The effects of short term L-citrulline supplementation on wave reflection responses to cold exposure with concurrent isometric exercise

Short-Term L-Citrulline Supplementation Does Not Affect Blood Pressure, Pulse Wave Reflection, or Arterial Stiffness at Rest and during Isometric Exercise in Older Males

Hypertension and arterial stiffness are significant factors contributing to cardiovascular disease. L-citrulline, a nitric oxide precursor, has been proposed as a nutritional, non-pharmacological blood pressure-lowering intervention. This study aimed to investigate the impact of L-citrulline on central and peripheral blood pressure, pulse wave reflection, and central arterial stiffness at rest and during an isometric knee extension exercise protocol. Twelve older males received 6 g of L-citrulline or a placebo for six days using a double-blind crossover design. Blood hemodynamics parameters (i.e., aortic and brachial systolic and diastolic blood pressure, mean arterial pressure, pulse pressure, heart rate), pulse wave reflection (i.e., augmented pressure, augmentation index, forward/backward wave pressure), and arterial stiffness (i.e., carotid-femoral pulse wave velocity) were measured at baseline, post-supplementation, and during isometric exercise. No significant effects of L-citrulline supplementation were observed at rest or during exercise on blood pressure, pulse wave reflection, or arterial stiffness. Both central and peripheral blood pressure were increased during the exercise, which is consistent with isometric contractions. The results of the present study do not support any blood pressure-lowering effect of short-term L-citrulline at rest or during low-intensity isometric exercise compared to the pre-exercise values in older males.

Watermelon consumption decreases risk factors of cardiovascular diseases: A systematic review and meta-analysis of randomized controlled trials

This meta-analysis was conducted to examine the effects of watermelon supplementation on cardiovascular diseases (CVDs) risk factors in randomized controlled trials (RCTs). The comprehensive search was done in Cochrane Library databases, ISI Web of Science, PubMed, and Scopus up to March 2022. A random-effect model was used for computing weighted mean differences (WMD). Standard methods were applied to examine publication bias, sensitivity analysis, and heterogeneity. Of the 8962 identified studies, 9 RCTs were included in the final analysis. Watermelon consumption significantly decreased systolic blood pressure (SBP), total cholesterol (TC) and low-density lipoprotein (LDL). In addition, watermelon consumption led to a significant increase in fasting blood sugar (FBS). However, there was not any significant difference in other outcomes of interest including diastolic blood pressure (DBP), heart rate (HR), BMI, body fat, and serum levels of arginine, insulin, and CRP after watermelon supplementation. The current findings provide promising evidence of the antihypertensive effect of watermelon. However, due to the lack of evidence in human research, the result regarding the remaining outcomes needs to be used with caution. Furter RCTs with longer follow-ups and larger sample sizes should be done to confirm the current findings.

Dietary Arginine and Citrulline Supplements for Cardiovascular Health and Athletic Performance: A Narrative Review

The global market for nutritional supplements (NS) is growing rapidly, and the use of L-arginine (Arg), L-citrulline (Cit), and citrulline malate (CitMal) supplements has been shown to enhance cardiovascular health and athletic performance. Over the past decade, Arg, Cit, and CitMal supplements have received considerable attention from researchers in the field of exercise nutrition, who have investigated their potential effects on hemodynamic function, endothelial function, aerobic and anaerobic capacity, strength, power, and endurance. Previous studies were reviewed to determine the potential impact of Arg, Cit, and CitMal supplements on cardiovascular health and exercise performance. By synthesizing the existing literature, the study aimed to provide insight into the possible uses and limitations of these supplements for these purposes. The results showed that both recreational and trained athletes did not see improved physical performance or increased nitric oxide (NO) synthesis with 0.075 g or 6 g doses of Arg supplement per body weight. However, 2.4 to 6 g of Cit per day for 7 to 16 days of various NSs had a positive impact, increasing NO synthesis, enhancing athletic performance indicators, and reducing feelings of exertion. The effects of an 8 g acute dose of CitMal supplement were inconsistent, and more research is needed to determine its impact on muscle endurance performance. Based on the positive effects reported in previous studies, further testing is warranted in various populations that may benefit from nutritional supplements, including aerobic and anaerobic athletes, resistance-trained individuals, elderly people, and clinical populations, to determine the impact of different doses, timing of ingestion, and long-term and acute effects of Arg, Cit, and CitMal supplements on cardiovascular health and athletic performance.

