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Bradley AP, Roehl AS, Smith J, McGrath R, Hackney KJ. Muscle specific declines in oxygen saturation during acute ambulation with hands-free and conventional mobility devices. Front Sports Act Living 2023; 5:1210880. [PMID: 38155751 PMCID: PMC10753011 DOI: 10.3389/fspor.2023.1210880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Accepted: 11/27/2023] [Indexed: 12/30/2023] Open
Abstract
Disuse is associated with reduced muscle oxygen saturation (SmO2). Improving oxygen delivery to tissues is important for healing, preventing muscle atrophy, and reducing the risk of deep vein thrombosis. Mobility devices are used during disuse periods to ambulate and protect the injured limb. This study examined SmO2 in walking and ambulation with various mobility devices. Thirty-eight participants randomly completed four, ten-minute trials which included: (1) walking, (2) medical kneeling scooter (MKS), (3) hands-free crutch (HFC), and (4) axillary crutch (AC). During each trial, near infrared spectroscopy sensors were placed on the vastus lateralis (VL), biceps femoris (BF), and lateral gastrocnemius (LG) of the right limb. Compared to walking, all mobility devices showed a decline in SmO2 in the VL of ∼10% (mean ± SD; 75% ± 12%-65% ± 17%, P < 0.05). In the BF, SmO2 declined ∼9% in AC compared to walking (76% ± 12%-67% ± 17%, P = 0.025). In the LG, SmO2 declined in AC (64% ± 16%) compared to MKS (70% ± 15%, P = 0.005). There were no differences in LG SmO2 compared to walking (69% ± 13%) in MKS (P > 0.05) or HFC (65% ± 15%, P > 0.05). In young, healthy volunteers, the use of mobility devices altered muscle oxygenation in several muscles. AC reduced muscle oxygenation in the VL, BF, and LG; while MKS and HFC maintained BF and LG muscle oxygenation at a level consistent with ambulatory walking.
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Affiliation(s)
| | | | | | | | - Kyle J. Hackney
- Department of Health, Nutrition, and Exercise Sciences, North Dakota State University, Fargo, ND, United States
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2
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Thurston TS, Weavil JC, Georgescu VP, Wan HY, Birgenheier NM, Morrissey CK, Jessop JE, Amann M. The exercise pressor reflex - a pressure-raising mechanism with a limited role in regulating leg perfusion during locomotion in young healthy men. J Physiol 2023; 601:4557-4572. [PMID: 37698303 PMCID: PMC10592099 DOI: 10.1113/jp284870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Accepted: 08/15/2023] [Indexed: 09/13/2023] Open
Abstract
We investigated the role of the exercise pressor reflex (EPR) in regulating the haemodynamic response to locomotor exercise. Eight healthy participants (23 ± 3 years,V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ : 49 ± 6 ml/kg/min) performed constant-load cycling exercise (∼36/43/52/98%V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ ; 4 min each) without (CTRL) and with (FENT) lumbar intrathecal fentanyl attenuating group III/IV locomotor muscle afferent feedback and, thus, the EPR. To avoid different respiratory muscle metaboreflex and arterial chemoreflex activation during FENT, subjects mimicked the ventilatory response recorded during CTRL. Arterial and leg perfusion pressure (femoral arterial and venous catheters), femoral blood flow (Doppler-ultrasound), microvascular quadriceps blood flow index (indocyanine green), cardiac output (inert gas breathing), and systemic and leg vascular conductance were quantified during exercise. There were no cardiovascular and ventilatory differences between conditions at rest. Pulmonary ventilation, arterial blood gases and oxyhaemoglobin saturation were not different during exercise. Furthermore, cardiac output (-2% to -12%), arterial pressure (-7% to -15%) and leg perfusion pressure (-8% to -22%) were lower, and systemic (up to 16%) and leg (up to 27%) vascular conductance were higher during FENT compared to CTRL. Leg blood flow, microvascular quadriceps blood flow index, and leg O2 -transport and utilization were not different between conditions (P > 0.5). These findings reflect a critical role of the EPR in the autonomic control of the heart, vasculature and, ultimately, arterial pressure during locomotor exercise. However, the lack of a net effect of the EPR on leg blood flow challenges the idea of this cardiovascular reflex as a key determinant of leg O2 -transport during locomotor exercise in healthy, young individuals. KEY POINTS: The role of the exercise pressor reflex (EPR) in regulating leg O2 -transport during human locomotion remains uncertain. We investigated the influence of the EPR on the cardiovascular response to cycling exercise. Lumbar intrathecal fentanyl was used to block group III/IV leg muscle afferents and debilitate the EPR at intensities ranging from 30% to 100%V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ . To avoid different respiratory muscle metaboreflex and arterial chemoreflex activation during exercise with blocked leg muscle afferents, subjects mimicked the ventilatory response recorded during control exercise. Afferent blockade increased leg and systemic vascular conductance, but reduced cardiac output and arterial-pressure, with no net effect on leg blood flow. The EPR influenced the cardiovascular response to cycling exercise by contributing to the autonomic control of the heart and vasculature, but did not affect leg blood flow. These findings challenge the idea of the EPR as a key determinant of leg O2 -transport during locomotor exercise in healthy, young individuals.
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Affiliation(s)
- Taylor S. Thurston
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, UT
| | - Joshua C. Weavil
- Geriatric Research, Education, and Clinical Center, Salt Lake City VAMC, UT
| | - Vincent P. Georgescu
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, UT
| | - Hsuan-Yu Wan
- Department of Anesthesiology, University of Utah, Salt Lake City, UT
| | | | | | - Jacob E. Jessop
- Department of Anesthesiology, University of Utah, Salt Lake City, UT
| | - Markus Amann
- Department of Anesthesiology, University of Utah, Salt Lake City, UT
- Geriatric Research, Education, and Clinical Center, Salt Lake City VAMC, UT
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3
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Alpenglow JK, Bunsawat K, Francisco MA, Craig JC, Iacovelli JJ, Ryan JJ, Wray DW. Evidence of impaired functional sympatholysis in patients with heart failure with preserved ejection fraction. Am J Physiol Heart Circ Physiol 2023; 325:H806-H813. [PMID: 37566111 PMCID: PMC10659321 DOI: 10.1152/ajpheart.00450.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 08/05/2023] [Accepted: 08/10/2023] [Indexed: 08/12/2023]
Abstract
Exercising muscle blood flow is reduced in patients with heart failure with a preserved ejection fraction (HFpEF), which may be related to disease-related changes in the ability to overcome sympathetic nervous system (SNS)-mediated vasoconstriction during exercise, (i.e., "functional sympatholysis"). Thus, in 12 patients with HFpEF (69 ± 7 yr) and 11 healthy controls (Con, 69 ± 4 yr), we examined forearm blood flow (FBF), mean arterial pressure (MAP), and forearm vascular conductance (FVC) during rhythmic handgrip exercise (HG) at 30% of maximum voluntary contraction with or without lower-body negative pressure (LBNP, -20 mmHg) to increase SNS activity and elicit peripheral vasoconstriction. SNS-mediated vasoconstrictor responses were determined as LBNP-induced changes (%Δ) in FVC, and the "magnitude of sympatholysis" was calculated as the difference between responses at rest and during exercise. At rest, the LBNP-induced change in FVC was significantly lesser in HFpEF compared with Con (HFpEF: -9.5 ± 5.5 vs. Con: -21.0 ± 8.0%; P < 0.01). During exercise, LBNP-induced %ΔFVC was significantly attenuated in Con compared with rest (HG: -5.8 ± 6.0%; P < 0.05) but not in HFpEF (HG: -9.9 ± 2.5%; P = 0.88). Thus, the magnitude of sympatholysis was lesser in HFpEF compared with Con (HFpEF: 0.4 ± 4.7 vs. Con: -15.2 ± 11.8%; P < 0.01). These data demonstrate a diminished ability to attenuate SNS-mediated vasoconstriction in HFpEF and provide new evidence suggesting impaired functional sympatholysis in this patient group.NEW & NOTEWORTHY Data from the current study suggest that functional sympatholysis, or the ability to adequately attenuate sympathetic nervous system (SNS)-mediated vasoconstriction during exercise, is impaired in patients with heart failure with preserved ejection fraction (HFpEF). These observations extend the current understanding of HFpEF pathophysiology by implicating inadequate functional sympatholysis as an important contributor to reduced exercising muscle blood flow in this patient group.
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Affiliation(s)
- Jeremy K Alpenglow
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah, United States
| | - Kanokwan Bunsawat
- Division of Geriatrics, Department of Internal Medicine, University of Utah, Salt Lake City, Utah, United States
- Geriatric Research, Education, and Clinical Center, Veterans Affairs Medical Center, Salt Lake City, Utah, United States
| | - Michael A Francisco
- Division of Geriatrics, Department of Internal Medicine, University of Utah, Salt Lake City, Utah, United States
- Geriatric Research, Education, and Clinical Center, Veterans Affairs Medical Center, Salt Lake City, Utah, United States
| | - Jesse C Craig
- Division of Geriatrics, Department of Internal Medicine, University of Utah, Salt Lake City, Utah, United States
- Geriatric Research, Education, and Clinical Center, Veterans Affairs Medical Center, Salt Lake City, Utah, United States
| | - Jarred J Iacovelli
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah, United States
| | - John J Ryan
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of Utah, Salt Lake City, Utah, United States
| | - D Walter Wray
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah, United States
- Division of Geriatrics, Department of Internal Medicine, University of Utah, Salt Lake City, Utah, United States
- Geriatric Research, Education, and Clinical Center, Veterans Affairs Medical Center, Salt Lake City, Utah, United States
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4
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Horiuchi M. Effects of arm cranking exercise on muscle oxygenation between active and inactive muscles in people with spinal cord injury. J Spinal Cord Med 2021; 44:931-939. [PMID: 32379545 PMCID: PMC8725684 DOI: 10.1080/10790268.2020.1754649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
Objective: We investigated the effects of the incremental arm-cranking exercise (ACE) on tissue oxygen saturation (StO2) between active and inactive muscles, and the relationship between peak oxygen uptake (VO2peak) and changes in the StO2 in inactive muscles.Design: Observational study.Setting: Community-based supervised intervention.Participants: The participants were individuals with motor and sensory complete spinal cord injury (complete SCI; n = 8) and motor complete but sensory incomplete SCI (incomplete SCI; n = 8), and able-bodied (AB) individuals (n = 8) matched for age, height, and body mass index.Intervention: The ACE was performed at a rate increasing by 10 watts min-1 until exhaustion.Outcome Measures: VO2peak, heart rate (HR), and StO2.Results: While VO2peak was similar among the groups, peak HR was significantly higher in both SCI groups than in the AB (P < 0.05). In active muscles (biceps brachii), no differences in the StO2 were observed among the groups (P > 0.05). In inactive muscles (vastus lateralis), the StO2 in the AB and the incomplete SCI began to decrease at approximately 40% of the peak work rate; however, they remained unchanged in the complete SCI. The reductions in StO2 in the AB were significantly greater than in the incomplete SCI.Conclusions: These results suggest that sympathetic vasoconstriction occurred in the incomplete SCI and AB, although it did not occur in the complete SCI, probably due to a reduction in sympathetic nerve activity. Sympathetic vasoconstriction in inactive muscles may not contribute to an individual's VO2peak regardless of their group.
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Affiliation(s)
- Masahiro Horiuchi
- Northern Region Life Long Sports Center, Hokusho University, Ebetsu-city, Hokkaido, Japan,Division of Human Environmental Science, Mount Fuji Research Institute, Fuji-yoshida-city, Yamanashi, Japan,Correspondence to: Masahiro Horiuchi, Northern Region Life Long Sports Center, Hokusho University, Bunkyoudai-23, Ebetsu-ity, Hokkaido, Japan, 0698511;Ph: +81-555-72-6198. E-mail:
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5
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The influence of short-term high-altitude acclimatization on cerebral and leg tissue oxygenation post-orthostasis. Eur J Appl Physiol 2021; 121:3095-3102. [PMID: 34319446 DOI: 10.1007/s00421-021-04765-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 07/06/2021] [Indexed: 10/20/2022]
Abstract
PURPOSE Orthostasis at sea level decreases brain tissue oxygenation and increases risk of syncope. High altitude reduces brain and peripheral muscle tissue oxygenation. This study determined the effect of short-term altitude acclimatization on cerebral and peripheral leg tissue oxygenation index (TOI) post-orthostasis. METHOD Seven lowlanders completed a supine-to-stand maneuver at sea level (450 m) and for 3 consecutive days at high altitude (3776 m). Cardiorespiratory measurements and near-infrared spectroscopy-derived oxygenation of the frontal lobe (cerebral TOI) and vastus lateralis (leg TOI) were measured at supine and 5-min post-orthostasis. RESULTS After orthostasis at sea level, cerebral TOI decreased [mean Δ% (95% confidential interval): - 4.5%, (- 7.5, - 1.5), P < 0.001], whilst leg TOI was unchanged [- 4.6%, (- 10.9, 1.7), P = 0.42]. High altitude had no effect on cerebral TOI following orthostasis [days 1-3: - 2.3%, (- 5.3, 0.7); - 2.4%, (- 5.4, 0.6); - 2.1%, (- 5.1, 0.9), respectively, all P > 0.05], whereas leg TOI decreased [days 1-3: - 12.0%, (- 18.3, - 5.7); - 12.1%, (- 18.4, - 5.8); - 10.2%, (- 16.5, - 3.9), respectively, all P < 0.001]. This response did not differ with days spent at high altitude, despite evidence of cardiorespiratory acclimatization [increased peripheral oxygen saturation (supine: P = 0.01; stand: P = 0.02) and decreased end-tidal carbon dioxide (supine: P = 0.003; stand: P = 0.01)]. CONCLUSION Cerebral oxygenation is preferentially maintained over leg oxygenation post-orthostasis at high altitude, suggesting different vascular regulation between cerebral and peripheral circulations. Short-term acclimatization to high altitude did not alter cerebral and leg oxygenation responses to orthostasis.
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6
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Terwoord JD, Racine ML, Hearon CM, Luckasen GJ, Dinenno FA. ATP and acetylcholine interact to modulate vascular tone and α 1-adrenergic vasoconstriction in humans. J Appl Physiol (1985) 2021; 131:566-574. [PMID: 34166116 DOI: 10.1152/japplphysiol.00205.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The vascular endothelium senses and integrates numerous inputs to regulate vascular tone. Recent evidence reveals complex signal processing within the endothelium, yet little is known about how endothelium-dependent stimuli interact to regulate blood flow. We tested the hypothesis that combined stimulation of the endothelium with adenosine triphosphate (ATP) and acetylcholine (ACh) elicits greater vasodilation and attenuates α1-adrenergic vasoconstriction compared with combination of ATP or ACh with the endothelium-independent dilator sodium nitroprusside (SNP). We assessed forearm vascular conductance (FVC) in young adults (6 women, 7 men) during local intra-arterial infusion of ATP, ACh, or SNP alone and in the following combinations: ATP + ACh, SNP + ACh, and ATP + SNP, wherein the second dilator was coinfused after attaining steady state with the first dilator. By design, each dilator evoked a similar response when infused separately (ΔFVC, ATP: 48 ± 4; ACh: 57 ± 6; SNP: 53 ± 6 mL·min-1·100 mmHg-1; P ≥ 0.62). Combined infusion of the endothelium-dependent dilators evoked greater vasodilation than combination of either dilator with SNP (ΔFVC from first dilator, ATP + ACh: 45 ± 9 vs. SNP + ACh: 18 ± 7 and ATP + SNP: 26 ± 4 mL·min-1·100 mmHg-1, P < 0.05). Phenylephrine was subsequently infused to evaluate α1-adrenergic vasoconstriction. Phenylephrine elicited less vasoconstriction during infusion of ATP or ACh versus SNP (ΔFVC, -25 ± 3 and -29 ± 4 vs. -48 ± 3%; P < 0.05). The vasoconstrictor response to phenylephrine was further diminished during combined infusion of ATP + ACh (-13 ± 3%; P < 0.05 vs. ATP or ACh alone) and was less than that observed when either dilator was combined with SNP (SNP + ACh: -26 ± 3%; ATP + SNP: -31 ± 4%; both P < 0.05 vs. ATP + ACh). We conclude that endothelium-dependent agonists interact to elicit vasodilation and limit α1-adrenergic vasoconstriction in humans.NEW & NOTEWORTHY The results of this study highlight the vascular endothelium as a critical site for integration of vasomotor signals in humans. To our knowledge, this is the first study to demonstrate that combined stimulation of the endothelium with ATP and ACh results in enhanced vasodilation compared with combination of either ATP or ACh with an endothelium-independent dilator. Furthermore, we show that ATP and ACh interact to modulate α1-adrenergic vasoconstriction in human skeletal muscle in vivo.
