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).

Four-week administration of an energy and protein dense oral nutritional supplement improves micronutrient concentrations but does not completely correct deficiencies in institutionalized malnourished older adults.

Introduction: Poor food intake is common among elderly living in nursing homes, leading to micronutrient deficiency (MD). There are no recommendations for the management of MD in malnourished older adults. Methods: We conducted a single arm, open-label, multicenter interventional study in institutionalized malnourished older adults to describe the effect of a 4-week daily energy and protein dense oral nutritional supplementation (ONS, 600 kcal, 30 g protein per unit) containing 50% of the recommended daily micronutrient intake on micronutrient status. Plasma concentrations of vitamins (A, B9, B12, C, E), magnesium (Mg), selenium (Se) and zinc (Zn), and erythrocyte vitamin B9 were measured at baseline and after 4 weeks. Results: Forty-six participants completed the study (age 87.4 ± 6.6). At baseline, the most frequent MD were Se (48%), Zn (35%), Mg (24%) and vitamin C (24%). Plasma concentrations of vitamins B9, B12, C and E, Mg, Se and Zn significantly increased and the proportion of subjects with at least one MD decreased (p = 0.006). However, after 4 weeks, 40% of subjects still had at least one MD. Discussion: ONS consumption improved micronutrient status but did not correct MD in all participants. Our data suggest that the prescription of vitamin, mineral and trace element supplementation should be considered in institutionalized malnourished older adults in addition to high energy and high protein ONS.

Glutamate: A Safe Nutrient, Not Just a Simple Additive.

BACKGROUND: In 2017, a European Food Safety Authority (EFSA) opinion on the use of glutamate and its salts as food additives led to an Acceptable Daily Intake (ADI) of 30 mg/kg body weight/day. Then, in 2021, an EFSA statement presented a proposal for harmonizing the establishment of Health-Based Guidance Values for nutrients that are also regulated substances (including food additives). The present review argues that the 2017 glutamate ADI is unsuitable because safety of glutamate should firstly consider its status as a nutrient and not only as an additive. SUMMARY: Glutamate is a non-essential amino acid playing a key role in nitrogen homeostasis. The dietary exposure to glutamate in adults is extensive, due to its ubiquitous presence in foods, under three forms: bound to proteins, naturally free and free form added as an additive. Glutamate naturally included in proteins is the major source of dietary glutamate. Thus, since it plays a role in nitrogen homeostasis, it is a nutrient before being an additive. Its pharmacokinetics are largely impacted by concomitant food intake, but the extent to which plasma glutamate concentration must rise to have deleterious effects is never encountered in humans consuming glutamate in their daily diets. This is due to the fact that glutamate is highly metabolized in the splanchnic area. KEY MESSAGE: Glutamate should be considered as a safe nutrient before being considered as an additive by risk assessor.

Glycine increases fat-free mass in malnourished haemodialysis patients: a randomized double-blind crossover trial.

BACKGROUND: Protein energy wasting is associated with negative outcome in patients under chronic haemodialysis (HD). Branched-chain amino acids (BCAAs) may increase the muscle mass. This post hoc analysis of a controlled double-blind randomized crossover study assessed the impact of BCAAs on nutritional status, physical function, and quality of life. METHODS: We included 36 chronic HD patient features of protein energy wasting as plasma albumin <38 g/L, and dietary intakes <30 kcal/kg/day and <1 g protein/kg/day. Patients received either oral BCAA (2 × 7 g/day) or glycine (2 × 7 g/day) for 4 months (Period 1), followed by a washout period of 1 month, and then received the opposite supplement (Period 2). The outcomes were lean body mass measured by dual-energy X-ray absorptiometry, fat-free mass index measured by bioelectrical impedance, resting energy expenditure, dietary intake and appetite rating, physical activity and function, quality of life, and blood parameters. Analyses were performed by multiple mixed linear regressions including type of supplementation, months, period, sex, and age as fixed effects and subjects as random intercepts. RESULTS: Twenty-seven patients (61.2 ± 13.7 years, 41% women) were compliant to the supplementations (consumption >80% of packs) and completed the study. BCAA did not affect lean body mass index and body weight, but significantly decreased fat-free mass index, as compared with glycine (coeff -0.27, 95% confidence interval -0.43 to -0.10, P = 0.002, respectively). BCAA and glycine intake had no effect on the other clinical parameters, blood chemistry tests, or plasma amino acids. CONCLUSIONS: Branched-chain amino acid did not improve lean body mass as compared with glycine. Unexpectedly, glycine improved fat-free mass index in HD patients, as compared with BCAA. Whether long-term supplementation with glycine improves the clinical outcome remains to be demonstrated.

