You are here

Effect of L-Citrulline Supplementation on Vascular and Cardiac Autonomic Responses to Post-Exercise Muscle Ischemia Concurrent with Cold Pressor Test

Title: The Effect of L-Citrulline Supplementation on Vascular and Cardiac Autonomic Responses to Post-Exercise Muscle Ischemia Concurrent with Cold Pressor Test.
65 views
9 downloads
Name(s): Kalfon, Roy, author
Figueroa, Arturo, professor directing thesis
Ormsbee, Michael, committee member
Tenenbaum, Gershon, committee member
Department of Nutrition, Food, and Exercise Science, degree granting department
Florida State University, degree granting institution
Type of Resource: text
Genre: Text
Issuance: monographic
Date Issued: 2014
Publisher: Florida State University
Place of Publication: Tallahassee, Florida
Physical Form: computer
online resource
Extent: 1 online resource
Language(s): English
Abstract/Description: BACKGROUND: Epidemiological studies have shown that cardiovascular events are more prevalent in the winter than in other season. Although the exact mechanisms are not completely understood, previous findings indicate that acute cold exposure increases sympathetic activity, arterial stiffness (pulse wave velocity [PWV]), and blood pressure (BP) as well as impairs endothelial function. Moreover, obesity is characterized by increased sympathetic activity and BP, which may further represent a potential mechanism responsible for cardiovascular events. There is increasing evidence that recovery from an acute bout of exercise is a vulnerable phase for cardiac events. Therefore, the elucidation of cardiovascular responses to post-exercise recovery concurrent with cold exposure in overweight/obese individuals is of clinical importance. Submaximal isometric-handgrip (IHG) exercise has been previously used as a means for evaluating the role of the exercise pressor reflex (muscle metaboreflex) on the cardiovascular system and cardiac autonomic function. The exercise pressor reflex can be evaluated using the technique of post-exercise muscle ischemia (PEMI), which by trapping metabolites in a previously exercised muscle, sustains the vascular sympathetic stimulation evoked during exercise in a controlled fashion. Recently, oral supplementation with the amino acid L-citrulline (L-cit) has been proposed as a possible adjunct treatment for hypertension and arterial stiffness. L-cit is known to enhance the bioavailability of L-arginine, the endothelial substrate for the potent vasodilator nitric oxide (NO). Our group demonstrated that L-cit supplementation effectively attenuates the hemodynamic responses to cold pressor test (CPT); however, the potential cardio-protective effects of L-cit supplementation to reduce cold-induced hypertension (CIH) during exercise pressor reflex activation have yet to be evaluated. PURPOSE: The aim of this study was twofold. 1) To evaluate the acute effects of the exercise pressor reflex imposed by PEMI and PEMI concurrent with CPT (PEMI+CPT) on hemodynamics, arterial stiffness, and cardiac autonomic modulation in healthy overweight/obese men, and 2) to examine the effects of a 14-day course of L-cit supplementation on hemodynamics, arterial stiffness, and cardiac autonomic modulation during IHG exercise, PEMI, and PEMI+CPT in healthy overweight/obese men. METHODS: Sixteen healthy young (24 ± 1.5 y) overweight/obese men were randomly assigned to receive either placebo (maltodextrin) or L-cit (6 g/day) for 14 days in a cross-over fashion. Following 5 min of resting measurements, the participants were asked to perform two trials in a randomized order. In one trial, the participants perform a 2-min IHG exercise (30% of maximal voluntary