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Affiliation(s)
- Janée D Terwoord
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado
| | - Matthew L Racine
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado
| | - Christopher M Hearon
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado
| | - Gary J Luckasen
- Medical Center of the Rockies Foundation, University of Colorado Health, Loveland, Colorado
| | - Frank A Dinenno
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado
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7
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Spectral Analysis of Muscle Hemodynamic Responses in Post-Exercise Recovery Based on Near-Infrared Spectroscopy. SENSORS 2021; 21:s21093072. [PMID: 33924973 PMCID: PMC8125689 DOI: 10.3390/s21093072] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 04/14/2021] [Accepted: 04/20/2021] [Indexed: 12/02/2022]
Abstract
Spectral analysis of blood flow or blood volume oscillations can help to understand the regulatory mechanisms of microcirculation. This study aimed to explore the relationship between muscle hemodynamic response in the recovery period and exercise quantity. Fifteen healthy subjects were required to perform two sessions of submaximal plantarflexion exercise. The blood volume fluctuations in the gastrocnemius lateralis were recorded in three rest phases (before and after two exercise sessions) using near-infrared spectroscopy. Wavelet transform was used to analyze the total wavelet energy of the concerned frequency range (0.005–2 Hz), which were further divided into six frequency intervals corresponding to six vascular regulators. Wavelet amplitude and energy of each frequency interval were analyzed. Results showed that the total energy raised after each exercise session with a significant difference between rest phases 1 and 3. The wavelet amplitudes showed significant increases in frequency intervals I, III, IV, and V from phase 1 to 3 and in intervals III and IV from phase 2 to 3. The wavelet energy showed similar changes with the wavelet amplitude. The results demonstrate that local microvascular regulators contribute greatly to the blood volume oscillations, the activity levels of which are related to the exercise quantity.
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8
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Barbosa TC, Young BE, Stephens BY, Nandadeva D, Kaur J, Keller DM, Fadel PJ. Functional sympatholysis is preserved in healthy young Black men during rhythmic handgrip exercise. Am J Physiol Regul Integr Comp Physiol 2020; 319:R323-R328. [PMID: 32783690 DOI: 10.1152/ajpregu.00105.2020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Black men have attenuated increases in forearm vascular conductance (FVC) and forearm blood flow (FBF) during moderate- and high-intensity rhythmic handgrip exercise compared with White men, but the underlying mechanisms are unclear. Here, we tested for the first time the hypothesis that functional sympatholysis (i.e., attenuation of sympathetic vasoconstriction in the exercising muscles) is impaired in Black men compared with White men. Thirteen White and 14 Black healthy young men were studied. FBF (duplex Doppler ultrasound) and mean arterial pressure (MAP; Finometer) were measured at rest and during rhythmic handgrip exercise at 30% maximal voluntary contraction. FVC was calculated as FBF/MAP. Sympathetic activation was induced via lower body negative pressure (LBNP) at -20 Torr for 2 min at rest and from the 3rd to the 5th min of handgrip. Sympathetic vasoconstriction was assessed as percent reductions in FVC during LBNP. The groups presented similar resting FVC, FBF, and MAP. During LBNP at rest, reductions in FVC were not different between White (-35 ± 10%) and Black men (-32 ± 14%, P = 0.616), indicating similar reflex-induced sympathetic vasoconstriction. During handgrip exercise, there were minimal reductions in FVC with LBNP in either group (White: -1 ± 7%; Black: +1 ± 8%; P = 0.523), indicating functional sympatholysis in both groups. Thus, contrary to our hypothesis, our findings indicate a preserved functional sympatholysis in healthy young Black men compared with White men, suggesting that this mechanism does not appear to contribute to reduced exercise hyperemia during moderate-intensity rhythmic handgrip in this population.
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Affiliation(s)
- Thales C Barbosa
- Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington, Arlington, Texas
| | - Benjamin E Young
- Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington, Arlington, Texas
| | - Brandi Y Stephens
- Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington, Arlington, Texas
| | - Damsara Nandadeva
- Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington, Arlington, Texas
| | - Jasdeep Kaur
- Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington, Arlington, Texas
| | - David M Keller
- Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington, Arlington, Texas
| | - Paul J Fadel
- Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington, Arlington, Texas
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9
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Sarma S, Howden E, Carrick-Ranson G, Lawley J, Hearon C, Samels M, Everding B, Livingston S, Adams-Huet B, Palmer MD, Levine BD. Elevated exercise blood pressure in middle-aged women is associated with altered left ventricular and vascular stiffness. J Appl Physiol (1985) 2020; 128:1123-1129. [PMID: 32240019 DOI: 10.1152/japplphysiol.00458.2019] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Women are at higher risk for developing heart failure with preserved ejection fraction (HFpEF). We examined the utility of peak exercise blood pressure (BP) in identifying preclinical features of HFpEF, namely vascular and cardiac stiffness in middle-aged women. We studied 47 healthy, nonobese middle-aged women (53 ± 5 yr). Oxygen uptake (V̇o2) and BP were assessed at rest and maximal treadmill exercise. Resting cardiac function and stiffness were assessed by echocardiography and invasive measurement (right heart catheterization) of left ventricular (LV) filling pressure under varying preloads. LV stiffness was calculated by curve fit of the diastolic portion of the pressure-volume curve. Aortic pulse-wave velocity was measured by arterial tonometry. Body fat was measured using dual-energy X-ray absorptiometry. Subjects in the highest exercise BP tertile had peak systolic BP of 201 ± 11 compared with 142 ± 19 mmHg in the lowest tertile (P < 0.001). Higher exercise BP was associated with increased age, percentage body fat, smaller LV size, slower LV relaxation, and increased LV and vascular stiffness. After adjustment, LV and arterial stiffness remained significantly associated with peak exercise BP. There was a trend toward increased body fat and slowed LV relaxation (both P < 0.07). In otherwise healthy middle-aged women, elevated exercise BP was independently associated with increased vascular stiffness and a smaller, stiffer LV, functional and structural risk factors characteristic for stages A and B HFpEF.NEW & NOTEWORTHY Women are at increased risk for heart failure with preserved ejection fraction (HFpEF) largely due to higher prevalence of arterial and cardiac stiffening. We were able to identify several subclinical markers of early (stages A and B) HFpEF pathophysiology largely on the basis of exercise blood pressure (BP) response in otherwise healthy middle-aged women. Exercise BP response may be an inexpensive screening tool to identify women at highest risk for developing future HFpEF.
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Affiliation(s)
- Satyam Sarma
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas.,Department of Internal Medicine, University of Texas Southwestern Medical Center Dallas, Dallas, Texas
| | - Erin Howden
- Baker Heart and Diabetes Institute, Melbourne, Australia
| | | | - Justin Lawley
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Christopher Hearon
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
| | - Mitchel Samels
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
| | - Braden Everding
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
| | - Sheryl Livingston
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
| | - Beverley Adams-Huet
- Department of Internal Medicine, University of Texas Southwestern Medical Center Dallas, Dallas, Texas
| | - M Dean Palmer
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas
| | - Benjamin D Levine
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas.,Department of Internal Medicine, University of Texas Southwestern Medical Center Dallas, Dallas, Texas
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10
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Limberg JK, Casey DP, Trinity JD, Nicholson WT, Wray DW, Tschakovsky ME, Green DJ, Hellsten Y, Fadel PJ, Joyner MJ, Padilla J. Assessment of resistance vessel function in human skeletal muscle: guidelines for experimental design, Doppler ultrasound, and pharmacology. Am J Physiol Heart Circ Physiol 2019; 318:H301-H325. [PMID: 31886718 DOI: 10.1152/ajpheart.00649.2019] [Citation(s) in RCA: 84] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The introduction of duplex Doppler ultrasound almost half a century ago signified a revolutionary advance in the ability to assess limb blood flow in humans. It is now widely used to assess blood flow under a variety of experimental conditions to study skeletal muscle resistance vessel function. Despite its pervasive adoption, there is substantial variability between studies in relation to experimental protocols, procedures for data analysis, and interpretation of findings. This guideline results from a collegial discussion among physiologists and pharmacologists, with the goal of providing general as well as specific recommendations regarding the conduct of human studies involving Doppler ultrasound-based measures of resistance vessel function in skeletal muscle. Indeed, the focus is on methods used to assess resistance vessel function and not upstream conduit artery function (i.e., macrovasculature), which has been expertly reviewed elsewhere. In particular, we address topics related to experimental design, data collection, and signal processing as well as review common procedures used to assess resistance vessel function, including postocclusive reactive hyperemia, passive limb movement, acute single limb exercise, and pharmacological interventions.
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Affiliation(s)
- Jacqueline K Limberg
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri
| | - Darren P Casey
- Department of Physical Therapy and Rehabilitation Science, Carver College of Medicine, University of Iowa, Iowa City, Iowa.,François M. Abboud Cardiovascular Research Center, Carver College of Medicine, University of Iowa, Iowa City, Iowa.,Fraternal Order of Eagles Diabetes Research, Carver College of Medicine, University of Iowa, Iowa City, Iowa
| | - Joel D Trinity
- Geriatric Research, Education, and Clinical Center, Veterans Affairs Medical Center, Salt Lake City, Utah.,Department of Internal Medicine, Division of Geriatrics, University of Utah, Salt Lake City, Utah.,Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah
| | | | - D Walter Wray
- Geriatric Research, Education, and Clinical Center, Veterans Affairs Medical Center, Salt Lake City, Utah.,Department of Internal Medicine, Division of Geriatrics, University of Utah, Salt Lake City, Utah.,Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah
| | - Michael E Tschakovsky
- School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada
| | - Daniel J Green
- School of Human Sciences (Exercise and Sport Science), University of Western Australia, Perth, Western Australia, Australia
| | - Ylva Hellsten
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Paul J Fadel
- Department of Kinesiology, University of Texas at Arlington, Arlington, Texas
| | | | - Jaume Padilla
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri.,Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri
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11
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Bunsawat K, Grigoriadis G, Schroeder EC, Rosenberg AJ, Rader MM, Fadel PJ, Clifford PS, Fernhall B, Baynard T. Preserved ability to blunt sympathetically-mediated vasoconstriction in exercising skeletal muscle of young obese humans. Physiol Rep 2019; 7:e14068. [PMID: 31033212 PMCID: PMC6487469 DOI: 10.14814/phy2.14068] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Accepted: 03/29/2019] [Indexed: 01/22/2023] Open
Abstract
Sympathetic vasoconstriction is attenuated in exercising muscles to assist in matching of blood flow with metabolic demand. This "functional sympatholysis" may be impaired in young obese individuals due to greater sympathetic activation and/or reduced local vasodilatory capacity of both small and large arteries, but this remains poorly understood. We tested the hypothesis that functional sympatholysis is impaired in obese individuals compared with normal-weight counterparts. In 36 obese and normal-weight young healthy adults (n = 18/group), we measured forearm blood flow and calculated forearm vascular conductance (FVC) responses to reflex increases in sympathetic nerve activity induced by lower body negative pressure (LBNP) at rest and during rhythmic handgrip exercise at 15% and 30% of the maximal voluntary contraction (MVC). FVC was normalized to lean forearm mass. In normal-weight individuals, LBNP evoked a decrease in FVC (-16.1 ± 5.7%) in the resting forearm, and the reduction in FVC (15%MVC: -8.1 ± 3.3%; 30%MVC: -1.0 ± 4.0%) was blunted during exercise in an intensity-dependent manner (P < 0.05). Similarly, in obese individuals, LBNP evoked a comparable decrease in FVC (-10.9 ± 5.7%) in the resting forearm, with the reduction in FVC (15%MVC: -9.7 ± 3.3%; 30%MVC: -0.3 ± 4.0%) also blunted during exercise in an intensity-dependent manner (P < 0.05). The magnitude of sympatholysis was similar between groups (P > 0.05) and was intensity-dependent (P < 0.05). Our findings suggest that functional sympatholysis is not impaired in young obese individuals without overt cardiovascular diseases.
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Affiliation(s)
- Kanokwan Bunsawat
- Integrative Physiology LaboratoryDepartment of Kinesiology and NutritionCollege of Applied Health SciencesUniversity of Illinois at ChicagoChicagoIllinois
| | - Georgios Grigoriadis
- Integrative Physiology LaboratoryDepartment of Kinesiology and NutritionCollege of Applied Health SciencesUniversity of Illinois at ChicagoChicagoIllinois
| | - Elizabeth C. Schroeder
- Integrative Physiology LaboratoryDepartment of Kinesiology and NutritionCollege of Applied Health SciencesUniversity of Illinois at ChicagoChicagoIllinois
| | - Alexander J. Rosenberg
- Integrative Physiology LaboratoryDepartment of Kinesiology and NutritionCollege of Applied Health SciencesUniversity of Illinois at ChicagoChicagoIllinois
| | - Melissa M. Rader
- Integrative Physiology LaboratoryDepartment of Kinesiology and NutritionCollege of Applied Health SciencesUniversity of Illinois at ChicagoChicagoIllinois
| | - Paul J. Fadel
- Department of KinesiologyCollege of Nursing and Health InnovationUniversity of Texas at ArlingtonArlingtonTexas
| | - Philip S. Clifford
- Integrative Physiology LaboratoryDepartment of Kinesiology and NutritionCollege of Applied Health SciencesUniversity of Illinois at ChicagoChicagoIllinois
| | - Bo Fernhall
- Integrative Physiology LaboratoryDepartment of Kinesiology and NutritionCollege of Applied Health SciencesUniversity of Illinois at ChicagoChicagoIllinois
| | - Tracy Baynard
- Integrative Physiology LaboratoryDepartment of Kinesiology and NutritionCollege of Applied Health SciencesUniversity of Illinois at ChicagoChicagoIllinois
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12
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Sprick JD, Downey RM, Morison DL, Fonkoue IT, Li Y, DaCosta D, Rapista D, Park J. Functional sympatholysis is impaired in end-stage renal disease. Am J Physiol Regul Integr Comp Physiol 2019; 316:R504-R511. [PMID: 30726117 DOI: 10.1152/ajpregu.00380.2018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Patients with end-stage renal disease (ESRD) have decreased exercise capacity and exercise intolerance that contribute to cardiovascular risk. One potential mechanism underlying exercise intolerance in ESRD is impaired ability to oppose sympathetically mediated vasoconstriction within exercising skeletal muscle (i.e., functional sympatholysis, FS). We hypothesized that ESRD patients have impaired FS compared with healthy (CON) and hypertensive (HTN) controls and that impaired FS is related to circulating levels of the uremic toxin asymmetric dimethyl arginine (ADMA), an endogenous nitric oxide synthase inhibitor. Near-infrared spectroscopy-derived oxygen tissue saturation index (TSI) of the forearm muscle was measured continuously in 33 participants (9 CON, 14 HTN, 10 ESRD) at rest and during low-dose (-20 mmHg) lower body negative pressure (LBNP), moderate rhythmic handgrip exercise, and LBNP with concomitant handgrip exercise (LBNP+handgrip). Resting muscle TSI was lower in ESRD than in CON and HTN groups (CON = 67.8 ± 1.9%, HTN = 67.2 ± 1.1%, ESRD = 62.7 ± 1.5%, P = 0.03). Whereas CON and HTN groups had an attenuation in sympathetically mediated reduction in TSI during LBNP + handgrip compared with LBNP alone (P ≤ 0.05), this response was not present in ESRD (P = 0.71), suggesting impaired FS. There was no difference in plasma [ADMA] between groups (CON = 0.47 ± 0.05 µmol/l, HTN = 0.42 ± 0.06 µmol/l, ESRD = 0.63 ± 0.14 µmol/l, P = 0.106) and no correlation between plasma [ADMA] and resting muscle TSI (P = 0.84) or FS (P = 0.75). Collectively, these findings suggest that ESRD patients have lower muscle perfusion at rest and impaired FS but that these derangements are not related to circulating [ADMA].
