L-Citrulline supplementation attenuates aortic pressure and pressure waves during metaboreflex activation in postmenopausal women

Postmenopausal women have augmented pressure wave responses to low-intensity isometric handgrip exercise (IHG) due to an overactive metaboreflex (postexercise muscle ischaemia, PEMI), contributing to increased aortic systolic blood pressure (SBP). Menopause-associated endothelial dysfunction via arginine (ARG) and nitric oxide deficiency may contribute to exaggerated exercise SBP responses. L-Citrulline supplementation (CIT) is an ARG precursor that decreases SBP, pulse pressure (PP) and pressure wave responses to cold exposure in older adults. We investigated the effects of CIT on aortic SBP, PP, and pressure of forward (Pf) and backward (Pb) waves during IHG and PEMI in twenty-two postmenopausal women. Participants were randomised to CIT (10 g/d) or placebo (PL) for 4 weeks. Aortic haemodynamics were assessed via applanation tonometry at rest, 2 min of IHG at 30 % of maximal strength, and 3 min of PEMI. Responses were analysed as change (Δ) from rest to IHG and PEMI at 0 and 4 weeks. CIT attenuated ΔSBP (−9 ± 2 v. −1 ± 1 mmHg, P = 0·006), ΔPP (−5 ± 2 v. 0 ± 1 mmHg, P = 0·03), ΔPf (−6 ± 2 v. −1 ± 1 mmHg, P = 0·01) and ΔPb (−3 ± 1 v. 0 ± 1 mmHg, P = 0·02) responses to PEMI v. PL. The ΔPP during PEMI was correlated with ΔPf (r = 0·743, P < 0·001) and ΔPb (r = 0·724, P < 0·001). Citrulline supplementation attenuates the increase in aortic pulsatile load induced by muscle metaboreflex activation via reductions in forward and backward pressure wave amplitudes in postmenopausal women.

Effects of dietary L-Citrulline supplementation on growth performance, meat quality, and fecal microbial composition in finishing pigs

Gut microbiota play an important role in the gut ecology and development of pigs, which is always regulated by nutrients. This study investigated the effect of L-Citrulline on growth performance, carcass characteristics, and its potential regulatory mechanism. The results showed that 1% dietary L-Citrulline supplementation for 52 days significantly increased final weight, liveweight gain, carcass weight, and average backfat and markedly decreased drip loss (p < 0.05) of finishing pigs compared with the control group. Microbial analysis of fecal samples revealed a marked increase in α-diversity and significantly altered composition of gut microbiota in finishing pigs in response to L-Citrulline. In particular, these altered gut microbiota at the phylum and genus level may be mainly involved in the metabolic process of carbohydrate, energy, and amino acid, and exhibited a significant association with final weight, carcass weight, and backfat thickness. Taken together, our data revealed the potential role of L-Citrulline in the modulation of growth performance, carcass characteristics, and the meat quality of finishing pigs, which is most likely associated with gut microbiota.

Absence of Effects of L-Arginine and L-Citrulline on Inflammatory Biomarkers and Oxidative Stress in Response to Physical Exercise: A Systematic Review with Meta-Analysis

BACKGROUND

The repercussions on oxidative and inflammatory stress markers under the effects of arginine and citrulline in response to exercise are not fully reached. We completed a systematic review to investigate the effects of L-Citrulline or L-Arginine on oxidative stress and inflammatory biomarkers following exercise. EMBASE, MEDLINE (PubMed), Cochrane Library, CINAHL, LILACS, and Web of Science databases were used to record the trials. This study includes randomized controlled trials (RCTs) and non-RCTs with subjects over 18 years old. Those under the intervention protocol consumed L-Citrulline or L-Arginine, and the controls ingested placebo. We recognized 1080 studies, but only 7 were included (7 studies in meta-analysis). We observed no difference between pre- vs. post-exercise for oxidative stress (subtotal = -0.21 [CI: -0.56, 0.14], p = 0.24, and heterogeneity = 0%. In the sub-group "L-Arginine" we found a subtotal = -0.29 [-0.71, 0.12], p = 0.16, and heterogeneity = 0%. For the "L-Citrulline" subgroup we observed a subtotal = 0.00 [-0.67, 0.67], p = 1.00, and heterogeneity was not applicable. No differences were observed between groups (p = 0.47), and I² = 0%) or in antioxidant activity (subtotal = -0.28 [-1.65, 1.08], p = 0.68, and heterogeneity = 0%). In the "L-Arginine" sub-group, we found a subtotal = -3.90 [-14.18, 6.38], p = 0.46, and heterogeneity was not applicable. For the "L-Citrulline" subgroup, we reported a subtotal = -0.22 [-1.60, 1.16], p = 0.75, and heterogeneity was not applicable. No differences were observed between groups (p = 0.49), and I² = 0%), inflammatory markers (subtotal = 8.38 [-0.02, 16.78], p = 0.05, and heterogeneity = 93%. Tests for subgroup differences were not applicable, and anti-inflammatory markers (subtotal = -0.38 [-1.15, 0.39], p = 0.34 and heterogeneity = 15%; testing for subgroup differences was not applicable). In conclusion, our systematic review and meta-analysis found that L-Citrulline and L-Arginine did not influence inflammatory biomarkers and oxidative stress after exercise.