Subchronic Tolerance Trials of Graded Oral Supplementation with Phenylalanine or Serine in Healthy Adults.

Phenylalanine and serine are amino acids used in dietary supplements and nutritional products consumed by healthy consumers; however, the safe level of phenylalanine or serine supplementation is unknown. The objective of this study was to conduct two 4-week clinical trials to evaluate the safety and tolerability of graded dosages of oral phenylalanine and oral serine. Healthy male adults (n = 60, 38.2 ± 1.8y) completed graded dosages of either phenylalanine or serine supplement (3, 6, 9 and 12 g/d) for 4 weeks with 2-week wash-out periods in between. Primary outcomes included vitals, a broad spectrum of circulating biochemical analytes, body weight, sleep quality and mental self-assessment. At low dosages, minor changes in serum electrolytes and plasma non-essential amino acids glutamine and aspartic acid concentrations were observed. Serine increased its plasma concentrations at high supplemental dosages (9 and 12 g/day), and phenylalanine increased plasma tyrosine concentrations at 12 g/day, but those changes were not considered toxicologically relevant. No other changes in measured parameters were observed, and study subjects tolerated 4-week-long oral supplementation of phenylalanine or serine without treatment-related adverse events. A clinical, no-observed-adverse-effect-level (NOAEL) of phenylalanine and serine supplementation in healthy adult males was determined to be 12 g/day.

Combined effect of citrulline and lactoserum on amino acid availability in aged rats.

OBJECTIVE: Age-associated sarcopenia is due to anabolic resistance to feeding. Muscle protein synthesis is improved by fast proteins (e.g., lactoserum), which increase peripheral amino acid (AA) bioavailability more rapidly than slow proteins (e.g., casein), and by citrulline. Citrulline, which limits splanchnic sequestration of AA, may more effectively increase peripheral AA bioavailability when combined with lactoserum than with casein when administered as an oral nutritional protein supplement. METHODS: In this study, 25 fasted aged rats received a single gavage administration of lactoserum or casein 0.4 g/kg, alone or with citrulline 0.4 g/kg, and AA pharmacokinetics, glucose, insulin, triglycerides, and insulin-like growth factor 1 (IGF1) were monitored for 4 h. At 4 h, muscle protein and AA contents and protein synthesis activation were measured. RESULTS: While lactoserum was associated with higher AA availability, citrulline exerts only limited effects on the plasma profile of AAs from the two proteins. Maximum plasma citrulline was reached earlier with casein (T90 min) than with lactoserum (T120 min). A protein x citrulline interaction was observed for some plasma and muscle AA levels with a significant activation of mechanistic target of rapamycin complex 1 (mTORC1) signaling suggesting higher anabolism with the combination of citrulline and lactoserum. Lower plasma and muscle AA levels with citrulline and lactoserum compared to lactoserum alone suggest a greater AA utilization in a context of muscle anabolic signaling activation. CONCLUSION: Provision of a citrulline-lactoserum combination as a nutritional supplement could therefore be beneficial in terms of muscle protein balance and prevention of sarcopenia. Further studies are warranted to evaluate the efficacy of this combination.

Dose-dependent beneficial effects of citrulline supplementation in short bowel syndrome in rats.