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Affiliation(s)
- Justin D Sprick
- Division of Renal Medicine, Department of Medicine, Emory University School of Medicine , Atlanta, Georgia.,Department of Veterans Affairs Health Care System, Decatur, Georgia
| | - Ryan M Downey
- Division of Renal Medicine, Department of Medicine, Emory University School of Medicine , Atlanta, Georgia.,Department of Veterans Affairs Health Care System, Decatur, Georgia
| | - Doree Lynn Morison
- Division of Renal Medicine, Department of Medicine, Emory University School of Medicine , Atlanta, Georgia.,Department of Veterans Affairs Health Care System, Decatur, Georgia
| | - Ida T Fonkoue
- Division of Renal Medicine, Department of Medicine, Emory University School of Medicine , Atlanta, Georgia.,Department of Veterans Affairs Health Care System, Decatur, Georgia
| | - Yunxiao Li
- Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University , Atlanta, Georgia
| | - Dana DaCosta
- Division of Renal Medicine, Department of Medicine, Emory University School of Medicine , Atlanta, Georgia.,Department of Veterans Affairs Health Care System, Decatur, Georgia
| | - Derick Rapista
- Division of Renal Medicine, Department of Medicine, Emory University School of Medicine , Atlanta, Georgia.,Department of Veterans Affairs Health Care System, Decatur, Georgia
| | - Jeanie Park
- Division of Renal Medicine, Department of Medicine, Emory University School of Medicine , Atlanta, Georgia.,Department of Veterans Affairs Health Care System, Decatur, Georgia
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13
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Caldwell JT, Sutterfield SL, Post HK, Lovoy GM, Banister HR, Hammer SM, Ade CJ. Vasoconstrictor responsiveness through alterations in relaxation time and metabolic rate during rhythmic handgrip contractions. Physiol Rep 2018; 6:e13933. [PMID: 30511427 PMCID: PMC6277543 DOI: 10.14814/phy2.13933] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 10/29/2018] [Accepted: 10/31/2018] [Indexed: 11/24/2022] Open
Abstract
Increasing the relaxation phase of the contraction-relaxation cycle will increase active skeletal muscle blood flow ( Q ˙ m ). However, it remains unknown if this increase in Q ˙ m alters the vasoconstriction responses in active skeletal muscle. This investigation determined if decreasing mechanical impedance would impact vasoconstriction of the active skeletal muscle. Eight healthy men performed rhythmic handgrip exercise under three different conditions; "low" duty cycle at 20% maximal voluntary contraction (MVC), "low" duty cycle at 15% MVC, and "high" duty cycle at 20% MVC. Relaxation time between low and high duty cycles were 2.4 sec versus 1.5 sec, respectively. During steady-state exercise lower body negative pressure (LBNP) was used to evoke vasoconstriction. Finger photoplethysmography and Doppler ultrasound derived diameters and velocities were used to measure blood pressure, forearm blood flow (FBF: mL min-1 ) and forearm vascular conductance (FVC: mL min-1 mmHg) throughout testing. The low duty cycle increased FBF and FVC versus the high duty cycle under steady-state conditions at 20% MVC (P < 0.01). The high duty cycle had the greatest attenuation in %ΔFVC (-1.9 ± 3.8%). The low duty cycle at 20% (-13.3 ± 1.4%) and 15% MVC (-13.1 ± 2.5%) had significantly greater vasoconstriction than the high duty cycle (both: P < 0.01) but were not different from one another (P = 0.99). When matched for work rate and metabolic rate ( V ˙ O 2 ), the high duty cycle had greater functional sympatholysis than the low duty cycle. However, despite a lower V ˙ O 2 , there was no difference in functional sympatholysis between the low duty cycle conditions. This may suggest that increases in Q ˙ m play a role in functional sympatholysis when mechanical compression is minimized.
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Affiliation(s)
| | | | - Hunter K. Post
- Department of KinesiologyKansas State UniversityManhattanKansas
| | | | | | - Shane M. Hammer
- Department of KinesiologyKansas State UniversityManhattanKansas
| | - Carl J. Ade
- Department of KinesiologyKansas State UniversityManhattanKansas
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Horiuchi M, Endo J, Dobashi S, Handa Y, Kiuchi M, Koyama K. Muscle oxygenation profiles between active and inactive muscles with nitrate supplementation under hypoxic exercise. Physiol Rep 2018; 5:5/20/e13475. [PMID: 29066597 PMCID: PMC5661236 DOI: 10.14814/phy2.13475] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2017] [Revised: 09/08/2017] [Accepted: 09/11/2017] [Indexed: 12/02/2022] Open
Abstract
Whether dietary nitrate supplementation improves exercise performance or not is still controversial. While redistribution of sufficient oxygen from inactive to active muscles is essential for optimal exercise performance, no study investigated the effects of nitrate supplementation on muscle oxygenation profiles between active and inactive muscles. Nine healthy males performed 25 min of submaximal (heart rate ~140 bpm; EXsub) and incremental cycling (EXmax) until exhaustion under three conditions: (A) normoxia without drink; (B) hypoxia (FiO2 = 13.95%) with placebo (PL); and (c) hypoxia with beetroot juice (BR). PL and BR were provided for 4 days. Oxygenated and deoxygenated hemoglobin (HbO2 and HHb) were measured in vastus lateralis (active) and biceps brachii (inactive) muscles, and the oxygen saturation of skeletal muscle (StO2; HbO2/total Hb) were calculated. During EXsub, BR suppressed the HHb increases in active muscles during the last 5 min of exercise. During EXmax, time to exhaustion with BR (513 ± 24 sec) was significantly longer than with PL (490 ± 39 sec, P < 0.05). In active muscles, BR suppressed the HHb increases at moderate work rates during EXmax compared to PL (P < 0.05). In addition, BR supplementation was associated with greater reductions in HbO2 and StO2 at higher work rates in inactive muscles during EXmax. Collectively, these findings indicate that short‐term dietary nitrate supplementation improved hypoxic exercise tolerance, perhaps, due to suppressed increases in HHb in active muscles at moderate work rates. Moreover, nitrate supplementation caused greater reductions in oxygenation in inactive muscle at higher work rates during hypoxic exercise.
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Affiliation(s)
- Masahiro Horiuchi
- Division of Human Environmental Science, Mt. Fuji Research Institute, Fuji-yoshida, Japan
| | - Junko Endo
- Division of Human Environmental Science, Mt. Fuji Research Institute, Fuji-yoshida, Japan
| | - Shohei Dobashi
- Graduate School Department of Interdisciplinary, University of Yamanashi, Kofu, Japan
| | - Yoko Handa
- Division of Human Environmental Science, Mt. Fuji Research Institute, Fuji-yoshida, Japan
| | - Masataka Kiuchi
- Graduate School Department of Interdisciplinary, University of Yamanashi, Kofu, Japan
| | - Katsuhiro Koyama
- Graduate School Department of Interdisciplinary, University of Yamanashi, Kofu, Japan
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15
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Rosenberry R, Chung S, Nelson MD. Skeletal Muscle Neurovascular Coupling, Oxidative Capacity, and Microvascular Function with 'One Stop Shop' Near-infrared Spectroscopy. J Vis Exp 2018. [PMID: 29553570 DOI: 10.3791/57317] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Exercise represents a major hemodynamic stress that demands a highly coordinated neurovascular response in order to match oxygen delivery to metabolic demand. Reactive hyperemia (in response to a brief period of tissue ischemia) is an independent predictor of cardiovascular events and provides important insight into vascular health and vasodilatory capacity. Skeletal muscle oxidative capacity is equally important in health and disease, as it determines the energy supply for myocellular processes. Here, we describe a simple, non-invasive approach using near-infrared spectroscopy to assess each of these major clinical endpoints (reactive hyperemia, neurovascular coupling, and muscle oxidative capacity) during a single clinic or laboratory visit. Unlike Doppler ultrasound, magnetic resonance images/spectroscopy, or invasive catheter-based flow measurements or muscle biopsies, our approach is less operator-dependent, low-cost, and completely non-invasive. Representative data from our lab taken together with summary data from previously published literature illustrate the utility of each of these end-points. Once this technique is mastered, application to clinical populations will provide important mechanistic insight into exercise intolerance and cardiovascular dysfunction.
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Affiliation(s)
- Ryan Rosenberry
- Applied Physiology and Advanced Imaging Laboratory, Department of Kinesiology, University of Texas at Arlington
| | - Susie Chung
- Applied Physiology and Advanced Imaging Laboratory, Department of Kinesiology, University of Texas at Arlington
| | - Michael D Nelson
- Applied Physiology and Advanced Imaging Laboratory, Department of Kinesiology, University of Texas at Arlington;
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16
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Mueller PJ, Clifford PS, Crandall CG, Smith SA, Fadel PJ. Integration of Central and Peripheral Regulation of the Circulation during Exercise: Acute and Chronic Adaptations. Compr Physiol 2017; 8:103-151. [DOI: 10.1002/cphy.c160040] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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17
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Victor RG, Sweeney HL, Finkel R, McDonald CM, Byrne B, Eagle M, Goemans N, Vandenborne K, Dubrovsky AL, Topaloglu H, Miceli MC, Furlong P, Landry J, Elashoff R, Cox D. A phase 3 randomized placebo-controlled trial of tadalafil for Duchenne muscular dystrophy. Neurology 2017; 89:1811-1820. [PMID: 28972192 PMCID: PMC5664308 DOI: 10.1212/wnl.0000000000004570] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Accepted: 07/28/2017] [Indexed: 12/14/2022] Open
Abstract
OBJECTIVE To conduct a randomized trial to test the primary hypothesis that once-daily tadalafil, administered orally for 48 weeks, lessens the decline in ambulatory ability in boys with Duchenne muscular dystrophy (DMD). METHODS Three hundred thirty-one participants with DMD 7 to 14 years of age taking glucocorticoids were randomized to tadalafil 0.3 mg·kg-1·d-1, tadalafil 0.6 mg·kg-1·d-1, or placebo. The primary efficacy measure was 6-minute walk distance (6MWD) after 48 weeks. Secondary efficacy measures included North Star Ambulatory Assessment and timed function tests. Performance of Upper Limb (PUL) was a prespecified exploratory outcome. RESULTS Tadalafil had no effect on the primary outcome: 48-week declines in 6MWD were 51.0 ± 9.3 m with placebo, 64.7 ± 9.8 m with low-dose tadalafil (p = 0.307 vs placebo), and 59.1 ± 9.4 m with high-dose tadalafil (p = 0.538 vs placebo). Tadalafil also had no effect on secondary outcomes. In boys >10 years of age, total PUL score and shoulder subscore declined less with low-dose tadalafil than placebo. Adverse events were consistent with the known safety profile of tadalafil and the DMD disease state. CONCLUSIONS Tadalafil did not lessen the decline in ambulatory ability in boys with DMD. Further studies should be considered to confirm the hypothesis-generating upper limb data and to determine whether ambulatory decline can be slowed by initiation of tadalafil before 7 years of age. CLINICALTRIALSGOV IDENTIFIER NCT01865084. CLASSIFICATION OF EVIDENCE This study provides Class I evidence that tadalafil does not slow ambulatory decline in 7- to 14-year-old boys with Duchenne muscular dystrophy.
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Affiliation(s)
- Ronald G Victor
- From the Cedars-Sinai Medical Center (R.G.V.), Los Angeles, CA; University of Florida (H.L.S., B.B., K.V.), Gainesville; Nemours Children's Hospital (R.F.), Orlando, FL; University of California at Davis (C.M.M.), Sacramento; Newcastle University (M.E.), Newcastle Upon Tyne, UK; University Hospitals Leuven (N.G.), Belgium; Instituto de Neurociencias-Fundacion Favaloro (A.L.D.), Buenos Aires, Argentina; Hacettepe University School of Medicine (H.T.), Ankara, Turkey; UCLA (M.C.M., R.E.), Los Angeles, CA; Parent Project Muscular Dystrophy (P.F.), Hackensack, NJ; Eli Lilly Canada, Eli Lilly and Company, Toronto, ON (J.L.); and Eli Lilly and Company (D.C.), Indianapolis, IN.