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.

Pathophysiology of Preeclampsia and L-Arginine/L-Citrulline Supplementation as a Potential Strategy to Improve Birth Outcomes

In preeclampsia, the shallow invasion of cytotrophoblast cells to uterine spiral arteries, leading to a reduction in placental blood flow, is associated with an imbalance of proangiogenic/antiangiogenic factors to impaired nitric oxide (NO) production. Proangiogenic factors, such as vascular endothelial growth factor (VEGF) and placental growth factor (PlGF), require NO to induce angiogenesis through antioxidant regulation mechanisms. At the same time, there are increases in antiangiogenic factors in preeclampsia, such as soluble fms-like tyrosine kinase type 1 receptor (sFIt1) and toll-like receptor 9 (TLR9), which are mechanism derivates in the reduction of NO bioavailability and oxidative stress in placenta.Different strategies have been proposed to prevent or alleviate the detrimental effects of preeclampsia. However, the only intervention to avoid the severe consequences of the disease is the interruption of pregnancy. In this scenario, different approaches have been analysed to treat preeclamptic pregnant women safely. The supplementation with amino acids is one of them, especially those associated with NO synthesis. In this review, we discuss emerging concepts in the pathogenesis of preeclampsia to highlight L-arginine and L-citrulline supplementation as potential strategies to improve birth outcomes. Clinical and experimental data concerning L-arginine and L-citrulline supplementation have shown benefits in improving NO availability in the placenta and uterine-placental circulation, prolonging pregnancy in patients with gestational hypertension and decreasing maternal blood pressure.

L-Citrulline supplementation attenuates aortic pulse pressure and wave reflection responses to cold stress in older adults

BACKGROUND AND AIMS

Augmented aortic systolic blood pressure (SBP) and wave reflection via sympathetic-mediated vasoconstriction elevates the risk for adverse cardiovascular events in older adults. L-citrulline (L-CIT) supplementation has shown to reduce aortic SBP and pulse pressure (PP) responses to cold pressor test (CPT) induced sympathoactivation in young men. The aim of this study was to elucidate the efficacy of L-CIT supplementation to attenuate aortic hemodynamic responses to CPT in older adults.

METHODS AND RESULTS

Sixteen older adults were randomly assigned to placebo or L-CIT (6 g/day) for 14-days in a crossover, double-blind, placebo-controlled design. Brachial SBP and aortic SBP, PP, augmented pressure (AP), augmentation index standardized at 75 bpm (AIx@75), and pressure of the forward (Pf) and reflected (Pb) waves were evaluated at rest and during CPT pre- and post-intervention. Although no hemodynamic changes at rest, brachial SBP (Δ-12 ± 18 vs. Δ4 ± 14 mmHg; P = 0.008) and aortic SBP (Δ-10 ± 14 vs. Δ4 ± 12 mmHg; P = 0.005), PP (Δ-10 ± 12 vs. Δ4 ± 11 mmHg; P = 0.002), AP (Δ-4 ± 4 vs. Δ2 ± 7 mmHg; P = 0.004), AIx@75 (Δ-3.2 ± 7.2 vs. Δ2.2 ± 6.9%; P = 0.038), Pf (Δ-6 ± 10 vs. Δ3 ± 9 mmHg; P = 0.019), and Pb (Δ-4 ± 6 vs. Δ2 ± 6 mmHg; P = 0.008) responses to the CPT were significantly attenuated following L-CIT supplementation vs. placebo.

