Specific amino acids in the critically ill patient--exogenous glutamine/arginine: a common denominator?

Synthesis of novel fluorescence probes and their application in the enantioselective recognition of arginine

Arginine (Arg) plays a crucial and multifaceted role in various biological processes, encompassing cell division, wound healing, immune system modulation, and plant signaling. This study introduced a pair of novel chiral fluorescent probes, (R)-5 and (S)-5, constructed upon the BINOL framework, which exhibited enantiomeric selectivity and sensitivity to d-Arg/l-Arg in fluorescence experiments. These probes offered a simple, rapid, low-cost, and highly selective method for detecting Arg enantiomers, thereby providing a highly sensitive approach for their qualitative and quantitative analysis. The enantioselective fluorescence enhancement ratios {ef = [(I1 - I0)/(I2 - I0) = ΔI1/ΔI2]} of (R)-5 and (S)-5 to Arg were 1694 and 5163, respectively. Moreover, the probes demonstrated the capability to detect the concentration of d-Arg and l-Arg with a limit of detection of 4.84 × 10-7 M and 3.35 × 10-7 M, respectively, as well as determine the enantiomeric excess. These probes exhibited high chemical selectivity and enantioselectivity, enabling the identification of different configurations of Arg, quantification of Arg concentrations, and determination of the enantiomeric composition of Arg. This study provides valuable insights for the development of sensitive and selective chiral molecular detection methods, significantly advancing our comprehension of the relationship between Arg concentration and probe fluorescence response.

Implications for the Metabolic Fate of Oral Glutamine Supplementation within Plasma and Erythrocytes of Patients with Sickle Cell Disease: A Pharmacokinetics Study

OBJECTIVES

L-Glutamine is FDA-approved for sickle cell disease (SCD), yet the mechanism(s)-of-action are poorly understood. We performed a pharmacokinetics (pK) study to determine the metabolic fate of glutamine supplementation on plasma and erythrocyte amino acids in patients with SCD.

DESIGN

A pK study was performed where patients with SCD fasting for >8hours received oral L-glutamine (10 grams). Blood was analyzed at baseline, 30/60/90minutes/2/3/4/8 hrs. A standardized diet was administered to all participants at 3 established time-points (after 2/5/7hrs). A subset of patients also had pK studies performed without glutamine supplementation to follow normal diurnal fluctuations in amino acids.

SETTING

Comprehensive SCD Center in Oakland, California RESULTS: Five patients with SCD were included, three of whom performed pK studies both with and without glutamine supplementation. Average age was 50.6 ± 5.6 years, 60% were female, 40% SS, 60% SC. Plasma glutamine levels increased significantly after oral glutamine supplementation, compared to minimal fluctuations with diet. Plasma glutamine concentration peaked within 30-minutes of ingestion (p=0.01) before decreasing to a plateau by 2-hours that remained higher than baseline by 8hours. Oral glutamine also increased plasma arginine concentration, which peaked by 4-hrs (p=0.03) and remained elevated through 8-hrs. Erythrocyte glutamine levels began to increase by 8-hours, while erythrocyte arginine concentration peaked at 4-hours.

CONCLUSIONS

Oral glutamine supplementation acutely improved glutamine and arginine bioavailability in both plasma and erythrocytes. This is the first study to demonstrate that glutamine therapy increases arginine bioavailability and may provide insight into shared mechanisms-of-action between these conditionally-essential amino acids.

A Novel UPLC-MS/MS Method Identifies Organ-Specific Dipeptide Profiles

BACKGROUND

Amino acids have a central role in cell metabolism, and intracellular changes contribute to the pathogenesis of various diseases, while the role and specific organ distribution of dipeptides is largely unknown.

METHOD

We established a sensitive, rapid and reliable UPLC-MS/MS method for quantification of 36 dipeptides. Dipeptide patterns were analyzed in brown and white adipose tissues, brain, eye, heart, kidney, liver, lung, muscle, sciatic nerve, pancreas, spleen and thymus, serum and urine of C57BL/6N wildtype mice and related to the corresponding amino acid profiles.

RESULTS

A total of 30 out of the 36 investigated dipeptides were detected with organ-specific distribution patterns. Carnosine and anserine were most abundant in all organs, with the highest concentrations in muscles. In liver, Asp-Gln and Ala-Gln concentrations were high, in the spleen and thymus, Glu-Ser and Gly-Asp. In serum, dipeptide concentrations were several magnitudes lower than in organ tissues. In all organs, dipeptides with C-terminal proline (Gly-Pro and Leu-Pro) were present at higher concentrations than dipeptides with N-terminal proline (Pro-Gly and Pro-Leu). Organ-specific amino acid profiles were related to the dipeptide profile with several amino acid concentrations being related to the isomeric form of the dipeptides. Aspartate, histidine, proline and serine tissue concentrations correlated with dipeptide concentrations, when the amino acids were present at the C- but not at the N-terminus.

CONCLUSION

Our multi-dipeptide quantification approach demonstrates organ-specific dipeptide distribution. This method allows us to understand more about the dipeptide metabolism in disease or in healthy state.

