Acute psychological and physical stress transiently enhances brachial artery flow-mediated dilation stimulated by exercise-induced increases in shear stress

2014 ◽  
Vol 39 (8) ◽  
pp. 927-936 ◽  
Author(s):  
Ingrid C. Szijgyarto ◽  
Veronica J. Poitras ◽  
Brendon J. Gurd ◽  
Kyra E. Pyke
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Brachial Artery ◽  
Stress Responses ◽  
Physical Stress ◽  
Flow Mediated Dilation ◽  
Trial Effect ◽  
Condition Effect ◽  
Exercise Induced ◽  
The Impact

Exercise elevates conduit artery shear stress and stimulates flow-mediated dilation (FMD). However, little is known regarding the impact of acute psychological and physical stress on this response. The purpose of this study was to examine the impact of the Trier Social Stress Test (TSST (speech and arithmetic tasks)) and a cold pressor test (CPT) with and without social evaluation (SE) on exercise-induced brachial artery FMD (EX-FMD). A total of 59 healthy male subjects were randomly assigned to 1 of 3 conditions: TSST, CPT, or CPT with SE. During 6 min of handgrip exercise, brachial artery EX-FMD was assessed before and 15 and 35 min poststress with echo and Doppler ultrasound. Shear stress was estimated as shear rate, calculated as brachial artery mean blood velocity/brachial artery diameter. Results are means ± SD. All conditions elicited significant physiological stress responses. Salivary cortisol increased from 4.6 ± 2.4 nmol/L to 10.0 ± 5.0 nmol/L (p < 0.001; condition effect: p = 0.292). Mean arterial pressure increased from 98.6 ± 12.1 mm Hg to 131.9 ± 18.7 mm Hg (p < 0.001; condition effect: p = 0.664). Exercise shear rate did not differ between conditions (p = 0.592), although it was modestly lower poststress (prestress: 72.3 ± 4.5 s−1; 15 min poststress: 70.8 ± 5.4 s−1; 35 min poststress: 70.6 ± 6.1 s−1; trial effect: p = 0.011). EX-FMD increased from prestress to 15 min poststress in all conditions (prestress: 6.2% ± 2.8%; 15 min poststress: 7.9% ± 3.2%; 35 min poststress: 6.6% ± 2.9%; trial effect: p < 0.001; condition effect: p = 0.611). In conclusion, all conditions elicited similar stress responses that transiently enhanced EX-FMD. This response may help to support muscle perfusion during stress.

Impact of controlling shear rate on flow-mediated dilation responses in the brachial artery of humans

2004 ◽  
Vol 97 (2) ◽  
pp. 499-508 ◽  
Author(s):  
Kyra E. Pyke ◽  
Erin M. Dwyer ◽  
Michael E. Tschakovsky
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Brachial Artery ◽  
Reactive Hyperemia ◽  
Flow Mediated Dilation ◽  
Response Peak ◽  
Dependent Flow ◽  
Flow Mediated Vasodilation ◽  
The Impact ◽  
Forearm Occlusion

The reactive hyperemia test (RHtest) evokes a transient increase in shear stress as a stimulus for endothelial-dependent flow-mediated vasodilation (EDFMD). We developed a noninvasive method to create controlled elevations in brachial artery (BA) shear rate (SR, estimate of shear stress), controlled hyperemia test (CHtest), and assessed the impact of this vs. the RHtest approach on EDFMD. Eight healthy subjects participated in two trials of each test on 3 separate days. For the CHtest, SR was step increased from 8 to 50 s−1, created by controlled release of BA compression during forearm heating. For the RHtest, transient increases in SR were achieved after 5 min of forearm occlusion. BA diameter and blood flow velocity (ultrasound) were measured upstream of compression and occlusion sites. Both tests elicited significant dilation (RHtest: 6.33 ± 3.12%; CHtest: 3.00 ± 1.05%). The CHtest resulted in 1) reduced between-subject SR and EDFMD variability vs. the RHtest [SR coefficient of variation (CV): 4.9% vs. 36.6%; EDFMD CV: 36.16% vs. 51.80%] and 2) virtual elimination of the impact of BA diameter on the peak EDFMD response (peak EDFMD vs. baseline diameter for RHtest, r2 = 0.64, P < 0.01, vs. CHtest, r2 = 0.14, P < 0.01). Normalization of the RHtest EDFMD response to the magnitude of the SR stimulus eliminated test differences in between-subject response variability. Reductions in trial-to-trial and day-to-day SR variability with the CHtest did not reduce EDFMD variability. Between-subject SR variability contributes to EDFMD variability with the RHtest. SR controls with the CHtest or RHtest response normalization are essential for examining EDFMD between groups differing in baseline arterial diameter.