CONCLUSIONS

L-CIT supplementation attenuated aortic pulsatile pressure and pressure wave reflection responses to CPT in older adults, providing possible cardioprotection during cold-induced sympathoactivation in older adults.

Dietary L-citrulline influences body temperature and inflammatory responses during nitric oxide synthase inhibition and endotoxin challenge in chickens

Recent studies have revealed the role of L-citrulline (L-CIT) in thermoregulation, but very little is known about the mechanisms involved. In this study, nitric oxide synthase inhibition and endotoxin-induced fever were used to investigate the effects of L-CIT on body temperature and inflammatory responses. In experiment 1, NW-nitro-L-arginine methyl ester (L-NAME, 150 mg/kg BW), was i. p. injected into chicks fed with basal (CON) or L-CIT diets for 14 days. In experiment 2, Lipopolysaccharide (LPS, 2 mg/kg BW) was i. p. injected following 21d feeding with CON or L-CIT diets. In experiment 3, chickens were injected with either L-NAME, LPS, or L-NAME + LPS following 26 days feeding with CON or L-CIT diets. The rectal (RT), ear (ET), and core body temperature (CBT) of chickens were examined. Results showed that L-NAME effectively decreased the RT, ET, CBT, and plasma NO concentration. In contrast, LPS increased NO levels and initiated hyperthermia by increasing RT, ET, CBT, and PGE2 levels. L-CIT diet reduced the mean CBT in experiment 1 and diminished the NO level, PGE2 level, and mean RT in experiment 3. Co-administration of L-CIT + LPS upregulated IL-6 expression, whereas, LPS injection alone induced IL-10, IL-1β, and TLR4 gene expressions. Therefore, this study reveals that L-CIT-induced hypothermia was related to NO inhibition and a decrease in PGE2 concentration. Conversely, LPS induced hyperthermia was associated with an increase in both NO and PGE2 concentrations.

Effects of L-Citrulline Supplementation and Aerobic Training on Vascular Function in Individuals with Obesity across the Lifespan

Children with obesity are at higher risk for developing cardiometabolic diseases that once were considered health conditions of adults. Obesity is commonly associated with cardiometabolic risk factors such as dyslipidemia, hyperglycemia, hyperinsulinemia and hypertension that contribute to the development of endothelial dysfunction. Endothelial dysfunction, characterized by reduced nitric oxide (NO) production, precedes vascular abnormalities including atherosclerosis and arterial stiffness. Thus, early detection and treatment of cardiometabolic risk factors are necessary to prevent deleterious vascular consequences of obesity at an early age. Non-pharmacological interventions including L-Citrulline (L-Cit) supplementation and aerobic training stimulate endothelial NO mediated vasodilation, leading to improvements in organ perfusion, blood pressure, arterial stiffness, atherosclerosis and metabolic health (glucose control and lipid profile). Few studies suggest that the combination of L-Cit supplementation and exercise training can be an effective strategy to counteract the adverse effects of obesity on vascular function in older adults. Therefore, this review examined the efficacy of L-Cit supplementation and aerobic training interventions on vascular and metabolic parameters in obese individuals.

Treatment with L-Citrulline in patients with post-polio syndrome: A single center, randomized, double blind, placebo-controlled trial

This single-centered, randomized, double-blind, placebo-controlled study reports the results of L-Citrulline treatment for 24 weeks in patients with post-polio syndrome (PPS). Twenty-nine patients were randomized and assigned into receiving a treatment of 15 g L-Citrulline or placebo. The primary endpoint was the change of the 6 min walking distance test. Secondary endpoints included motor function measure, quantitative muscle strength, quantitative MRI and self-reported impairment questionnaires. Patients receiving L-Citrulline walked 17.5 longer in the 6 min walking distance test when compared to placebo group, however not statistically significant (95% CI = -14.69; 49.68, p = 0.298). None of the secondary endpoints showed a statistically significant change in the L-Citrulline group when compared to placebo group. The motor function measure showed a change of -0.78 (95% CI= [-3.39; 1.83] p = 0.563). Muscle degeneration of leg muscles assessed with quantitative MRI indicated no significant change (estimate= -0.01, 95% CI =-0.13; 0.11, p = 0.869). L-Citrulline was safe and well tolerated. In conclusion, administration of 15 g L-Citrulline daily for 24 weeks to patients with PPS showed no beneficial treatment effect in timed muscle function.

