Impact of supplementation with L-citrulline/arginine after liver transplantation in individuals with Urea Cycle Disorders

OBJECTIVE

Liver transplantation (LTx) is an intervention when medical management is not sufficiently preventing individuals with urea cycle disorders (UCDs) from the occurrence of hyperammonemic events. Supplementation with L-citrulline/arginine is regularly performed prior to LTx to support ureagenesis and is often continued after the intervention. However, systematic studies assessing the impact of long-term L-citrulline/arginine supplementation in individuals who have undergone LTx is lacking to date.

METHODS

Using longitudinal data collected systematically, a comparative analysis was carried out by studying the effects of long-term L-citrulline/arginine supplementation vs. no supplementation on health-related outcome parameters (i.e., anthropometric, neurological, and cognitive outcomes) in individuals with UCDs who have undergone LTx. Altogether, 52 individuals with male ornithine transcarbamylase deficiency, citrullinemia type 1 and argininosuccinic aciduria and a pre-transplant "severe" disease course who have undergone LTx were investigated by using recently established and validated genotype-specific in vitro enzyme activities.

RESULTS

Long-term supplementation of individuals with L-citrulline/arginine who have undergone LTx (n = 16) does neither appear to alter anthropometric nor neurocognitive endpoints when compared to their severity-adjusted counterparts that were not supplemented (n = 36) after LTx with mean observation periods between four to five years. Moreover, supplementation with L-citrulline/arginine was not associated with an increase of disease-specific plasma arithmetic mean values for the respective amino acids when compared to the non-supplemented control cohort.

CONCLUSION

Although supplementation with L-citrulline/arginine is often continued after LTx, this pilot study does neither identify altered long-term anthropometric or neurocognitive health-related outcomes nor does it find an adequate biochemical response as reflected by the unaltered plasma arithmetic mean values for L-citrulline or L-arginine. Further prospective analyses in larger samples and even longer observation periods will provide more insight into the usefulness of long-term supplementation with L-citrulline/arginine for individuals with UCDs who have undergone LTx.

Multi-dose enteral L-citrulline administration in premature infants at risk of developing pulmonary hypertension associated with bronchopulmonary dysplasia

OBJECTIVE

Information is needed to guide the design of randomized controlled trials (RCTs) evaluating L-citrulline therapy for premature infants with pulmonary hypertension associated with bronchopulmonary dysplasia (BPD-PH). Based on our single-dose pharmacokinetic study, we evaluated the ability of a multi-dose enteral L-citrulline strategy to achieve a target trough steady-state L-citrulline plasma concentration and its tolerability in premature infants.

STUDY DESIGN

Plasma L-citrulline concentrations were measured in six premature infants receiving 60 mg/kg L-citrulline every 6 h for 72 h before the first and last L-citrulline doses. L-citrulline concentrations were compared to concentration-time profiles from our previous study.

RESULTS

Target trough plasma L-citrulline concentrations were achieved in 2/6 subjects. No serious adverse events occurred.

CONCLUSIONS

Multi-dose L-citrulline was well tolerated. These results will assist in the design of phase II RCTs evaluating L-citrulline dosage strategies to achieve target plasma L-citrulline concentrations in infants at risk for BPD-PH.

CLINICAL TRIALS

gov ID: NCT03542812.

Perinatal Use of Citrulline Rescues Hypertension in Adult Male Offspring Born to Pregnant Uremic Rats

The growing recognition of the association between maternal chronic kidney disease (CKD) and fetal programming highlights the increased vulnerability of hypertension in offspring. Potential mechanisms involve oxidative stress, dysbiosis in gut microbiota, and activation of the renin-angiotensin system (RAS). Our prior investigation showed that the administration of adenine to pregnant rats resulted in the development of CKD, ultimately causing hypertension in their adult offspring. Citrulline, known for enhancing nitric oxide (NO) production and possessing antioxidant and antihypertensive properties, was explored for its potential to reverse high blood pressure (BP) in offspring born to CKD dams. Male rat offspring, both from normal and adenine-induced CKD models, were randomly assigned to four groups (8 animals each): (1) control, (2) CKD, (3) citrulline-treated control rats, and (4) citrulline-treated CKD rats. Citrulline supplementation successfully reversed elevated BP in male progeny born to uremic mothers. The protective effects of perinatal citrulline supplementation were linked to an enhanced NO pathway, decreased expression of renal (pro)renin receptor, and changes in gut microbiota composition. Citrulline supplementation led to a reduction in the abundance of Monoglobus and Streptococcus genera and an increase in Agothobacterium Butyriciproducens. Citrulline's ability to influence taxa associated with hypertension may be linked to its protective effects against maternal CKD-induced offspring hypertension. In conclusion, perinatal citrulline treatment increased NO availability and mitigated elevated BP in rat offspring from uremic mother rats.

A Randomized Feasibility Trial of Stereotactic Prostate Radiation Therapy With or Without Elective Nodal Irradiation in High-Risk Localized Prostate Cancer (SPORT Trial)

PURPOSE

The aim of this study was to establish the feasibility of a randomized clinical trial comparing SABR with prostate-only (P-SABR) or with prostate plus pelvic lymph nodes (PPN-SABR) in patients with unfavorable intermediate- or high-risk localized prostate cancer and to explore potential toxicity biomarkers.

METHODS AND MATERIALS

Thirty adult men with at least 1 of the following features were randomized 1:1 to P-SABR or PPN-SABR: clinical magnetic resonance imaging stage T3a N0 M0, Gleason score ≥7 (4+3), and prostate-specific antigen >20 ng/mL. P-SABR patients received 36.25 Gy/5 fractions/29 days, and PPN-SABR patients received 25 Gy/5 fractions to pelvic nodes, with the final cohort receiving a boost to the dominant intraprostatic lesion of 45 to 50 Gy. Phosphorylated gamma-H2AX (γH2AX) foci numbers, citrulline levels, and circulating lymphocyte counts were quantified. Acute toxicity information (Common Terminology Criteria for Adverse Events, version 4.03) was collected weekly at each treatment and at 6 weeks and 3 months. Physician-reported late Radiation Therapy Oncology Group (RTOG) toxicity was recorded from 90 days to 36 months postcompletion of SABR. Patient-reported quality of life (Expanded Prostate Cancer Index Composite and International Prostate Symptom Score) scores were recorded with each toxicity time point.

RESULTS

The target recruitment was achieved, and treatment was successfully delivered in all patients. A total of 0% and 6.7% (P-SABR) and 6.7% and 20.0% (PPN-SABR) experienced acute grade ≥2 gastrointestinal (GI) and genitourinary (GU) toxicity, respectively. At 3 years, 6.7% and 6.7% (P-SABR) and 13.3% and 33.3% (PPN-SABR) had experienced late grade ≥2 GI and GU toxicity, respectively. One patient (PPN-SABR) had late grade 3 GU toxicity (cystitis and hematuria). No other grade ≥3 toxicity was observed. In addition, 33.3% and 60% (P-SABR) and 64.3% and 92.9% (PPN-SABR) experienced a minimally clinically important change in late Expanded Prostate Cancer Index Composite bowel and urinary summary scores, respectively. γH2AX foci numbers at 1 hour after the first fraction were significantly higher in the PPN-SABR arm compared with the P-SABR arm (P = .04). Patients with late grade ≥1 GI toxicity had significantly greater falls in circulating lymphocytes (12 weeks post-radiation therapy, P = .01) and a trend toward higher γH2AX foci numbers (P = .09) than patients with no late toxicity. Patients with late grade ≥1 bowel toxicity and late diarrhea experienced greater falls in citrulline levels (P = .05).

CONCLUSIONS

A randomized trial comparing P-SABR with PPN-SABR is feasible with acceptable toxicity. Correlations of γH2AX foci, lymphocyte counts, and citrulline levels with irradiated volume and toxicity suggest potential as predictive biomarkers. This study has informed a multicenter, randomized, phase 3 clinical trial in the United Kingdom.