| | - H Lee Sweeney
- From the Cedars-Sinai Medical Center (R.G.V.), Los Angeles, CA; University of Florida (H.L.S., B.B., K.V.), Gainesville; Nemours Children's Hospital (R.F.), Orlando, FL; University of California at Davis (C.M.M.), Sacramento; Newcastle University (M.E.), Newcastle Upon Tyne, UK; University Hospitals Leuven (N.G.), Belgium; Instituto de Neurociencias-Fundacion Favaloro (A.L.D.), Buenos Aires, Argentina; Hacettepe University School of Medicine (H.T.), Ankara, Turkey; UCLA (M.C.M., R.E.), Los Angeles, CA; Parent Project Muscular Dystrophy (P.F.), Hackensack, NJ; Eli Lilly Canada, Eli Lilly and Company, Toronto, ON (J.L.); and Eli Lilly and Company (D.C.), Indianapolis, IN
| | - Richard Finkel
- From the Cedars-Sinai Medical Center (R.G.V.), Los Angeles, CA; University of Florida (H.L.S., B.B., K.V.), Gainesville; Nemours Children's Hospital (R.F.), Orlando, FL; University of California at Davis (C.M.M.), Sacramento; Newcastle University (M.E.), Newcastle Upon Tyne, UK; University Hospitals Leuven (N.G.), Belgium; Instituto de Neurociencias-Fundacion Favaloro (A.L.D.), Buenos Aires, Argentina; Hacettepe University School of Medicine (H.T.), Ankara, Turkey; UCLA (M.C.M., R.E.), Los Angeles, CA; Parent Project Muscular Dystrophy (P.F.), Hackensack, NJ; Eli Lilly Canada, Eli Lilly and Company, Toronto, ON (J.L.); and Eli Lilly and Company (D.C.), Indianapolis, IN
| | - Craig M McDonald
- From the Cedars-Sinai Medical Center (R.G.V.), Los Angeles, CA; University of Florida (H.L.S., B.B., K.V.), Gainesville; Nemours Children's Hospital (R.F.), Orlando, FL; University of California at Davis (C.M.M.), Sacramento; Newcastle University (M.E.), Newcastle Upon Tyne, UK; University Hospitals Leuven (N.G.), Belgium; Instituto de Neurociencias-Fundacion Favaloro (A.L.D.), Buenos Aires, Argentina; Hacettepe University School of Medicine (H.T.), Ankara, Turkey; UCLA (M.C.M., R.E.), Los Angeles, CA; Parent Project Muscular Dystrophy (P.F.), Hackensack, NJ; Eli Lilly Canada, Eli Lilly and Company, Toronto, ON (J.L.); and Eli Lilly and Company (D.C.), Indianapolis, IN
| | - Barry Byrne
- From the Cedars-Sinai Medical Center (R.G.V.), Los Angeles, CA; University of Florida (H.L.S., B.B., K.V.), Gainesville; Nemours Children's Hospital (R.F.), Orlando, FL; University of California at Davis (C.M.M.), Sacramento; Newcastle University (M.E.), Newcastle Upon Tyne, UK; University Hospitals Leuven (N.G.), Belgium; Instituto de Neurociencias-Fundacion Favaloro (A.L.D.), Buenos Aires, Argentina; Hacettepe University School of Medicine (H.T.), Ankara, Turkey; UCLA (M.C.M., R.E.), Los Angeles, CA; Parent Project Muscular Dystrophy (P.F.), Hackensack, NJ; Eli Lilly Canada, Eli Lilly and Company, Toronto, ON (J.L.); and Eli Lilly and Company (D.C.), Indianapolis, IN
| | - Michelle Eagle
- From the Cedars-Sinai Medical Center (R.G.V.), Los Angeles, CA; University of Florida (H.L.S., B.B., K.V.), Gainesville; Nemours Children's Hospital (R.F.), Orlando, FL; University of California at Davis (C.M.M.), Sacramento; Newcastle University (M.E.), Newcastle Upon Tyne, UK; University Hospitals Leuven (N.G.), Belgium; Instituto de Neurociencias-Fundacion Favaloro (A.L.D.), Buenos Aires, Argentina; Hacettepe University School of Medicine (H.T.), Ankara, Turkey; UCLA (M.C.M., R.E.), Los Angeles, CA; Parent Project Muscular Dystrophy (P.F.), Hackensack, NJ; Eli Lilly Canada, Eli Lilly and Company, Toronto, ON (J.L.); and Eli Lilly and Company (D.C.), Indianapolis, IN
| | - Nathalie Goemans
- From the Cedars-Sinai Medical Center (R.G.V.), Los Angeles, CA; University of Florida (H.L.S., B.B., K.V.), Gainesville; Nemours Children's Hospital (R.F.), Orlando, FL; University of California at Davis (C.M.M.), Sacramento; Newcastle University (M.E.), Newcastle Upon Tyne, UK; University Hospitals Leuven (N.G.), Belgium; Instituto de Neurociencias-Fundacion Favaloro (A.L.D.), Buenos Aires, Argentina; Hacettepe University School of Medicine (H.T.), Ankara, Turkey; UCLA (M.C.M., R.E.), Los Angeles, CA; Parent Project Muscular Dystrophy (P.F.), Hackensack, NJ; Eli Lilly Canada, Eli Lilly and Company, Toronto, ON (J.L.); and Eli Lilly and Company (D.C.), Indianapolis, IN
| | - Krista Vandenborne
- From the Cedars-Sinai Medical Center (R.G.V.), Los Angeles, CA; University of Florida (H.L.S., B.B., K.V.), Gainesville; Nemours Children's Hospital (R.F.), Orlando, FL; University of California at Davis (C.M.M.), Sacramento; Newcastle University (M.E.), Newcastle Upon Tyne, UK; University Hospitals Leuven (N.G.), Belgium; Instituto de Neurociencias-Fundacion Favaloro (A.L.D.), Buenos Aires, Argentina; Hacettepe University School of Medicine (H.T.), Ankara, Turkey; UCLA (M.C.M., R.E.), Los Angeles, CA; Parent Project Muscular Dystrophy (P.F.), Hackensack, NJ; Eli Lilly Canada, Eli Lilly and Company, Toronto, ON (J.L.); and Eli Lilly and Company (D.C.), Indianapolis, IN
| | - Alberto L Dubrovsky
- From the Cedars-Sinai Medical Center (R.G.V.), Los Angeles, CA; University of Florida (H.L.S., B.B., K.V.), Gainesville; Nemours Children's Hospital (R.F.), Orlando, FL; University of California at Davis (C.M.M.), Sacramento; Newcastle University (M.E.), Newcastle Upon Tyne, UK; University Hospitals Leuven (N.G.), Belgium; Instituto de Neurociencias-Fundacion Favaloro (A.L.D.), Buenos Aires, Argentina; Hacettepe University School of Medicine (H.T.), Ankara, Turkey; UCLA (M.C.M., R.E.), Los Angeles, CA; Parent Project Muscular Dystrophy (P.F.), Hackensack, NJ; Eli Lilly Canada, Eli Lilly and Company, Toronto, ON (J.L.); and Eli Lilly and Company (D.C.), Indianapolis, IN
| | - Haluk Topaloglu
- From the Cedars-Sinai Medical Center (R.G.V.), Los Angeles, CA; University of Florida (H.L.S., B.B., K.V.), Gainesville; Nemours Children's Hospital (R.F.), Orlando, FL; University of California at Davis (C.M.M.), Sacramento; Newcastle University (M.E.), Newcastle Upon Tyne, UK; University Hospitals Leuven (N.G.), Belgium; Instituto de Neurociencias-Fundacion Favaloro (A.L.D.), Buenos Aires, Argentina; Hacettepe University School of Medicine (H.T.), Ankara, Turkey; UCLA (M.C.M., R.E.), Los Angeles, CA; Parent Project Muscular Dystrophy (P.F.), Hackensack, NJ; Eli Lilly Canada, Eli Lilly and Company, Toronto, ON (J.L.); and Eli Lilly and Company (D.C.), Indianapolis, IN
| | - M Carrie Miceli
- From the Cedars-Sinai Medical Center (R.G.V.), Los Angeles, CA; University of Florida (H.L.S., B.B., K.V.), Gainesville; Nemours Children's Hospital (R.F.), Orlando, FL; University of California at Davis (C.M.M.), Sacramento; Newcastle University (M.E.), Newcastle Upon Tyne, UK; University Hospitals Leuven (N.G.), Belgium; Instituto de Neurociencias-Fundacion Favaloro (A.L.D.), Buenos Aires, Argentina; Hacettepe University School of Medicine (H.T.), Ankara, Turkey; UCLA (M.C.M., R.E.), Los Angeles, CA; Parent Project Muscular Dystrophy (P.F.), Hackensack, NJ; Eli Lilly Canada, Eli Lilly and Company, Toronto, ON (J.L.); and Eli Lilly and Company (D.C.), Indianapolis, IN
| | - Pat Furlong
- From the Cedars-Sinai Medical Center (R.G.V.), Los Angeles, CA; University of Florida (H.L.S., B.B., K.V.), Gainesville; Nemours Children's Hospital (R.F.), Orlando, FL; University of California at Davis (C.M.M.), Sacramento; Newcastle University (M.E.), Newcastle Upon Tyne, UK; University Hospitals Leuven (N.G.), Belgium; Instituto de Neurociencias-Fundacion Favaloro (A.L.D.), Buenos Aires, Argentina; Hacettepe University School of Medicine (H.T.), Ankara, Turkey; UCLA (M.C.M., R.E.), Los Angeles, CA; Parent Project Muscular Dystrophy (P.F.), Hackensack, NJ; Eli Lilly Canada, Eli Lilly and Company, Toronto, ON (J.L.); and Eli Lilly and Company (D.C.), Indianapolis, IN
| | - John Landry
- From the Cedars-Sinai Medical Center (R.G.V.), Los Angeles, CA; University of Florida (H.L.S., B.B., K.V.), Gainesville; Nemours Children's Hospital (R.F.), Orlando, FL; University of California at Davis (C.M.M.), Sacramento; Newcastle University (M.E.), Newcastle Upon Tyne, UK; University Hospitals Leuven (N.G.), Belgium; Instituto de Neurociencias-Fundacion Favaloro (A.L.D.), Buenos Aires, Argentina; Hacettepe University School of Medicine (H.T.), Ankara, Turkey; UCLA (M.C.M., R.E.), Los Angeles, CA; Parent Project Muscular Dystrophy (P.F.), Hackensack, NJ; Eli Lilly Canada, Eli Lilly and Company, Toronto, ON (J.L.); and Eli Lilly and Company (D.C.), Indianapolis, IN
| | - Robert Elashoff
- From the Cedars-Sinai Medical Center (R.G.V.), Los Angeles, CA; University of Florida (H.L.S., B.B., K.V.), Gainesville; Nemours Children's Hospital (R.F.), Orlando, FL; University of California at Davis (C.M.M.), Sacramento; Newcastle University (M.E.), Newcastle Upon Tyne, UK; University Hospitals Leuven (N.G.), Belgium; Instituto de Neurociencias-Fundacion Favaloro (A.L.D.), Buenos Aires, Argentina; Hacettepe University School of Medicine (H.T.), Ankara, Turkey; UCLA (M.C.M., R.E.), Los Angeles, CA; Parent Project Muscular Dystrophy (P.F.), Hackensack, NJ; Eli Lilly Canada, Eli Lilly and Company, Toronto, ON (J.L.); and Eli Lilly and Company (D.C.), Indianapolis, IN
| | - David Cox
- From the Cedars-Sinai Medical Center (R.G.V.), Los Angeles, CA; University of Florida (H.L.S., B.B., K.V.), Gainesville; Nemours Children's Hospital (R.F.), Orlando, FL; University of California at Davis (C.M.M.), Sacramento; Newcastle University (M.E.), Newcastle Upon Tyne, UK; University Hospitals Leuven (N.G.), Belgium; Instituto de Neurociencias-Fundacion Favaloro (A.L.D.), Buenos Aires, Argentina; Hacettepe University School of Medicine (H.T.), Ankara, Turkey; UCLA (M.C.M., R.E.), Los Angeles, CA; Parent Project Muscular Dystrophy (P.F.), Hackensack, NJ; Eli Lilly Canada, Eli Lilly and Company, Toronto, ON (J.L.); and Eli Lilly and Company (D.C.), Indianapolis, IN
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18
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Abstract
Study Design Controlled laboratory study. Background Spinal manipulation (SM) can trigger a cascade of responses involving multiple systems, including the sympathetic nervous system and the endocrine system, specifically, the hypothalamic-pituitary axis. However, no manual therapy study has investigated the neuroendocrine response to SM (ie, sympathetic nervous system-hypothalamic-pituitary axis) in the same trial. Objective To determine short-term changes in sympathetic nervous system activity, heart rate variability, and endocrine activity (cortisol, testosterone, and testosterone-cortisol [T/C] ratio) following a thoracic SM. Methods Twenty-four healthy men aged between 18 and 45 years were randomized into 2 groups: thoracic SM (n = 12) and sham (n = 12). Outcome measures were salivary cortisol (micrograms per deciliter), salivary testosterone (picograms per milliliter), T/C ratio, heart rate variability, and changes in oxyhemoglobin concentration of the right calf muscle (micromoles per liter). Measurements were done before and at 5 minutes, 30 minutes, and approximately 6 hours after intervention. Results A statistically significant group-by-time interaction was noted for T/C ratio (P<.05) and salivary cortisol (P<.01) concentrations. Significant between-group differences were noted for salivary cortisol concentration at 5 minutes (mean difference, 0.35; 95% confidence interval: 0.12, 0.6; interaction: P<.01) and for T/C ratio at 6 hours postintervention (mean difference, -0.09; 95% confidence interval: -0.16, -0.04; P = .02). However, SM did not differentially alter oxyhemoglobin, testosterone, or heart rate variability relative to responses in the sham group. Conclusion Thoracic SM resulted in an immediate decrease in salivary cortisol concentration and reduced T/C ratio 6 hours after intervention. A pattern of immediate sympathetic excitation was also observed in the SM group. J Orthop Sports Phys Ther 2017;47(9):617-627. Epub 13 Jul 2017. doi:10.2519/jospt.2017.7348.
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Mitchell JH. Abnormal cardiovascular response to exercise in hypertension: contribution of neural factors. Am J Physiol Regul Integr Comp Physiol 2017; 312:R851-R863. [PMID: 28381455 DOI: 10.1152/ajpregu.00042.2017] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 03/10/2017] [Accepted: 03/22/2017] [Indexed: 02/02/2023]
Abstract
During both dynamic (e.g., endurance) and static (e.g., strength) exercise there are exaggerated cardiovascular responses in hypertension. This includes greater increases in blood pressure, heart rate, and efferent sympathetic nerve activity than in normal controls. Two of the known neural factors that contribute to this abnormal cardiovascular response are the exercise pressor reflex (EPR) and functional sympatholysis. The EPR originates in contracting skeletal muscle and reflexly increases sympathetic efferent nerve activity to the heart and blood vessels as well as decreases parasympathetic efferent nerve activity to the heart. These changes in autonomic nerve activity cause an increase in blood pressure, heart rate, left ventricular contractility, and vasoconstriction in the arterial tree. However, arterial vessels in the contracting skeletal muscle have a markedly diminished vasoconstrictor response. The markedly diminished vasoconstriction in contracting skeletal muscle has been termed functional sympatholysis. It has been shown in hypertension that there is an enhanced EPR, including both its mechanoreflex and metaboreflex components, and an impaired functional sympatholysis. These conditions set up a positive feedback or vicious cycle situation that causes a progressively greater decrease in the blood flow to the exercising muscle. Thus these two neural mechanisms contribute significantly to the abnormal cardiovascular response to exercise in hypertension. In addition, exercise training in hypertension decreases the enhanced EPR, including both mechanoreflex and metaboreflex function, and improves the impaired functional sympatholysis. These two changes, caused by exercise training, improve the muscle blood flow to exercising muscle and cause a more normal cardiovascular response to exercise in hypertension.
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Affiliation(s)
- Jere H Mitchell
- Cardiology Division, University of Texas Southwestern Medical Center, Dallas, Texas
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20
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Velasco A, Solow E, Price A, Wang Z, Arbique D, Arbique G, Adams-Huet B, Schwedhelm E, Lindner JR, Vongpatanasin W. Differential effects of nebivolol vs. metoprolol on microvascular function in hypertensive humans. Am J Physiol Heart Circ Physiol 2016; 311:H118-24. [PMID: 27199121 PMCID: PMC4967201 DOI: 10.1152/ajpheart.00237.2016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Accepted: 05/05/2016] [Indexed: 02/02/2023]
Abstract
Use of β-adrenergic receptor (AR) blocker is associated with increased risk of fatigue and exercise intolerance. Nebivolol is a newer generation β-blocker, which is thought to avoid this side effect via its vasodilating property. However, the effects of nebivolol on skeletal muscle perfusion during exercise have not been determined in hypertensive patients. Accordingly, we performed contrast-enhanced ultrasound perfusion imaging of the forearm muscles in 25 untreated stage I hypertensive patients at rest and during handgrip exercise at baseline or after 12 wk of treatment with nebivolol (5-20 mg/day) or metoprolol succinate (100-300 mg/day), with a subsequent double crossover for 12 wk. Metoprolol and nebivolol each induced a reduction in the resting blood pressure and heart rate (130.9 ± 2.6/81.7 ± 1.8 vs. 131.6 ± 2.7/80.8 ± 1.5 mmHg and 63 ± 2 vs. 64 ± 2 beats/min) compared with baseline (142.1 ± 2.0/88.7 ± 1.4 mmHg and 75 ± 2 beats/min, respectively, both P < 0.01). Metoprolol significantly attenuated the increase in microvascular blood volume (MBV) during handgrip at 12 and 20 repetitions/min by 50% compared with baseline (mixed-model P < 0.05), which was not observed with nebivolol. Neither metoprolol nor nebivolol affected microvascular flow velocity (MFV). Similarly, metoprolol and nebivolol had no effect on the increase in the conduit brachial artery flow as determined by duplex Doppler ultrasound. Thus our study demonstrated a first direct evidence for metoprolol-induced impairment in the recruitment of microvascular units during exercise in hypertensive humans, which was avoided by nebivolol. This selective reduction in MBV without alteration in MFV by metoprolol suggested impaired vasodilation at the precapillary arteriolar level.
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Affiliation(s)
- Alejandro Velasco
- Hypertension Section, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Elizabeth Solow
- Rheumatology Division, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Angela Price
- Hypertension Section, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Zhongyun Wang
- Hypertension Section, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Debbie Arbique
- Hypertension Section, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Gary Arbique
- Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Beverley Adams-Huet
- Department of Clinical Sciences, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Edzard Schwedhelm
- Department of Clinical Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; and
| | - Jonathan R Lindner
- Knight Cardiovascular Center, Oregon Health and Science University, Portland, Oregon
| | - Wanpen Vongpatanasin
- Hypertension Section, University of Texas Southwestern Medical Center, Dallas, Texas; Rheumatology Division, University of Texas Southwestern Medical Center, Dallas, Texas;
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Abstract
Aerobic exercise training leads to cardiovascular changes that markedly increase aerobic power and lead to improved endurance performance. The functionally most important adaptation is the improvement in maximal cardiac output which is the result of an enlargement in cardiac dimension, improved contractility, and an increase in blood volume, allowing for greater filling of the ventricles and a consequent larger stroke volume. In parallel with the greater maximal cardiac output, the perfusion capacity of the muscle is increased, permitting for greater oxygen delivery. To accommodate the higher aerobic demands and perfusion levels, arteries, arterioles, and capillaries adapt in structure and number. The diameters of the larger conduit and resistance arteries are increased minimizing resistance to flow as the cardiac output is distributed in the body and the wall thickness of the conduit and resistance arteries is reduced, a factor contributing to increased arterial compliance. Endurance training may also induce alterations in the vasodilator capacity, although such adaptations are more pronounced in individuals with reduced vascular function. The microvascular net increases in size within the muscle allowing for an improved capacity for oxygen extraction by the muscle through a greater area for diffusion, a shorter diffusion distance, and a longer mean transit time for the erythrocyte to pass through the smallest blood vessels. The present article addresses the effect of endurance training on systemic and peripheral cardiovascular adaptations with a focus on humans, but also covers animal data.