Oral L-citrulline and Transresveratrol Supplementation Improves Erectile Function in Men With Phosphodiesterase 5 Inhibitors: A Randomized, Double-Blind, Placebo-Controlled Crossover Pilot Study

INTRODUCTION

Phosphodiesterase type 5 inhibitors (PDE5i) are first-line therapy for most men with erectile dysfunction (ED). If ineffective, vacuum erection devices, intracavernous injections, and penile prosthesis implantation are suitable as second- or third-line therapies. However, very few patients select these therapies. It is critically important to improve erectile function with oral administration of effective agents. Administration of L-citrulline or transresveratrol in animal experiments has been reported to improve erectile function, but few such experiments have been performed on humans with ED.

AIM

We aimed to investigate the efficacy of combination therapy of L-citrulline and transresveratrol in patients with ED despite their use of PDE5i.

METHODS

In this randomized, double-blind, placebo-controlled crossover pilot study, men with ED (Sexual Health Inventory for Men [SHIM] score below 16) despite on-demand use of PDE5i received a placebo for 1 month or the active treatment (L-citrulline 800 mg/day and transresveratrol 300 mg/day) for another month. Patients continued on-demand use of PDE5i.

MAIN OUTCOME MEASURE

The SHIM score, Erection Hardness Score (EHS), Aging Male Symptoms Scale-sexual domain (AMS-SD), and adverse events were examined.

RESULTS

20 patients ages 29-78 years were enrolled, and after 6 men withdrew, 13 concluded the study without adverse events. Mean SHIM score for the active treatment increased significantly (10.96 ± 1.21) compared with baseline (8.32 ± 1.21) and placebo (8.31 ± 1.23) (both P < .05). Mean EHS score for the active treatment (2.56 ± 0.26) also increased from baseline (2.31 ± 0.26), but not significantly (P = .79). Mean AMS-SD score was not significantly different in either group.

CONCLUSION

To our knowledge, this is the first study to show that combination therapy of L-citrulline and transresveratrol is effective for ED treatment in men with added on-demand use of PDE5i. This combination supplement may be added if PDE5i is insufficient. Shirai M, Hiramatsu I, Aoki Y, et al. Oral L-citrulline and Transresveratrol Supplementation Improves Erectile Function in Men With Phosphodiesterase 5 Inhibitors: A Randomized, Double-Blind, Placebo-Controlled Crossover Pilot Study. Sex Med 2018;6:291-296.

Microbial Production of Amino Acid-Related Compounds

Corynebacterium glutamicum is the workhorse of the production of proteinogenic amino acids used in food and feed biotechnology. After more than 50 years of safe amino acid production, C. glutamicum has recently also been engineered for the production of amino acid-derived compounds, which find various applications, e.g., as synthons for the chemical industry in several markets including the polymer market. The amino acid-derived compounds such as non-proteinogenic ω-amino acids, α,ω-diamines, and cyclic or hydroxylated amino acids have similar carbon backbones and functional groups as their amino acid precursors. Decarboxylation of amino acids may yield ω-amino acids such as β-alanine, γ-aminobutyrate, and δ-aminovalerate as well as α,ω-diamines such as putrescine and cadaverine. Since transamination is the final step in several amino acid biosynthesis pathways, 2-keto acids as immediate amino acid precursors are also amenable to production using recombinant C. glutamicum strains. Approaches for metabolic engineering of C. glutamicum for production of amino acid-derived compounds will be described, and where applicable, production from alternative carbon sources or use of genome streamline will be referred to. The excellent large-scale fermentation experience with C. glutamicum offers the possibility that these amino acid-derived speciality products may enter large-volume markets.