Brachial artery flow-mediated dilation during handgrip exercise: evidence for endothelial transduction of the mean shear stimulus

2008 ◽  
Vol 294 (6) ◽  
pp. H2669-H2679 ◽  
Author(s):  
K. E. Pyke ◽  
V. Poitras ◽  
M. E. Tschakovsky
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Phase I ◽  
Brachial Artery ◽  
Muscle Activation ◽  
Flow Mediated Dilation ◽  
Stimulus Response ◽  
The Mean ◽  
Forearm Exercise ◽  
Exercise Induced

Exercise elevates shear stress in the supplying conduit artery. Although this is the most relevant physiological stimulus for flow-mediated dilation (FMD), the fluctuating pattern of shear that occurs may influence the shear stress-FMD stimulus response relationship. This study tested the hypothesis that the brachial artery FMD response to a step increase in shear is influenced by the fluctuating characteristics of the stimulus, as evoked by forearm exercise. In 16 healthy subjects, we examined FMD responses to step increases in shear rate in three conditions: stable shear upstream of heat-induced forearm vasodilation (FHStable); fluctuating shear upstream of heat-induced forearm vasodilation and rhythmic forearm cuff inflation/deflation (FHFluctuating); and fluctuating shear upstream of exercise-induced forearm vasodilation (FEStep Increase). The mean increase in shear rate (±SD) was the same in all trials (FHFluctuating: 51.69 ± 15.70 s−1; FHStable: 52.16 ± 14.10 s−1; FEStep Increase: 50.14 ± 13.03 s−1 P = 0.131). However, the FHFluctuating and FEStep Increase trials resulted in a fluctuating shear stress stimulus with rhythmic high and low shear periods that were 96.18 ± 24.54 and 11.80 ± 7.30 s−1, respectively. The initial phase of FMD (phase I) was followed by a second, delayed-onset FMD and was not different between conditions (phase I: FHFluctuating: 5.63 ± 2.15%; FHStable: 5.33 ± 1.85%; FEStep Increase: 5.30 ± 2.03%; end-trial: FHFluctuating: 7.76 ± 3.40%; FHStable: 7.00 ± 3.03%; FEStep Increase: 6.68 ± 3.04%; P = 0.196). Phase I speed also did not differ ( P = 0.685). In conclusion, the endothelium transduced the mean shear when exposed to shear fluctuations created by a typical handgrip protocol. Muscle activation did not alter the FMD response. Forearm exercise may provide a viable technique to investigate brachial artery FMD in humans.

Are the dynamic response characteristics of brachial artery flow-mediated dilation sensitive to the magnitude of increase in shear stimulus?

2008 ◽  
Vol 105 (1) ◽  
pp. 282-292 ◽  
Author(s):  
K. E. Pyke ◽  
J. A. Hartnett ◽  
M. E. Tschakovsky
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Dynamic Response ◽  
Phase I ◽  
Brachial Artery ◽  
Flow Mediated Dilation ◽  
Final Phase ◽  
Stimulus Magnitude ◽  
Brachial Artery Diameter ◽  
Response Characteristics