OBJECTIVES: Supplementing diet with citrulline has proved an efficient means of preserving nitrogen balance and improving nutritional status after massive intestinal resection. The aim of this study was to model the action of citrulline in gut-resected rats using a dose-ranging study focused on skeletal muscle nitrogen homeostasis. METHODS: Forty-six rats were randomly assigned to one of the following groups: citrulline 0.5 g·kg·d-1 (n = 9), citrulline 1 g·kg·d-1 (n = 7), citrulline 2.5 g·kg·d-1 (n = 8), citrulline 5 g·kg·d-1 (n = 8), control (n = 6), and sham (n = 8). The sham group underwent transection and the other groups underwent resection of 80% of the small intestine. All rats were then fed enteral nutrition (EN; all diets were isocaloric and isonitrogenous). After 10 d, the rats were sacrificed to measure and analyze animal weight; duodenum, jejunum, and ileum weight; and muscle trophicity. Protein fractional synthesis rate (FSR) and mammalian target of rapamycin complex (mTORC)1 activation were measured in the tibialis muscle. RESULTS: There was a significant dose-dependent association between rat weight and citrulline dose up to 2.5 g·kg·d-1 (P = 0.004). There was a significant improvement in tibialis weight correlated to plasma citrulline. Net protein FSR in the tibialis tended to be greater after resection and tended to return to baseline after citrulline supplementation. Citrulline supplementation significantly decreased the activated phosphorylated forms of S6 K1 (P = 0.003) and S6 RP (P = 0.003), with a significant positive association between myofibrillar FSR and activation of S6 K1 (r = 0.614; P = 0.02) and S6 RP (r = 0.601; P = 0.023). Jejunum weight was significantly positively correlated with plasma citrulline (r = 0.319; P = 0.0345). CONCLUSION: Citrulline promotes body weight gain, preserves muscle trophicity, and enhances intestinal adaptation in a dose-dependent manner in a model of resected rats.

Behaviour of plasma citrulline after bariatric surgery in the BARIASPERM cohort.

BACKGROUND: Plasma citrulline is currently used in clinical practice as a marker of small bowel functional mass. Behaviour of plasma citrulline after bariatric surgery and its link with post-operative outcome are still poorly understood. OBJECTIVE: Primary objective was to compare plasma citrulline 12 months after two types of bariatric surgery with pre-operative concentrations. Secondary objectives were to search for correlation between plasma citrulline variation and body weight and fat mass loss. DESIGN: This is an ancillary study of the BARIASPERM study. Forty-six adult men (mean age 38.9 ± 7.9 years) who underwent gastric bypass (GB, n = 20) or sleeve gastrectomy (SG, n = 26) were included in this prospective study. Plasma citrulline was measured at baseline, 6 months and 12 months after surgery, as well as total body weight and fat mass measured by dual x-ray absorptiometry (DEXA). RESULTS: Plasma citrulline increased significantly 12 months after surgery, both after gastric bypass and sleeve gastrectomy (respectively 30.2% [18.3-42.2] and 17.8% [5.8-29.7]). The increase was significantly higher after GB than after SG (p = 0.02) while total body weight and fat mass loss were not significantly different between GB and SG. The increase in plasma citrulline levels tended to be positively correlated with both weight and fat mass loss however the association did not reach statistical significance (p = 0.07 and p = 0.06 respectively). CONCLUSION: These results confirm the increase in plasma citrulline after GB published in two previous small studies. Citrulline also significantly increased after SG, and in spite of similar weight loss obtained with both surgery types, citrulline increase was higher after GB than SG. This suggests different modifications of intestinal functional mass after these two different techniques.

Assessment of transthyretin cut-off values for a better screening of malnutrition: Retrospective determination and prospective validation.

The use of transthyretin (TTR, prealbumin) as a marker of malnutrition and the definition of associated cut-offs are a matter of debate. In order to clarify this issue, we performed a retrospective study and then a prospective validation one. In the first study, data from 23,617 consecutive patients from our University hospital were analysed. Using the 0.11 and 0.05 g/L cut-off values defined by the French Health Authority, only 3.13% and 0.49% appeared malnourished or severely malnourished indicating that these cut-off values are clearly inappropriate. In the prospective study, consecutive patients were stratified for normal (≥0.2 g/L) or low (<0.2 g/L) TTR, and normal (<15 mg/L) or high (≥15 mg/L) C-reactive protein, hence defining 4 groups (n = 50 to 57/group), and data were analysed according to nutritional status estimated from patient files. Receiver operating characteristic (ROC) curve of TTR level associated with malnutrition allowed setting cut-off values at 0.17 and 0.12 g/L for malnutrition and severe malnutrition respectively.