Characteristics of L-citrulline transport through blood-brain barrier in the brain capillary endothelial cell line (TR-BBB cells)

Background

_L-Citrulline is a neutral amino acid and a major precursor of _L-arginine in the nitric oxide (NO) cycle. Recently it has been reported that _L-citrulline prevents neuronal cell death and protects cerebrovascular injury, therefore, _L-citrulline may have a neuroprotective effect to improve cerebrovascular dysfunction. Therefore, we aimed to clarify the brain transport mechanism of _L-citrulline through blood-brain barrier (BBB) using the conditionally immortalized rat brain capillary endothelial cell line (TR-BBB cells), as an in vitro model of the BBB.

Methods

The uptake study of [¹⁴C] L-citrulline, quantitative real-time polymerase chain reaction (PCR) analysis, and rLAT1, system b^0,+, and CAT1 small interfering RNA study were performed in TR-BBB cells.

Results

The uptake of [¹⁴C] _L-citrulline was a time-dependent, but ion-independent manner in TR-BBB cells. The transport process involved two saturable components with a Michaelis–Menten constant of 30.9 ± 1.0 μM (Km₁) and 1.69 ± 0.43 mM (Km₂). The uptake of [¹⁴C] _L-citrulline in TR-BBB cells was significantly inhibited by neutral and cationic amino acids, but not by anionic amino acids. In addition, [¹⁴C]_L-citrulline uptake in the cells was markedly inhibited by 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH), which is the inhibitor of the large neutral amino acid transporter 1 (LAT1), B⁰, B^0,+ and harmaline, the inhibitor of system b^0,+. Gabapentin and _L-dopa as the substrates of LAT1 competitively inhibited the uptake of [¹⁴C] _L-citrulline. IC₅₀ values for _L-dopa, gabapentin, _L-phenylalanine and _L-arginine were 501 μM, 223 μM, 68.9 μM and 33.4 mM, respectively. The expression of mRNA for LAT1 was predominantly increased 187-fold in comparison with that of system b^0,+ in TR-BBB cells. In the studies of LAT1, system b^0,+ and CAT1 knockdown via siRNA transfection into TR-BBB cells, the transcript level of LAT1 and [¹⁴C] _L-citrulline uptake by LAT1 siRNA were significantly reduced compared with those by control siRNA in TR-BBB cells.

Conclusions

Our results suggest that transport of _L-citrulline is mainly mediated by LAT1 in TR-BBB cells. Delivery strategy for LAT1-mediated transport and supply of L-citrulline to the brain may serve as therapeutic approaches to improve its neuroprotective effect in patients with cerebrovascular disease.

A novel voltammetric sensor based on poly(l-Citrulline)/SWCNTs composite film modified electrode for sensitive determination of picroside II

A novel voltammetric sensor was constructed by simple dripping single-walled carbon nanotubes (SWCNTs) on to the glass carbon electrode (GCE) firstly and electro-polymerizing L-Citrulline film subsequently. The resulting poly(L-Citrulline)/SWCNTs/GCE showed a significant voltammetric response to picroside II due to the synergistic effect of SWCNTs and poly(L-Citrulline) film. The first electroanalytical method of picroside II was proposed with detection linear range from 8.0 × 10(-8) to 5.0 × 10(-6) mol L(-1) and a detection limit of 3 × 10(-8) mol L(-1). The high sensitivity, selectivity and long-term stability made the sensor suitable for the determination of picroside II. Moreover, based on the systematically investigation and some kinetics parameters calculated in the experimentation, the reaction mechanism of picroside II at the poly(L-Citrulline)/SWCNTs modified GCE was obtained reliably. Lastly, the proposed sensor was used for the determination of picroside II in real sample with satisfactory results. This work promoted the potential applications of amino acid materials and SWCNTs in electro-chemical sensors.

Oral L-citrulline supplementation enhances cycling time trial performance in healthy trained men: Double-blind randomized placebo-controlled 2-way crossover study

Background

Many human studies report that nitric oxide (NO) improves sport performance. This is because NO is a potential modulator of blood flow, muscle energy metabolism, and mitochondrial respiration during exercise. L-Citrulline is an amino acid present in the body and is a potent endogenous precursor of L-arginine, which is a substrate for NO synthase. Here, we investigated the effect of oral L-citrulline supplementation on cycling time trial performance in humans.