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Affiliation(s)
- Ylva Hellsten
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Michael Nyberg
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
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22
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Shoemaker JK, Badrov MB, Al-Khazraji BK, Jackson DN. Neural Control of Vascular Function in Skeletal Muscle. Compr Physiol 2015; 6:303-29. [PMID: 26756634 DOI: 10.1002/cphy.c150004] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The sympathetic nervous system represents a fundamental homeostatic system that exerts considerable control over blood pressure and the distribution of blood flow. This process has been referred to as neurovascular control. Overall, the concept of neurovascular control includes the following elements: efferent postganglionic sympathetic nerve activity, neurotransmitter release, and the end organ response. Each of these elements reflects multiple levels of control that, in turn, affect complex patterns of change in vascular contractile state. Primarily, this review discusses several of these control layers that combine to produce the integrative physiology of reflex vascular control observed in skeletal muscle. Beginning with three reflexes that provide somewhat dissimilar vascular patterns of response despite similar changes in efferent sympathetic nerve activity, namely, the baroreflex, chemoreflex, and muscle metaboreflex, the article discusses the anatomical and physiological bases of postganglionic sympathetic discharge patterns and recruitment, neurotransmitter release and management, and details of regional variations of receptor density and responses within the microvascular bed. Challenges are addressed regarding the fundamentals of measurement and how conclusions from one response or vascular segment should not be used as an indication of neurovascular control as a generalized physiological dogma. Whereas the bulk of the article focuses on the vasoconstrictor function of sympathetic neurovascular integration, attention is also given to the issues of sympathetic vasodilation as well as the impact of chronic changes in sympathetic activation and innervation on vascular health. © 2016 American Physiological Society.
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Affiliation(s)
- J K Shoemaker
- School of Kinesiology, Western University, London, Ontario, Canada.,Department of Physiology and Pharmacology, Western University, London, Ontario, Canada
| | - M B Badrov
- School of Kinesiology, Western University, London, Ontario, Canada
| | - B K Al-Khazraji
- Department of Medical Biophysics, Western University, London, Ontario, Canada
| | - D N Jackson
- Department of Medical Biophysics, Western University, London, Ontario, Canada
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23
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Nelson MD, Rosenberry R, Barresi R, Tsimerinov EI, Rader F, Tang X, Mason O, Schwartz A, Stabler T, Shidban S, Mobaligh N, Hogan S, Elashoff R, Allen JD, Victor RG. Sodium nitrate alleviates functional muscle ischaemia in patients with Becker muscular dystrophy. J Physiol 2015; 593:5183-200. [PMID: 26437761 DOI: 10.1113/jp271252] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Accepted: 09/21/2015] [Indexed: 12/26/2022] Open
Abstract
Becker muscular dystrophy (BMD) is a progressive X-linked muscle wasting disease for which there is no treatment. BMD is caused by in-frame mutations in the gene encoding dystrophin, a structural cytoskeletal protein that also targets other proteins to the sarcolemma. Among these is neuronal nitric oxide synthase mu (nNOSμ), which requires specific spectrin-like repeats (SR16/17) in dystrophin's rod domain and the adaptor protein α-syntrophin for sarcolemmal targeting. When healthy skeletal muscle is exercised, sarcolemmal nNOSμ-derived nitric oxide (NO) attenuates α-adrenergic vasoconstriction, thus optimizing perfusion. In the mdx mouse model of dystrophinopathy, this protective mechanism (functional sympatholysis) is defective, resulting in functional muscle ischaemia. Treatment with a NO-donating non-steroidal anti-inflammatory drug (NSAID) alleviates this ischaemia and improves the murine dystrophic phenotype. In the present study, we report that, in 13 men with BMD, sympatholysis is defective mainly in patients whose mutations disrupt sarcolemmal targeting of nNOSμ, with the vasoconstrictor response measured as a decrease in muscle oxygenation (near infrared spectroscopy) to reflex sympathetic activation. Then, in a single-arm, open-label trial in 11 BMD patients and a double-blind, placebo-controlled cross-over trial in six patients, we show that acute treatment with oral sodium nitrate, an inorganic NO donor without a NSIAD moiety, restores sympatholysis and improves post-exercise hyperaemia (Doppler ultrasound). By contrast, sodium nitrate improves neither sympatholysis, nor hyperaemia in healthy controls. Thus, a simple NO donor recapitulates the vasoregulatory actions of sarcolemmal nNOS in BMD patients, and constitutes a putative novel therapy for this disease.
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Affiliation(s)
- Michael D Nelson
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Ryan Rosenberry
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Rita Barresi
- NSCT Diagnostic & Advisory Service for Rare Neuromuscular Diseases, Institute of Genetic Medicine, Newcastle upon Tyne, UK
| | | | - Florian Rader
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Xiu Tang
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - O'Neil Mason
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Avery Schwartz
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Thomas Stabler
- Duke Institute of Molecular Physiology, Duke University Medical Centre, Durham, NC, USA
| | - Sarah Shidban
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Neigena Mobaligh
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Shomari Hogan
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Robert Elashoff
- Department of Biomathematics, University of California Los Angeles, Los Angeles, CA, USA
| | - Jason D Allen
- Clinical Exercise Science Program, Institute of Sport, Exercise and Active Living (ISEAL), Victoria University, Melbourne, VIC, Australia
| | - Ronald G Victor
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
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24
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Cardiovascular Reflexes Activity and Their Interaction during Exercise. BIOMED RESEARCH INTERNATIONAL 2015; 2015:394183. [PMID: 26557662 PMCID: PMC4628760 DOI: 10.1155/2015/394183] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2015] [Revised: 07/26/2015] [Accepted: 07/28/2015] [Indexed: 02/07/2023]
Abstract
Cardiac output and arterial blood pressure increase during dynamic exercise notwithstanding the exercise-induced vasodilation due to functional sympatholysis. These cardiovascular adjustments are regulated in part by neural reflexes which operate to guarantee adequate oxygen supply and by-products washout of the exercising muscles. Moreover, they maintain adequate perfusion of the vital organs and prevent excessive increments in blood pressure. In this review, we briefly summarize neural reflexes operating during dynamic exercise with particular emphasis on their interaction.
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25
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Nyberg M, Hellsten Y. Reduced blood flow to contracting skeletal muscle in ageing humans: is it all an effect of sand through the hourglass? J Physiol 2015; 594:2297-305. [PMID: 26095873 DOI: 10.1113/jp270594] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2015] [Accepted: 06/05/2015] [Indexed: 01/27/2023] Open
Abstract
The ability to sustain a given absolute submaximal workload declines with advancing age, likely to be due to a lower level of blood flow and O2 delivery to the exercising muscles. Given that physical inactivity mimics many of the physiological changes associated with ageing, separating the physiological consequences of ageing and physical inactivity can be challenging; yet, observations from cross-sectional and longitudinal studies on the effects of physical activity have provided some insight. Physical activity has the potential to offset the age-related decline in blood flow to contracting skeletal muscle during exercise where systemic blood flow is not limited by cardiac output, thereby improving O2 delivery and allowing for an enhanced energy production from oxidative metabolism. The mechanisms underlying the increase in blood flow with regular physical activity include improved endothelial function and the ability for functional sympatholysis - an attenuation of the vasoconstrictor effect of sympathetic nervous activity. These vascular adaptations with physical activity are likely to be an effect of improved nitric oxide and ATP signalling. Collectively, precise matching of blood flow and O2 delivery to meet the O2 demand of the active skeletal muscle of aged individuals during conditions where systemic blood flow is not limited by cardiac output seems to a large extent to be related to the level of physical activity.
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Affiliation(s)
- Michael Nyberg
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Denmark
| | - Ylva Hellsten
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Denmark
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26
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Horiuchi M, Endo J, Thijssen DHJ. Impact of ischemic preconditioning on functional sympatholysis during handgrip exercise in humans. Physiol Rep 2015; 3:3/2/e12304. [PMID: 25713329 PMCID: PMC4393211 DOI: 10.14814/phy2.12304] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Repeated bouts of ischemia followed by reperfusion, known as ischemic preconditioning (IPC), is found to improve exercise performance. As redistribution of blood from the inactive areas to active skeletal muscles during exercise (i.e., functional sympatholysis) is important for exercise performance, we examined the hypothesis that IPC improves functional sympatholysis in healthy, young humans. In a randomized study, 15 healthy young men performed a 10-min resting period, dynamic handgrip exercise at 10% maximal voluntary contraction (MVC), and 25% MVC. This protocol was preceded by IPC (IPC; 4 × 5-min 220-mmHg unilateral occlusion) or a sham intervention (CON; 4 × 5-min 20-mmHg unilateral occlusion). Near-infrared spectroscopy was used to assess changes in oxygenated hemoglobin and myoglobin in skeletal muscle (HbO2 + MbO2) in response to sympathetic activation (via cold pressor test (CPT)) at baseline and during handgrip exercise (at 10% and 25%). In resting conditions, HbO2 + MbO2 significantly decreased during CPT (−11.0 ± 1.0%), which was significantly larger during the IPC-trial (−13.8 ± 1.2%, P = 0.006). During handgrip exercise at 10% MVC, changes in HbO2 + MbO2 in response to the CPT were blunted after IPC (−8.8 ± 1.5%) and CON (−8.3 ± 0.4%, P = 0.593). During handgrip exercise at 25% MVC, HbO2 + MbO2 in response to the CPT increased (2.0 ± 0.4%), whereas this response was significantly larger when preceded by IPC (4.2 ± 0.6%, P = 0.027). Collectively, these results indicate that IPC-induced different vascular changes at rest and during moderate exercise in response to sympathetic activation. This suggests that, in healthy volunteers, exposure to IPC may alter tissue oxygenation during sympathetic stimulation at rest and during exercise.
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Affiliation(s)
- Masahiro Horiuchi
- Division of Human Environmental Science, Mt. Fuji Research Institute, Fuji-yoshida cityYamanashi, Japan
| | - Junko Endo
- Division of Human Environmental Science, Mt. Fuji Research Institute, Fuji-yoshida cityYamanashi, Japan
| | - Dick H J Thijssen
- Research Institute of Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK Radboud University Medical Center, Radboud Institute for Health Sciences, Nijmegen, Netherlands
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27
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Jelani QUA, Norcliffe-Kaufmann L, Kaufmann H, Katz SD. Vascular endothelial function and blood pressure regulation in afferent autonomic failure. Am J Hypertens 2015; 28:166-72. [PMID: 25128693 DOI: 10.1093/ajh/hpu144] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Familial dysautonomia (FD) is a rare hereditary disease characterized by loss of afferent autonomic neural fiber signaling and consequent profound impairment of arterial baroreflex function and blood pressure regulation. Whether vascular endothelial dysfunction contributes to defective vasomotor control in this form of afferent autonomic failure is not known. METHODS We assessed blood pressure response to orthostatic stress and vascular endothelial function with brachial artery reactivity testing in 34 FD subjects with afferent autonomic failure and 34 healthy control subjects. RESULTS Forty-four percent of the afferent autonomic failure subjects had uncontrolled hypertension at supine rest (median systolic blood pressure = 148mm Hg, interquartile range (IQR) = 144-155mm Hg; median diastolic blood pressure = 83mm Hg, IQR = 78-105mm Hg), and 88% had abnormal response to orthostatic stress (median decrease in systolic blood pressure after upright tilt = 48mm Hg, IQR = 29-61mm Hg). Flow-mediated brachial artery reactivity did not differ in subjects with afferent autonomic failure vs. healthy control subjects (median = 6.00%, IQR = 1.86-11.77%; vs. median = 6.27%, IQR = 4.65-9.34%; P = 0.75). In afferent autonomic failure subjects, brachial artery reactivity was not associated with resting blood pressure or the magnitude of orthostatic hypotension but was decreased in association with reduced glomerular filtration rate (r = 0.62; P < 0.001). CONCLUSIONS Brachial artery reactivity was preserved in subjects with afferent autonomic failure despite the presence of marked blood pressure dysregulation. Comorbid renal dysfunction was associated with reduced brachial artery reactivity.
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Affiliation(s)
- Qurat-Ul-Ain Jelani
- Leon H. Charney Division of Cardiology, New York University School of Medicine, New York University Langone Medical Center, New York, New York
| | - Lucy Norcliffe-Kaufmann
- Dysautonomia Center, New York University School of Medicine, New York University Langone Medical Center, New York, New York
| | - Horacio Kaufmann
- Dysautonomia Center, New York University School of Medicine, New York University Langone Medical Center, New York, New York
| | - Stuart D Katz
- Leon H. Charney Division of Cardiology, New York University School of Medicine, New York University Langone Medical Center, New York, New York;
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28
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Functional sympatholysis in hypertension. Auton Neurosci 2014; 188:64-8. [PMID: 25458424 DOI: 10.1016/j.autneu.2014.10.019] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2014] [Revised: 08/14/2014] [Accepted: 10/13/2014] [Indexed: 11/22/2022]
Abstract
Sympathetic vasoconstriction is normally attenuated in exercising muscle by local changes in muscle metabolites and other substances that reduce vascular responsiveness to α-adrenergic receptor activation. Termed functional sympatholysis, this protective mechanism is thought to optimize muscle blood flow distribution to match perfusion with metabolic demand. Emerging evidence from both animal and human studies indicate that functional sympatholysis is impaired in hypertension and may constitute an important underlying cause of skeletal muscle malperfusion during exercise in this common cardiovascular condition. Findings from studies of animal models of hypertension and patients with essential hypertension will be integrated in this review to provide insight into the underlying mechanisms responsible for inappropriate sympathetic vasoconstriction in exercising muscle and the treatment options that may restore functional sympatholysis and improve muscle perfusion during exercise.
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29
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Mortensen SP, Nyberg M, Gliemann L, Thaning P, Saltin B, Hellsten Y. Exercise training modulates functional sympatholysis and α-adrenergic vasoconstrictor responsiveness in hypertensive and normotensive individuals. J Physiol 2014; 592:3063-73. [PMID: 24860173 DOI: 10.1113/jphysiol.2014.273722] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Essential hypertension is linked to an increased sympathetic vasoconstrictor activity and reduced tissue perfusion. We investigated the role of exercise training on functional sympatholysis and postjunctional α-adrenergic responsiveness in individuals with essential hypertension. Leg haemodynamics were measured before and after 8 weeks of aerobic training (3-4 times per week) in eight hypertensive (47 ± 2 years) and eight normotensive untrained individuals (46 ± 1 years) during arterial tyramine infusion, arterial ATP infusion and/or one-legged knee extensions. Before training, exercise hyperaemia and leg vascular conductance (LVC) were lower in the hypertensive individuals (P < 0.05) and tyramine lowered exercise hyperaemia and LVC in both groups (P < 0.05). Training lowered blood pressure in the hypertensive individuals (P < 0.05) and exercise hyperaemia was similar to the normotensive individuals in the trained state. After training, tyramine did not reduce exercise hyperaemia or LVC in either group. When tyramine was infused at rest, the reduction in blood flow and LVC was similar between groups, but exercise training lowered the magnitude of the reduction in blood flow and LVC (P < 0.05). There was no difference in the vasodilatory response to infused ATP or in muscle P2Y2 receptor content between the groups before and after training. However, training lowered the vasodilatory response to ATP and increased skeletal muscle P2Y2 receptor content in both groups (P < 0.05). These results demonstrate that exercise training improves functional sympatholysis and reduces postjunctional α-adrenergic responsiveness in both normo- and hypertensive individuals. The ability for functional sympatholysis and the vasodilator and sympatholytic effect of intravascular ATP appear not to be altered in essential hypertension.