Creatinine-to-cystatin C ratio and bioelectrical impedance analysis for the assessement of low lean body mass in cancer patients: Comparison to L3-computed tomography scan.

OBJECTIVES: Lean body mass (LBM) is an important prognostic factor in patients with cancer. Although the L3-computed tomography (CT) scan is considered a reference method for assessment, a convenient and easily available method for longitudinal follow-up is required. Although bioelectrical impedance analysis (BIA) is widely used, its accuracy is questioned; plasma creatinine-to-cystatin C (CC) ratio could be an attractive alternative. The aim of this study was to evaluate the ability of the CC ratio and BIA to detect myopenia in patients with cancer compared with the use of the CT scan as a standard. METHODS: Patients with any kind of cancer had body composition evaluation by CT scan, BIA, and CC. Statistical analysis included correlation test, Bland-Altman, and receiver operating characteristic curve analysis. RESULTS: Forty-four patients (14 women) were included. Of the participants, 59% had myopenia on CT scan. Both BIA LBM and CC ratio were well correlated with CT scan LBM (r = 0.763 and 0.648, respectively) but concordance analysis revealed a 3-kg constant bias toward BIA compared with CT scan. In terms of ability to detect myopenia, areas under the curve (AUC) for BIA were 0.675 and 0.388 for men and women, respectively. For CC ratio, AUCs were 0.813 and 0.673. CONCLUSION: This study demonstrated that LBM assessed by the CC ratio or BIA is well correlated with that determined by L3-CT scan. The ability of the CC ratio to detect myopenia was better than that of BIA. Findings from the present study demonstrated that CC ratio can be conveniently used in patients with cancer as a reliable biomarker of muscularity.

Proposals for Upper Limits of Safe Intake for Methionine, Histidine, and Lysine in Healthy Humans.

Based on research presented during the 10th Amino Acid Assessment Workshop, no observed adverse effect levels (NOAELs) for supplemental methionine at 46 mg/(kg·d) (∼3.2 g/d), for supplemental histidine at 8.0 g/d, and for supplemental lysine at 6.0 g/d have been proposed. These NOAELs are relevant to healthy adults and are applicable only to high-purity amino acids administered in fortified foods or dietary supplements. Because individuals are exposed to the above supplemental amino acids in the context of complex combinations of essential amino acids or individually in dietary supplements for various physiologic benefits, such as body fat reduction, skin conditioning, mental energy increase, or herpes simplex treatments, the above safety recommendations will make an important contribution to regulatory and nutritional practices.

Metabolic Consequences of Supplemented Methionine in a Clinical Context.

The central position of methionine (Met) in protein metabolism indicates the importance of this essential amino acid for growth and maintenance of lean body mass. Therefore, Met might be a tempting candidate for supplementation. However, because Met is also the precursor of homocysteine (Hcy), a deficient intake of B vitamins or excessive intake of Met may result in hyperhomocysteinemia (HHcy), which is a risk factor for cardiovascular disease. This review discusses the evidence generated in preclinical and clinical studies on the importance and potentially harmful effects of Met supplementation and elaborates on potential clinical applications of supplemental Met with reference to clinical studies performed over the past 20 y. Recently acquired knowledge about the NOAEL (no observed adverse effect level) of 46.3 mg · kg-1 · d-1 and the LOAEL (lowest observed adverse effect level) of 91 mg · kg-1 · d-1 of supplemented Met will guide the design of future studies to further establish the role of Met as a potential (safe) candidate for nutritional supplementation in clinical applications.

Hypervitaminosis A is associated with immunological non-response in HIV-1-infected adults: a case-control study.

