Microneurographic characterization of sympathetic responses during 1-leg exercise in young and middle-aged humans

Notarius, Catherine F.; Millar, Philip J.; Doherty, Connor J.; Incognito, Anthony V.; Haruki, Nobuhiko; O’Donnell, Emma; Floras, John S.

doi:10.1139/apnm-2018-0101

Cited by 11 publications

(26 citation statements)

References 44 publications

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“…The purpose of their recruitment was to determine how closely sympathetic responses of trained HFrEF patients approximated those of middle-aged healthy subjects. Although the mean age of the control group was slightly lower than that of participants with HFrEF, in healthy subjects age does not affect the MSNA burst frequency response to exercise at these intensities (36).…”

Section: Limitationsmentioning

confidence: 67%

Training heart failure patients with reduced ejection fraction attenuates muscle sympathetic nerve activation during mild dynamic exercise

Notarius

Millar

Keir

et al. 2019

American Journal of Physiology-Regulatory, Integrative and Comp

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We have shown that muscle sympathetic nerve activity (MSNA) is elevated at rest in patients with heart failure due to reduced ejection fraction (HFrEF) and, in contrast to healthy subjects, increases during moderate dynamic 1‐leg exercise. We hypothesized that exercise training in HFrEF may reduce MSNA during both mild and moderate intensity 1‐leg dynamic exercise and static handgrip; attenuate the muscle metaboreflex; and improve skin blood flow. We studied 27 stable, medicated HFrEF patients (6 women; mean age 65 ± 2 SE [range 42 to 80] years; mean left ventricular ejection fraction 30 ± 1% [range 12–40]); of either ischemic (n=18) or non‐ischemic (n=9) etiology, both before and after 6 months of cardiac rehabilitation (aerobic exercise for 45 minutes, 5 times per week at 60–70 % of VO2peak); plus 18 healthy, age and sex‐matched, medication‐free volunteers (6 women; mean age 57 ± 2 [range 48 to 72]). Before and after training, we assessed VO2peak (open‐circuit spirometry); the skin blood flow (SBF) response to reactive hyperemia (laser flowtometry); and fibular MSNA (microneurography) at rest (n=18), during 1‐leg cycling (2 min each unloaded and at 50% of VO2peak, n=16) and, to assess the muscle metaboreflex, during post‐handgrip ischemia (PHGI) after 2 min of 30% static handgrip (HG). In HFrEF, pre‐training VO2peak and skin vasodilatation were lower (P<0.001) and resting MSNA higher compared to controls (P=0.01). Exercise training improved VO2peak by 3.0±1.0 ml·kg−1·min−1 (P<0.001) and increased the SBF vasdilatory response in HFrEF to a mean value similar to controls (P=0.78). Relative to pre‐training, resting MSNA decreased by 6.0±2.0 bursts/min (P=0.01, N=18) and 7.3±3.4 burst/100 heartbeats (P=0.04). During 1‐leg cycling, MSNA decreased in control (P=0.01) but increased in HFrEF (P<0.001). Exercise training attenuated MSNA burst frequency and incidence during unloaded (P=0.04) but not loaded cycling (P=0.34). The rise in MSNA burst frequency during HG in HFrEF was unaffected by training, but its elevation during PHGI was abolished (P<0.05). We conclude that the exaggerated metaboreflex of HFrEF is attenuated by exercise training. This may contribute to a lower MSNA during mild but not moderate intensity cycling. Support or Funding Information Supported by Heart and Stroke Foundation of Ontario and Canadian Institutes for Health Research This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

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Section: Limitationsmentioning

confidence: 67%

Training heart failure patients with reduced ejection fraction attenuates muscle sympathetic nerve activation during mild dynamic exercise