Enteral citrulline supplementation versus placebo on SOFA score on day 7 in mechanically ventilated critically ill patients: the IMMUNOCITRE randomized clinical trial

BACKGROUND

Restoring plasma arginine levels through enteral administration of L-citrulline in critically ill patients may improve outcomes. We aimed to evaluate whether enteral L-citrulline administration reduced organ dysfunction based on the Sequential Organ Failure Assessment (SOFA) score and affected selected immune parameters in mechanically ventilated medical intensive care unit (ICU) patients.

METHODS

A randomized, double-blind, multicenter clinical trial of enteral administration of L-citrulline versus placebo for critically ill adult patients under invasive mechanical ventilation without sepsis or septic shock was conducted in four ICUs in France between September 2016 and February 2019. Patients were randomly assigned to receive enteral L-citrulline (5 g) every 12 h for 5 days or isonitrogenous, isocaloric placebo. The primary outcome was the SOFA score on day 7. Secondary outcomes included SOFA score improvement (defined as a decrease in total SOFA score by 2 points or more between day 1 and day 7), secondary infection acquisition, ICU length of stay, plasma amino acid levels, and immune biomarkers on day 3 and day 7 (HLA-DR expression on monocytes and interleukin-6).

RESULTS

Of 120 randomized patients (mean age, 60 ± 17 years; 44 [36.7%] women; ICU stay 10 days [IQR, 7-16]; incidence of secondary infections 25 patients (20.8%)), 60 were allocated to L-citrulline and 60 were allocated to placebo. Overall, there was no significant difference in organ dysfunction as assessed by the SOFA score on day 7 after enrollment (4 [IQR, 2-6] in the L-citrulline group vs. 4 [IQR, 2-7] in the placebo group; Mann‒Whitney U test, p = 0.9). Plasma arginine was significantly increased on day 3 in the treatment group, while immune parameters remained unaffected.

CONCLUSION

Among mechanically ventilated ICU patients without sepsis or septic shock, enteral L-citrulline administration did not result in a significant difference in SOFA score on day 7 compared to placebo.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier NCT02864017 (date of registration: 11 August 2016).

Variant in the allosteric domain of CPS1 protein associated with effectiveness of N-carbamoyl glutamate therapy in neonatal onset CPS1 deficiency

OBJECTIVES

Carbamoyl phosphate synthetase 1 (CPS1) deficiency is a severe urea cycle disorder. Patients can present with hyperammonemic coma in the first days of life. Treatment includes nitrogen scavengers, reduced protein intake and supplementation with L-arginine and/or L-citrulline. N-carbamoyl glutamate (NCG) has been hypothesized to stimulate the residual CPS1 function, although only few patients are reported.

CASE PRESENTATION

We report a patient with neonatal-onset CPS1 deficiency who received NCG in association with nitrogen scavenger and L-citrulline. The patient carried the novel variants CPS1-c.2447A>G p.(Gln816Arg) and CPS1-c.4489T>C p.(Tyr1497His). The latter is localized in the C-terminal allosteric domain of the protein, and is implicated in the binding of the natural activator N-acetyl-L-glutamate. NCG therapy was effective in controlling ammonia levels, allowing to increase the protein intake.

CONCLUSIONS

Our data show that the response to NCG can be indicated based on the protein structure. We hypothesize that variants in the C-terminal domain may be responsive to NCG therapy.

Anti-citrullinated protein antibodies as biomarkers in rheumatoid arthritis

INTRODUCTION

The serological biomarker anti-citrullinated protein antibodies (ACPAs) may have several functions but is especially important for the diagnosis of rheumatoid arthritis (RA) along with clinical symptoms.

AREAS COVERED

This review provides an overview of ACPAs, which are useful in RA diagnostics and may improve our understanding of disease etiology. PubMed was searched with combinations of words related to antibodies recognizing epitopes containing the post-translationally modified amino acid citrulline in combination with rheumatoid arthritis; cyclic citrullinated peptide, CCP, anti-CCP, anti-citrullinated protein antibodies, ACPA, citrullination, peptide/protein arginine deiminase, PAD, filaggrin, vimentin, keratin, collagen, perinuclear factor, EBNA1, EBNA2, and others. From this search, we made a qualitative extract of publications relevant to the discovery, characterization, and clinical use of these antibodies in relation to RA. We highlight significant findings and identify areas for improvement.

EXPERT OPINION

ACPAs have high diagnostic sensitivity and specificity for RA and recognize citrullinated epitopes from several proteins. The best-performing single epitope originates from Epstein-Barr Virus nuclear antigen 2 and contains a central Cit-Gly motif, which is recognized by ACPAS when located in a flexible peptide structure. In addition, ACPAs may also have prognostic value, especially in relation to early treatment, although ACPAs' main function is to aid in the diagnosis of RA.

Pharmacokinetics of L-Citrulline in Neonates at Risk of Developing Bronchopulmonary Dysplasia-Associated Pulmonary Hypertension

BACKGROUND

Options to treat pulmonary hypertension (PH) in neonates with bronchopulmonary dysplasia (BPD) are few and largely ineffective. Improving the bioavailability of nitric oxide (NO) might be an efficacious treatment for BPD-PH. When administered orally, the NO-L-arginine precursor, L-citrulline, increases NO production in children and adults, however, pharmacokinetic (PK) studies of oral L-citrulline have not been performed in infants and children.

OBJECTIVES

This study characterized the PK of enterally administered L-citrulline in neonates at risk of developing BPD-PH to devise a model-informed dosing strategy.

METHODS AND RESULTS

Ten premature neonates (≤ 28 weeks gestation) were administered a single dose of 150 mg/kg (powder form solubilized in sterile water) oral L-citrulline at 32 ± 1 weeks postmenstrual age. Due to the need to limit blood draws, time windows were used to maximize the sampling over the dosing interval by assigning neonates to one of two groups (ii) samples collected pre-dose and at 1- and 2.5-h post-dose, and (ii) pre-dose and 0.25- and 3-h post-dose. The L-arginine concentrations (µmol/L) and the L-citrulline (µmol/L) plasma concentration-time data were evaluated using non-compartmental analysis (Phoenix WinNonlin version 8.1). Optimal dosage strategies were derived using a simulation-based methodology. Simulated doses of 51.5 mg or 37.5 mg/kg given four times a day produced steady-state concentrations close to a target of 50 µmol/L. The volume of distribution (V/F) and clearance (CL/F) were 302.89 ml and 774.96 ml/h, respectively, with the drug exhibiting a half-life of 16 minutes. The AUC from the time of dosing to the time of last concentration was 1473.3 h*μmol/L, with Cmax and Tmax of 799 μmol/L and 1.55 h, respectively.

CONCLUSION

This is the first PK study in neonates presenting data that can be used to inform dosing strategies in future randomized controlled trials evaluating enteral L-citrulline as a potential treatment to reduce PH associated with BPD in premature neonates.

REGISTRATION

Clinical trials.gov Identifier: NCT03542812.

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.

Folic acid, either solely or combined with L-citrulline, improves NO signaling and ameliorates chronic hypoxia-induced pulmonary hypertension in newborn pigs

Concomitant with developing pulmonary hypertension (PH), newborn piglets exposed to chronic hypoxia develop pulmonary vascular NO signaling impairments. PH is reduced and NO signaling is improved in chronically hypoxic piglets treated with the NO-arginine precursor, L-citrulline. Folic acid positively impacts NO signaling. We evaluated whether the effect on NO signaling and PH is greater using co-treatment with folic acid and L-citrulline than either alone. From day 3 to day 10 of hypoxia, piglets were treated solely with folic acid, solely with L-citrulline, or co-treated with both. Catheters were placed to measure in vivo hemodynamics. NO production was measured in vitro in dissected pulmonary arteries. Compared to normoxic piglets, pulmonary vascular resistance (PVR) was elevated and NO production was reduced in untreated hypoxic piglets. Regardless of treatment strategy, PVR was less in all three treated groups of hypoxic piglets when compared to the untreated hypoxic group. In addition, for all three groups of treated hypoxic piglets, NO production was higher than the untreated group. Improvements in PVR and NO production did not differ between piglets co-treated with folic acid and L-citrulline and those treated solely with either. Thus, the impact on NO production and PVR was not augmented by combining folic acid and L-citrulline treatments. Nonetheless, treatment with folic acid, either singly or when combined with L-citrulline, increases NO production and inhibits PH in chronically hypoxic newborn piglets. Folic acid merits consideration as a therapy for PH in human infants with chronic heart and lung conditions that are associated with chronic hypoxia.