For people living with HIV, determinants of immunological non-response (INR) to combined antiretroviral therapy (cART) have not been fully elucidated. In a case-control study, we evaluated the influence of the nutritional and antioxidant status in HIV-1 adults whose cART was initiated between January 2001 and December 2013. Cases had persistent CD4 counts < 350/µL vs. > 350/µL for controls, after at least 2 years of cART with persistent viral loads (VL) < 50 copies/mL. Twelve cases and twenty-eight control subjects with the same CD4 count at cART initiation were compared for their nutritional and antioxidant status after age adjustment at dosage assessment. Patients were predominantly male (70%), Caucasian (82%) and at AIDS stage (62%). The median age was 53, and the median CD4 count was 245/mm3 for cases and 630/mm3 for controls after a median time of 7 years on cART. Despite higher energy intakes in cases, anthropometric data was comparable between groups who had similar vitamins B9/B12/C/D/E, zinc, citrulline and glutamine levels. Nine cases (75%) and 8 controls (29%) had hypervitaminosis A (> 2.70 µmol/L) (p = 0.030). Cases had lower erythrocyte resistance when exposed to a controlled free radical attack (p = 0.014). Most cases had hypervitaminosis A and altered antioxidant capacities that could affect immunological response. Wide-scale studies are required, but in the meantime, screening of their vitamin A status must be encouraged in these patients.

Effect of citrulline on muscle protein turnover in an in vitro model of muscle catabolism.

OBJECTIVE: Muscle net catabolism, as seen after severe trauma or sepsis or in postoperative situations, is mediated by hormones (e.g., cortisol) and proinflammatory cytokines (e.g., tumor necrosis factor alpha [TNF-α]). Specific amino acids may be able to limit this muscle mass loss. Citrulline (CIT) stimulates muscle protein synthesis in various situations, but little data exist on hypercatabolic situations and the effects on protein breakdown are unknown. Our aim was to assess the effect of CIT on protein turnover in an in vitro model of muscle hypercatabolism. METHODS: Myotubes derived from C2C12 myoblasts were treated with 150 nM dexamethasone (DEX), 10 ng/mL TNF-α, or 0.006% ethanol (as control [CON]) for 24 h. Subsequently, myotubes were incubated with or without 5 mM CIT for 6 h. Muscle protein synthesis rate was evaluated by the surface sensing of translation method and by l-[3,5-3H]tyrosine (Tyr) incorporation. The muscle protein breakdown rate was evaluated from Tyr release into culture medium. CIT action was analyzed by non-parametric Kruskal-Wallis and Mann-Whitney tests. RESULTS: CIT treatment significantly increased protein synthesis rates compared with the DEX or TNF-α group (surface sensing of translation method; DEX + CIT versus DEX; P = 0.03 and TNF-α+CIT versus TNF-α; P = 0.05) and significantly decreased protein breakdown rate in the CON and DEX groups (CON + CIT versus CON; P = 0.05 and DEX + CIT versus DEX; P = 0.05). CONCLUSIONS: CIT treatment regulated muscle protein turnover in an in vitro model of muscle net catabolism. Exploring the underlying mechanisms would also be of interest.

Hypermetabolism is an independent prognostic factor of survival in metastatic non-small cell lung cancer patients.