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Affiliation(s)
- Stefan P Mortensen
- Department of Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark Copenhagen Muscle Research Centre, Rigshospitalet, Copenhagen, Denmark
| | - Michael Nyberg
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Lasse Gliemann
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Pia Thaning
- Copenhagen Muscle Research Centre, Rigshospitalet, Copenhagen, Denmark
| | - Bengt Saltin
- Copenhagen Muscle Research Centre, Rigshospitalet, Copenhagen, Denmark
| | - Ylva Hellsten
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
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30
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Mizuno M, Iwamoto GA, Vongpatanasin W, Mitchell JH, Smith SA. Exercise training improves functional sympatholysis in spontaneously hypertensive rats through a nitric oxide-dependent mechanism. Am J Physiol Heart Circ Physiol 2014; 307:H242-51. [PMID: 24816260 DOI: 10.1152/ajpheart.00103.2014] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Functional sympatholysis is impaired in hypertensive animals and patients. Exercise training (ET) improves functional sympatholysis through a nitric oxide (NO)-dependent mechanism in normotensive rats. However, whether ET has similar physiological benefits in hypertension remains to be elucidated. Thus we tested the hypothesis that the impairment in functional sympatholysis in hypertension is reversed by ET through a NO-dependent mechanism. In untrained normotensive Wistar-Kyoto rats (WKYUT; n = 13), untrained spontaneously hypertensive rats (SHRUT; n = 13), and exercise-trained SHR (SHRET; n = 6), changes in femoral vascular conductance (FVC) were examined during lumbar sympathetic nerve stimulation (1, 2.5, and 5 Hz) at rest and during muscle contraction. The magnitude of functional sympatholysis (Δ%FVC = Δ%FVC muscle contraction - Δ%FVC rest) in SHRUT was significantly lower than WKYUT (1 Hz: -2 ± 4 vs. 13 ± 3%; 2.5 Hz: 9 ± 3 vs. 21 ± 3%; and 5 Hz: 12 ± 3 vs. 26 ± 3%, respectively; P < 0.05). Three months of voluntary wheel running significantly increased maximal oxygen uptake in SHRET compared with nontrained SHRUT (78 ± 6 vs. 62 ± 4 ml·kg(-1)·min(-1), respectively; P < 0.05) and restored the magnitude of functional sympatholysis in SHRET (1 Hz: 9 ± 2%; 2.5 Hz: 20 ± 4%; and 5 Hz: 34 ± 5%). Blockade of NO synthase (NOS) by N(G)-nitro-l-arginine methyl ester attenuated functional sympatholysis in WKYUT but not SHRUT. Furthermore, NOS inhibition significantly diminished the improvements in functional sympatholysis in SHRET. These data demonstrate that impairments in functional sympatholysis are normalized via a NO mechanism by voluntary wheel running in hypertensive rats.
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Affiliation(s)
- Masaki Mizuno
- Department of Health Care Sciences, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Gary A Iwamoto
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Wanpen Vongpatanasin
- Department of Hypertension Section University of Texas Southwestern Medical Center, Dallas, Texas; and Division of Cardiology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Jere H Mitchell
- Division of Cardiology, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Scott A Smith
- Department of Health Care Sciences, University of Texas Southwestern Medical Center, Dallas, Texas; Division of Cardiology, University of Texas Southwestern Medical Center, Dallas, Texas
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31
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Nelson MD, Rader F, Tang X, Tavyev J, Nelson SF, Miceli MC, Elashoff RM, Sweeney HL, Victor RG. PDE5 inhibition alleviates functional muscle ischemia in boys with Duchenne muscular dystrophy. Neurology 2014; 82:2085-91. [PMID: 24808022 DOI: 10.1212/wnl.0000000000000498] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
OBJECTIVE To determine whether phosphodiesterase type 5 (PDE5) inhibition can alleviate exercise-induced skeletal muscle ischemia in boys with Duchenne muscular dystrophy (DMD). METHODS In 10 boys with DMD and 10 healthy age-matched male controls, we assessed exercise-induced attenuation of reflex sympathetic vasoconstriction, i.e., functional sympatholysis, a protective mechanism that matches oxygen delivery to metabolic demand. Reflex vasoconstriction was induced by simulated orthostatic stress, measured as the decrease in forearm muscle oxygenation with near-infrared spectroscopy, and performed when the forearm muscles were rested or lightly exercised with rhythmic handgrip exercise. Then, the patients underwent an open-label, dose-escalation, crossover trial with single oral doses of tadalafil or sildenafil. RESULTS The major new findings are 2-fold: first, sympatholysis is impaired in boys with DMD-producing functional muscle ischemia-despite contemporary background therapy with corticosteroids alone or in combination with cardioprotective medication. Second, PDE5 inhibition with standard clinical doses of either tadalafil or sildenafil alleviates this ischemia in a dose-dependent manner. Furthermore, PDE5 inhibition also normalizes the exercise-induced increase in skeletal muscle blood flow (measured by Doppler ultrasound), which is markedly blunted in boys with DMD. CONCLUSIONS These data provide in-human proof of concept for PDE5 inhibition as a putative new therapeutic strategy for DMD. CLASSIFICATION OF EVIDENCE This study provides Class IV evidence that in patients with DMD, PDE5 inhibition restores functional sympatholysis.
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Affiliation(s)
- Michael D Nelson
- From The Heart Institute (M.D.N., F.R., X.T., R.G.V.), and Department of Pediatrics (J.T.), Cedars-Sinai Medical Center, Los Angeles; Departments of Human Genetics (S.F.N.) and Pathology and Laboratory Medicine (S.F.N.), David Geffen School of Medicine at UCLA, Los Angeles; Department of Microbiology Immunology and Molecular Genetics (M.C.M.), David Geffen School of Medicine and College of Letters and Sciences, UCLA, Los Angeles; Department of Biomathematics (R.M.E.), and Department of Biostatistics, School of Public Health (R.M.E.), University of California, Los Angeles; and Pennsylvania Muscle Institute (H.L.S.), Department of Medicine, University of Pennsylvania, Philadelphia
| | - Florian Rader
- From The Heart Institute (M.D.N., F.R., X.T., R.G.V.), and Department of Pediatrics (J.T.), Cedars-Sinai Medical Center, Los Angeles; Departments of Human Genetics (S.F.N.) and Pathology and Laboratory Medicine (S.F.N.), David Geffen School of Medicine at UCLA, Los Angeles; Department of Microbiology Immunology and Molecular Genetics (M.C.M.), David Geffen School of Medicine and College of Letters and Sciences, UCLA, Los Angeles; Department of Biomathematics (R.M.E.), and Department of Biostatistics, School of Public Health (R.M.E.), University of California, Los Angeles; and Pennsylvania Muscle Institute (H.L.S.), Department of Medicine, University of Pennsylvania, Philadelphia
| | - Xiu Tang
- From The Heart Institute (M.D.N., F.R., X.T., R.G.V.), and Department of Pediatrics (J.T.), Cedars-Sinai Medical Center, Los Angeles; Departments of Human Genetics (S.F.N.) and Pathology and Laboratory Medicine (S.F.N.), David Geffen School of Medicine at UCLA, Los Angeles; Department of Microbiology Immunology and Molecular Genetics (M.C.M.), David Geffen School of Medicine and College of Letters and Sciences, UCLA, Los Angeles; Department of Biomathematics (R.M.E.), and Department of Biostatistics, School of Public Health (R.M.E.), University of California, Los Angeles; and Pennsylvania Muscle Institute (H.L.S.), Department of Medicine, University of Pennsylvania, Philadelphia
| | - Jane Tavyev
- From The Heart Institute (M.D.N., F.R., X.T., R.G.V.), and Department of Pediatrics (J.T.), Cedars-Sinai Medical Center, Los Angeles; Departments of Human Genetics (S.F.N.) and Pathology and Laboratory Medicine (S.F.N.), David Geffen School of Medicine at UCLA, Los Angeles; Department of Microbiology Immunology and Molecular Genetics (M.C.M.), David Geffen School of Medicine and College of Letters and Sciences, UCLA, Los Angeles; Department of Biomathematics (R.M.E.), and Department of Biostatistics, School of Public Health (R.M.E.), University of California, Los Angeles; and Pennsylvania Muscle Institute (H.L.S.), Department of Medicine, University of Pennsylvania, Philadelphia
| | - Stanley F Nelson
- From The Heart Institute (M.D.N., F.R., X.T., R.G.V.), and Department of Pediatrics (J.T.), Cedars-Sinai Medical Center, Los Angeles; Departments of Human Genetics (S.F.N.) and Pathology and Laboratory Medicine (S.F.N.), David Geffen School of Medicine at UCLA, Los Angeles; Department of Microbiology Immunology and Molecular Genetics (M.C.M.), David Geffen School of Medicine and College of Letters and Sciences, UCLA, Los Angeles; Department of Biomathematics (R.M.E.), and Department of Biostatistics, School of Public Health (R.M.E.), University of California, Los Angeles; and Pennsylvania Muscle Institute (H.L.S.), Department of Medicine, University of Pennsylvania, Philadelphia
| | - M Carrie Miceli
- From The Heart Institute (M.D.N., F.R., X.T., R.G.V.), and Department of Pediatrics (J.T.), Cedars-Sinai Medical Center, Los Angeles; Departments of Human Genetics (S.F.N.) and Pathology and Laboratory Medicine (S.F.N.), David Geffen School of Medicine at UCLA, Los Angeles; Department of Microbiology Immunology and Molecular Genetics (M.C.M.), David Geffen School of Medicine and College of Letters and Sciences, UCLA, Los Angeles; Department of Biomathematics (R.M.E.), and Department of Biostatistics, School of Public Health (R.M.E.), University of California, Los Angeles; and Pennsylvania Muscle Institute (H.L.S.), Department of Medicine, University of Pennsylvania, Philadelphia
| | - Robert M Elashoff
- From The Heart Institute (M.D.N., F.R., X.T., R.G.V.), and Department of Pediatrics (J.T.), Cedars-Sinai Medical Center, Los Angeles; Departments of Human Genetics (S.F.N.) and Pathology and Laboratory Medicine (S.F.N.), David Geffen School of Medicine at UCLA, Los Angeles; Department of Microbiology Immunology and Molecular Genetics (M.C.M.), David Geffen School of Medicine and College of Letters and Sciences, UCLA, Los Angeles; Department of Biomathematics (R.M.E.), and Department of Biostatistics, School of Public Health (R.M.E.), University of California, Los Angeles; and Pennsylvania Muscle Institute (H.L.S.), Department of Medicine, University of Pennsylvania, Philadelphia
| | - H Lee Sweeney
- From The Heart Institute (M.D.N., F.R., X.T., R.G.V.), and Department of Pediatrics (J.T.), Cedars-Sinai Medical Center, Los Angeles; Departments of Human Genetics (S.F.N.) and Pathology and Laboratory Medicine (S.F.N.), David Geffen School of Medicine at UCLA, Los Angeles; Department of Microbiology Immunology and Molecular Genetics (M.C.M.), David Geffen School of Medicine and College of Letters and Sciences, UCLA, Los Angeles; Department of Biomathematics (R.M.E.), and Department of Biostatistics, School of Public Health (R.M.E.), University of California, Los Angeles; and Pennsylvania Muscle Institute (H.L.S.), Department of Medicine, University of Pennsylvania, Philadelphia
| | - Ronald G Victor
- From The Heart Institute (M.D.N., F.R., X.T., R.G.V.), and Department of Pediatrics (J.T.), Cedars-Sinai Medical Center, Los Angeles; Departments of Human Genetics (S.F.N.) and Pathology and Laboratory Medicine (S.F.N.), David Geffen School of Medicine at UCLA, Los Angeles; Department of Microbiology Immunology and Molecular Genetics (M.C.M.), David Geffen School of Medicine and College of Letters and Sciences, UCLA, Los Angeles; Department of Biomathematics (R.M.E.), and Department of Biostatistics, School of Public Health (R.M.E.), University of California, Los Angeles; and Pennsylvania Muscle Institute (H.L.S.), Department of Medicine, University of Pennsylvania, Philadelphia.
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Horiuchi M, Fadel PJ, Ogoh S. Differential effect of sympathetic activation on tissue oxygenation in gastrocnemius and soleus muscles during exercise in humans. Exp Physiol 2013; 99:348-58. [PMID: 24163424 DOI: 10.1113/expphysiol.2013.075846] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? The normal ability of sympathetic nerves to cause vasoconstriction is blunted in exercising skeletal muscle, a phenomenon termed 'functional sympatholysis'. Animal studies suggest that functional sympatholysis appears to occur preferentially in fast-twitch type II glycolytic compared with slow-twitch type I oxidative skeletal muscle. We asked whether these findings can be extended to humans. What is the main finding and its importance? We show that skeletal muscles composed largely of fast-twitch type II fibres may also be more sensitive to functional sympatholysis in humans, particularly at lower exercise intensities. Additionally, independent of muscle fibre type composition, the magnitude of sympatholysis is strongly related to exercise-induced increases in metabolic demand. Animal studies suggest that functional sympatholysis appears to occur preferentially in glycolytic (largely type II) compared with oxidative (largely type I) skeletal muscle. Whether these findings can be extended to humans currently remains unclear. In 12 healthy male subjects, vasoconstrictor responses in gastrocnemius (i.e. primarily type II) and soleus muscles (i.e. primarily type I) were measured using near-infrared spectroscopy to detect decreases in muscle oxygenation (HbO(2)) in response to sympathetic activation evoked by a cold pressor test (CPT). The HbO(2) responses to a CPT at rest were compared with responses during steady-state plantar flexion exercise (30 repetitions min(-1)) performed at 10, 20 and 40% maximal voluntary contraction (MVC) for 6 min. In resting conditions, HbO(2) at the gastrocnemius (-14 ± 1%) and soleus muscles (-16 ± 1%) decreased significantly during CPT, with no differences between muscles. During planter flexion at 20% MVC, the change in HbO(2) in response to the CPT was blunted in gastrocnemius but not soleus, whereas during 40% MVC both muscles exhibited a significant attenuation to sympathetic activation. The decreases in HbO(2) in response to the CPT during exercise were significantly correlated with the metabolic demands of exercise (the decreases in HbO(2) in response to steady-state plantar flexion) in both gastrocnemius and soleus muscles. Collectively, these results suggest that skeletal muscles composed mainly of glycolytic type II fibres are more sensitive to functional sympatholysis, particularly at lower intensities of exercise. Moreover, the blunting of sympathetic vasoconstriction during exercise is strongly related to metabolic demand; an effect that appears independent of fibre type composition.
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Affiliation(s)
- Masahiro Horiuchi
- * Department of Biomedical Engineering, Toyo University, Kujirai 2100, Kawagoe City, Saitama 350-8585, Japan.
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Martin EA, Barresi R, Byrne BJ, Tsimerinov EI, Scott BL, Walker AE, Gurudevan SV, Anene F, Elashoff RM, Thomas GD, Victor RG. Tadalafil alleviates muscle ischemia in patients with Becker muscular dystrophy. Sci Transl Med 2013. [PMID: 23197572 DOI: 10.1126/scitranslmed.3004327] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Becker muscular dystrophy (BMD) is a progressive X-linked muscle wasting disease for which there is no treatment. Like Duchenne muscular dystrophy (DMD), BMD is caused by mutations in the gene encoding dystrophin, a structural cytoskeletal protein that also targets other proteins to the muscle sarcolemma. Among these is neuronal nitric oxide synthase (nNOSμ), which requires certain spectrin-like repeats in dystrophin's rod domain and the adaptor protein α-syntrophin to be targeted to the sarcolemma. When healthy skeletal muscle is subjected to exercise, sarcolemmal nNOSμ-derived NO attenuates local α-adrenergic vasoconstriction, thereby optimizing perfusion of muscle. We found previously that this protective mechanism is defective-causing functional muscle ischemia-in dystrophin-deficient muscles of the mdx mouse (a model of DMD) and of children with DMD, in whom nNOSμ is mislocalized to the cytosol instead of the sarcolemma. We report that this protective mechanism also is defective in men with BMD in whom the most common dystrophin mutations disrupt sarcolemmal targeting of nNOSμ. In these men, the vasoconstrictor response, measured as a decrease in muscle oxygenation, to reflex sympathetic activation is not appropriately attenuated during exercise of the dystrophic muscles. In a randomized placebo-controlled crossover trial, we show that functional muscle ischemia is alleviated and normal blood flow regulation is fully restored in the muscles of men with BMD by boosting NO-cGMP (guanosine 3',5'-monophosphate) signaling with a single dose of the drug tadalafil, a phosphodiesterase 5A inhibitor. These results further support an essential role for sarcolemmal nNOSμ in the normal modulation of sympathetic vasoconstriction in exercising human skeletal muscle and implicate the NO-cGMP pathway as a putative new target for treating BMD.