The purpose of this study was to determine the dynamic characteristics of brachial artery dilation in response to step increases in shear stress [flow-mediated dilation (FMD)]. Brachial artery diameter (BAD) and mean blood velocity (MBV) (Doppler ultrasound) were obtained in 15 healthy subjects. Step increases in MBV at two shear stimulus magnitudes were investigated: large (L; maximal MBV attainable), and small (S; MBV at 50% of the large step). Increase in shear rate (estimate of shear stress: MBV/BAD) was 76.8 ± 15.6 s−1 for L and 41.4 ± 8.7 s−1 for S. The peak %FMD was 14.5 ± 3.8% for L and 5.7 ± 2.1% for S ( P < 0.001). Both the L (all subjects) and the S step trials (12 of 15 subjects) elicited a biphasic diameter response with a fast initial phase (phase I) followed by a slower final phase. Relative contribution of phase I to total FMD when two phases occurred was not sensitive to shear rate magnitude ( r2 = 0.003, slope P = 0.775). Parameters quantifying the dynamics of the FMD response [time delay (TD), time constant (τ)] were also not sensitive to shear rate magnitude for both phases (phase I: TD r2 = 0.03, slope P = 0.376, τ r2 = 0.04, slope P = 0.261; final phase: TD r2 = 0.07, slope P = 0.169, τ r2 = 0.07, slope P = 0.996). These data support the existence of two distinct mechanisms, or sets of mechanisms, in the human conduit artery FMD response that are proportionally sensitive to shear stimulus magnitude and whose dynamic response is not sensitive to shear stimulus magnitude.

The impact of acute mental stress on brachial artery flow-mediated dilation differs when shear stress is elevated by reactive hyperemia versus handgrip exercise

2013 ◽  
Vol 38 (5) ◽  
pp. 498-506 ◽  
Author(s):  
Ingrid C. Szijgyarto ◽  
Trevor J. King ◽  
Jennifer Ku ◽  
Veronica J. Poitras ◽  
Brendon J. Gurd ◽  
...  
Keyword(s):  
Shear Stress ◽  
Brachial Artery ◽  
Mental Stress ◽  
Stress Reactivity ◽  
Reactive Hyperemia ◽  
Blood Velocity ◽  
Flow Mediated Dilation ◽  
Handgrip Exercise ◽  
Stress Task ◽  
The Impact

Acute mental stress can impair brachial artery (BA) flow-mediated dilation (FMD) in response to reactive hyperemia (RH) induced increases in shear stress. Handgrip exercise (HGEX) is emerging as a useful tool to increase shear stress for FMD assessment; however, the impact of acute mental stress on HGEX-FMD is unknown. The purpose of this study was to determine whether acute mental stress attenuates RH- and HGEX-induced BA-FMD to a similar extent. In 2 counterbalanced visits, 16 healthy males (19–27 years of age) performed RH-FMD or HGEX-FMD tests after a counting control task (prestress FMD) and a speech and arithmetic stress task (poststress FMD). BA diameter and mean blood velocity were assessed with echo and Doppler ultrasound, respectively. Shear stress was estimated using shear rate (SR = BA blood velocity/BA diameter). Mean arterial pressure (MAP), heart rate (HR), and salivary cortisol were used to assess stress reactivity. Results are expressed as mean ± SE. The stress task elevated MAP (Δ24.0 ± 2.6 mm Hg) and HR (Δ15.5 ± 1.9 beats·min–1), but not cortisol (prestress vs. poststress: 4.4 ± 0.7 nmol·L–1 vs. 4.7 ± 0.7 nmol·L–1; p = 0.625). There was no difference between the pre- and poststress SR stimulus for RH (p = 0.115) or HGEX (p = 0.664). RH-FMD decreased from 5.2% ± 0.6% prestress to 4.1% ± 0.5% poststress (p = 0.071); however, stress did not attenuate HGEX-FMD (prestress vs. poststress: 4.1% ± 0.6% vs. 5.3% ± 0.6%; p = 0.154). The pre- to poststress change in FMD was significantly different in the RH-FMD vs. the HGEX-FMD test (–1.1% ± 0.6% vs. +1.1% ± 0.8%; p = 0.015). In conclusion, acute mental stress appears to have a disparate impact on FMD stimulated by RH vs. HGEX induced increases in shear stress.

scholarly journals Examining the acute effects of retrograde versus low mean shear rate on flow-mediated dilation

