populations and for evaluating translational strategies designed to alter CAD in patients.
Topics: Adult; Aged; Case-Control Studies; Coronary Artery Disease; Coronary Circulation; Coronary Vessels; Endothelium, Vascular; Enzyme Inhibitors; Exercise; Female; Hand Strength; Heart Function Tests; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Nitric Oxide; Nitric Oxide Synthase Type III; Vasoconstriction; Vasodilation; omega-N-Methylarginine
PubMed: 25820391
DOI: 10.1152/ajpheart.00023.2015 -
European Journal of Applied Physiology Aug 2015We hypothesized exercise vasodilation would be greater in women due to nitric oxide synthase (NOS) and cyclooxygenase (COX) signaling. (Comparative Study)
Comparative Study
PURPOSE
We hypothesized exercise vasodilation would be greater in women due to nitric oxide synthase (NOS) and cyclooxygenase (COX) signaling.
METHODS
45 healthy adults (23 women, W, 22 men, M, 26 ± 1 years) completed two 10-min trials of dynamic forearm exercise at 15 % intensity. Forearm blood flow (FBF; Doppler ultrasound), arterial pressure (brachial catheter), and forearm lean mass were measured to calculate relative forearm vascular conductance (FVCrel) = FBF 100 mmHg(-1) 100 g(-1) lean mass. Local intra-arterial infusion of L-NMMA or ketorolac acutely inhibited NOS and COX, respectively. In Trial 1, the first 5 min served as control exercise (CON), followed by 5 min of L-NMMA or ketorolac over the last 5 min of exercise. In Trial 2, the remaining drug was infused during 5-10 min, to achieve combined NOS-COX inhibition (double blockade, DB).
RESULTS
Are mean ± SE. Women exhibited 29 % greater vasodilation in CON (ΔFVCrel, 19 ± 1 vs. 15 ± 1, p = 0.01). L-NMMA reduced ΔFVCrel (p < 0.001) (W: Δ -2.3 ± 1.3 vs. M: Δ -3.7 ± 0.8, p = 0.25); whereas, ketorolac modestly increased ΔFVCrel (p = 0.04) similarly between sexes (W: Δ 1.6 ± 1.1 vs. M: Δ 2.0 ± 1.6, p = 0.78). DB was also found to be similar between the sexes (p = 0.85).
CONCLUSION
These data clearly indicate women produce a greater exercise vasodilator response. Furthermore, contrary to experiments in animal models, these data are the first to demonstrate vascular control by NOS and COX is similar between sexes.
Topics: Adolescent; Adult; Cyclooxygenase Inhibitors; Enzyme Inhibitors; Exercise; Female; Forearm; Hemodynamics; Humans; Ketorolac; Male; Nitric Oxide Synthase; Prostaglandin-Endoperoxide Synthases; Regional Blood Flow; Sex Characteristics; Ultrasonography; Vascular Resistance; Vasodilation; Young Adult; omega-N-Methylarginine
PubMed: 25820143
DOI: 10.1007/s00421-015-3160-6 -
PloS One 2015The compensatory increase in hepatic arterial flow with a decrease in portal venous flow is known as the hepatic arterial buffer response. In cirrhosis with elevated...
INTRODUCTION
The compensatory increase in hepatic arterial flow with a decrease in portal venous flow is known as the hepatic arterial buffer response. In cirrhosis with elevated portal pressure, the vascular resistance of the hepatic artery is decreased. Whether this lower resistance of the hepatic artery is a consequence of portal hypertension or not remains unknown.
STUDY AIM
The aim of the study was to investigate the hepatic arterial resistance and response to vasoconstriction in cirrhosis without portal hypertension (normal portal resistance).
METHODS
Cirrhosis was induced by CCl4-inhalation for 8 weeks (8W, normal portal resistance) and for 12-14 weeks (12W, elevated portal resistance). Bivascular liver perfusion was performed at 8W or 12W and dose response curves of methoxamine were obtained in the presence or absence of LNMMA (nitric oxide synthase blocker). Vascular resistances of the hepatic artery (HAR), portal vein (PVR) and sinusoids (SVR) were measured. Western Blot (WB) and Immunohistochemistry (IHC) were done to measure eNOS and HIF 1a expression.