contraction) followed by a 3-min PEMI. Following a 15-min recovery period, the participants were asked to perform a 2-min IHG exercise followed by a 3-min PEMI concurrent with CPT. Brachial systolic BP (bSBP), brachial diastolic BP (bDBP), aortic systolic BP (aSBP), aortic diastolic BP (aDBP), augmentation index (AIx), first (P1) and second systolic peak (P2, wave reflection magnitude), brachial-ankle PWV (baPWV, arterial stiffness), heart rate (HR), and HR variability (HRV, cardiac autonomic modulation) were evaluated at rest, during IHG, PEMI, and PEMI+CPT. All measurements were re-evaluated after 14 days. RESULTS: Height, weight, body mass index, and waist circumference were 1.72 ± 0.01 m, 86.8 ± 3.7 kg, 29.3 ± 1.1 kg/m2, and 98 ± 3 cm, respectively. At baseline, all hemodynamic parameters increased (P<0.01) during IHG exercise and remained elevated during PEMI and PEMI+CPT. BSBP, bDBP, aSBP, aDBP, P1, and P2 were higher (P<0.01) during PEMI+CPT compared to PEMI. Sympathetic activity increased similarly during IHG and PEMI with a further increase during PEMI+CPT. During PEMI+CPT, HR and low frequency components of the HRV (LnLF and nLF, markers of sympathetic activity) were higher (P<0.05) whereas the high frequency (LnHF), a marker of parasympathetic activity, was decreased (P<0.01) compared to PEMI. There were no significant changes in all hemodynamic parameters at rest after the treatments. During IHG, L-cit significantly decreased bDBP (-10 ± 3 mmHg; P<0.01), aSBP (-8 ± 3 mmHg; P<0.05), AIx (-14.2 ± 3.1 %; P<0.05), and P2 (-8 ± 3 mmHg; P<0.01) compared to no changed after placebo. During PEMI, L-cit significantly decreased bDBP (-10 ± 3 mmHg; P<0.05), aDBP (-8 ± 2 mmHg; P<0.01), and AIx (-8.6 ± 2.0 %; P<0.01) compared to no changes after placebo. During PEMI+CPT, L-cit significantly decreased bSBP (-11 ± 3 mmHg; P<0.01), bDBP (-11 ± 2 mmHg; P<0.01), aSBP (-13 ± 3 mmHg; P<0.01), aDBP (-10 ± 2 mmHg; P<0.01), AIx (-13.8 ± 2.2 %; P<0.01), P1 (-7 ± 2 mmHg; P<0.01), P2 (-14 ± 3 mmHg; P<0.01) and baPWV (-0.9 ± 0.4 m/s; P<0.05). There were no significant changes in all HRV parameters after the treatments. CONCLUSIONS: The present study demonstrates that post-exercise metaboreflex activation concurrent with cold exposure imposes an additional cardiovascular stress due to increased sympathetic activity. In addition, we showed that L-cit supplementation attenuates the exercise pressor responses imposed by IHG exercise and PEMI. Furthermore, we showed that L-cit supplementation is an effective means to decrease the CIH responses during post-exercise metaboreflex activation. In conclusion, L-cit supplementation may be a potential adjunct treatment to reduce the CIH responses and ultimately provide cardio-protective effect to those who perform exercise in low environmental temperatures.
Identifier: FSU_migr_etd-8820 (IID)
Submitted Note: A Thesis submitted to the Department of Nutrition, Food and Exercise Sciences in partial fulfillment of the requirements for the degree of Master of Science.
Degree Awarded: Spring Semester, 2014.
Date of Defense: March 28, 2014.
Bibliography Note: Includes bibliographical references.
Advisory Committee: Arturo Figueroa, Professor Directing Thesis; Michael Ormsbee, Committee Member; Gershon Tenenbaum, Committee Member.
Subject(s): Nutrition
Food
Exercise
Persistent Link to This Record: http://purl.flvc.org/fsu/fd/FSU_migr_etd-8820
Owner Institution: FSU

Choose the citation style.
Kalfon, R. (2014). The Effect of L-Citrulline Supplementation on Vascular and Cardiac Autonomic Responses to Post-Exercise Muscle Ischemia Concurrent with Cold Pressor Test. Retrieved from http://purl.flvc.org/fsu/fd/FSU_migr_etd-8820