2019 ◽  
Vol 126 (5) ◽  
pp. 1335-1342 ◽  
Author(s):  
Joshua C. Tremblay ◽  
Arman S. Grewal ◽  
Kyra E. Pyke
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Endothelial Function ◽  
Brachial Artery ◽  
Duplex Ultrasound ◽  
Flow Mediated Dilation ◽  
Relative Contribution ◽  
Stress Components ◽  
Retrograde Shear

Arterial endothelial function is acutely and chronically regulated by blood flow-associated shear stress. An acute intervention employing modest forearm cuff occlusion to simultaneously increase retrograde and decrease mean brachial artery shear rate for 30 min evokes transient impairments in flow-mediated dilation (FMD). However, the independent influence of the low mean versus the retrograde shear stress components is unclear. Healthy young adults [ n = 24 (12 women, 12 men); 22 ± 2 yr, body mass index = 25 ± 2 kg/m2 (mean ± SD)] completed three laboratory visits within 1 wk. Visits consisted of 45 min of supine rest followed by a brachial artery FMD test (duplex ultrasound) before and after a 30-min intervention: control (shear rate unchanged), cuff (mean shear rate decreased, retrograde shear rate increased), or arterial compression (mean shear rate decreased, no increase in retrograde shear rate). The mean shear rate on the compression visit was targeted to match that achieved on the cuff visit. Cuff and compression trials decreased mean shear rate to a similar extent (cuff: 43 ± 22 s−1, compression: 43 ± 21 s−1; P = 0.850) compared with control (65 ± 21 s−1; both P < 0.001), with the retrograde component elevated only in the former (cuff: −83 ± 30 s−1, compression: −7 ± 5 s−1; P < 0.001). FMD decreased by 29 ± 30% ( P < 0.001) after the cuff intervention and 32 ± 24% ( P < 0.001) after the compression trial but was unchanged on the control visit (−0.3 ± 18%; P = 0.754). This was not altered by accounting for the shear rate stimulus. An increased retrograde shear stress does not appear to be obligatory for the transient reduction in FMD achieved after a 30-min exposure to low mean shear stress. These findings provide novel mechanistic insight on the regulation of endothelial function in vivo. NEW & NOTEWORTHY Low mean and retrograde shear stress are considered atherogenic; however, their relative contribution to the acute regulation of endothelial function in humans is unclear. Matched reductions in mean shear stress (30 min), with and without increases in retrograde shear stress, elicited equivalent reductions in flow-mediated dilation in men and women. These findings afford novel insight regarding the shear stress components governing the acute (dys)regulation of conduit artery endothelial function in vivo.

scholarly journals Evidence of sex differences in the acute impact of oscillatory shear stress on endothelial function

2019 ◽  
Vol 126 (2) ◽  
pp. 314-321 ◽  
Author(s):  
Joshua C. Tremblay ◽  
Taylor V. Stimpson ◽  
Kyra E. Pyke
Keyword(s):  
Shear Stress ◽  
Sex Differences ◽  
Shear Rate ◽  
Endothelial Function ◽  
Oscillatory Shear ◽  
Flow Mediated Dilation ◽  
Similar Stimulus ◽  
Men And Women ◽  
Oscillatory Shear Stress ◽  
The Impact