The Effects of Consuming Amino Acids L-Arginine, L-Citrulline (and Their Combination) as a Beverage or Powder, on Athletic and Physical Performance: A Systematic Review

Consumption of amino acids L-arginine (L-Arg) and L-citrulline (L-Cit) are purported to increase nitric oxide (NO) production and improve physical performance. Clinical trials have shown relatively more favorable outcomes than not after supplementing with L-Cit and combined L-Arg and L-Cit. However, in most studies, other active ingredients such as malate were included in the supplement. Therefore, the aim of this study was to determine the efficacy of consuming standalone L-Arg, L-Cit, and their combination (in the form of powder or beverage) on blood NO level and physical performance markers. A systematic review was undertaken following PRISMA 2020 guidelines (PROSPERO: CRD42021287530). Four electronic databases (PubMed, Ebscohost, Science Direct, and Google scholar) were used. An acute dose of 0.075 g/kg of L-Arg or 6 g L-Arg had no significant increase in NO biomarkers and physical performance markers (p > 0.05). Consumption of 2.4 to 6 g/day of L-Cit over 7 to 16 days significantly increased NO level and physical performance markers (p < 0.05). Combined L-Arg and L-Cit supplementation significantly increased circulating NO, improved performance, and reduced feelings of exertion (p < 0.05). Standalone L-Cit and combined L-Arg with L-Cit consumed over several days effectively increases circulating NO and improves physical performance and feelings of exertion in recreationally active and well-trained athletes.

Effects of L-citrulline supplementation and watermelon consumption on longer-term and postprandial vascular function and cardiometabolic risk markers: A meta-analysis of randomized controlled trials in adults

L-citrulline may improve non-invasive vascular function and cardiometabolic risk markers through increases in L-arginine bioavailability and nitric oxide synthesis. A meta-analysis of randomized controlled trials (RCTs) was performed to examine longer-term and postprandial effects of L-citrulline supplementation and watermelon consumption on these markers for cardiovascular disease in adults. Summary estimates of weighted mean differences (WMDs) in vascular function and cardiometabolic risk markers with accompanying 95% confidence intervals (CIs) were calculated using random or fixed-effect meta-analyses. Seventeen RCTs were included involving an L-citrulline intervention, of which six studied postprandial and twelve longer-term effects. Five studies investigated longer-term effects of watermelon consumption and five assessed effects during the postprandial phase. Longer-term L-citrulline supplementation improved brachial artery flow-mediated vasodilation (FMD) by 0.9 %-point (95 % CI: 0.7 to 1.1, P < 0.001). Longer-term watermelon consumption improved pulse wave velocity by 0.9 m/s (95% CI: 0.1 to 1.5, P < 0.001), while effects on FMD were not studied. No postprandial effects on vascular function markers were found. Postprandial glucose concentrations decreased by 0.6 mmol/L (95% CI: 0.4 to 0.7, P < 0.001) following watermelon consumption, but no other longer-term or postprandial effects were observed on cardiometabolic risk markers. To conclude, longer-term L-citrulline supplementation and watermelon consumption may improve vascular function, suggesting a potential mechanism by which increased L-citrulline intake beneficially affects cardiovascular health outcomes in adults. No effects on postprandial vascular function markers were found, while more research is needed to investigate effects of L-citrulline and watermelon on risk markers related to cardiometabolic health.

Dynamic and isometric handgrip exercise increases wave reflection in healthy young adults