PEG-G-CSF and L-Citrulline Combination Therapy for Mitigating Skin Wound Combined Radiation Injury in a Mouse Model

Radiation combined injury (RCI, radiation exposure coupled with other forms of injury, such as burn, wound, hemorrhage, blast, trauma and/or sepsis) comprises approximately 65% of injuries from a nuclear explosion, and greatly increases the risk of morbidity and mortality when compared to that of radiation injury alone. To date, no U.S. Food and Drug Administration (FDA)-approved countermeasures are available for RCI. Currently, three leukocyte growth factors (Neupogen®, Neulasta® and Leukine®) have been approved by the FDA for mitigating the hematopoietic acute radiation syndrome. However these granulocyte-colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) products have failed to increase 30-day survival of mice after RCI, suggesting a more complicated biological mechanism is in play for RCI than for radiation injury. In the current study, the mitigative efficacy of combination therapy using pegylated (PEG)-G-CSF (Neulasta) and -citrulline was evaluated in an RCI mouse model. L-citrulline is a neutral alpha-amino acid shown to improve vascular endothelial function in cardiovascular diseases. Three doses of PEG-G-CSF at 1 mg/kg, subcutaneously administered on days 1, 8 and 15 postirradiation, were supplemented with oral -citrulline (1 g/kg), once daily from day 1 to day 21 postirradiation. The combination treatment significantly improved the 30-day survival of mice after RCI from 15% (vehicle-treated) to 42%, and extended the median survival time by 4 days, as compared to vehicle controls. In addition, the combination therapy significantly increased body weight and bone marrow stem and progenitor cell clonogenicity in RCI mice, and accelerated recovery from RCI-induced intestinal injury, compared to animals treated with vehicle. Treatment with -citrulline alone also accelerated skin wound healing after RCI. In conclusion, these data indicate that the PEG-G-CSF and -citrulline combination therapy is a potentially effective countermeasure for mitigating RCI, likely by enhancing survival of the hematopoietic stem/progenitor cells and accelerating recovery from the RCI-induced intestinal injury and skin wounds.

Protective effects of citrulline supplementation in ulcerative colitis rats

It has been reported that supplementing certain amino acids has therapeutic effects on ulcerative colitis (UC). We intend to explore whether citrulline (Cit) supplementation has protective effects on UC. Fifteen male Wistar rats were divided into normal control group (NC group), UC group and UC+Cit group, with five rats in each group. The UC model was established by TNBS/ethanol method. Rats in UC+Cit group were intragastrically administered with Cit for 7 consecutive days after modeling. All rats were sacrificed after 7 days. Blood samples were collected to detect the number of monocytes. Colon tissues were taken for HE staining. Immunohistochemistry staining for CD68 and p-STAT3 were performed to detect the infiltration of monocytes and the phosphorylation of STAT3 in colon tissues. The concentrations of MCP-1, IL-6 and IL-17A and the protein expression of p-STAT3 in colon tissues were measured by ELISA and western blot methods, respectively. The body weight of UC group rats decreased significantly after 7 days (p<0.05). However, the weight loss of UC+Cit group rats was not statistically significant (p>0.05). The number of peripheral blood monocytes in UC+Cit group was significantly lower than that in UC group (p<0.05), and the infiltration of CD68-positive monocytes in the colon tissue of UC+Cit group was significantly reduced than that in UC group. The concentrations of MCP-1, IL-6 and IL-17A and the expression of p-STAT3 in colon tissues of UC+Cit group rats were significantly lower than those in UC group (both p<0.05). Our study suggests that Cit supplementation may be a potential therapy for UC.

Daily watermelon consumption decreases plasma sVCAM-1 levels in overweight and obese postmenopausal women

Postmenopausal status is associated with an increase in total and abdominal body fat as well as increased incidence of insulin resistance and cardiovascular disease. The purpose of this study was to determine if watermelon supplementation affects select systemic markers of atherosclerosis and measures of insulin resistance in overweight and obese postmenopausal women. We hypothesized that overweight and obese postmenopausal women consuming 100% watermelon puree daily for 6 weeks would have improved levels of select systemic markers connected with cardiovascular disease without changing markers of insulin resistance. To test this hypothesis, overweight and obese postmenopausal women were recruited to participate in this study. Participants were randomly assigned to either the control group (no intervention) or the watermelon puree group (WM) for 6 weeks. Plasma concentration of markers connected with atherosclerosis and glycemic control were measured pre- and poststudy. A significant 6% decrease in soluble vascular cell adhesion molecule-1 occurred pre- to poststudy in WM, P = .003. The pattern of change in fasting blood glucose (P = .633), insulin (P = .158), and homeostatic model assessment-estimated insulin resistance (P = .174) did not differ between groups. Pre- to poststudy increases were measured in the fasting plasma concentration of l-arginine (8%, P = .005), cis-lycopene (32%, P = .003), and trans-lycopene (42%, P = .003) in WM. We conclude that 6 weeks of watermelon supplementation improved soluble vascular cell adhesion molecule-1 levels, a marker connected to atherogenesis, independent of changes in body composition or glycemic control.

Effect of Combination l-Citrulline and Metformin Treatment on Motor Function in Patients With Duchenne Muscular Dystrophy: A Randomized Clinical Trial

IMPORTANCE

Nitric oxide precursors, such as the amino acid l-arginine and the biguanide antidiabetic drug metformin, have been associated with metabolism and muscle function in patients with Duchenne muscular dystrophy (DMD). The treatment of DMD remains an unmet medical need.

OBJECTIVE

To evaluate the benefits and harms of a combination of l-citrulline and metformin treatment among patients with DMD.

DESIGN, SETTING, AND PARTICIPANTS

A single-center randomized double-blind placebo-controlled parallel-group clinical trial was conducted between December 12, 2013, and March 30, 2016, at the University Children's Hospital Basel in Switzerland. A total of 47 ambulant male patients aged 6.5 to 10 years with genetically confirmed DMD were recruited locally and from the patient registries of Switzerland, Germany, Austria, and France. Data were analyzed from April 6, 2016, to September 5, 2019.

INTERVENTIONS

Patients in the treatment group received 2500 mg of l-citrulline and 250 mg of metformin (combination therapy) 3 times a day for 26 weeks compared with patients in the control group, who received placebo.

MAIN OUTCOMES AND MEASURES

The primary end point was the change in transfer and standing posture, as assessed by the first dimension of the Motor Function Measure, version 32, from baseline to week 26. Secondary end points included assessments of timed function, quantitative muscle force, biomarkers for muscle necrosis, and adverse events. The 2 prespecified subgroups comprised patients who were able to walk 350 m or more in 6 minutes (stable subgroup) and patients who were not able to walk 350 m in 6 minutes (unstable subgroup) at baseline.

RESULTS

Among 49 ambulant male children with DMD who were screened for eligibility, 47 patients with a mean (SD) age of 8.2 (1.1) years were randomized to a treatment group receiving combination therapy (n = 23) or a control group receiving placebo (n = 24), and 45 patients completed the study. No significant differences between groups were found in the results of timed function and muscle force tests for overall, proximal and axial, and distal motor function. Among patients receiving combination therapy, the Motor Function Measure first dimension subscore decrease was 5.5% greater than that of patients receiving placebo (95% CI, -1.0% to 12.1%; P = .09). The administration of combination therapy had significantly favorable effects on the first dimension subscore decrease among the 29 patients in the stable subgroup (6.7%; 95% CI, 0.9%-12.6%; P = .03) but not among the 15 patients in the unstable subgroup (3.9%; 95% CI, -13.2% to 20.9%; P = .63). Overall, the treatment was well tolerated with only mild adverse effects.

CONCLUSIONS AND RELEVANCE

Treatment with combination therapy was not associated with an overall reduction in motor function decline among ambulant patients with DMD; however, a reduction in motor function decline was observed among the stable subgroup of patients treated with combination therapy. The statistically nonsignificant difference of distal motor function in favor of combination therapy and the reduced degeneration of muscle tissue appear to support the treatment concept, but the study may have lacked sufficient statistical power. Further research exploring this treatment option with a greater number of patients is warranted.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT01995032.