Acutely imposed oscillatory shear stress (OSS) reduces reactive hyperemia flow-mediated dilation (RH-FMD) in conduit arteries of men; however, whether a similar impairment occurs in women or with FMD in response to a controlled, sustained shear stress stimulus (SS-FMD) is unknown. The purpose of this study was to determine the impact of OSS on RH-FMD and SS-FMD in men and women. OSS was provoked in the brachial artery using a 30-min forearm cuff inflation (70 mmHg). Healthy men [ n = 16, 25 yr (SD 3)] and women [ n = 16, 21 yr (SD 2)] completed the OSS intervention twice (separate days). Brachial artery endothelial function was assessed pre- and postintervention via either RH-FMD or 6 min of handgrip SS-FMD using Duplex ultrasound. The RH-FMD stimulus was calculated as shear rate area under the curve 60 s postdeflation (SRAUC60), whereas SS-FMD shear rate was targeted to produce a similar stimulus pre- and postintervention. The OSS intervention decreased RH-FMD in both sexes [men: 6.2% (SD 3.4) to 5.2% (SD 3.0); women: 5.4% (SD 2.0) to 3.1% (SD 1.8), P < 0.001), although this was accompanied by a reduced SRAUC60. There was no significant effect of the intervention on RH-FMD with SRAUC60 as a covariate ( P = 0.310). Handgrip exercise elicited a similar stimulus before and after the intervention ( P = 0.287) in men and women ( P = 0.873). Men demonstrated blunted SS-FMD [4.8% (SD 1.9) to 3.2% (SD 1.9), P < 0.001], whereas women displayed preserved SS-FMD following the intervention [3.5% (SD 1.9) to 4.0% (SD 1.9), P = 0.061]. The lower SS-FMD in men but not women following OSS provides evidence of sex differences in the effects of OSS on conduit artery endothelial function. NEW & NOTEWORTHY Acute exposure to oscillatory shear stress induces transient endothelial dysfunction in men; however, whether women experience similar impairments is unknown. Following acutely imposed oscillatory shear stress, there was a decrease in flow-mediated dilation stimulated by a physiologically relevant sustained increase in shear stress in men but not in premenopausal women. These findings demonstrate, for the first time in humans that there are sex differences in the impact of oscillatory shear stress on endothelial function.

scholarly journals Opposing effects of shear-mediated dilation and myogenic constriction on artery diameter in response to handgrip exercise in humans

2015 ◽  
Vol 119 (8) ◽  
pp. 858-864 ◽  
Author(s):  
Ceri L. Atkinson ◽  
Howard H. Carter ◽  
Louise H. Naylor ◽  
Ellen A. Dawson ◽  
Petra Marusic ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Shear Stress ◽  
Shear Rate ◽  
Arterial Pressure ◽  
Brachial Artery ◽  
Muscle Sympathetic Nerve Activity ◽  
Handgrip Exercise ◽  
Brachial Artery Diameter ◽  
The Impact

While the impact of changes in blood flow and shear stress on artery function are well documented, the acute effects of increases in arterial pressure are less well described in humans. The aim of this study was to assess the effect of 30 min of elevated blood pressure, in the absence of changes in shear stress or sympathetic nervous system (SNS) activation, on conduit artery diameter. Ten healthy male subjects undertook three sessions of 30 min unilateral handgrip exercise at 5, 10, and 15% of maximal voluntary contractile (MVC) strength. Brachial artery shear rate and blood flow profiles were measured simultaneously during exercise in the active and contralateral resting arms. Bilateral brachial artery diameter was simultaneously assessed before and immediately postexercise. In a second experiment, six subjects repeated the 15% MVC condition while continuous vascular measurements were collected during muscle sympathetic nerve activity (MSNA) assessment using peroneal microneurography. We found that unilateral handgrip exercise at 5, 10, and 15% MVC strength induced stepwise elevations in blood pressure ( P < 0.01, Δmean arterial pressure: 7.06 ± 2.44, 8.50 ± 2.80, and 18.35 ± 3.52 mmHg, P < 0.01). Whereas stepwise increases were evident in shear rate in the exercising arm ( P < 0.001), no changes were apparent in the nonexercising limb ( P = 0.42). Brachial artery diameter increased in the exercising arm ( P = 0.02), but significantly decreased in the nonexercising arm ( P = 0.03). At 15% MVC, changes in diameter were significantly different between arms (interaction effect: P = 0.01), whereas this level of exertion produced no significant changes in MSNA. We conclude that acute increases in transmural pressure, independent of shear rate and changes in SNS activation, reduce arterial caliber in normotensive humans in vivo. These changes in diameter were mitigated by exercise-induced elevations in shear rate in the active limb.

scholarly journals Fluctuation in shear rate, with unaltered mean shear rate, improves brachial artery flow-mediated dilation in healthy, young men

2019 ◽  
Vol 126 (6) ◽  
pp. 1687-1693 ◽  
Author(s):  
Sophie M. Holder ◽  
Ellen A. Dawson ◽  
Áine Brislane ◽  
Jonny Hisdal ◽  
Daniel J. Green ◽  
...  
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Endothelial Function ◽  
Brachial Artery ◽  
Negative Pressure ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Flow Mediated Dilation ◽  
Conduit Artery ◽  
Artery Flow