Early return and increased magnitude of wave reflection augments pulsatile load, wastes left ventricular effort, and is associated with cardiovascular events. Acute handgrip (HG) exercise increases surrogate measures of wave reflection such as augmentation index. However, augmentation index does not allow distinguishing between timing versus magnitude of wave reflection and is affected by factors other than wave reflection per se. Wave separation analysis decomposes central pressure into relative contributions of forward (Pf) and backward (Pb) pressure wave amplitudes to calculate reflection magnitude (RM = Pb/Pf) and determine the timing of apparent wave reflection return. We tested the hypothesis that acute dynamic and isometric HG exercise increases RM and decreases reflected wave transit time (RWTT). Applanation tonometry was used to record radial artery pressure waveforms in 30 adults (25 ± 4 yr) at baseline and during dynamic and isometric HG exercise. Wave separation analysis was performed offline using a physiological flow wave to derive Pf, Pb, RM, and RWTT. We found that RM increased during dynamic and isometric HG exercise compared with baseline (P = 0.04 and P < 0.01, respectively; baseline 40 ± 5, dynamic 43 ± 6, isometric 43 ± 7%). Meanwhile, RWTT decreased during dynamic and isometric HG exercise compared with baseline (P = 0.03 and P < 0.001, respectively; baseline 164 ± 23, dynamic 155 ± 23, isometric 148 ± 20 ms). Moreover, the changes in RM and RWTT were not different between dynamic and isometric HG exercise. The present data suggest that wave reflection timing (RWTT) and magnitude (RM) are important factors that contribute to increased central blood pressure during HG exercise.NEW & NOTEWORTHY This study demonstrated that wave reflection magnitude is increased while reflected wave transit time is decreased during handgrip exercise in healthy young adults. The larger backward pressure waves and earlier return of these pressure waves were not different between dynamic and isometric handgrip exercise. These acute changes in wave reflection during handgrip exercise transiently augment pulsatile load.

Effect of oral L-citrulline on brachial and aortic blood pressure defined by resting status: evidence from randomized controlled trials

Background

Experimental evidence indicates that oral L-citrulline (L-Cit) may reduce resting blood pressure (BP) as well as BP responses to exercise and cold exposure (non-resting). However, results from human intervention trials are inconsistent. This study aims to summarize the clinical evidence regarding the effects of L-Cit supplementation on brachial systolic blood pressure (SBP), brachial diastolic blood pressure (DBP), in addition to aortic SBP and aortic DBP at rest and non-resting conditions.

Methods

Multiple databases including PubMed, Embase, Cochrane library, Web of Science, and Clinical Trials were searched systematically. Randomized controlled trials of human participants were quantitatively meta-analyzed.

Results

Fourteen trials contained in eight studies were available for quantitative syntheses for brachial BP. Results showed that L-Cit supplementation significantly reduced both brachial SBP (− 4.490 mmHg, 95% CI: − 7.332 to − 1.648, P = 0.002) and brachial DBP (− 3.629 mmHg, 95% CI: − 5.825 to − 1.434, P = 0.001). Nine of the trials were meta-analyzed for aortic BP which showed that L-Cit intervention significantly reduced aortic SBP (− 6.763 mmHg, 95% CI: − 10.991 to − 2.534, P = 0.002), but not aortic DBP (− 3.396 mmHg, 95% CI: − 7.418 to 0.627, P = 0.098). The observed reducing effects of L-Cit appeared stronger for non-resting than for resting brachial SBP (P for difference = 0.044).

Conclusion

L-Cit supplementation significantly decreased non-resting brachial and aortic SBP. Brachial DBP was significantly lowered by L-Cit regardless of resting status. Given the relatively small number of available trials in the stratified analyses and the potential limitations of these trials, the present findings should be interpreted cautiously and need to be confirmed in future well-designed trials with a larger sample size.

Modulation of muscle protein synthesis by amino acids: what consequences for the secretome? A preliminary in vitro study

The modulation by amino acids of muscle secretome is largely unknown. In this study, we investigate the effect of hyperaminoacidemia or specific amino acids (citrulline or leucine) on protein synthesis and secretome in myotubes. All conditions stimulate muscle protein synthesis, and secretome is differently modulated depending of the amino acids considered. In conclusion, the activation of protein synthesis by amino acids induces different modulations of the muscle secretome, proposing a new role of amino acids in the regulation of muscle function.

Effect of acute watermelon juice supplementation on post-submaximal exercise heart rate recovery, blood lactate, blood pressure, blood glucose and muscle soreness in healthy non-athletic men and women

The objective of this study was to determine the effects of a single pre-exercise dose of watermelon juice on submaximal post-exercise heart rate (HR) recovery, blood lactate (BL), blood pressure (BP), blood glucose (BG), and muscle soreness in healthy adults. In a randomised crossover design, 27 healthy non-athletic participants (13 males/14 females) consumed 355 mL of watermelon juice, Gatorade, sugar water, or water. HR and BL were significantly higher post-exercise, and both watermelon juice and sugar water increased postprandial BG. However, there were no significant differences among the supplements in HR recovery, BL, or post-exercise muscle soreness. Watermelon juice prevented increased post-exercise systolic and diastolic BP in females, but not in males. More research is warranted to examine the effect of sex on the efficacy of watermelon consumption for controlling BP.