Notarius

Millar

Keir

et al. 2019

American Journal of Physiology-Regulatory, Integrative and Comp

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“…) and single‐leg exercise (Notarius et al . ), which may have augmented the reductions in pressure for these patients following ET A receptor antagonism. Based on the current reductions in leg MAP, systemic diastolic blood pressure and concomitant central cardiovascular responses (increase in heart rate, stroke volume and cardiac output) in the present investigation, we speculate that acutely administered ET A receptor antagonism in both legs or systemically during a whole body exercise modality, where such central cardiovascular responses are more limited, may deleteriously lower systemic MAP in hypertensive individuals.…”

Section: Discussionmentioning

confidence: 99%

The role of endothelin A receptors in peripheral vascular control at rest and during exercise in patients with hypertension

Craig

Broxterman

Cerbie

et al. 2019

The Journal of Physiology

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Key pointsr Exercise in patients with hypertension can be accompanied by an abnormal cardiovascular response that includes attenuated blood flow and an augmented pressor response.r Endothelin-1, a very potent vasoconstrictor, is a key modulator of blood flow and pressure during in health and has been implicated as a potential cause of the dysfunction in hypertension.r We assessed the role of endothelin-1, acting through endothelin A (ET A ) receptors, in modulating the central and peripheral cardiovascular responses to exercise in patients with hypertension via local antagonism of these receptors during exercise.r ET A receptor antagonism markedly increased leg blood flow, vascular conductance, oxygen delivery, and oxygen consumption during exercise; interestingly, these changes occurred in the presence of reduced leg perfusion pressure, indicating that these augmentations were driven by changes in vascular resistance.r These data indicate that ET A receptor antagonism could be a viable therapeutic approach to improve blood flow during exercise in hypertension.Abstract Patients with hypertension can exhibit impaired muscle blood flow and exaggerated increases in blood pressure during exercise. While endothelin (ET)-1 plays a role in regulating blood flow and pressure during exercise in health, little is known about the role of ET-1 in the cardiovascular response to exercise in hypertension. Therefore, eight volunteers diagnosed with hypertension were studied during exercise with either saline or BQ-123 (ET A receptor antagonist) Jesse C. Craig completed his PhD at Kansas State University in 2018. He is currently a postdoctoral fellow in the Utah Vascular Research Laboratory under the tutelage of Professor Joel D. Trinity. This investigation was carried out as part of an NIH T32 fellowship through the Divisions of Cardiovascular Medicine and Geriatrics. Jesse is interested in how local factors (nitric oxide, reactive oxygen species, endothelin) influence oxygen delivery and utilization in health and disease. The long-term goal of his research is to gain a greater understanding of the mechanisms contributing to dysfunction at the vascular and skeletal muscle systems interface. infusion following a 2-week withdrawal of anti-hypertensive medications. The common femoral artery and vein were catheterized for drug infusion, blood collection and blood pressure measurements, and leg blood flow was measured by Doppler ultrasound. Patients exercised at both absolute (0, 5, 10, 15 W) and relative (40, 60, 80% peak power) intensities. BQ-123 increased blood flow at rest (79 ± 87 ml/min; P = 0.03) and augmented the exercise-induced hyperaemia at most intensities (80% saline: 3818±1222 vs. BQ-123: 4812±1469 ml/min; P = 0.001). BQ-123 reduced leg MAP at rest (−8 ± 4 mmHg; P < 0.001) and lower intensities (0-10 W; P < 0.05). Systemic diastolic blood pressure was reduced (0 W, 40%; P < 0.05), but systemic MAP was defended by an increased cardiac output. The exercise pressor response ( MAP) did not differ between conditions (80% sa...