RESULTS
HAR in both groups of cirrhotic animals (8W and 12W) were lower compared to controls. Dose response curves to methoxamine revealed lower HAR in both cirrhotic models (8W and 12W) regardless the magnitude of portal resistance. LNMMA corrected the dose response curves in cirrhosis (8W and 12W) to control. WB and IHC show increased protein expression of eNOS and HIF1a in 8W and 12W.
CONCLUSION
Hepatic arterial resistance is decreased in cirrhosis independent of portal resistance. Vasodilation of the hepatic artery in cirrhosis seems to be influenced by hypoxia rather than increase in portal resistance. Nitric oxide is the main vasodilator.
Topics: Animals; Blotting, Western; Dose-Response Relationship, Drug; Hepatic Artery; Hypertension, Portal; Hypoxia-Inducible Factor 1, alpha Subunit; Immunohistochemistry; Liver Cirrhosis; Male; Methoxamine; Nitric Oxide Synthase Type III; Perfusion; Rats, Wistar; Vascular Resistance; Vasodilation; omega-N-Methylarginine
PubMed: 25793622
DOI: 10.1371/journal.pone.0121229 -
British Journal of Clinical Pharmacology Sep 2015Nebivolol is a selective β1 -receptor antagonist with vasodilating properties. In patients with essential hypertension, we tested the hypothesis that nebivolol... (Randomized Controlled Trial)
Randomized Controlled Trial
AIMS
Nebivolol is a selective β1 -receptor antagonist with vasodilating properties. In patients with essential hypertension, we tested the hypothesis that nebivolol increases systemic and renal nitric oxide (NO) availability using L-N(G) -monomethyl arginine (L-NMMA) as an inhibitor of NO production.
METHODS
In a randomized, placebo-controlled, crossover study, patients with essential hypertension were treated with nebivolol for five days, along with a standardized diet and fluid intake. We examined the acute effects of systemic NO synthase inhibition with L-NMMA on brachial blood pressure (bBP), pulse wave velocity (PWV) and central blood pressure (cBP) estimated by applanation tonometry, glomerular filtration rate (GFR), fractional excretion of sodium (FENa ), urinary excretion of both aquaporin-2 (u-AQP2) and epithelial sodium channels (u-ENaCγ ), and plasma concentrations of nitrate/nitrite (p-NOx ) and vasoactive hormones after five days' treatment with placebo and nebivolol.
RESULTS
Nebivolol significantly reduced PWV, bBP, cBP and plasma renin, angiotensin II and aldosterone concentrations. The renal parameters, p-NOx and plasma arginine vasopressin concentration were not changed by nebivolol. There was no difference between nebivolol and placebo in the response to L-NMMA, with LMMA inducing a similar increase in PWV, bBP and cBP and a similar decrease in GFR, uAQP2 and u-ENaCγ and FENa [mean change -0.62% (95% confidence interval {CI} -0.40 to -0.84) during placebo vs. -0.57% (95% CI -0.46 to -0.68; P = 0.564) during nebivolol treatment]. Vasoactive hormones were changed to a similar extend by L-NMMA during administration of nebivolol and placebo.
CONCLUSIONS
Nebivolol did not change p-NOx , and inhibition of NO synthesis induced the same response in blood pressure, GFR, renal tubular function and vasoactive hormones during nebivolol and placebo. Thus, the data did not support the hypothesis that nebivolol changes vascular and renal NO availability in patients with essential hypertension.
Topics: Adrenergic beta-1 Receptor Antagonists; Adult; Aged; Blood Pressure; Blood Pressure Monitoring, Ambulatory; Cross-Over Studies; Double-Blind Method; Female; Glomerular Filtration Rate; Humans; Hypertension; Kidney Tubules; Male; Middle Aged; Nebivolol; Nitric Oxide; Treatment Outcome; omega-N-Methylarginine
PubMed: 25778445
DOI: 10.1111/bcp.12627 -
Journal of Applied Physiology... May 2015Inhibition of nitric oxide synthase (NOS) significantly attenuates the increase in skeletal muscle glucose uptake during contraction/exercise, and a greater attenuation...
