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McMillan NJ, Jacob DW, Shariffi B, Harper JL, Foster GE, Manrique-Acevedo C, Padilla J, Limberg JK. Effect of acute intranasal insulin administration on muscle sympathetic nerve activity in healthy young adults. Am J Physiol Heart Circ Physiol 2024; 327:H000. [PMID: 38787381 PMCID: PMC11390129 DOI: 10.1152/ajpheart.00253.2024] [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: 04/22/2024] [Revised: 05/14/2024] [Accepted: 05/23/2024] [Indexed: 05/25/2024]
Abstract
Systemic insulin increases muscle sympathetic nerve activity (MSNA) via both central actions within the brainstem and peripheral activation of the arterial baroreflex. Augmented MSNA during hyperinsulinemia likely restrains peripheral vasodilation and contributes to the maintenance of blood pressure (BP). However, in the absence of insulin action within the peripheral vasculature, whether central insulin stimulation increases MSNA and influences peripheral hemodynamics in humans remains unknown. Herein, we hypothesized intranasal insulin administration would increase MSNA and BP in healthy young adults. Participants were assigned to time control [TC, n = 13 (5 females/8 males), 28 ± 1 yr] or 160 IU of intranasal insulin administered over 5 min [n = 15 (5 females/10 males), 26 ± 2 yr]; five (1 female/4 males) participants completed both conditions. MSNA (fibular microneurography), BP (finger photoplethysmography), and leg blood flow (LBF, femoral Doppler ultrasound) were assessed at baseline, and 15 and 30 min following insulin administration. Leg vascular conductance [LVC = (LBF ÷ mean BP) × 100] was calculated. Venous insulin and glucose concentrations remained unchanged throughout (P > 0.05). Following intranasal insulin administration, MSNA (burst frequency; baseline = 100%; minute 15, 121 ± 8%; minute 30, 118 ± 6%; P = 0.009, n = 7) and mean BP (baseline = 100%; minute 15, 103 ± 1%; minute 30, 102 ± 1%; P = 0.003) increased, whereas LVC decreased (baseline = 100%; minute 15, 93 ± 3%; minute 30, 99 ± 3%; P = 0.03). In contrast, MSNA, mean BP, and LVC were unchanged in TC participants (P > 0.05). We provide the first evidence that intranasal insulin administration in healthy young adults acutely increases MSNA and BP and decreases LVC. These results enhance mechanistic understanding of the sympathetic and peripheral hemodynamic response to insulin.NEW & NOTEWORTHY Systemic insulin increases muscle sympathetic nerve activity (MSNA) via central actions within the brainstem and peripheral activation of the arterial baroreflex. In the absence of peripheral insulin action, whether central insulin stimulation increases MSNA and influences peripheral hemodynamics in humans was unknown. We provide the first evidence that intranasal insulin administration increases MSNA and blood pressure and reduces leg vascular conductance. These results enhance mechanistic understanding of the sympathetic and hemodynamic response to insulin.
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Affiliation(s)
- Neil J McMillan
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri, United States
- NextGen Precision Health, University of Missouri, Columbia, Missouri, United States
| | - Dain W Jacob
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri, United States
| | - Brian Shariffi
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri, United States
| | - Jennifer L Harper
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri, United States
| | - Glen E Foster
- School of Health and Exercise Sciences, Centre for Heart, Lung, and Vascular Health, University of British Columbia, Kelowna, Canada
| | - Camila Manrique-Acevedo
- NextGen Precision Health, University of Missouri, Columbia, Missouri, United States
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Missouri, Columbia, Missouri, United States
- Research Services, Harry S. Truman Memorial Veterans Hospital, Columbia, Missouri, United States
| | - Jaume Padilla
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri, United States
- NextGen Precision Health, University of Missouri, Columbia, Missouri, United States
- Research Services, Harry S. Truman Memorial Veterans Hospital, Columbia, Missouri, United States
| | - Jacqueline K Limberg
- Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri, United States
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri, United States
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Shafer BM, West CR, Foster GE. Advancements in the neurocirculatory reflex response to hypoxia. Am J Physiol Regul Integr Comp Physiol 2024; 327:R1-R13. [PMID: 38738293 PMCID: PMC11380992 DOI: 10.1152/ajpregu.00237.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 04/16/2024] [Accepted: 04/29/2024] [Indexed: 05/14/2024]
Abstract
Hypoxia is a pivotal factor in the pathophysiology of various clinical conditions, including obstructive sleep apnea, which has a strong association with cardiovascular diseases like hypertension, posing significant health risks. Although the precise mechanisms linking hypoxemia-associated clinical conditions with hypertension remains incompletely understood, compelling evidence suggests that hypoxia induces plasticity of the neurocirculatory control system. Despite variations in experimental designs and the severity, frequency, and duration of hypoxia exposure, evidence from animal and human models consistently demonstrates the robust effects of hypoxemia in triggering reflex-mediated sympathetic activation. Both acute and chronic hypoxia alters neurocirculatory regulation and, in some circumstances, leads to sympathetic outflow and elevated blood pressures that persist beyond the hypoxic stimulus. Dysregulation of autonomic control could lead to adverse cardiovascular outcomes and increase the risk of developing hypertension.