BACKGROUND & AIMS: Metastatic non-small cell lung cancer (NSCLC) is the first cause of cancer death worldwide. Increased resting energy expenditure (REE) is frequent among cancer patients and may contribute to cancer cachexia. The aim of this study was to examine the prognostic value of increased REE in metastatic NSCLC patients. METHODS: This observational study was conducted between June 2012 and November 2017 in the outpatient unit of the oncology department of Cochin hospital, Paris. Consecutive patients with newly diagnosed stage IV NSCLC underwent measurement of REE by indirect calorimetry before treatment initiation. Uni- and multivariate analysis of overall survival (OS, Cox models) included age, sex, smoking habit, histological subtype, performance status, body mass index, weight loss, albumin and CRP levels and the ratio of measured REE to the REE predicted by the Harris Benedict formula (mREE/pREE). RESULTS: 144 patients were enrolled: mean age 64 years, 63% male, 90% non-squamous carcinoma, including 17% with ALK/EGFR alteration. In univariate analysis, tobacco consumption (p = 0.007), histo-molecular subtype (p < 10-3), performance status (p = 0.04), weight loss (p < 10-4), albumin (p < 10-4), CRP (p = 0.001) and mREE/pREE ratio (>vs ≤ 120%: HR = 2.16, p < 10-3) were significant prognostic factors of OS. Median OS were 6.1 and 17.3 months in patients with mREE/pREE ratio > and ≤120%, respectively. In multivariate analysis, histo-molecular subtype (non-squamous ALK/EGFR mutated vs squamous carcinoma: HR = 0.25, p = 0.006), weight loss (>vs ≤ 5%: HR = 1.98, p = 0.004), albumin (≥vs < 35 g/L: HR = 0.56, p = 0.02) and mREE/pREE ratio (> vs ≤120%: HR = 1.90, p = 0.004) were identified as independent prognostic factors. CONCLUSIONS: Elevated resting energy expenditure emerges as an independent prognostic factor in metastatic NSCLC.

Lean Body Mass and Endocrine Status But Not Age Are Determinants of Resting Energy Expenditure in Patients with Non-Small Cell Lung Cancer.

BACKGROUND: Cancer and aging are both frequently associated with malnutrition, a factor of poor prognosis. In adult cancer patients, this may be related in part to impaired energy metabolism, with higher than predicted resting energy expenditure (REE) in about 50% of patients. We hypothesized that frequently impaired energy metabolism in elderly patients could potentiate cancer-associated hypermetabolism, further promoting risk of malnutrition. OBJECTIVE: To study the hypermetabolic response to cancer in a predominantly aged population and the potential underlying determinants. METHODS: This was a cross-sectional exploratory study in patients with non-small-cell lung cancer. REE was measured by indirect calorimetry. Body composition was determined from a single CT scan imaging at L3 level. Endocrine, inflammatory, nutritional and metabolic status were evaluated. RESULTS: Twenty-seven patients, of median age 68 years (range 32-81) completed the study. In this population, mean measured REE was 7.5% higher than calculated REE. Sex and weight accounted for about 51% of REE variations, whereas age accounted only for 4%. However, these parameters did not explain the REE-to-lean body mass (LBM) ratio variations, suggesting that they influenced REE only through their effect on LBM. Among the other parameters evaluated, only the thyroid-stimulating hormone and interleukin-6 plasma levels appeared to have an influence on REE. The study of the consequences of this increase in REE-to-LBM ratio showed a growing inability of patients to meet their energy needs but showed no effect on nutritional markers such as transthyretin. CONCLUSIONS: The results of this pilot study suggest that in our population, age was not an important factor of REE. The elevated energy metabolism was associated with patients' failure to increase their energy intakes sufficiently, which can contribute to the development of cachexia. CLINICAL TRIAL: This trial is registered at clinicaltrials.gov under NCT0314.

Citrulline prevents age-related LTP decline in old rats.

The prevalence of cognitive decline is increasing as the ageing population is considerably growing. Restricting this age-associated process has become a challenging public health issue. The age-related increase in oxidative stress plays a major role in cognitive decline, because of its harmful effect on functional plasticity of the brain, such as long-term potentiation (LTP). Here, we show that citrulline (Cit) has powerful antioxidant properties that can limit ex vivo oxidative stress-induced LTP impairment in the hippocampus. We also illustrate that a three-month Cit supplementation has a protective effect on LTP in aged rats in vivo. The identification of a Cit oxidation byproduct in vitro suggests that the antioxidant properties of Cit could result from its own oxidation. Cit supplementation may be a promising preventive nutritional approach to limit age-related cognitive decline.

Is N-Carbamoyl Putrescine, the Decarboxylation Derivative of Citrulline, a Regulator of Muscle Protein Metabolism in Rats?