Increase in mean shear stress represents an important and potent hemodynamic stimulus to improve conduit artery endothelial function in humans. No previous study has examined whether fluctuations in shear rate patterns, without altering mean shear stress, impacts conduit artery endothelial function. This study examined the hypothesis that 30-min exposure to fluctuations in shear rate patterns, in the presence of unaltered mean shear rate, improves brachial artery flow-mediated dilation. Fifteen healthy men (27.3 ± 5.0 yr) completed the study. Bilateral brachial artery flow-mediated dilation was assessed before and after unilateral exposure to 30 min of intermittent negative pressure (10 s, −40mmHg; 7 s, 0 mmHg) to induce fluctuation in shear rate, while the contralateral arm was exposed to a resting period. Negative pressure significantly increased shear rate, followed by a decrease in shear rate upon pressure release (both P < 0.001). Across the 30-min intervention, mean shear rate was not different compared with baseline ( P = 0.458). A linear mixed model revealed a significant effect of time observed for flow-mediated dilation ( P = 0.029), with exploratory post hoc analysis showing an increase in the intervention arm (∆FMD +2.0%, P = 0.008), but not in the contralateral control arm (∆FMD +0.5%, P = 0.664). However, there was no effect for arm ( P = 0.619) or interaction effect ( P = 0.096). In conclusion, we found that fluctuations in shear patterns, with unaltered mean shear, improves brachial artery flow-mediated dilation. These novel data suggest that fluctuations in shear pattern, even in the absence of altered mean shear, represent a stimulus to acute change in endothelial function in healthy individuals. NEW & NOTEWORTHY Intermittent negative pressure applied to the forearm induced significant fluctuations in antegrade and retrograde shear rate, while mean shear was preserved relative to baseline. Our exploratory study revealed that brachial artery flow-mediated dilation was significantly improved following 30-min exposure to intermittent negative pressure. Fluctuations in blood flow or shear rate, with unaltered mean shear, may have important implications for vascular health; however, further research is required to identify the underlying mechanisms and potential long-term health benefits.

Exercise-mediated changes in conduit artery wall thickness in humans: role of shear stress

2011 ◽  
Vol 301 (1) ◽  
pp. H241-H246 ◽  
Author(s):  
Dick H. J. Thijssen ◽  
Ellen A. Dawson ◽  
Inge C. L. van den Munckhof ◽  
Toni M. Tinken ◽  
Evert den Drijver ◽  
...  
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Exercise Training ◽  
Wall Thickness ◽  
Brachial Artery ◽  
Arterial Wall ◽  
Cuff Inflation ◽  
Artery Wall ◽  
Brachial Artery Diameter ◽  
Exercise Induced

Episodic increases in shear stress have been proposed as a mechanism that induces training-induced adaptation in arterial wall remodeling in humans. To address this hypothesis in humans, we examined bilateral brachial artery wall thickness using high-resolution ultrasound in healthy men across an 8-wk period of bilateral handgrip training. Unilaterally, shear rate was attenuated by cuff inflation around the forearm to 60 mmHg. Grip strength, forearm volume, and girth improved similarly between the limbs. Acute bouts of handgrip exercise increased shear rate ( P < 0.005) in the noncuffed limb, whereas cuff inflation successfully decreased exercise-induced increases in shear. Brachial blood pressure responses similarly increased during exercise in both the cuffed and noncuffed limbs. Handgrip training had no effect on baseline brachial artery diameter, blood flow, or shear rate but significantly decreased brachial artery wall thickness after 6 and 8 wk (ANOVA, P < 0.001) and wall-to-lumen ratio after week 8 (ANOVA, P = 0.005). The magnitude of decrease in brachial artery wall thickness and wall-to-lumen ratio after exercise training was similar in the noncuffed and cuffed arms. These results suggest that exercise-induced changes in shear rate are not obligatory for arterial wall remodeling during a period of 8 wk of exercise training in healthy humans.

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