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.

Effectiveness of arginase inhibitors against experimentally induced stroke

Stroke is a lethal disease, but it disables more than it kills. Stroke is the second leading cause of death and the most frequent cause of permanent disability in adults worldwide, with 90% of survivors having residual deficits. The pathophysiology of stroke is complex and involves a strong inflammatory response associated with oxidative stress and activation of several proteolytic enzymes. The current study was designed to investigate the effect of arginase inhibitors (L-citruline and L-ornithine) against ischemic stroke induced in rats by middle cerebral artery occlusion (MCAO). MCAO resulted in alteration in rat behavior, brain infarct, and edema associated with disruption of the blood-brain barrier (BBB). This was mediated through overexpression of arginase I and II, inducible NOS (iNOS), malondialdehyde (MDA), advanced glycation end products (AGEs), TNF-α, and IL-1β and downregulation of endothelial nitric oxide synthase (eNOS). Treatment with L-citruline and L-ornithine and the standard neuroprotective drug cerebrolysin ameliorated all the deleterious effects of stroke. These results indicate the possible use of arginase inhibitors in the treatment of stroke after suitable clinical trials are done.

Experience of correcting endothelial dysfunction in children-residents of radioactively contaminated areas by nitric oxide potential donator citrulline

OBJECTIVE

to determine the effectiveness of citrulline use for correcting endothelial dysfunction in children resi dents of radioactively contaminated areas.

MATERIALS AND METHODS

A group of children residents of radioactively contaminated areas with the presence of clinical and paraclinical signs of endothelial dysfunction was selected to assess the effectiveness of correcting endothelial dysfunction by the usage of NO potential donator - citrulline according to the data of selective screen ing. There were determined the biochemical parameters of the content of NO stable metabolites, L arginine, lipid peroxidation, antioxidant enzymes in the blood serum; the indices of cellular and humoral immunity; the instrumen tal indices of vascular endothelium dependent reaction on occlusion test, the lung ventilation capacity, the bioelec tric activity of the myocardium, the autonomic regulation of the cardiovascular system.Examined children were received a course of citrulline malate.

RESULTS AND CONCLUSIONS

An increased content of serum L arginine, nitrite, and amounts of NO metabolites was established in children with endothelial dysfunction who were received a course of citrulline malate. Bronchospasm elimination was noted in the significant part of examined patients after the drug use. Decreased recovery period and increased period of hypercompensation for thermographic circulation index in the test with post occlusion reac tive hyperemia were detected by an evaluation of indicators for vascular endothelium dependent vasodilatation using thermographic method indicating an increased endothelial vasomotor capacity. There was tendency to improve the processes of autonomic regulation of the heart rhythm and repolarization of the heart muscle. The antioxidant effect of used citrulline malate course was determined as: decreased content of serum LPO end products that react with thiobarbituric acid under elevated activity of antioxidant - catalase. An increase in the percentage of T lymphocyte, normalization of their subpopulation composition was noted in dynamics of citrulline malate application.

Citrulline Malate Does Not Improve Muscle Recovery after Resistance Exercise in Untrained Young Adult Men

The effects of citrulline malate (CM) on muscle recovery from resistance exercise remains unknown. We aimed to determine if citrulline malate supplementation improves muscle recovery after a single session of high-intensity resistance exercise (RE) in untrained young adult men. Nine young adult men (24.0 ± 3.3 years) participated in a double-blind crossover study in which they received 6 g of CM and placebo (PL) on two occasions, separated by a seven-day washout period. Each occasion consisted of a single session of high-intensity RE (0 h) and three subsequent fatigue tests sessions (at 24, 48, and 72 h) to assess the time course of muscle recovery. During the tests sessions, we assessed the following variables: number of maximum repetitions, electromyographic signal (i.e., root mean square (RMS) and median frequency (MF)), muscle soreness and perceived exertion, as well as blood levels of creatine kinase (CK), lactate, insulin, and testosterone:cortisol ratio. CK levels increased at 24 h post-exercise and remained elevate at 48 and 72 h, with no difference between CM and PL conditions. Muscle soreness increased at 24 h post-exercise, which progressively returned to baseline at 72 h in both conditions. Lactate levels increased immediately post-exercise and remained elevated at 24, 48, and 72 h in both conditions. No significant treatment × time interaction was found for all dependents variables (maximum repetitions, perceived exertion, CK, lactate, RMS, MF, and testosterone:cortisol ratio) during the recovery period. In conclusion, our data indicate that CM supplementation (single 6 g dose pre-workout) does not improve the muscle recovery process following a high-intensity RE session in untrained young adult men.

Neonatal Citrulline Supplementation and Later Exposure to a High Fructose Diet in Rats Born with a Low Birth Weight: A Preliminary Report

A low birth weight (LBW) leads to a higher risk of metabolic syndrome in adulthood. Literature suggests that citrulline supplementation in adulthood prevents the effect of a high fructose diet on energy metabolism. Whether neonatal citrulline supplementation would alter early growth or energy metabolism in the long-term in rats with LBW is unknown. LBW pups born from dams fed a low (4%) protein diet, were nursed by normally-fed dams and received isonitrogenous supplements of either l-citrulline or l-alanine by gavage from the sixth day of life until weaning, and were subsequently exposed to 10%-fructose in drinking water from weaning to 90 days of age. The oral glucose tolerance was tested (OGTT) at 70 days of age, and rats were sacrificed at 90 days of age. Pre-weaning citrulline supplementation failed to alter the growth trajectory, OGTT, plasma triglycerides, or fat mass accretion in adulthood; yet, it was associated with increased liver triglycerides, decreased liver total cholesterol, and a distinct liver lipidomic profile that may result in a predisposition to liver disease. We conclude that pre-weaning supplementation with citrulline does not impact early growth, but might impact liver fat metabolism in adulthood upon exposure to a high fructose diet.

Treatment with L-citrulline in patients with post-polio syndrome: study protocol for a single-center, randomised, placebo-controlled, double-blind trial

BACKGROUND

Post-polio syndrome (PPS) is a condition that affects polio survivors years after recovery from an initial acute infection by the Poliomyelitis virus. Most often, patients who suffered from polio start to experience gradual new weakening in muscles, a gradual decrease in the size of muscles (muscle atrophy) and fatigue years after the acute illness. L-citrulline is known to change muscular metabolism synthesis by raising nitric oxide (NO) levels and increasing protein synthesis. This investigator-initiated, randomised, placebo-controlled, double-blind, trial aims to demonstrate that L-citrulline positively influences muscle function and increases muscular energy production in patients with PPS.

METHODS/DESIGN

Thirty ambulant PPS patients will be recruited in Switzerland. Patients will be randomly allocated to one of the two arms of the study (placebo:verum 1:1). After a 24-week run-in phase to observe natural disease history and progression, participants will be treated either with L-citrulline or placebo for 24 weeks. The primary endpoint is change in the 6-min Walking Distance Test. Secondary endpoints will include motor function measure, quantitative muscle force, quantitative muscle magnetic resonance imaging and magnetic resonance spectroscopy and serum biomarker laboratory analysis DISCUSSION: The aim of this phase IIa trial is to determine if treatment with L-citrulline shows a positive effect on clinical function and paraclinical biomarkers in PPS. If treatment with L-citrulline shows positive effects, this might represent a cost-efficient symptomatic therapy for PPS patients.

TRIAL REGISTRATION

ClinicalTrial.gov, ID: NCT02801071 . Registered on 6 June 2016.