The Effects of Oral l-Arginine and l-Citrulline Supplementation on Blood Pressure

Nitric oxide (NO) is a well-known vasodilator produced by the vascular endothelium via the enzyme endothelial nitric oxide synthase (eNOS). The inadequate production of NO has been linked to elevated blood pressure (BP) in both human and animal studies, and might be due to substrate inaccessibility. This review aimed to investigate whether oral administration of the amino acids l-arginine (Arg) and l-citrulline (Cit), which are potential substrates for eNOS, could effectively reduce BP by increasing NO production. Both Arg and Cit are effective at increasing plasma Arg. Cit is approximately twice as potent, which is most likely due to a lower first-pass metabolism. The current data suggest that oral Arg supplementation can lower BP by 5.39/2.66 mmHg, which is an effect that is comparable with diet changes and exercise implementation. The antihypertensive properties of Cit are more questionable, but are likely in the range of 4.1/2.08 to 7.54/3.77 mmHg. The exact mechanism by which Cit and Arg exert their effect is not fully understood, as normal plasma Arg concentration greatly exceeds the Michaelis constant (K_m) of eNOS. Thus, elevated plasma Arg concentrations would not be expected to increase endogenous NO production significantly, but have nonetheless been observed in other studies. This phenomenon is known as the "l-arginine paradox".

Effect of L-citrulline supplementation on blood pressure: a systematic review and meta-analysis of randomized controlled trials

The objective of this study was to systematically investigate the efficacy of oral L-citrulline supplementation on systolic and diastolic blood pressure. Studies were identified by a search of electronic databases from inception to April 2018, and combined and stratified analyses were used. Fifteen trials were identified, and data from 424 participants were included. Pooled analysis showed significant reductions in systolic blood pressure by -7.54 mmHg (95% confidence interval (CI): -9.44, -5.63; P < 0.001, I² = 14%) and diastolic blood pressure by -3.77 mmHg (95% CI: -5.67, -1.86, P < 0.001, I² = 42%) following oral supplementation of L-citrulline or a watermelon extract. No changes were detected in controls. Significant heterogeneity (I² = 42%, P = 0.04) was found for diastolic blood pressure, and subgroup analysis showed significant improvements in systolic and diastolic blood pressure, particularly for study durations: ≥6 weeks, lower doses: ≤4 g/day, and in participants with higher baseline values: ≥130/85 mmHg. In conclusion, L-citrulline improves systolic and diastolic blood pressure and may be more efficacious in pre-hypertensive and hypertensive populations.

l-Citrulline Supplementation: Impact on Cardiometabolic Health

Diminished bioavailability of nitric oxide (NO), the gaseous signaling molecule involved in the regulation of numerous vital biological functions, contributes to the development and progression of multiple age- and lifestyle-related diseases. While l-arginine is the precursor for the synthesis of NO by endothelial-nitric oxide synthase (eNOS), oral l-arginine supplementation is largely ineffective at increasing NO synthesis and/or bioavailability for a variety of reasons. l-citrulline, found in high concentrations in watermelon, is a neutral alpha-amino acid formed by enzymes in the mitochondria that also serves as a substrate for recycling l-arginine. Unlike l-arginine, l-citrulline is not quantitatively extracted from the gastrointestinal tract (i.e., enterocytes) or liver and its supplementation is therefore more effective at increasing l-arginine levels and NO synthesis. Supplementation with l-citrulline has shown promise as a blood pressure lowering intervention (both resting and stress-induced) in adults with pre-/hypertension, with pre-clinical (animal) evidence for atherogenic-endothelial protection. Preliminary evidence is also available for l-citrulline-induced benefits to muscle and metabolic health (via vascular and non-vascular pathways) in susceptible/older populations. In this review, we examine the impact of supplementing this important urea cycle intermediate on cardiovascular and metabolic health outcomes and identify future directions for investigating its therapeutic impact on cardiometabolic health.