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Affiliation(s)
- Brooke M Shafer
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Christopher R West
- International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, British Columbia, Canada
- Centre for Chronic Disease Prevention and Management, University of British Columbia, Kelowna, British Columbia, Canada
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Glen E Foster
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
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D'Alesio G, Stumpp LI, Sciarrone P, Navari A, Gentile F, Borrelli C, Ballanti S, Degl'Innocenti E, Carrasco A, Costa AC, Andrade A, Mannini A, Macefield VG, Emdin M, Passino C, Mazzoni A, Giannoni A, Oddo CM. An open computational toolbox to analyze multi- and single-unit sympathetic nerve activity in microneurography. BIOPHYSICS REVIEWS 2024; 5:021401. [PMID: 38895135 PMCID: PMC11184970 DOI: 10.1063/5.0202385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/04/2024] [Accepted: 05/08/2024] [Indexed: 06/21/2024]
Abstract
Microelectrode recordings from human peripheral and cranial nerves provide a means to study both afferent and efferent axonal signals at different levels of detail, from multi- to single-unit activity. Their analysis can lead to advancements both in diagnostic and in the understanding of the genesis of neural disorders. However, most of the existing computational toolboxes for the analysis of microneurographic recordings are limited in scope or not open-source. Additionally, conventional burst-based metrics are not suited to analyze pathological conditions and are highly sensitive to distance of the microelectrode tip from the active axons. To address these challenges, we developed an open-source toolbox that offers advanced analysis capabilities for studying neuronal reflexes and physiological responses to peripheral nerve activity. Our toolbox leverages the observation of temporal sequences of action potentials within inherently cyclic signals, introducing innovative methods and indices to enhance analysis accuracy. Importantly, we have designed our computational toolbox to be accessible to novices in biomedical signal processing. This may include researchers and professionals in healthcare domains, such as clinical medicine, life sciences, and related fields. By prioritizing user-friendliness, our software application serves as a valuable resource for the scientific community, allowing to extract advanced metrics of neural activity in short time and evaluate their impact on other physiological variables in a consistent and standardized manner, with the final aim to widen the use of microneurography among researchers and clinicians.
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Affiliation(s)
- Giacomo D'Alesio
- The BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy
| | | | | | - Alessandro Navari
- Cardiovascular Medicine Department, Fondazione Toscana Gabriele Monasterio, Pisa, Italy
| | | | - Chiara Borrelli
- Medical Research Center, University of Iowa, Iowa City, Iowa, USA
| | - Sara Ballanti
- The BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy
| | | | | | | | - Alexandre Andrade
- Instituto de Biofísica e Engenharia Biomédica, Faculdade de Ciências da Universidade de Lisboa, Lisbon, Portugal
| | - Andrea Mannini
- Artificial Intelligence for Rehabilitation Laboratory, Fondazione Don Carlo Gnocchi IRCCS, Florence, Italy
| | | | | | | | - Alberto Mazzoni
- The BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy
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Teixeira AL, Nardone M, Fernandes IA, Millar PJ, Vianna LC. Intra- and interday reliability of sympathetic transduction to blood pressure in young, healthy adults. J Appl Physiol (1985) 2024; 136:917-927. [PMID: 38385178 DOI: 10.1152/japplphysiol.00009.2024] [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: 01/05/2024] [Revised: 02/07/2024] [Accepted: 02/20/2024] [Indexed: 02/23/2024] Open
Abstract
Microneurographic recordings of muscle sympathetic nerve activity (MSNA) and the succeeding changes in beat-to-beat blood pressure (i.e., sympathetic transduction) provide important insights into the neural control of the circulation in humans. Despite its widespread use, the reliability of this technique remains unknown. Herein, we assessed the intra- and interday test-retest reliability of signal-averaging sympathetic transduction to blood pressure. Data were analyzed from 15 (9 M/6 F) young, healthy participants who completed two baseline recordings of fibular nerve MSNA separated by 60 min (intraday). The interday reliability was obtained in a subset of participants (n = 13, 9 M/4 F) who completed a follow-up MSNA study. Signal-averaging sympathetic transduction was quantified as peak change in diastolic (DBP) and mean arterial pressure (MAP) following a burst of MSNA. Analyses were also computed considering different MSNA burst sizes (quartiles of normalized MSNA) and burst patterns (singlets, couplets, triplets, and quadruplets+), as well as nonburst responses. Intraclass-correlation coefficients (ICCs) were used as the main reliability measure. Peak changes in MAP [intraday: ICC = 0.76 (0.30-0.92), P = 0.006; interday: ICC = 0.91 (0.63-0.97), P < 0.001] demonstrated very good to excellent reliability. Sympathetic transduction of MSNA burst size displayed moderate to very good reliability, though the reliability of MSNA burst pattern was poor to very good. Nonburst responses revealed poor intraday [ICC = 0.37 (-1.05 to 0.80), P = 0.21], but very good interday [ICC = 0.76 (0.18-0.93), P = 0.01] reliability. Intraday reliability measures were consistently lower than interday reliability. Similar results were obtained using DBP. Collectively, these findings provide evidence that the burst-triggering signal-averaging technique is a reliable measure of sympathetic transduction to blood pressure in young, healthy adults.NEW & NOTEWORTHY We found that signal-averaging sympathetic transduction to blood pressure displayed very good to excellent intra- and interday test-retest reliability in healthy, young adults. Reliability analyses according to muscle sympathetic burst size, burst pattern, and nonburst response were less consistent. Results were similar when using diastolic or mean arterial pressure in the transduction calculation. These findings suggest that the signal-averaging technique can be used with confidence to investigate sympathetic transduction to blood pressure in humans across time.