Acute ingestion of citrulline stimulates nitric oxide synthesis but does not increase blood flow in healthy young and older adults with heart failure

To determine if age-associated vascular dysfunction in older adults with heart failure (HF) is due to insufficient synthesis of nitric oxide (NO), we performed two separate studies: 1) a kinetic study with a stable isotope tracer method to determine in vivo kinetics of NO metabolism, and 2) a vascular function study using a plethysmography method to determine reactive hyperemic forearm blood flow (RH-FBF) in older and young adults in the fasted state and in response to citrulline ingestion. In the fasted state, NO synthesis (per kg body wt) was ∼ 50% lower in older vs. young adults and was related to a decreased rate of appearance of the NO precursor arginine. Citrulline ingestion (3 g) stimulated de novo arginine synthesis in both older [6.88 ± 0.83 to 35.40 ± 4.90 μmol · kg body wt(-1) · h(-1)] and to a greater extent in young adults (12.02 ± 1.01 to 66.26 ± 4.79 μmol · kg body wt(-1) · h(-1)). NO synthesis rate increased correspondingly in older (0.17 ± 0.01 to 2.12 ± 0.36 μmol · kg body wt(-1) · h(-1)) and to a greater extent in young adults (0.36 ± 0.04 to 3.57 ± 0.47 μmol · kg body wt(-1) · h(-1)). Consistent with the kinetic data, RH-FBF in the fasted state was ∼ 40% reduced in older vs. young adults. However, citrulline ingestion (10 g) failed to increase RH-FBF in either older or young adults. In conclusion, citrulline ingestion improved impaired NO synthesis in older HF adults but not RH-FBF, suggesting that factors other than NO synthesis play a role in the impaired RH-FBF in older HF adults, and/or it may require a longer duration of supplementation to be effective in improving RH-FBF.

Improvement of erectile function by a combination of French maritime pine bark and roburins with aminoacids

AIM

Primary objective of the study was the evaluation of effects of a combination of plant extracts and aminoacids on erectile function (ED).

METHODS

The study was performed as a randomized, placebo-controlled, double-blind, cross-over study. 50 men with moderate ED received a combination of Pycnogenol®, roburins, L-arginine, L-citrulline or placebo. Sexual wellness was evaluated by the International Index of Erectile Function (IIEF).

RESULTS

Treatment over a period of one month restored erectile function to normal.

CONCLUSION

The combination offers an option for treatment of ED without unwanted effects.

Sperm quality in men is improved by supplementation with a combination of L-arginine, L-citrullin, roburins and Pycnogenol®

AIM

The aim of this study was to investigate the influence of Prelox®R, a combination of French maritime pine bark extract (Pycnogenol®), L-arginine, L-citrulline and roburins, on male fertility.

METHODS

Sperm quality of 50 subfertile men was tested in monthly intervals in a double-blind, randomized, placebo controlled, crossover study. Patients received 2 tablets Prelox®R or placebo twice daily during test periods. Following a run-in period of 1 month, patients received either Prelox®R or a placebo for 1 month. After a wash-out period of 1 month, patients received Prelox®R or a placebo in a crossover manner for 1 month. Sperm volume, concentration of spermatozoa, total count, motility, vitality and morphology were measured by standard methods of calculation of the Fertility Index (FI) in monthly intervals. Activity of e-NOS in sperm was evaluated in parallel by measuring the quantity of L-citulline produced from L-arginine.

RESULTS

Supplementation with Prelox®R enhanced sperm volume and concentration, motility, vitality and morphology significantly versus placebo. The Fertility Index rose to normal values during treatment with Prelox®R. e-NOS activity in sperm was elevated by Prelox®R. No adverse effects were reported.

CONCLUSION

Prelox®R offers a safe method to improve quality of human spermatozoa in subfertile men.

Putative approaches to bypass the citrulline-specific autoimmune response in rheumatoid arthritis

The major autoantigens in the inflamed synovium in rheumatoid arthritis (RA) are citrullinated peptides. Citrullinated peptides are employed in diagnostic kits for detection of anti-citrullinated protein antibodies (ACPA), a serological marker with high specificity and sensitivity in the diagnosis of RA, and have been included in the new ACR/EULAR classification criteria for RA. ACPA-positive R patients suffer from an erosive and more aggressive disease compared to ACPA-negative patients. In view of the mounting indications that ACPA plays a seminal role in the pathogenesis of RA, it might be valuable to. pursue a specific treatment aiming ACPA as a target. We found that citrullinated peptides, which contain a unique amino acid, citrulli`ne, alter the protein structure within the connective tissue, leading to tolerance breakdown and triggering the autoimmune response in RA. However, with different doses and routes of administration, citrullinated peptides can promote immune tolerance rather than induction of disease.

Cross-sectional observational study of 208 patients with non-classical urea cycle disorders

Urea cycle disorders (UCDs) are inherited disorders of ammonia detoxification often regarded as mainly of relevance to pediatricians. Based on an increasing number of case studies it has become obvious that a significant number of UCD patients are affected by their disease in a non-classical way: presenting outside the newborn period, following a mild course, presenting with unusual clinical features, or asymptomatic patients with only biochemical signs of a UCD. These patients are surviving into adolescence and adulthood, rendering this group of diseases clinically relevant to adult physicians as well as pediatricians. In preparation for an international workshop we collected data on all patients with non-classical UCDs treated by the participants in 20 European metabolic centres. Information was collected on a cohort of 208 patients 50% of which were ≥ 16 years old. The largest subgroup (121 patients) had X-linked ornithine transcarbamylase deficiency (OTCD) of whom 83 were female and 29% of these were asymptomatic. In index patients, there was a mean delay from first symptoms to diagnosis of 1.6 years. Cognitive impairment was present in 36% of all patients including female OTCD patients (in 31%) and those 41 patients identified presymptomatically following positive newborn screening (in 12%). In conclusion, UCD patients with non-classical clinical presentations require the interest and care of adult physicians and have a high risk of neurological complications. To improve the outcome of UCDs, a greater awareness by health professionals of the importance of hyperammonemia and UCDs, and ultimately avoidance of the still long delay to correctly diagnose the patients, is crucial.

Lady Prelox® improves sexual function in generally healthy women of reproductive age

AIM

This supplement study evaluates the Female Sexual Function Index (FSFI) of 100 healthy women (37 to 45 years) with moderate sexual dysfunction who underwent a management program of lifestyle, diet, exercise, and stress control. In association with the management program a group of these women also used the supplement Lady Prelox® in tablets (20 mg Pycnogenol® pine bark extract, 200 mg L-arginine, 200 mg L-citrulline and 50 mg Rosvita® rose hip extract) for eight weeks.

METHODS

One group of women was supplemented with Lady Prelox® for 8 weeks. The nine-item FSFI questionnaire was used for evaluation of women's sexual function at inclusion (baseline), after four weeks, and after eight weeks of management and supplementation. Variation in oxidative stress was also evaluated by measuring plasma free radicals.

RESULTS

Following supplementation with Lady Prelox® the mean total FSFI scores increased from 14.96±2.68 to 28.25±2.35 after four weeks and 33.91±2.7 after eight weeks. Treatment values were significantly higher than in controls (who used only the management plan) with baseline values of 17.92±2.32 and scores of 23.45±1.82 after four weeks and to 23.52±2.20 after eight weeks. Women in the Lady Prelox® group had an initial value of plasma free radicals (PFR) of 398±29 Carr units: this value decreased to 344:28 at 4 weeks (P<0.05) and 332:31 at 8 weeks (P<0.05). Lower changes were observed in controls with an initial value of 389±33, decreasing to 377±32 (P<0.05) at 4 weeks and to 365; 33 (P<0.05) at 8 weeks (value significantly higher in controls not using Lady Prelox®). The supplementation was well tolerated; no unwanted effects occurred and no women had to stop the supplementation.

CONCLUSION

The study suggests that supplementation with Lady Prelox significantly improves sexual function across all domains evaluated by the FSFI in healthy women of late reproductive age. The improvement in FSFI is also associated with a significant decrease in oxidative stress.