Impact of l-citrulline supplementation on oxygen uptake kinetics during walking

Supplementation with l-citrulline (Cit) has been shown to improve muscle oxygenation and oxygen uptake kinetics during moderate- to high-intensity cycling in young men. The aim of this study was to test the hypothesis that Cit would improve oxygen uptake kinetics during walking in older and young adults. In a randomized, double-blind study, 26 (15 women, 11 men) adults between the ages of 20-35 years (n = 15) and 64-86 years (n = 11) completed 7-day periods of taking placebo and Cit (6 g/day) in a crossover manner. Participants walked on a treadmill at 40% heart rate reserve while pulmonary oxygen uptake was measured using indirect calorimetry. Net oxygen cost, mean response time (MRT), and the oxygen deficit were calculated before and after each supplement period. There was no significant change (P > 0.05) in net oxygen cost, MRT, or the oxygen deficit after Cit in older adults, while young adults showed a decrease (P = 0.05) in the oxygen deficit after Cit that tended (P = 0.053) to be different than the change after placebo. Sex-stratified analysis revealed that Cit decreased MRT (P = 0.04, Cohen's d = 0.41) and the oxygen deficit (P < 0.01, Cohen's d = 0.56) in men with the change after Cit being greater than the change after placebo (MRT: -4.5 ± 2.1 vs. 3.4 ± 2.1 s, P = 0.01; deficit: -0.15 ± 0.05 vs. 0.01 ± 0.05 L, P = 0.02). All oxygen uptake parameters were unchanged (P > 0.05) following Cit and placebo in women. Cit does not alter the oxygen cost of moderate-intensity walking in young or older adults, but Cit improved the rate of rise in oxygen uptake at exercise onset in men.

The Assessment of short-term effect of L-Citrulline on endothelial function via FMD to NMD ratio in known CAD patients: A randomized, cross-over clinical trial (Clinical trial number: NCT02638727)

Background. Recent studies have confirmed the essential and paramount role of the L-Citrulline on the nitric oxide regulation and the endothelial function improvement.

Materials and Methods. In this cross-over clinical trial, thirty patients, diagnosed with coronary artery disease (CAD) and flow mediated dilation to nitroglycerin dependent vasodilation (FMD/NMD) ratio less than 1, were included. The patients were randomly divided into two groups of 15 patients and underwent treatment by L-Citrulline or placebo for 15 days, in 2 step protocol. The indicators of assessment in the current study were the ratio of the FMD/NMD and FMD value.

Results. In the current cross-over clinical trial, the mean of FMD to NMD ratio and mean FMD value of all patients before starting the protocol were 0.91 ± 0.08 and 4.04 ± 0.51 mm, respectively. The final results of study showed that following L-Citrulline administration, mean FMD to NMD ratio and mean FMD value were enhanced to: 1.03 ± 0.09 and 4.96 ± 0.72 mm, respectively, which were statistically significant (P<0.001 and P<0.001, respectively). However, following placebo administration, mean FMD to NMD ratio and mean FMD value were receded to: 0.92 ± 0.09 and 4.06 ± 0.22 mm, respectively, which were not statistically significant (P = 0.75 and P = 0.89, respectively). Moreover, the improvement of mean FMD to NMD ratio (0.12 ± 0.02) and mean FMD value (0.92 ± 0.16 mm), following L-Citrulline administration, were statistically significant in comparison with the change of mean FMD to NMD ratio (0.01 ± 0.002) and mean FMD value (0.02 ± 0.003), following placebo administration (P<0.001 and P<0.001, respectively).

Conclusion. L-Citrulline treatment can lead to improvement of the endothelial function in patients diagnosed with CAD which are assessed via FMD to NMD ratio FMD value enhancements.

Influence of L-citrulline and watermelon supplementation on vascular function and exercise performance

PURPOSE OF REVIEW

L-Citrulline, either synthetic or in watermelon, may improve vascular function through increased L-arginine bioavailability and nitric oxide synthesis. This article analyses potential vascular benefits of L-citrulline and watermelon supplementation at rest and during exercise.

RECENT FINDINGS

There is clear evidence that acute L-citrulline ingestion increases plasma L-arginine, the substrate for endothelial nitric oxide synthesis. However, the subsequent acute improvement in nitric oxide production and mediated vasodilation is inconsistent, which likely explains the inability of acute L-citrulline or watermelon to improve exercise tolerance. Recent studies have shown that chronic L-citrulline supplementation increases nitric oxide synthesis, decreases blood pressure, and may increase peripheral blood flow. These changes are paralleled by improvements in skeletal muscle oxygenation and performance during endurance exercise. The antihypertensive effect of L-citrulline/watermelon supplementation is evident in adults with prehypertension or hypertension, but not in normotensives. However, L-citrulline supplementation may attenuate the blood pressure response to exercise in normotensive men.