N-carbamoyl putrescine (NCP), the decarboxylation derivative of citrulline, metabolically related to polyamines, may exert biological effects in mammals. The aim of this study was (i) to evaluate the nutritional properties of NCP in healthy rats and (ii) to determine the effect of NCP administration on muscle metabolism in malnourished old rats. The nutritional properties of NCP were first evaluated in 20 8-week-old male rats randomized to receive for two weeks a standard diet either alone (C group) or supplemented with NCP, 5 or 50 mg/kg/d. In a second study, 29 malnourished 18-month-old male rats were studied either before or after a 4-day refeeding with a standard diet either alone (REN group) or supplemented with NCP, 1 or 10 mg/kg/d. NCP had no effect on weight gain and body composition in either of the two studies. In healthy rats, muscle protein content was significantly increased in the soleus with NCP 5 mg/kg/d. A decrease in plasma glutamine and kidney spermine was observed at the 50 mg/kg/d dose; otherwise, no significant changes in plasma chemistry and tissue polyamines were observed. In malnutrition-induced sarcopenic old rats, refeeding with NCP 10 mg/kg/d was associated with higher tibialis weight and a trend for increased protein content in extensor digitorum longus (EDL). While the muscle protein synthesis rate was similar between groups, ribosomal protein S6 kinase was increased in tibialis and higher in the EDL in NCP-treated rats. The muscle RING-finger protein-1 expression was decreased in tibialis and urinary 3-methyl-histidine to creatinine ratio slightly lower with the supply of NCP. However, this initial period of refeeding was also associated with elevated fasted plasma triglycerides and glucose, significant in NCP groups, suggesting glucose intolerance and possibly insulin resistance. NCP was well-tolerated in healthy young-adults and in malnourished old rats. In healthy adults, NCP at 5 mg/kg/d induced a significant increase in protein content in the soleus, a type I fiber-rich muscle. In malnourished old rats, NCP supply during refeeding, may help to preserve lean mass by limiting protein breakdown; however, these effects may be limited in our model by a possible immediate refeeding-associated glucose intolerance.

Impact of 3-week citrulline supplementation on postprandial protein metabolism in malnourished older patients: The Ciproage randomized controlled trial.

BACKGROUND: Citrulline (CIT), is not extracted by the splanchnic area, can stimulate muscle protein synthesis and could potentially find clinical applications in conditions involving low amino acid (AA) intake, such as in malnourished older subjects. OBJECTIVE: Our purpose was to research the effects of CIT supplementation on protein metabolism in particular on non-oxidative leucine disposal (NOLD, primary endpoint), and splanchnic extraction of amino acids in malnourished older patients. DESIGN: This prospective randomized multicenter study determined whole-body and liver protein synthesis, splanchnic protein metabolism and appendicular skeletal muscle mass (ASMM) in 24 malnourished older patients [80-92 years; 18 women and 6 men] in inpatient rehabilitation units. All received an oral dose of 10 g of CIT or an equimolar mixture of six non-essential amino acids (NEAAs), as isonitrogenous placebo, for 3 weeks. RESULTS: NOLD and albumin fractional synthesis rates were not different between the NEAA and CIT groups. Splanchnic extraction of dietary amino acid tended to decrease (p = 0.09) in the CIT group (45.2%) compared with the NEAA group (60.3%). Total differences in AA and NEAA area under the curves between fed-state and postabsorptive-state were significantly higher in the CIT than in the NEAA group. There were no significant differences for body mass index, fat mass (FM), lean mass (LM) or ASMM in the whole population except for a tendential decrease in FM for the citrulline group (p = 0.089). Compared with Day 1, lean mass and ASMM significantly increased (respectively p = 0.016 and p = 0.018) at Day 20 in CIT-treated women (mean respective increase of 1.7 kg and 1.1 kg), and fat mass significantly decreased (p = 0.001) at Day 20 in CIT-group women (mean decrease of 1.3 kg). CONCLUSIONS: Our results demonstrate that CIT supplementation has no effect on whole-body protein synthesis or liver protein synthesis in malnourished older subjects. However, CIT supplementation was associated with a higher systemic AA availability. In the subgroup of women, CIT supplementation increased LM and ASMM, and decreased FM.