Protective effect of the nitric oxide pathway in L-citrulline renal ischaemia-reperfusion injury in rats

To observe the protective effects of L-citrulline on the renal I/R injury and elucidate the mechanisms involved, 48 rats were randomized into eight groups: Group 1: sham operated; Group 2: I/R (45 min renal ischaemia and 24 h reperfusion); Group 3: I/R + L-citrulline (300 mg/kg, i.g.); Group 4: I/R + L-citrulline (600 mg/kg, i.g.); Group 5: I/R + L-citrulline (900 mg/kg, i.g.); Group 6: I/R + normal saline (NS, i.g.); Group 7: I/R + N sup ω nitro-L-arginine ester (L-NAME, 20 mg/kg, i.p.); Group 8: I/R + L-citrulline (900 mg/kg, i.g.) + L-NAME (20 mg/ kg, i.p.). At the end of the reperfusion period, serum was collected and the kidneys underwent histological and biochemical examinations. Our results showed that pre-treatment with L-citrulline (300, 600, and 900 mg/kg) significantly ameliorated the renal injury caused by I/R. Moreover, L-citrulline prevented induction of lipid peroxidation and increased the activity of superoxide dismutase and the levels of glutathione and nitric oxide. The I/R-induced decreases in total nitric oxide synthase activity, inducible nitric oxide activity, constitutive nitric oxide activity and endothelial nitric oxide protein expression in the renal cortex were significantly prevented. However, the L-citrulline-mediated protection was significantly antagonized by co-administration of L-NAME. These results suggested that L-citrulline administration exhibited significant protection against renal I/R injury. This protective effect, at least in part, via up-regulation of the endothelial nitric oxide protein expression and constitutive nitric oxide synthase activity, maintained production of nitric oxide at the basal level.

Citrulline and arginine utility in treating nitric oxide deficiency in mitochondrial disorders

Mitochondrial diseases arise as a result of dysfunction of the respiratory chain, leading to inadequate ATP production required to meet the energy needs of various organs. On the other hand, nitric oxide (NO) deficiency can occur in mitochondrial diseases and potentially play major roles in the pathogenesis of several complications including stroke-like episodes, myopathy, diabetes, and lactic acidosis. NO deficiency in mitochondrial disorders can result from multiple factors including decreased NO production due to endothelial dysfunction, NO sequestration by cytochrome c oxidase, NO shunting into reactive nitrogen species formation, and decreased availability of the NO precursors arginine and citrulline. Arginine and citrulline supplementation can result in increased NO production and hence potentially have therapeutic effects on NO deficiency-related manifestations of mitochondrial diseases. Citrulline is a more efficient NO donor than arginine as it results in a greater increase in de novo arginine synthesis, which plays a major role in driving NO production. This concept is supported by the observation that the three enzymes responsible for recycling citrulline to NO (argininosuccinate synthase and lyase, and nitric oxide synthase) function as a complex that can result in compartmentalizing NO synthesis and channeling citrulline efficiently to NO synthesis. Clinical research evaluating the effect of arginine and citrulline in mitochondrial diseases is limited to uncontrolled open label studies demonstrating that arginine administration to subjects with MELAS syndrome results in improvement in the clinical symptoms associated with stroke-like episodes and a decrease in the frequency and severity of these episodes. Therefore, controlled clinical studies of the effects of arginine or citrulline supplementation on different aspects of mitochondrial diseases are needed to explore the potential therapeutic effects of these NO donors.

Protective effect of l-citrulline against ethanol-induced gastric ulcer in rats

We examined the protective effect of l-citrulline on ethanol-induced gastric ulcer in rats. Administration of l-citrulline at doses of 300, 600 and 900mg/kg body weight prior to ethanol ingestion protected the stomach from ulceration. The gastric lesions were significantly attenuated by all doses of l-citrulline as compared to the ethanol group. Pre-treatment with l-citrulline prevented the oxidative damage and the decrease of nitric oxide content as well as the increase of the myeloperoxidase activity. Consequently, significant changes observed included the attenuation in the elevation in total nitric oxide synthase activity and inducible nitric oxide synthase activity as well as the decrease in constitutive nitric oxide synthase activity in the gastric mucosa induced by ethanol. Analysis of serum cytokines of ethanol-induced rats showed a moderate decrease in interleukin-10 with considerable increase of interleukin-6 while l-citrulline inhibited the acute alteration of cytokines. These results suggested the gastroprotective effect of l-citrulline.

The first Korean case of lysinuric protein intolerance: presented with short stature and increased somnolence

Lysinuric protein intolerance (LPI) is a rare inherited metabolic disease, caused by defective transport of dibasic amino acids. Failure to thrive, hepatosplenomegaly, hematological abnormalities, and hyperammonemic crisis are major clinical features. However, there has been no reported Korean patient with LPI as of yet. We recently encountered a 3.7-yr-old Korean girl with LPI and the diagnosis was confirmed by amino acid analyses and the SLC7A7 gene analysis. Her initial chief complaint was short stature below the 3rd percentile and increased somnolence for several months. Hepatosplenomegaly was noted, as were anemia, leukopenia, elevated levels of ferritin and lactate dehydrogenase, and hyperammonemia. Lysine, arginine, and ornithine levels were low in plasma and high in urine. The patient was a homozygote with a splicing site mutation of IVS4+1G > A in the SLC7A7. With the implementation of a low protein diet, sodium benzoate, citrulline and L-carnitine supplementation, anemia, hyperferritinemia, and hyperammonemia were improved, and normal growth velocity was observed.

L-citrulline attenuates arrested alveolar growth and pulmonary hypertension in oxygen-induced lung injury in newborn rats

Bronchopulmonary dysplasia (BPD) is characterized by arrested alveolar development and complicated by pulmonary hypertension (PH). NO promotes alveolar growth. Inhaled NO (iNO) ameliorates the BPD phenotype in experimental models and in some premature infants. Arginosuccinate synthetase (ASS) and arginosuccinate lyase (ASL) convert L-citrulline to L-arginine; L-citrulline is regenerated during NO synthesis from L-arginine. Plasma levels of these NO precursors are low in PH. We hypothesized that L-citrulline prevents experimental O2-induced BPD in newborn rats. Rat pups were assigned from birth through postnatal day (P) 14 to room air (RA), RA + L-citrulline, 95% hyperoxia (BPD model), and 95%O2 + L-citrulline. Rat pups exposed to hyperoxia had fewer and enlarged air spaces and decreased capillary density, mimicking human BPD. This was associated with decreased plasma L-arginine and L-citrulline concentrations on P7. L-citrulline treatment significantly increased plasma L-arginine and L-citrulline concentrations and increased ASL protein expression in hyperoxia. L-citrulline preserved alveolar and vascular growth in O2-exposed pups and decreased pulmonary arterial medial wall thickness (MWT) and right ventricular hypertrophy (RVH). Increased lung arginase (ARG) activity in O2-exposed pups was reversed by L-citrulline treatment. L-citrulline supplementation prevents hyperoxia-induced lung injury and PH in newborn rats. L-citrulline may represent a novel therapeutic alternative to iNO for prevention of BPD.

Nutrient intake in lysinuric protein intolerance

Lysinuric protein intolerance (LPI) is a rare autosomal recessive disorder characterized by defective transport of cationic amino acids. Poor intestinal absorption and increased renal loss of arginine, ornithine and lysine lead to low plasma concentrations of these amino acids and, subsequently, to impaired urea cycle function. The patients therefore have decreased nitrogen tolerance, which may lead to hyperammonaemia after ingestion of normal amounts of dietary protein. As a protective mechanism, most patients develop strong aversion to protein-rich foods early in life. Oral supplementation with citrulline, which is absorbed normally and metabolized to arginine and ornithine, improves protein tolerance to some extent, as do sodium benzoate and sodium phenylbutyrate also used by some patients. Despite effective prevention of hyperammonaemia, the patients still consume a very restricted diet, which may be deficient in energy, essential amino acids and some vitamins and minerals. To investigate the potential nutritional problems of patients with lysinuric protein intolerance, 77 three- to four-day food records of 28 Finnish LPI patients aged 1.5-61 years were analysed. The data suggest that the patients are clearly at risk for many nutritional deficiencies, which may contribute to their symptoms. Their diet is highly deficient in calcium, vitamin D, iron and zinc. Individualized nutritional supplementation accompanied by regular monitoring of dietary intake is therefore an essential part of the treatment of LPI.