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Affiliation(s)
- Elizabeth A Martin
- The Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
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Price A, Raheja P, Wang Z, Arbique D, Adams-Huet B, Mitchell JH, Victor RG, Thomas GD, Vongpatanasin W. Differential effects of nebivolol versus metoprolol on functional sympatholysis in hypertensive humans. Hypertension 2013; 61:1263-9. [PMID: 23547240 DOI: 10.1161/hypertensionaha.113.01302] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In young healthy humans, sympathetic vasoconstriction is markedly blunted during exercise to optimize blood flow to the metabolically active muscle. This phenomenon known as functional sympatholysis is impaired in hypertensive humans and rats by angiotensin II-dependent mechanisms, involving oxidative stress and inactivation of nitric oxide (NO). Nebivolol is a β1-adrenergic receptor blocker that has NO-dependent vasodilatory and antioxidant properties. We therefore asked whether nebivolol would restore functional sympatholysis in hypertensive humans. In 21 subjects with stage 1 hypertension, we measured muscle oxygenation and forearm blood flow responses to reflex increases in sympathetic nerve activity evoked by lower body negative pressure at rest, and during rhythmic handgrip exercise at baseline, after 12 weeks of nebivolol (5-20 mg/d) or metoprolol (100-300 mg/d), using a double-blind crossover design. We found that nebivolol had no effect on lower body negative pressure-induced decreases in oxygenation and forearm blood flow in resting forearm (from -29±5% to -30±5% and from -29±3% to -29±3%, respectively; P=NS). However, nebivolol attenuated the lower body negative pressure-induced reduction in oxygenation and forearm blood flow in exercising forearm (from -14±4% to -1±5% and from -15±2% to -6±2%, respectively; both P<0.05). This effect of nebivolol on oxygenation and forearm blood flow in exercising forearm was not observed with metoprolol in the same subjects, despite a similar reduction in blood pressure. Nebivolol had no effect on sympathetic nerve activity at rest or during handgrip, suggesting a direct effect on vascular function. Thus, our data demonstrate that nebivolol restored functional sympatholysis in hypertensive humans by a mechanism that does not involve β1-adrenergic receptors. Clinical Trial Registration- URL: http://www.clinicaltrials.gov. Unique identifier: NCT01502787.
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Affiliation(s)
- Angela Price
- Hypertension Section, Cardiology Division, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, U9.400, Dallas, TX 75390-8586, USA
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Murias JM, Spencer MD, Keir DA, Paterson DH. Systemic and vastus lateralis muscle blood flow and O2 extraction during ramp incremental cycle exercise. Am J Physiol Regul Integr Comp Physiol 2013; 304:R720-5. [PMID: 23515617 DOI: 10.1152/ajpregu.00016.2013] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
During ramp incremental cycling exercise increases in pulmonary O2 uptake (Vo2p) are matched by a linear increase in systemic cardiac output (Q). However, it has been suggested that blood flow in the active muscle microvasculature does not display similar linearity in blood flow relative to metabolic demand. This study simultaneously examined both systemic and regional (microvascular) blood flow and O2 extraction during incremental cycling exercise. Ten young men (Vo2 peak = 4.2 ± 0.5 l/min) and 10 young women (Vo2 peak = 3.2 ± 0.5 l/min) were recruited to perform two maximal incremental cycling tests on separate days. The acetylene open-circuit technique and mass spectrometry and volume turbine were used to measure Q (every minute) and breath-by-breath Vo2p, respectively; systemic arterio-venous O2 difference (a-vO2diff) was calculated as Vo2p/Q on a minute-by-minute basis. Changes in near-infrared spectroscopy-derived muscle deoxygenation (Δ[HHb]) were used (in combination with Vo2p data) to estimate the profiles of peripheral O2 extraction and blood flow of the active muscle microvasculature. The systemic Q-to-Vo2p relationship was linear (~5.8 l/min increase in Q for a 1 l/min increase in Vo2p) with a-vO2diff displaying a hyperbolic response as exercise intensity increased toward Vo2 peak. The peripheral blood flow response profile was described by an inverted sigmoid curve, indicating nonlinear responses relative to metabolic demand. The Δ[HHb] profile increased linearly with absolute Vo2p until high-intensity exercise, thereafter displaying a "near-plateau". Results indicate that systemic blood flow and thus O2 delivery does not reflect the profile of blood flow changes at the level of the microvasculature.
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Affiliation(s)
- Juan M Murias
- Canadian Centre for Activity and Aging, School of Kinesiology, University of Western Ontario, London, Ontario, Canada
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36
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Thomas GD, Ye J, De Nardi C, Monopoli A, Ongini E, Victor RG. Treatment with a nitric oxide-donating NSAID alleviates functional muscle ischemia in the mouse model of Duchenne muscular dystrophy. PLoS One 2012; 7:e49350. [PMID: 23139842 PMCID: PMC3489726 DOI: 10.1371/journal.pone.0049350] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Accepted: 10/10/2012] [Indexed: 12/03/2022] Open
Abstract
In patients with Duchenne muscular dystrophy (DMD) and the standard mdx mouse model of DMD, dystrophin deficiency causes loss of neuronal nitric oxide synthase (nNOSμ) from the sarcolemma, producing functional ischemia when the muscles are exercised. We asked if functional muscle ischemia would be eliminated and normal blood flow regulation restored by treatment with an exogenous nitric oxide (NO)-donating drug. Beginning at 8 weeks of age, mdx mice were fed a standard diet supplemented with 1% soybean oil alone or in combination with a low (15 mg/kg) or high (45 mg/kg) dose of HCT 1026, a NO-donating nonsteroidal anti-inflammatory agent which has previously been shown to slow disease progression in the mdx model. After 1 month of treatment, vasoconstrictor responses to intra-arterial norepinephrine (NE) were compared in resting and contracting hindlimbs. In untreated mdx mice, the usual effect of muscle contraction to attenuate NE-mediated vasoconstriction was impaired, resulting in functional ischemia: NE evoked similar decreases in femoral blood flow velocity and femoral vascular conductance (FVC) in the contracting compared to resting hindlimbs (ΔFVC contraction/ΔFVC rest = 0.88±0.03). NE-induced functional ischemia was unaffected by low dose HCT 1026 (ΔFVC ratio = 0.92±0.04; P>0.05 vs untreated), but was alleviated by the high dose of the drug (ΔFVC ratio = 0.22±0.03; P<0.05 vs untreated or low dose). The beneficial effect of high dose HCT 1026 was maintained with treatment up to 3 months. The effect of the NO-donating drug HCT 1026 to normalize blood flow regulation in contracting mdx mouse hindlimb muscles suggests a putative novel treatment for DMD. Further translational research is warranted.
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MESH Headings
- Animals
- Anti-Inflammatory Agents, Non-Steroidal/pharmacology
- Anti-Inflammatory Agents, Non-Steroidal/therapeutic use
- Biomechanical Phenomena/drug effects
- Disease Models, Animal
- Feeding Behavior/drug effects
- Flurbiprofen/analogs & derivatives
- Flurbiprofen/pharmacology
- Flurbiprofen/therapeutic use
- Hemodynamics/drug effects
- Hindlimb/physiopathology
- Ischemia/drug therapy
- Ischemia/pathology
- Ischemia/physiopathology
- Male
- Mice
- Mice, Inbred C57BL
- Muscle Contraction
- Muscles/blood supply
- Muscles/drug effects
- Muscles/physiopathology
- Muscular Dystrophy, Animal/drug therapy
- Muscular Dystrophy, Animal/pathology
- Muscular Dystrophy, Animal/physiopathology
- Muscular Dystrophy, Duchenne/drug therapy
- Muscular Dystrophy, Duchenne/pathology
- Muscular Dystrophy, Duchenne/physiopathology
- Nitric Oxide Donors/pharmacology
- Nitric Oxide Donors/therapeutic use
- Norepinephrine
- Time Factors
- Vasoconstriction/drug effects
- Weight Gain/drug effects
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Affiliation(s)
- Gail D Thomas
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA.
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Mortensen SP, Nyberg M, Winding K, Saltin B. Lifelong physical activity preserves functional sympatholysis and purinergic signalling in the ageing human leg. J Physiol 2012; 590:6227-36. [PMID: 22966164 DOI: 10.1113/jphysiol.2012.240093] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Ageing is associated with an impaired ability to modulate sympathetic vasoconstrictor activity (functional sympatholysis) and a reduced exercise hyperaemia. The purpose of this study was to investigate whether a physically active lifestyle can offset the impaired functional sympatholysis and exercise hyperaemia in the leg and whether ATP signalling is altered by ageing and physical activity. Leg haemodynamics, interstitial [ATP] and P2Y(2) receptor content was determined in eight young (23 ± 1 years), eight lifelong sedentary elderly (66 ± 2 years) and eight lifelong active elderly (62 ± 2 years) men at rest and during one-legged knee extensions (12 W and 45% maximal workload (WL(max))) and arterial infusion of ACh and ATP with and without tyramine. The vasodilatory response to ACh was lowest in the sedentary elderly, higher in active elderly (P < 0.05) and highest in the young men (P < 0.05), whereas ATP-induced vasodilatation was lower in the sedentary elderly (P < 0.05). During exercise (12 W), leg blood flow, vascular conductance and VO2 was lower and leg lactate release higher in the sedentary elderly compared to the young (P < 0.05), whereas there was no difference between the active elderly and young. Interstitial [ATP] during exercise and P2Y(2) receptor content were higher in the active elderly compared to the sedentary elderly (P < 0.05). Tyramine infusion lowered resting vascular conductance in all groups, but only in the sedentary elderly during exercise (P < 0.05). Tyramine did not alter the vasodilator response to ATP infusion in any of the three groups. Plasma [noradrenaline] increased more during tyramine infusion in both elderly groups compared to young (P < 0.05). A lifelong physically active lifestyle can maintain an intact functional sympatholysis during exercise and vasodilator response to ATP despite a reduction in endothelial nitric oxide function. A physically active lifestyle increases interstitial ATP levels and skeletal muscle P2Y(2) receptor content.
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Affiliation(s)
- S P Mortensen
- The Copenhagen Muscle Research Centre, Rigshospitalet, Section 7641, Blegdamsvej 9, DK-2100 Copenhagen Ø, Denmark.
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Mortensen SP, Mørkeberg J, Thaning P, Hellsten Y, Saltin B. Two weeks of muscle immobilization impairs functional sympatholysis but increases exercise hyperemia and the vasodilatory responsiveness to infused ATP. Am J Physiol Heart Circ Physiol 2012; 302:H2074-82. [PMID: 22408019 DOI: 10.1152/ajpheart.01204.2011] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
During exercise, contracting muscles can override sympathetic vasoconstrictor activity (functional sympatholysis). ATP and adenosine have been proposed to play a role in skeletal muscle blood flow regulation. However, little is known about the role of muscle training status on functional sympatholysis and ATP- and adenosine-induced vasodilation. Eight male subjects (22 ± 2 yr, Vo(2max): 49 ± 2 ml O(2)·min(-1)·kg(-1)) were studied before and after 5 wk of one-legged knee-extensor training (3-4 times/wk) and 2 wk of immobilization of the other leg. Leg hemodynamics were measured at rest, during exercise (24 ± 4 watts), and during arterial ATP (0.94 ± 0.03 μmol/min) and adenosine (5.61 ± 0.03 μmol/min) infusion with and without coinfusion of tyramine (11.11 μmol/min). During exercise, leg blood flow (LBF) was lower in the trained leg (2.5 ± 0.1 l/min) compared with the control leg (2.6 ± 0.2 l/min; P < 0.05), and it was higher in the immobilized leg (2.9 ± 0.2 l/min; P < 0.05). Tyramine infusion lowers LBF similarly at rest, but, when tyramine was infused during exercise, LBF was blunted in the immobilized leg (2.5 ± 0.2 l/min; P < 0.05), whereas it was unchanged in the control and trained leg. Mean arterial pressure was lower during exercise with the trained leg compared with the immobilized leg (P < 0.05), and leg vascular conductance was similar. During ATP infusion, the LBF response was higher after immobilization (3.9 ± 0.3 and 4.5 ± 0.6 l/min in the control and immobilized leg, respectively; P < 0.05), whereas it did not change after training. When tyramine was coinfused with ATP, LBF was reduced in the immobilized leg (P < 0.05) but remained similar in the control and trained leg. Training increased skeletal muscle P2Y2 receptor content (P < 0.05), whereas it did not change with immobilization. These results suggest that muscle inactivity impairs functional sympatholysis and that the magnitude of hyperemia and blood pressure response to exercise is dependent on the training status of the muscle. Immobilization also increases the vasodilatory response to infused ATP.
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Affiliation(s)
- S P Mortensen
- The Copenhagen Muscle Research Centre, Rigshospitalet, Denmark.
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Zhang M, Hasegawa Y, Sakagami J, Ono T, Hori K, Maeda Y, Chen YJ. Effects of unilateral jaw clenching on cerebral/systemic circulation and related autonomic nerve activity. Physiol Behav 2012; 105:292-7. [DOI: 10.1016/j.physbeh.2011.07.028] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2011] [Revised: 07/26/2011] [Accepted: 07/27/2011] [Indexed: 10/17/2022]
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Fadel PJ, Farias Iii M, Gallagher KM, Wang Z, Thomas GD. Oxidative stress and enhanced sympathetic vasoconstriction in contracting muscles of nitrate-tolerant rats and humans. J Physiol 2011; 590:395-407. [PMID: 22106180 DOI: 10.1113/jphysiol.2011.218917] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Sympathetic vasoconstriction is normally attenuated in exercising muscle, but this functional sympatholysis is impaired in rats with hypertension or heart failure due to elevated levels of reactive oxygen species (ROS) in muscle. Whether ROS have a similar effect in the absence of cardiovascular disease or whether these findings extend to humans is not known. We therefore tested the hypothesis that chronic treatment with nitroglycerin (NTG) to induce nitrate tolerance, which is associated with excessive ROS production, impairs functional sympatholysis in healthy rats and humans. NTG treatment increased ethidium fluorescence in rat muscles and urinary F(2)-isoprostanes in humans, demonstrating oxidative stress. In vehicle-treated rats, sympathetic nerve stimulation (1 to 5 Hz) evoked decreases in femoral vascular conductance at rest (range, -30 to -63%) that were attenuated during hindlimb contraction (range, -2 to -31%; P < 0.05). In NTG-treated rats, vasoconstrictor responses were similar at rest, but were enhanced during contraction (range, -17 to -50%; P < 0.05 vs. vehicle). Infusion of the ROS scavenger tempol restored sympatholysis in these rats. In humans, reflex sympathetic activation during lower body negative pressure (LBNP) evoked decreases in muscle oxygenation in resting forearm (-12 ± 1%) that were attenuated during handgrip exercise (-3 ± 1%; P < 0.05). When these subjects became nitrate tolerant, LBNP-induced decreases in muscle oxygenation were unaffected at rest, but were enhanced during exercise (-9 ± 1%; P < 0.05 vs. before NTG). Collectively, these data indicate that functional sympatholysis is impaired in otherwise healthy nitrate-tolerant rats and humans by a mechanism probably involving muscle oxidative stress.
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Affiliation(s)
- Paul J Fadel
- Cedars-Sinai Medical Centre, 8700 Beverly Boulevard, Los Angeles, CA 90048, USA
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Limb oxygenation during the cold pressor test in spinal cord-injured humans. Clin Auton Res 2011; 22:71-8. [PMID: 21948381 DOI: 10.1007/s10286-011-0143-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2011] [Accepted: 08/15/2011] [Indexed: 10/17/2022]
Abstract
OBJECTIVE To investigate changes in tissue oxygenation in the arm and leg during the cold pressor test in humans with spinal cord injury (SCI). METHODS Subjects with SCI at cervical 6 (n=7) and subjects with SCI at thoracic 5 or thoracic 6 (n=5) experienced 3-min cold water immersion of the foot and subsequent 10-min recovery. Changes in tissue oxygenation and blood pressure were determined. Tissue oxygenation was assessed by hemoglobin/myoglobin concentration (Hb/MbO2) measured using near-infrared spectroscopy. RESULTS Mean arterial blood pressures increased significantly by 15±9 and 6±6 mmHg during cold water immersion in the cervical and thoracic SCI groups, respectively (P<0.001). Hb/MbO2 in the arm decreased significantly by 23±15 μM cm during cold water immersion only in the cervical SCI group (P<0.001), whereas Hb/MbO2 in the leg decreased significantly by 82±56 μM cm during cold water immersion only in the thoracic SCI group (P<0.001). INTERPRETATION Afferent activity coming from below the lesion due to cold stimuli would reflexively enhance sympathetic activity in both the arm and leg in individuals with cervical SCI but only in the leg in individuals with thoracic SCI. A decrease in tissue oxygenation might have been caused by sympathetic vasoconstriction. The reduction of tissue oxygenation in the arm was marked in individuals with cervical SCI, suggesting differential control of arm oxygenation and leg oxygenation in the region below SCI.