Inhibition of nitric oxide synthase (NOS) significantly attenuates the increase in skeletal muscle glucose uptake during contraction/exercise, and a greater attenuation is observed in individuals with Type 2 diabetes compared with healthy individuals. Therefore, NO appears to play an important role in mediating muscle glucose uptake during contraction. In this study, we investigated the involvement of neuronal NOSμ (nNOSμ), the main NOS isoform activated during contraction, on skeletal muscle glucose uptake during ex vivo contraction. Extensor digitorum longus muscles were isolated from nNOSμ(-/-) and nNOSμ(+/+) mice. Muscles were contracted ex vivo in a temperature-controlled (30°C) organ bath with or without the presence of the NOS inhibitor N(G)-monomethyl-l-arginine (L-NMMA) and the NOS substrate L-arginine. Glucose uptake was determined by radioactive tracers. Skeletal muscle glucose uptake increased approximately fourfold during contraction in muscles from both nNOSμ(-/-) and nNOSμ(+/+) mice. L-NMMA significantly attenuated the increase in muscle glucose uptake during contraction in both genotypes. This attenuation was reversed by L-arginine, suggesting that L-NMMA attenuated the increase in muscle glucose uptake during contraction by inhibiting NOS and not via a nonspecific effect of the inhibitor. Low levels of NOS activity (~4%) were detected in muscles from nNOSμ(-/-) mice, and there was no evidence of compensation from other NOS isoform or AMP-activated protein kinase which is also involved in mediating muscle glucose uptake during contraction. These results indicate that NO regulates skeletal muscle glucose uptake during ex vivo contraction independently of nNOSμ.
Topics: AMP-Activated Protein Kinases; Animals; Arginine; Biological Transport; Enzyme Inhibitors; Female; Glucose; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Muscle Contraction; Muscle, Skeletal; Nitric Oxide; Nitric Oxide Synthase Type I; Physical Conditioning, Animal; omega-N-Methylarginine
PubMed: 25749441
DOI: 10.1152/japplphysiol.00056.2015 -
American Journal of Physiology. Heart... Mar 2015In young healthy men, passive leg movement (PLM) elicits a robust nitric oxide (NO)-dependent increase in leg blood flow (LBF), thus providing a novel approach to assess... (Comparative Study)
Comparative Study
UNLABELLED
In young healthy men, passive leg movement (PLM) elicits a robust nitric oxide (NO)-dependent increase in leg blood flow (LBF), thus providing a novel approach to assess NO-mediated vascular function. While the magnitude of the LBF response to PLM is markedly reduced with age, the role of NO in this attenuated response in the elderly is unknown. Therefore, this study sought to determine the contribution of NO in the PLM-induced LBF with age. Fourteen male subjects (7 young, 24 ± 1 yr; and 7 old, 75 ± 3 yr) underwent PLM with and without NO synthase (NOS) inhibition achieved by intra-arterial infusion of N(G)-monomethyl-L-arginine (L-NMMA). LBF was determined second-by-second by Doppler ultrasound, and central hemodynamics were measured by finger photoplethysmography. NOS inhibition blunted the PLM-induced peak increase in LBF in the young (control: 668 ± 106;
L-NMMA
431 ± 95 Δml/min; P = 0.03) but had no effect in the old (control: 266 ± 98;
L-NMMA
251 ± 92 Δml/min; P = 0.59). Likewise, the magnitude of the reduction in the overall (i.e., area under the curve) PLM-induced LBF response to NOS inhibition was less in the old (LBF: -31 ± 18 ml) than the young (LBF: -129 ± 21 ml; P < 0.01). These findings suggest that the age-associated reduction in PLM-induced LBF in the elderly is primarily due to a reduced contribution to vasodilation from NO and therefore support the use of PLM as a novel approach to assess NO-mediated vascular function across the lifespan.
Topics: Adult; Age Factors; Aged; Arterial Pressure; Blood Flow Velocity; Enzyme Inhibitors; Femoral Artery; Heart Rate; Humans; Infusions, Intra-Arterial; Lower Extremity; Male; Muscle Contraction; Muscle, Skeletal; Nitric Oxide; Nitric Oxide Synthase; Regional Blood Flow; Stroke Volume; Ultrasonography; Vasodilation; Young Adult; omega-N-Methylarginine
PubMed: 25576629
DOI: 10.1152/ajpheart.00806.2014