Therapeutic use of citrulline in cardiovascular disease

L-citrulline is the natural precursor of L-arginine, substrate for nitric oxide synthase (NOS) in the production of NO. Supplemental administration L-arginine has been shown to be effective in improving NO production and cardiovascular function in cardiovascular diseases associated with endothelial dysfunction, such as hypertension, heart failure, atherosclerosis, diabetic vascular disease and ischemia-reperfusion injury, but the beneficial actions do not endure with chronic therapy. Substantial intestinal and hepatic metabolism of L-arginine to ornithine and urea by arginase makes oral delivery very ineffective. Additionally, all of these disease states as well as supplemental L-arginine enhance arginase expression and activity, thus reducing the effectiveness of L-arginine therapy. In contrast, L-citrulline is not metabolized in the intestine or liver and does not induce tissue arginase, but rather inhibits its activity. L-citrulline entering the kidney, vascular endothelium and other tissues can be readily converted to L-arginine, thus raising plasma and tissue levels of L-arginine and enhancing NO production. Supplemental L-citrulline has promise as a therapeutic adjunct in disease states associated with L-arginine deficiencies.

Long-term oral lysine supplementation in lysinuric protein intolerance

In lysinuric protein intolerance (LPI), defective transport of cationic amino acids at the basolateral membrane of the polar epithelial cells in the intestine and renal tubules leads to decreased intestinal absorption and excessive renal loss of lysine, arginine, and ornithine. Citrulline supplementation partially restores the function of the urea cycle that is impaired by deficiency of arginine and ornithine, but does not correct the chronic lysine deficiency. Previous attempts to supplement lysine orally have been hindered by profuse diarrhea, probably caused by excess lysine remaining unabsorbed in the gut. However, individually adjusted minute doses of L-lysine hydrochloride at mealtimes are tolerated well, but the long-term benefits of this therapy remain unknown. The aim of the study was to investigate the long-term benefits and possible adverse effects of oral lysine supplementation in patients with LPI. Supplementation of meals with low doses of oral lysine improved fasting plasma lysine concentrations in 27 Finnish patients with LPI without causing hyperammonemia or other recognizable side effects during 12 months of follow-up. In conclusion, low-dose oral lysine supplementation is potentially beneficial to patients with LPI and can be started safely at an early age.

Nitric oxide precursors and congenital heart surgery: a randomized controlled trial of oral citrulline

OBJECTIVE

The study sought to determine whether citrulline supplementation, a precursor to nitric oxide synthesis, is safe and efficacious in increasing plasma citrulline concentrations and decreasing the risk of postoperative pulmonary hypertension.

STUDY DESIGN

Forty children, undergoing cardiopulmonary bypass and at risk for pulmonary hypertension, were randomized to receive 5 perioperative doses (1.9 g/m2 per dose) of either oral citrulline or placebo. Plasma citrulline and arginine concentrations were measured at 5 time points. Measurements of systemic blood pressure and presence of pulmonary hypertension were collected.

RESULTS

Median citrulline concentrations were significantly higher in the citrulline group versus the placebo group immediately postoperatively (36 micromol/L vs 26 micromol/L, P = .012) and at 12 hours postoperatively (37 micromol/L vs 20 micromol/L, P = .015). Mean plasma arginine concentrations were significantly higher in the citrulline group versus the placebo group by 12 hours postoperatively (36 micromol/L vs 23 micromol/L, P = .037). Mean systemic blood pressure did not differ between groups (P = .53). Postoperative pulmonary hypertension developed in 9 patients, 6 of 20 (30%) in the placebo group and 3 of 20 (15%) in the citrulline group (P = .451), all of whom had plasma citrulline concentrations less than age-specific norms. Postoperative pulmonary hypertension did not develop in patients who demonstrated plasma citrulline concentrations in excess of 37 mumol/L (P = .036).

CONCLUSIONS

Oral citrulline supplementation safely increased plasma citrulline and arginine concentrations compared with placebo after cardiopulmonary bypass. Postoperative pulmonary hypertension did not occur in children with naturally elevated citrulline levels or elevations through supplementation. Oral citrulline supplementation may be effective in reducing postoperative pulmonary hypertension.

Almost all about citrulline in mammals

Citrulline (Cit, C6H13N3O3), which is a ubiquitous amino acid in mammals, is strongly related to arginine. Citrulline metabolism in mammals is divided into two fields: free citrulline and citrullinated proteins. Free citrulline metabolism involves three key enzymes: NO synthase (NOS) and ornithine carbamoyltransferase (OCT) which produce citrulline, and argininosuccinate synthetase (ASS) that converts it into argininosuccinate. The tissue distribution of these enzymes distinguishes three "orthogonal" metabolic pathways for citrulline. Firstly, in the liver, citrulline is locally synthesized by OCT and metabolized by ASS for urea production. Secondly, in most of the tissues producing NO, citrulline is recycled into arginine via ASS to increase arginine availability for NO production. Thirdly, citrulline is synthesized in the gut from glutamine (with OCT), released into the blood and converted back into arginine in the kidneys (by ASS); in this pathway, circulating citrulline is in fact a masked form of arginine to avoid liver captation. Each of these pathways has related pathologies and, even more interestingly, citrulline could potentially be used to monitor or treat some of these pathologies. Citrulline has long been administered in the treatment of inherited urea cycle disorders, and recent studies suggest that citrulline may be used to control the production of NO. Recently, citrulline was demonstrated as a potentially useful marker of short bowel function in a wide range of pathologies. One of the most promising research directions deals with the administration of citrulline as a more efficient alternative to arginine, especially against underlying splanchnic sequestration of amino acids. Protein citrullination results from post-translational modification of arginine; that occurs mainly in keratinization-related proteins and myelins, and insufficiencies in this citrullination occur in some auto-immune diseases such as rheumatoid arthritis, psoriasis or multiple sclerosis.

Effects of long-term inhibition of neuronal nitric oxide synthase (NOS1) in uninephrectomized diabetic rats

Nitric oxide (NO) has been implicated in the pathogenesis of renal hemodynamic changes in diabetes mellitus (DM). However, the role of NO in the pathophysiology of diabetic nephropathy remains controversial. Renal hemodynamic changes in experimental DM can be acutely normalized by selective inhibition of neuronal NO synthase (nNOS). This observation suggests a nephroprotective potential of nNOS inhibition in DM. To explore this issue we assessed the long-term effects (12 weeks) of selective nNOS inhibition with the specific inhibitor S-methyl-L-thiocitrulline (SMTC) in uninephrectomized control and streptozotocin-diabetic rats. No beneficial effects of SMTC were observed in nondiabetic controls. In contrast, SMTC delayed the development of proteinuria (32+/-8 vs. 53+/-9 mg/24h, week 8, p < 0.05) and glomerulosclerosis (GS, 0.30+/-0.08 vs. 0.57+/-0.05, p < 0.05) in diabetic rats. These effects coincided with early effects of treatment on the glomerular filtration rate, and were associated with lower renal expression of nNOS. Furthermore, SMTC-treated diabetic rats demonstrated reduced weight gain and urinary sodium excretion as compared to vehicle-treated counterparts, despite similar metabolic control and blood pressure. In summary, long-term nNOS inhibition had modest nephroprotective effects in uninephrectomized diabetic rats. These effects may be mediated by renal hemodynamic mechanisms, as well as by lower food (protein) intake.

Citrulline increases arginine pools and restores nitrogen balance after massive intestinal resection

OBJECTIVE

Arginine supplementation seems logical in situations where this amino acid becomes essential, for example after massive intestinal resection. Arginine is taken up and metabolised by the liver to a large extent and its supplementation is potentially unsafe. Citrulline is not captured by the liver and passes freely to the kidneys where it is metabolised to arginine, and so is a good candidate to generate arginine and thereby improve nutritional status.

METHODS

Twenty four rats were assigned to four groups: citrulline, arginine, control, and sham. The sham group underwent transection and the three other groups resection of 80% of the small intestine. All rats were fed by enteral nutrition and its composition was as follows: supplementation with citrulline in the citrulline group, supplementation with arginine in the arginine group, and standard polymeric enteral nutrition in the control and sham groups. All groups received isonitrogenous nutrition and citrulline and arginine intakes were equimolar in their respective groups. After 10 days, the rats were sacrificed.