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Casey DP, Joyner MJ. Local control of skeletal muscle blood flow during exercise: influence of available oxygen. J Appl Physiol (1985) 2011; 111:1527-38. [PMID: 21885800 DOI: 10.1152/japplphysiol.00895.2011] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Reductions in oxygen availability (O(2)) by either reduced arterial O(2) content or reduced perfusion pressure can have profound influences on the circulation, including vasodilation in skeletal muscle vascular beds. The purpose of this review is to put into context the present evidence regarding mechanisms responsible for the local control of blood flow during acute systemic hypoxia and/or local hypoperfusion in contracting muscle. The combination of submaximal exercise and hypoxia produces a "compensatory" vasodilation and augmented blood flow in contracting muscles relative to the same level of exercise under normoxic conditions. A similar compensatory vasodilation is observed in response to local reductions in oxygen availability (i.e., hypoperfusion) during normoxic exercise. Available evidence suggests that nitric oxide (NO) contributes to the compensatory dilator response under each of these conditions, whereas adenosine appears to only play a role during hypoperfusion. During systemic hypoxia the NO-mediated component of the compensatory vasodilation is regulated through a β-adrenergic receptor mechanism at low-intensity exercise, while an additional (not yet identified) source of NO is likely to be engaged as exercise intensity increases during hypoxia. Potential candidates for stimulating and/or interacting with NO at higher exercise intensities include prostaglandins and/or ATP. Conversely, prostaglandins do not appear to play a role in the compensatory vasodilation during exercise with hypoperfusion. Taken together, the data for both hypoxia and hypoperfusion suggest NO is important in the compensatory vasodilation seen when oxygen availability is limited. This is important from a basic biological perspective and also has pathophysiological implications for diseases associated with either hypoxia or hypoperfusion.
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Affiliation(s)
- Darren P Casey
- Dept. of Anesthesiology, Mayo Clinic, Rochester, MN 55905, USA.
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Kirby BS, Crecelius AR, Voyles WF, Dinenno FA. Modulation of postjunctional α-adrenergic vasoconstriction during exercise and exogenous ATP infusions in ageing humans. J Physiol 2011; 589:2641-53. [PMID: 21486772 DOI: 10.1113/jphysiol.2010.204081] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The ability to modulate sympathetic α-adrenergic vasoconstriction in contracting muscle is impaired with age. In young adults, adenosine triphosphate (ATP) has been shown to blunt sympathetic vasoconstrictor responsiveness similar to exercise. Therefore, we tested the hypothesis that modulation of postjunctional α-adrenergic vasoconstriction to exogenous ATP is impaired in ageing humans.We measured forearm blood flow (FBF; Doppler ultrasound) and calculated vascular conductance (FVC) to intra-arterial infusions of phenylephrine (α₁-agonist) and dexmedetomidine (α₂-agonist) during rhythmic handgrip exercise (15% MVC), a control non-exercise vasodilator condition (adenosine), and ATP infusion in seven older (64 ± 3 years) and seven young (22 ± 1 years) healthy adults. Forearm hyperaemia was matched across all vasodilatating conditions. During adenosine, forearm vasoconstrictor responses to direct α₁-stimulation were lower in older compared with young adults (ΔFVC=-25 ± 3% vs. -41 ± 5%; P <0.05), whereas the responses to α₂-stimulation were not different (-35±6% vs. -44 ± 8%; NS). During exercise, α₁-mediated vasoconstriction was significantly blunted compared with adenosine in both young (-9 ± 2% vs. -41 ± 5%) and older adults (-15 ± 2% vs. -25 ± 3%); however, the magnitude of sympatholysis was reduced in older adults (32 ± 13 vs. 74 ± 8%; P <0.05). Similarly, α₂-mediated vasoconstriction during exercise was significantly blunted in both young (-15 ± 4% vs. -44 ± 8%) and older adults (-26 ± 3% vs. -35 ± 6%), however the magnitude of sympatholysis was reduced in older adults (19 ± 8% vs. 60 ± 10%; P <0.05). During ATP, both α₁- and α₂-mediated vasoconstriction was nearly abolished in young and older adults (ΔFVC ∼ -5%), and the magnitude of sympatholysis was similar in both age groups (∼85-90%). Our findings indicate that the ability to modulate postjunctional α-adrenergic vasoconstriction during exercise is impaired with age, whereas the sympatholytic effect of exogenous ATP is preserved. Thus, if impairments in vascular control during exercise in older adults involve vasoactive ATP, we speculate that circulating ATP is reduced with advancing age.
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Affiliation(s)
- Brett S Kirby
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Vascular Physiology Research Group, Colorado State University, Fort Collins, CO 80523-1582, USA
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Hartwich D, Fowler KL, Wynn LJ, Fisher JP. Differential responses to sympathetic stimulation in the cerebral and brachial circulations during rhythmic handgrip exercise in humans. Exp Physiol 2011; 95:1089-97. [PMID: 20851860 DOI: 10.1113/expphysiol.2010.054387] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The sympathetic neural regulation of the cerebral circulation remains controversial. The purpose of the present study was to determine how exercise modulates the simultaneous responsiveness of the cerebral and brachial circulations to 'endogenous' sympathetic activation (cold pressor test). In nine healthy subjects, heart rate (HR) and mean arterial blood pressure (MAP) were continuously measured during cold pressor tests (4°C water) conducted at rest and during randomized bouts of rhythmic handgrip of 10, 25 and 40% of maximal voluntary contraction. Doppler ultrasound was used to examine brachial artery blood flow (FBF) and middle cerebral artery (MCA) mean blood velocity (V mean), and indices of vascular conductance were calculated for the brachial artery (forearm vascular conductance, FVC) and MCA (cerebral vascular conductance index, CVCi). End-tidal PCO2 (P ET.CO2) was evaluated on a breath-by-breath basis. Handgrip evoked increases in HR, FBF, FVC and MCA V mean (P < 0.05 versus rest), while MAP and CVCi were unchanged and P ET.CO2 fell slightly (P < 0.05 versus rest). Increases in MAP and HR during the cold pressor test were similar at rest and during all handgrip trials. Forearm vascular conductance was markedly reduced with the cold pressor test at rest (-45 ± 8%), but this vasoconstrictor effect was progressively attenuated with increasing exercise intensity (FVC -17 ± 3% during exercise at 40% of maximal voluntary contraction; P < 0.05). In contrast, the small reduction in CVCi with cold pressor test was similar at rest and during handgrip (approximately -5%). Our data indicate that while the marked vasoconstrictor responses to sympathetic activation in the skeletal muscle vasculature are blunted by handgrip exercise, the modest cerebrovascular responses to a cold pressor test remain unchanged.
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Affiliation(s)
- Doreen Hartwich
- School of Sport and Exercise Sciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
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Keller DM, Sander M, Stallknecht B, Crandall CG. α-Adrenergic vasoconstrictor responsiveness is preserved in the heated human leg. J Physiol 2011; 588:3799-808. [PMID: 20693291 DOI: 10.1113/jphysiol.2010.194506] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
This study tested the hypothesis that passive leg heating attenuates α-adrenergic vasoconstriction within that limb. Femoral blood flow (FBF, femoral artery ultrasound Doppler) and femoral vascular conductance (FVC, FBF/mean arterial blood pressure), as well as calf muscle blood flow (CalfBF, ¹³³xenon) and calf vascular conductance (CalfVC) were measured during intra-arterial infusion of an α₁-adrenoreceptor agonist, phenylephrine (PE, 0.025 to 0.8 μg kg₋₁ min₋₁) and an α₂-adrenoreceptor agonist, BHT-933 (1.0 to 10 μg kg₋₁ min₋₁) during normothermia and passive leg heating (water-perfused pant leg). Passive leg heating (∼46◦C water temperature) increased FVC from 4.5 ± 0.5 to 11.9 ± 1.3 ml min₋₁ mmHg₋₁ (P < 0.001). Interestingly, CalfBF (1.8±0.2 vs. 2.8±0.3mlmin₋₁ (100 g)₋₁) and CalfVC (2.0±0.3 vs. 3.9±0.5mlmin₋₁ (100 g)₋₁ mmHg₋₁ ×100) were also increased by this perturbation (P <0.05 for both). Infusion of PE and BHT-933 resulted in greater absolute decreases in FVC during leg heating compared to normothermic conditions (maximal decreases in FVC during heating vs. normothermia: PE: 7.8 ± 1.1 vs. 2.8 ± 0.5 ml min₋₁ mmHg₋₁; BHT-933: 8.6 ± 1.7 vs. 2.1 ± 0.4 ml min₋₁ mmHg₋₁; P < 0.01 for both). However, the nadir FVC during drug infusion was higher during passive leg heating compared to normothermic conditions (FVC at highest dose of respective drugs during heating vs. normothermic conditions: PE: 3.7 ± 0.4 vs. 2.0 ± 0.3 ml min₋₁ mmHg₋₁; BHT-933: 3.8 ± 0.2 vs. 2.1 ± 0.3 ml min₋₁ mmHg₋₁; P < 0.001 for both). Leg heating did not alter the responsiveness of CalfBF or CalfVC to either PE or BHT-933. Taken together, these observations suggest that local heating does not decrease α-adrenergic responsiveness.However, heat-induced vasodilatation opposes α-adrenergic vasoconstriction. Furthermore, passive heating of a limb causes not only an increase in skin blood flow but also in muscle blood flow.
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Affiliation(s)
- David M Keller
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, TX 75231, USA
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Vongpatanasin W, Wang Z, Arbique D, Arbique G, Adams-Huet B, Mitchell JH, Victor RG, Thomas GD. Functional sympatholysis is impaired in hypertensive humans. J Physiol 2011; 589:1209-20. [PMID: 21224235 DOI: 10.1113/jphysiol.2010.203026] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
In healthy individuals, sympathetic vasoconstriction is markedly blunted in exercising muscles to optimize blood flow to the metabolically active muscle fibres. This protective mechanism, termed functional sympatholysis, is impaired in rat models of angiotensin-dependent hypertension. However, the relevance of these findings to human hypertension is unknown. Therefore, in 13 hypertensive and 17 normotensive subjects we measured muscle oxygenation and forearm blood flow (FBF) responses to reflex increases in sympathetic nerve activity (SNA) evoked by lower body negative pressure (LBNP) at rest and during moderate-intensity rhythmic handgrip exercise. In the normotensives, LBNP caused decreases in oxygenation and FBF (−16 ± 2% and −23 ± 4%, respectively) in resting forearm but not in exercising forearm (−1 ± 2% and −1 ± 3%, respectively; P < 0.05 vs. rest). In the hypertensives, LBNP evoked decreases in oxygenation and FBF that were similar in the resting and exercising forearm (−14 ± 2% vs. −12 ± 2% and −20 ± 3% vs. −13 ± 2%, respectively; P > 0.05), indicating impaired functional sympatholysis. In the hypertensives, SNA was unexpectedly increased by 54 ± 11% during handgrip alone. However, when SNA was experimentally increased during exercise in the normotensives, sympatholysis was unaffected. Treatment for 4 weeks with the angiotensin receptor blocker irbesartan, but not with the thiazide-type diuretic chlorthalidone, restored sympatholysis in the hypertensives. These data provide the first evidence that functional sympatholysis is impaired in hypertensive humans by a mechanism that appears to involve an angiotensin-dependent increase in sympathetic vasoconstriction in the exercising muscles.
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Affiliation(s)
- Wanpen Vongpatanasin
- Hypertension Section, Cardiology Division, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., U9.400, Dallas, TX 75390-8586, USA.
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Malpas SC. Sympathetic nervous system overactivity and its role in the development of cardiovascular disease. Physiol Rev 2010; 90:513-57. [PMID: 20393193 DOI: 10.1152/physrev.00007.2009] [Citation(s) in RCA: 431] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
This review examines how the sympathetic nervous system plays a major role in the regulation of cardiovascular function over multiple time scales. This is achieved through differential regulation of sympathetic outflow to a variety of organs. This differential control is a product of the topographical organization of the central nervous system and a myriad of afferent inputs. Together this organization produces sympathetic responses tailored to match stimuli. The long-term control of sympathetic nerve activity (SNA) is an area of considerable interest and involves a variety of mediators acting in a quite distinct fashion. These mediators include arterial baroreflexes, angiotensin II, blood volume and osmolarity, and a host of humoral factors. A key feature of many cardiovascular diseases is increased SNA. However, rather than there being a generalized increase in SNA, it is organ specific, in particular to the heart and kidneys. These increases in regional SNA are associated with increased mortality. Understanding the regulation of organ-specific SNA is likely to offer new targets for drug therapy. There is a need for the research community to develop better animal models and technologies that reflect the disease progression seen in humans. A particular focus is required on models in which SNA is chronically elevated.
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Affiliation(s)
- Simon C Malpas
- Department of Physiology and the Auckland Bioengineering Institute, University of Auckland and Telemetry Research Ltd., Auckland, New Zealand.
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Sjøgaard G, Rosendal L, Kristiansen J, Blangsted AK, Skotte J, Larsson B, Gerdle B, Saltin B, Søgaard K. Muscle oxygenation and glycolysis in females with trapezius myalgia during stress and repetitive work using microdialysis and NIRS. Eur J Appl Physiol 2009; 108:657-69. [PMID: 19894061 DOI: 10.1007/s00421-009-1268-2] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/19/2009] [Indexed: 11/28/2022]
Abstract
The aim of this investigation was to study female workers active in the labour market for differences between those with trapezius myalgia (MYA) and without (CON) during repetitive pegboard (PEG) and stress (STR) tasks regarding (1) relative muscle load, (2) trapezius muscle blood flow, (3) metabolite accumulation, (4) oxygenation, and (5) pain development. Among 812 female employees (age 30-60 years) at 7 companies with high prevalence of neck/shoulder complaints, clinical examination identified 43 MYA and 19 CON. At rest, during PEG, and STR the trapezius muscle was measured using (1) EMG and MMG, (2) microdialysis, and (3) NIRS. Further, subjective pain ratings were scored (VAS). EMGrms in %MVE (Maximal Voluntary EMG-activity), was significantly higher among MYA than CON during PEG (11.74 +/- 9.09 vs. 7.42 +/- 5.56%MVE) and STR (5.47 +/- 5.00 vs. 3.28 +/- 1.94%MVE). MANOVA showed a group and time effect regarding data from the microdialysis: for MYA versus CON group differences demonstrated lower muscle blood flow and higher lactate and pyruvate concentrations. Potassium and glucose only showed time effects. NIRS showed similar initial decreases in oxygenation with PEG in both groups, but only in CON a significant increase back to baseline during PEG. VAS score at rest was highest among MYA and increased during PEG, but not for CON. The results showed significant differences between CON and MYA regarding muscle metabolism at rest and with PEG and STR. Higher relative muscle load during PEG and STR, insufficient muscle blood flow and oxygenation may account for the higher lactate, pyruvate and pain responses among MYA versus CON.
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Affiliation(s)
- Gisela Sjøgaard
- Institute of Sport Sciences and Clinical Biomechanics, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark.
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Effects of Exercise Training on Calf Tissue Oxygenation in Men With Intermittent Claudication. PM R 2009; 1:932-40. [DOI: 10.1016/j.pmrj.2009.08.453] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2009] [Revised: 08/05/2009] [Accepted: 08/30/2009] [Indexed: 11/20/2022]
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