SUMMARY

The beneficial vascular effects of L-citrulline/watermelon supplementation may stem from improvements in the L-arginine/nitric oxide pathway. Reductions in resting blood pressure with L-citrulline/watermelon supplementation may have major implications for individuals with prehypertension and hypertension. L-Citrulline supplementation, but not acute ingestion, have shown to improve exercise performance in young healthy adults.

Chronic l-citrulline supplementation improves cardiac sympathovagal balance in obese postmenopausal women: A preliminary report

The present study evaluated the impact of chronic l-citrulline (L-cit) supplementation on resting heart rate variability (HRV) and blood pressure (BP) in obese postmenopausal women. Participants were randomly assign to either an L-cit group (n=12) or a control group (n=11). HRV and BP were measured before and after 8weeks. There were significant decreases (P<0.05) in nLF (sympathetic activity), LnLF/LnHF (sympathovagal balance), and BP as well as a significant increase (P<0.05) in nHF (vagal tone) following L-cit compared with no changes after control. Our findings indicate that L-cit supplementation improves sympathovagal balance in obese postmenopausal women.

Oral nitrate and citrulline decrease blood pressure and increase vascular conductance in young adults: a potential therapy for heart failure

Purpose

Both inorganic nitrate and citrulline are known to alter the arginine–nitric oxide–nitrate system to increase the bioavailability of nitric oxide with potential benefits in the treatment of heart failure. However, their effects on cardiac electrical activity, vascular compliance and peripheral conductance are less well understood. This study examined the effect of nitrate and citrulline on cardiac electrical activity and blood flow.

Methods

Young adult subjects (n = 12) were recruited to investigate the effects of acute oral nitrate consumption (8 mg/kg) and chronic citrulline consumption (3 g/day) on cardiac electrical activity measured by ECG recording and blood pressure. Blood flow and vascular compliance were measured by IR-plethysmography at the thumb and the hallux.

Results

Nitrate (p < 0.05) and citrulline (p < 0.01) consumption both decreased diastolic blood pressure but had no effect on either pulse pressure or rate-pressure product (NS for both). Citrulline also decreased systolic pressure (p < 0.01). Nitrate and citrulline both decreased vascular compliance (p < 0.05 for both) prior to isometric grip exercise, but this was increased for nitrate following exercise (NS). Citrulline decreased R–R interval 9 % (p < 0.05) at rest and increased heart rate (p < 0.05) in addition to significantly decreasing pulse transit duration (6 %; p < 0.05). QRS duration was also decreased by 5 % for citrulline (p < 0.05) with the reduction in R–R interval.

Conclusion

Both nitrate and citrulline supplementation decreased vascular tone at rest but citrulline also altered sympathovagal balance to increase sympathetic tone. We suggest that both oral nitrate and citrulline may be suitable adjuvants for patients with heart failure to improve peripheral tissue oxygenation.

l-Citrulline supplementation attenuates blood pressure, wave reflection and arterial stiffness responses to metaboreflex and cold stress in overweight men

Combined isometric exercise or metaboreflex activation (post-exercise muscle ischaemia (PEMI)) and cold pressor test (CPT) increase cardiac afterload, which may lead to adverse cardiovascular events. l-Citrulline supplementation (l-CIT) reduces systemic arterial stiffness (brachial-ankle pulse wave velocity (baPWV)) at rest and aortic haemodynamic responses to CPT. The aim of this study was to determine the effect of l-CIT on aortic haemodynamic and baPWV responses to PEMI+CPT. In all, sixteen healthy, overweight/obese males (age 24 (sem 6) years; BMI 29·3 (sem 4·0) kg/m2) were randomly assigned to placebo or l-CIT (6 g/d) for 14 d in a cross-over design. Brachial and aortic systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP), aortic augmented pressure (AP), augmentation index (AIx), baPWV, reflection timing (Tr) and heart rate (HR) were evaluated at rest and during isometric handgrip exercise (IHG), PEMI and PEMI+CPT at baseline and after 14 d. No significant effects were evident after l-CIT at rest. l-CIT attenuated the increases in aortic SBP and wave reflection (AP and AIx) during IHG, aortic DBP, MAP and AIx during PEMI, and aortic SBP, DBP, MAP, AP, AIx and baPWV during PEMI+CPT compared with placebo. HR and Tr were unaffected by l-CIT in all conditions. Our findings demonstrate that l-CIT attenuates aortic blood pressure and wave reflection responses to exercise-related metabolites. Moreover, l-CIT attenuates the exaggerated arterial stiffness response to combined metaboreflex activation and cold exposure, suggesting a protective effect against increased cardiac afterload during physical stress.