RESULTS

Arginine concentration was higher (p<0.05) in plasma and muscle in the citrulline group than in the three other groups. Plasma levels of arginine were 110 (12), 79 (7), 167 (22), and 228 (13) mumol/l in the sham, control, arginine, and citrulline groups respectively. Arginine concentrations in the gastrocnemius were: 0.15 (0.02), 0.16 (0.02), 0.40 (0.05), and 0.94 (0.20) mumol/g, respectively. Citrulline preserved nitrogen balance in resected rats but not in arginine supplemented rats (mean J10: 2.27 (0.29), 1.67 (0.15), 1.98 (0.29), and 2.43 (0.41) g/24 hours in the sham, control, arginine, and citrulline groups, respectively).

CONCLUSION

Supplementing the diet with citrulline is a very efficient means of increasing arginine levels and improving nitrogen balance after massive intestinal resection. The results of this study form a strong rationale for citrulline supplementation in these patients.

Long-term outcome of patients with urea cycle disorders and the question of neonatal screening

With regard to the principles established for neonatal population screening, the question arises whether for patients with urea cycle disorders there is an accepted treatment which really affects the disease course and prognosis as compared to the natural history of these diseases. A retrospective study of 88 patients was performed. Based on questionnaires, the survival rate and neurodevelopmental outcome of patients treated with protein restriction alone was compared to the new therapy introduced in the 1980s with added citrulline/arginine, essential amino acids for improving the amino acid composition of the restricted natural protein and benzoate. Survival of patients with neonatal presentation was improved by the extensive therapy but this mostly at the cost of an increasing number of retarded patients. Long-term outcome did not differ significantly between the two treatments. Of all patients, 56% were symptomatic within 4 days of age and 67% within the 1st week. Thus a prevention of irreversible damage by neonatal screening on blood obtained at 3-4 days of life is questionable. Whether the benefit of obtaining a rapid diagnosis, e.g. for allowing proper counselling and prospective treatment, is acceptable for the parents of prospective patients remains open. The organisation of a dense network of specialised metabolic centres with sufficient staff and resources is a prior condition for any screening programme in order to ensure the rapid diagnosis, follow-up of treatment and counselling of a cumulative number of affected chronic patients needing this support. A commitment on a long-term basis by the institutions is needed in view of the health budget restrictions.

CONCLUSION

in the short term, the goal is to detect hyperammonaemic patients as early as possible with special emphasis on sick neonates. In practice, quantitative plasma ammonia determination without delay is recommended in any newborn for whom a sepsis work-up is considered and in children who refuse feeding or vomit and show alterations of consciousness and/or neurological symptoms.

Simplified method to assay total plasma peroxidase activity and ferriheme products in sickle cell anemia, with initial results in assessing clinical severity in a trial with citrulline therapy

A method using dianisidine is described to measure promptly the total plasma peroxidase (POX) activity of methemoglobin and other ferrihemes. Methemoglobin (35 mg/dL) is used as POX standard. Three-minute POX activities and total POX concentrations measured by a classic benzidine method were compared in a three-patient trial with citrulline supplementation. High POX values became progressively lower. In two of the patients, 3-minute POX activities were reduced more than total concentrations. Oral citrulline reduced harmful plasma ferriheme levels. Free ferriheme also exhibited POX activity. POX levels may be useful to judge severity in sickle cell anemia and to monitor therapeutic efficacy.

Late-onset presentation of ornithine transcarbamylase deficiency in a young woman with hyperammonemic coma

Ornithine transcarbamylase deficiency (OTCD) is an X-linked inherited disease and the most common inborn error in urea synthesis in human patients. In adult heterozygous patients, OTCD can be responsible for life-threatening hyperammonemic coma. We report the case of a 32-year-old woman admitted to our hospital with seizures after a recent high protein load. Her parents related a history of recurrent episodes of vomiting, meat refusal, lethargy, and convulsions since childhood, and measurement of plasma ammonemia levels was the key to early diagnosis of OTCD. We report the pathophysiologic characteristics, clinical features, clinical course, and differential diagnosis of OTCD and discuss the therapeutic options, including continuous venovenous hemodiafiltration and pharmacologic therapy for reduction of plasma ammonemia levels. A diagnosis of OTCD should be considered in adult nonhepatic patients with hyperammonemic coma, particularly if they have a history of protein avoidance and neurologic symptoms. Early recognition and appropriate treatment are critical to avoid severe brain damage and death.

[Nitrullin -- a new original Russian drug of the nitrosomethylurea group]

Hematologic thrombopenia and leukopenia formation limits use of nitrullin as a toxic hazard. The drug showed moderate effect in treating inoperable non-small cell cancer of the lung and satisfactory end results. The treatment had marked symptomatic effect in patients with this cancer and, as a consequence, improved the quality of life. Nutrullin had immuno-modulating effect. Its application alone or in combination with VPN showed good results in the management of small-cell cancer of the lung.

Oral citrulline as arginine precursor may be beneficial in sickle cell disease: early phase two results

L-Arginine may be a conditionally essential amino acid in children and adolescents with sickle cell disease, particularly as required substrate in the arginine-nitric oxide pathway for endogenous nitrovasodilation and vasoprotection. Vasoprotection by arginine is mediated partly by nitric oxide-induced inhibition of endothelial damage and inhibition of adhesion and activation of leukocytes. Activated leukocytes may trigger many of the complications, including vasoocclusive events and intimal hyperplasias. High blood leukocyte counts during steady states in the absence of infection are significant laboratory risk factors for adverse complications. L-Citrulline as precursor amino acid was given orally twice daily in daily doses of approximately 0.1 g/kg in a pilot Phase II clinical trial during steady states in four homozygous sickle cell disease subjects and one sickle cell-hemoglobin C disease patient (ages 10-18). There soon resulted dramatic improvements in symptoms of well-being, raised plasma arginine levels, and reductions in high total leukocyte and high segmented neutrophil counts toward or to within normal limits. Continued L-citrulline supplementation in compliant subjects continued to lessen symptomatology, to maintain plasma arginine concentrations greater than control levels, and to maintain nearly normal total leukocyte and neutrophil counts. Side effects or toxicity from citrulline were not experienced. Oral L-citrulline may portend very useful for palliative therapy in sickle cell disease. Placebo-controlled, long-term trials are now indicated.

[Use of citrulline malate (stimol) in patients with autonomic dystonia associated with arterial hypotension]

To study possibilities of a therapeutic correction of asthenic syndrome in individuals with chronic arterial hypotension with malate citrulline, the study was made of 12 women and 3 men with psychoautonomic syndrome (autonomic dystonia), combined with chronic constitutional arterial hypotension. Their age was from 27 to 45 years (mean age--37.6). A control group comprised 14 healthy individuals. Both a state of autonomic nervous system and manifestations of arterial hyportension were analyzed by means of complex scored questionnaires. Mental condition was assessed by the tests of Spilberger (evaluation of reactive and personal anxiety) and of Beck (estimation of depressive manifestations). In all the examined individuals with chronic arterial hypotension, there was psychoautonomic syndrome combined with complaints to asthenic manifestations, namely, to low performance and fatigue. Stimol was prescribed in the form of 50% solution in daily dose of 6 g (3 administrations). The therapy resulted in regression of clinical manifestations of both psychoautonomic syndrome and asthenic symptoms. A mechanism of the drug's action works through favourable changes in cerebral and muscular cells, that, in turn, had an influence on other manifestations of psychoautonomic syndrome.

Long-term management of patients with urea cycle disorders

The long-term treatment of patients with urea cycle disorders (UCDs) includes diet treatment and use of specific medications. Guidelines are provided for patients with a severe phenotype. However, treatment must be tailored for each individual, especially with regard to residual enzyme function and in vivo metabolic capacity. This will be reflected in tests used for monitoring therapy that should be performed on a periodic basis. The goal of therapy is to eliminate chronic complications, a laudable but rarely attainable goal. Sick-day rules are discussed. Chronic management also includes diverse services that are essential to the success of the metabolic program. These include neurologic and developmental evaluations, feeding team evaluation and therapy, physical and occupational therapies, speech therapy, school and educational services, social service intervention, psychologic services, and genetic counseling.

Ornithine transcarbamylase deficiency and pancreatitis

We describe a male patient with a Y202H ornithine transcarbamylase deficiency gene mutation who had pancreatitis while taking a low-protein diet, citrulline, and sodium phenylbutyrate.