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Affiliation(s)
- André L Teixeira
- NeuroV̇ASQ̇ - Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Brasília, Brazil
- Human Cardiovascular Physiology Laboratory, Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Massimo Nardone
- Human Cardiovascular Physiology Laboratory, Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Igor A Fernandes
- Human Neurovascular Control Laboratory, Department of Health and Kinesiology, Purdue University, West Lafayette, Indiana, United States
| | - Philip J Millar
- Human Cardiovascular Physiology Laboratory, Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Lauro C Vianna
- NeuroV̇ASQ̇ - Integrative Physiology Laboratory, Faculty of Physical Education, University of Brasília, Brasília, Brazil
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Gimhani D, Shanks J, Pachen M, Chang JWH, Ramchandra R. Sympathetic transduction of cardiac sympathetic nerve activity in healthy, conscious sheep. J Physiol 2024; 602:619-632. [PMID: 38329227 DOI: 10.1113/jp285079] [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: 06/01/2023] [Accepted: 01/16/2024] [Indexed: 02/09/2024] Open
Abstract
Sympathetic transduction is the study of how impulses of sympathetic nerve activity (SNA) affect end-organ function. Recently, the transduction of resting bursts of muscle SNA (MSNA) has been investigated and shown to have a role in the maintenance of blood pressure through changes in vascular tone in humans. In the present study, we investigate whether directly recorded resting cardiac SNA (CSNA) regulates heart rate (HR), coronary blood flow (CoBF), coronary vascular conductance (CVC), cardiac output (CO) and mean arterial pressure. Instrumentation was undertaken to record CSNA and relevant vascular variables in conscious sheep. Recordings were performed at baseline, as well as after the infusion of a β-adrenoceptor blocker (propranolol) to determine the role of β-adrenergic signalling in sympathetic transduction in the heart. The results show that after every burst of CSNA, there was a significant effect of time on HR (n = 10, ∆: +2.1 ± 1.4 beats min-1 , P = 0.002) and CO (n = 8, ∆: +100 ± 150 mL min-1 , P = 0.002) was elevated, followed by an increase in CoBF (n = 9, ∆: +0.76 mL min-1 , P = 0.001) and CVC (n = 8, ∆: +0.0038 mL min-1 mmHg-1 , P = 0.0028). The changes in HR were graded depending on the size and pattern of CSNA bursts. The HR response was significantly attenuated after the infusion of propranolol. Our study is the first to explore resting sympathetic transduction in the heart, suggesting that CSNA can dynamically change HR mediated by an action on β-adrenoceptors. KEY POINTS: Sympathetic transduction is the study of how impulses of sympathetic nerve activity (SNA) affect end-organ function. Previous studies have examined sympathetic transduction primarily in the skeletal muscle and shown that bursts of muscle SNA alter blood flow to skeletal muscle and mean arterial pressure, although this has not been examined in the heart. We investigated sympathetic transduction in the heart and show that, in the conscious condition, the size of bursts of SNA to the heart can result in incremental increases in heart rate and coronary blood flow mediated by β-adrenoceptors. The pattern of bursts of SNA to the heart also resulted in incremental increases in heart rate mediated by β-adrenoceptors. This is the first study to explore the transduction of bursts of SNA to the heart.
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Affiliation(s)
- Dilsha Gimhani
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Julia Shanks
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Mridula Pachen
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Joshua W-H Chang
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Rohit Ramchandra
- Department of Physiology, University of Auckland, Auckland, New Zealand
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