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Does l-citrulline supplementation improve exercise blood flow in older adults?

ABSTRACT: NEW FINDINGS:What is the central question of this study? Does short-term supplementation with l-citrulline in order to increase l-arginine improve exercise blood flow and peripheral dilatation responses to exercise in older adults? What is the main finding and its importance? l-Citrulline increased femoral blood flow by 11% and vascular conductance by 14% during lower-limb exercise in older men, whereas no changes were observed in older women. This modest improvement in bulk muscle blood flow in older men has implications for altering muscle metabolism that may result in enhanced exercise tolerance in older adults. l-Citrulline (Cit) increases l-arginine (Arg), the primary substrate for nitric oxide biosynthesis. We tested the hypothesis that muscle blood flow during exercise would be enhanced by Cit supplementation in older adults. Femoral artery blood flow was measured during calf exercise using Doppler ultrasound, and vascular conductance (FVC) was calculated in 25 older adults (13 women and 12 men) before and after 14 days of Cit (6 g day-1 ) and placebo (maltodextrin) in a randomized, double-blind, crossover study. Plasma [Arg] and resting blood pressure were also measured before and after each condition. Women and men were analysed separately because of significant sex-by-condition interactions for the change in exercise blood flow and FVC. Plasma [Arg] was increased by 30 and 35% after Cit (P < 0.01) in women and men, respectively, with no change after placebo. Citrulline lowered diastolic blood pressure in men (75 ± 9 versus 71 ± 6 mmHg, P = 0.02), but this variable remained unchanged in women. Blood flow and FVC during exercise at higher workloads were increased after Cit in men (flow, 521 ± 134 versus 584 ± 166 ml min-1 , P = 0.04; FVC, 5.0 ± 1.5 versus 5.8 ± 1.7 m, min mmHg-1 , P = 0.01) but were not different after placebo. These variables were not altered by Cit in women. Adjusting for baseline diastolic blood pressure removed (P = 0.10) the difference in FBF and FVC following Cit in men. These results indicate that l-citrulline has a modest effect of improving muscle blood flow during submaximal exercise in older men.

SUBMITTER: Gonzales JU

PROVIDER: S-EPMC5999519 | biostudies-literature | 2017 Dec

REPOSITORIES: biostudies-literature

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Does l-citrulline supplementation improve exercise blood flow in older adults?

Gonzales Joaquin U JU Raymond Andrea A Ashley John J Kim Youngdeok Y

Experimental physiology 20171013 12

<h4>New findings</h4>What is the central question of this study? Does short-term supplementation with l-citrulline in order to increase l-arginine improve exercise blood flow and peripheral dilatation responses to exercise in older adults? What is the main finding and its importance? l-Citrulline increased femoral blood flow by 11% and vascular conductance by 14% during lower-limb exercise in older men, whereas no changes were observed in older women. This modest improvement in bulk muscle blood ...[more]

PMID: 28940638

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Project description:Background and objectivesMobility limitation is common and has been linked to high energetic requirements of daily activities, including walking. The study objective was to determine whether two separate forms of exercise could reduce the energy cost of walking and secondary outcomes related to activity and participation domains among older adults with mobility limitation.Research design and methodsCommunity-dwelling older adults with self-reported mobility limitation (n = 72) were randomized to 12 weeks of twice-weekly, group-based, instructor-led timing and coordination, aerobic walking, or stretching and relaxation (active control) programs. The primary outcome was the energy cost of walking (mL O2/kg/m), assessed by a 5-minute treadmill walking test (0.8 m/s). Secondary outcomes were fatigability, physical activity, endurance, physical function, and life-space. Baseline-adjusted ANCOVAs were used to determine mean differences between exercise and control groups at 12 and 24 weeks.ResultsExercise session attendance was high: 86% for timing and coordination, 81% for aerobic walking, and 90% for stretching and relaxation. At 12 weeks, timing and coordination reduced the mean energy cost of walking by 15% versus stretching and relaxation (p = .008). Among those with high baseline cost, timing and coordination reduced mean energy cost by 20% versus stretching and relaxation (p = .055). Reductions were sustained at 24 weeks. Aerobic walking had no effect on the energy cost of walking at 12 or 24 weeks. At 12 weeks, there was a trend toward faster gait speed (by 0.1 m/s) in timing and coordination versus stretching and relaxation (p = .074). Fatigability, physical activity, endurance, physical function, and life-space did not change with timing and coordination or aerobic walking versus stretching and relaxation at 12 or 24 weeks.Discussion and implicationsTwelve weeks of timing and coordination, but not aerobic walking, reduced the energy cost of walking among older adults with mobility limitation, particularly among those with high baseline energy cost; reductions in energy cost were sustained following training cessation. Timing and coordination also led to a trend toward faster gait speed.

Project description:Background/Objectives:Raised blood pressure is a major problem in older adults. Using a random-effects model, a recent meta-analysis reported statistically significant reductions in both resting systolic blood pressure (SBP) and diastolic blood pressure (DBP) as a result of aerobic, resistance, and combined aerobic and resistance exercise in adults ?65 years. To provide more objective information regarding this nonpharmacologic approach, this study applied more robust methods to this data. Design:Meta-analysis of 41 randomized controlled trials representing 96 groups (52 exercise; 44 control). Setting:Any location where a randomized controlled trial could be conducted. Participants:Adults ?65 years. Intervention:Trials ?2 weeks that included aerobic, resistance, and/or combined aerobic and resistance exercise as the intervention. Measurements:The recently developed inverse heterogeneity model (IVhet) was used to pool findings and the Doi plot was used to examine for small-study effects. Absolute and relative differences between the IVhet and random-effects model were also calculated. Data were reported using the mean difference (exercise minus control) with nonoverlapping 95% confidence intervals considered statistically significant. Results:Statistically significant reductions in resting blood pressure were found as a result of aerobic exercise (SBP, -4.7 mmHg, 95% CI, -7.7 to -1.8; DBP, -2.0 mmHg, 95% CI -3.13 to -0.9), SBP but not DBP for resistance training (SBP, -7.0 mmHg, 95% CI, -10.5 to -3.4; DBP, -1.2 mmHg, 95% CI -2.7 to 0.3), and both SBP and DBP for combined aerobic and resistance training (SBP, -5.5 mmHg, 95% CI, -8.3 to -2.7; DBP, -3.7 mmHg, 95% CI -4.8 to -2.7). Conclusions:Exclusive of changes in DBP congruent with resistance training, exercise (aerobic, resistance, and combined aerobic and resistance) reduces resting SBP and DBP in older adults. These findings have practical implications when considering exercise for the prevention and treatment of raised blood pressure in older adults.

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Does l-citrulline supplementation improve exercise blood flow in older adults?

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Does l-citrulline supplementation improve exercise blood flow in older adults?

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