Effects of watermelon supplementation on aortic hemodynamic responses to the cold pressor test in obese hypertensive adults

BACKGROUND

Cold-induced increases in aortic blood pressure (BP) may cause adverse cardiac events in hypertensives by increasing ventricular afterload. L-citrulline supplementation reduces BP at baseline and during the cold pressor test (CPT), but the effect on wave reflection (augmentation pressure (AP) and index (AIx)) is controversial. Our aim was to assess the effect of L-citrulline-rich watermelon supplementation on aortic hemodynamic responses to CPT in hypertensive adults.

METHODS

Brachial systolic BP (bSBP) and aortic systolic BP (aSBP), AP, AIx, AIx adjusted to 75 beats/min (AIx75), reflection time (Tr), first (P1) and second systolic peak (P2; wave reflection magnitude), heart rate (HR), and systolic time index (STI; myocardial oxygen demand) at baseline and during CPT and magnitude of the response from baseline to CPT were evaluated in 13 individuals (10 women; 57±1 year; bSBP 151±5 mm Hg). Participants were randomized to a 6-week watermelon or placebo supplementation in a crossover design.

RESULTS

Watermelon reduced (P < 0.05) bSBP, aSBP, P1, and P2 at baseline and CPT compared with placebo; thus, increases from baseline to CPT were unaffected. Watermelon did not affect AP, AIx, AIx75, and STI at baseline but decreased (P < 0.05) AP and STI during CPT and the increases in AP (~5mm Hg) and AIx75 (~7.3%) from baseline to CPT.

CONCLUSIONS

Watermelon supplementation reduced aortic BP and myocardial oxygen demand during CPT and the magnitude of the cold-induced increase in wave reflection in obese adults with hypertension. Watermelon may provide cardioprotection by attenuating cold-induced aortic hemodynamic responses.

CLINICAL TRIALS REGISTRATION

Clinicaltrial.gov register, NCT01185041.

Central aortic blood pressure of hypertensive men during short-term cold exposure

BACKGROUND

Short- and long-term exposures to cold increase blood pressure and may explain the higher wintertime cardiovascular morbidity and mortality. Hypertensive subjects may be more susceptible to adverse cold-related cardiovascular health effects. The aim of our study was to assess the effect of short-term cold exposure on central aortic blood pressure among untreated hypertensive men.

METHODS

We conducted a population-based recruitment of 41 hypertensive men and a control group of 20 men without hypertension (aged 55-65 years) who underwent whole-body cold exposure (15-minute exposure to temperature -10 °C, wind 3 m/s, winter clothes). Central aortic blood pressure, augmentation index, and subendocardial viability ratio were measured by radial artery applanation tonometry.

RESULTS

Short-term cold exposure increased the central aortic blood pressure similarly both in both hypertensive men, from 130/93 to 162/107 mm Hg (P < 0.001) and men in the control group, from 114/81 to 142/91 mmHg (P < 0.001). Augmentation index increased by 12% (from 10% to 22%, P < 0.001; and from 16% to 28%, P < 0.001, respectively), whereas subendocardial viability ratio decreased 10% (from 188% to 177%, P = 0.001; and from 203% to 193%, P = 0.01, respectively) during cold exposure in both hypertensive men and control subjects.

CONCLUSIONS

Short-term cold exposure increases central aortic blood pressure and cardiac workload, and myocardial oxygen demand slightly increases in relation to blood supply in untreated hypertensive middle-aged men. Because of the higher baseline blood pressure among hypertensive subjects, the cold-induced rise in central aortic blood pressure may increase the risk of adverse cardiovascular health effects.