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“…However, several studies measured MSNA during head-down tilt and lower body negative pressure in elderly individuals and found that cardiopulmonary baroreflex control of sympathetic vasomotor outflow is not impaired with age in healthy humans Tanaka et al, 1999). To the best of our knowledge, no study has examined the effect of age on MSNA during dynamic exercise, except that of Notarius et al (2019); they found similar reductions in MSNA burst frequency (BF) during mild one-legged cycling between young (23 ± 1 years) and middle-aged (57 ± 2 years) healthy subjects. Thus, muscle pump-induced inhibition of sympathetic vasomotor outflow (i.e., cardiopulmonary baroreflex) during low-intensity exercise is apparently preserved in middle-aged individuals.…”

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confidence: 99%

“…Thus, muscle pump-induced inhibition of sympathetic vasomotor outflow (i.e., cardiopulmonary baroreflex) during low-intensity exercise is apparently preserved in middle-aged individuals. However, muscle pumping may be reduced in older subjects (Notarius et al, 2019;Proctor & Parker, 2006) because of a decrease in limb muscle mass (Frontera et al, 2000) and/or changes in venous compliance (Olsen & Lanne, 1998) with advancing age. Notarius et al (2019) did not estimate variables associated with the muscle pump-induced increase in venous return (e.g., a change in central venous pressure; CVP) that loads cardiopulmonary baroreceptors during cycling.…”

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confidence: 99%

“…However, muscle pumping may be reduced in older subjects (Notarius et al, 2019;Proctor & Parker, 2006) because of a decrease in limb muscle mass (Frontera et al, 2000) and/or changes in venous compliance (Olsen & Lanne, 1998) with advancing age. Notarius et al (2019) did not estimate variables associated with the muscle pump-induced increase in venous return (e.g., a change in central venous pressure; CVP) that loads cardiopulmonary baroreceptors during cycling. Therefore, to clarify the effect of age on sympathetic vasomotor outflow during dynamic exercise, it is necessary to investigate MSNA and CVP responses during cycling in much older (>65 years) individuals (Orimo et al, 2006).…”

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confidence: 99%

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Sympathetic vasomotor outflow during low‐intensity leg cycling in healthy older males

Katayama

Saito

Ishida

et al. 2022

Experimental Physiology

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Muscle sympathetic nerve activity (MSNA) is reduced during low-intensity dynamic leg exercise in young males. It is suggested that this inhibition is mediated by loading of the cardiopulmonary baroreceptors. The purpose of this study was to clarify the impact of age on MSNA during dynamic leg exercise. Nine younger males (YM, mean ± SD, 20 ± 1 years) and nine older males (OM, 72 ± 3 years) completed the study. The subjects performed two 4-min cycling exercises at 10% of their heart rate reserve using a cycle ergometer in a semirecumbent position (MSNA and estimated central venous pressure (eCVP) trials). MSNA was recorded via microneurography of the left radial nerve. The CVP was estimated based on peripheral venous pressure, which was monitored using a cannula in the right large antecubital vein. The magnitude of the increase in mean arterial blood pressure during leg cycling was larger in OM (+9.3 ± 5.5 mmHg) compared with YM (+2.8 ± 4.7 mmHg). MSNA burst frequency was decreased during cycling in both YM (-8.1 ± 3.8 bursts/min) and OM (-10.6 ± 3.3 bursts/min), but no significant difference was found between the two groups. The eCVP increased during exercise in both groups, and there was no difference in the changes in eCVP between YM (+1.1 ± 0.4 mmHg) and OM (+1.2 ± 0.7 mmHg). These data indicate that inhibition of sympathetic vasomotor outflow during low-intensity cycling appears in OM as seen in YM. It is possible that the muscle pump-induced loading of the cardiopulmonary baroreflex is preserved during cycling in healthy older males.

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Microneurographic characterization of sympathetic responses during 1-leg exercise in young and middle-aged humans

Cited by 11 publications

References 44 publications

Training heart failure patients with reduced ejection fraction attenuates muscle sympathetic nerve activation during mild dynamic exercise

Training heart failure patients with reduced ejection fraction attenuates muscle sympathetic nerve activation during mild dynamic exercise

The role of endothelin A receptors in peripheral vascular control at rest and during exercise in patients with hypertension

Sympathetic vasomotor outflow during low‐intensity leg cycling in healthy older males

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