Methods

A double-blind randomized placebo-controlled 2-way crossover study was employed. Twenty-two trained males consumed 2.4 g/day of L-citrulline or placebo orally for 7 days. On Day 8 they took 2.4 g of L-citrulline or placebo 1 h before a 4-km cycling time trial. Time taken to complete the 4 km cycle, along with power output/VO₂ ratio (PO/VO₂), plasma nitrite and nitrate (NOx) and amino acid levels, and visual analog scale (VAS) scores, was evaluated.

Results

L-Citrulline supplementation significantly increased plasma L-arginine levels and reduced completion time by 1.5 % (p < 0.05) compared with placebo. Moreover, L-citrulline significantly improved subjective feelings of muscle fatigue and concentration immediately after exercise.

Conclusions

Oral L-citrulline supplementation reduced the time take to complete a cycle ergometer exercise trial.

Trial registration

Current Controlled Trials UMIN000014278.

Comparison of inducible nitric oxide synthase activity in pancreatic islets of young and aged rats

OBJECTIVES

Some pathologic situations such as diabetes and metabolic syndrome are associated with alternation in nitric oxide level. Incidence of these condition increases with aging. On the other hand, insulin secretion is modulated by nitric oxide, and nitric oxide synthase (NOS) activity is also altered in diabetes. In this study, modification in the enzyme activity associated with aging and also optimized procedure for islet NOS assay was investigated.

MATERIALS AND METHODS

Male Wistar rats were randomly divided in two experimental groups: A: adult rats; were 4 month old and B: old rats; were 12 month old. In all groups, plasma glucose, insulin and NOX (nitrite + nitrate = NOX) were measured, and also insulin secretion in isolated pancreatic islet with or without L-NAME was investigated. Furthermore, the inducible NOS activity with L-citrulline measurement in islets was measured.

RESULTS

L-citrulline was quantified using one step HPLC column. Aging induced hyperglycemia (P<0.05) and excess plasma NOX (17.74 ± 1.664 and 26.25 ± 2.166 μmol/l in A and B groups respectively, P<0.05) with unaltered plasma insulin. Islet insulin secretion was significantly reduced in aging rats. L-NAME induced islet insulin secretion especially in aging rats (P=0.003). Inducible NOS activity in islets of aging rats was significantly higher than adult rats (1.082 ± 0.084 and 6.277 ± 0.475 pmol/min per mg protein in adult and aging rats, respectively, P<0.001).

CONCLUSION

These findings show that decreased in islet insulin secretion may be related to increase in iNOS activity in islets, which follows impaired carbohydrate metabolism in aging.

Effects of Oral L-Citrulline Supplementation on Lipoprotein Oxidation and Endothelial Dysfunction in Humans with Vasospastic Angina

BACKGROUND

Decreased nitric oxide (NO) bioavailability and increased lipid oxidation are associated with progressive endothelial dysfunction. L-Citrulline, the effective precursor of L-arginine which is essential as a substrate for endothelial NO synthase (eNOS), is effective in enhancing NO-dependent signaling. However, little is known about the efficacy of L-citrulline supplementation on lipoprotein oxidation and endothelial dysfunction.

METHODS

Twenty-two patients (aged 41 - 64 years old) diagnosed with vasospastic angina with flow-mediated dilation (FMD) of the brachial artery (< 5.5 %) received 800 mg/day of L-citrulline for 8 weeks. FMD (%), blood NOx, asymmetric dimethylarginine (ADMA), small dense LDL, oxidized lipids, amino acids concentrations were measured before and after supplementation.

RESULTS

Compared with baseline values, FMD (%) was significantly improved at 4 and 8 weeks as well as at 4 weeks after the end of intake. L-Citrulline supplementation caused a significant lowering of plasma ADMA levels. Plasma L-arginine/ADMA ratio and NOx levels rose markedly throughout the study period. Moreover, significant reductions of serum oxidized LDL and lectin-like oxidized LDL receptor 1 (LOX-1) ligand containing ApoB (LAB), an indicator of the biological activity of oxidized lipoprotein binding to LOX-1, were observed after L-citrulline intake.

CONCLUSIONS

L-Citrulline supplementation improves endothelial dysfunction, probably due to potentiating NO-dependent reactions and decreasing the state of lipoprotein oxidation in humans.