Effect of Preoperative Administration of Oral Arginine and Glutamine in Patients with Enterocutaneous Fistula Submitted to Definitive Surgery: a Prospective Randomized Trial

BACKGROUND

The use of glutamine and arginine has shown several advantages in postoperative outcomes in patients after gastrointestinal surgery. We determined the effects of its use in patients with enterocutaneous fistula after operative treatment.

PATIENTS AND METHODS

Forty patients with enterocutaneous fistula were randomly assigned to one of two groups. The control group received the standard medical care while the patients of the experimental group were supplemented with enteral administration of 4.5 g of arginine and 10 g of glutamine per day for 7 days prior to the surgery. The primary outcome variable was the recurrence of the fistula and the secondary outcomes were preoperative and postoperative serum concentrations of interleukin 6 and C-reactive protein and postoperative infectious complications.

RESULTS

Twenty patients were assigned to each group. The fistula recurred in two patients (10%) of the experimental group and in nine patients (45%) of the control group (P < 0.001). We found a total of 13 infectious complications in six patients of the control group (all with fistula recurrence) and none in the experimental group. Mean preoperative serum concentrations of interleukin 6 and C-reactive protein were lower in patients from the experimental group. In addition, these levels were lower in patients who had recurrence if compared to patients that did not recur.

CONCLUSION

Preoperative administration of oral arginine and glutamine could be valuable in the postoperative recovery of patients with enterocutaneous fistulas submitted to definitive surgery.

Rationally introduce AIE into chemosensor: A novel and efficient way to achieving ultrasensitive multi-guest sensing

Recently, ultrasensitive detection and multi-guest sensing have received extensive attention due to their high sensitivity and efficiency. Herein, we report a novel approach to achieve ultrasensitive detection of multi-analyte. This approach is concluded as "rationally introduce Aggregation-Induced Emission (AIE) into chemosensor". According to this approach, by rationally introducing self-assembly moiety, the obtained chemosensor DNS could serve as a novel AIEgen and show strong AIE in DMSO/H₂O (water fraction 80%) binary solution. Interestingly, a simple fluorescent sensor array based on the DNS has been developed. This sensor array could selectively sense Fe³⁺, Al³⁺, H₂PO₄^- and L-Arg in water solution. More importantly, this sensor array shows ultrasensitive detection for Fe³⁺, Al³⁺ and L-Arg. The LODs of the sensor array for Fe³⁺, Al³⁺ and L-Arg are in the range of 3.54×10^-9M to 9.42×10^-9M. Moreover, H₂PO₄^- could realize the reversible detection of Fe³⁺ in the DMSO/H₂O (water fraction 80%) solution. Meanwhile, DNS-based test papers and thin films were prepared, which could serve as test kits for convenient detection Fe³⁺, Al³⁺, and L-Arg in water. In addition, they could also act as efficient erasable fluorescent display materials.

Independent spectral characteristics of functionalized silver nanoparticles for colorimetric assay of arginine and spermine in biofluids

A colorimetric assay for selective and sensitive detection of arginine and spermine using 6-ATT-AgNPs as a probe.

Ratiometric fluorescent l-arginine and l-asparagine biosensors based on the oxazine 170 perchlorate-ethyl cellulose membrane

Ratiometric fluorescent l-arginine (Arg) and l-asparagine (Asn) biosensors were developed using an oxazine 170 perchlorate (O17) ethyl cellulose (EC) membrane and the enzymes entrapped into the matrix of EC and hydrogel polyurethane. The sensing principles were based on the hydrolysis reactions of urea and l-Arg under the catalysis of the urease and arginase to produce ammonia in the case of an l-Arg-sensing membrane and also on the hydrolysis reaction of l-Asn under the catalysis of asparaginase in the case of an l-Asn-sensing membrane. The O17-EC membrane reacted with the ammonia produced from the hydrolysis reactions and changed the fluorescence intensities at λ _em = 565 and 625 nm. The ratio of the fluorescence intensities at λ _em = 565 and 625 nm was proportional to the concentrations of l-Arg or l-Asn in the range of 0.1-10 mM. The LOD of the l-Arg- and l-Asn-sensing membranes was 0.082 ± 0.0014 and 0.074 ± 0.0023 mM, respectively. The sensing membranes also showed good quality in terms of response time, reversibility, and stability. The interference study demonstrated that some components such as amino acids had little negative effects on the performance of the sensing membranes for the detection of l-Arg and l-Asn. These simple and sensitive ratiometric fluorescent sensing membranes provide a basic or comprehensive method for detecting l-Arg and l-Asn in blood and urine samples as well as in the fermentation processes.

Acquired Amino Acid Deficiencies: A Focus on Arginine and Glutamine

Nonessential amino acids are synthesized de novo and therefore not diet dependent. In contrast, essential amino acids must be obtained through nutrition since they cannot be synthesized internally. Several nonessential amino acids may become essential under conditions of stress and catabolic states when the capacity of endogenous amino acid synthesis is exceeded. Arginine and glutamine are 2 such conditionally essential amino acids and are the focus of this review. Low arginine bioavailability plays a pivotal role in the pathogenesis of a growing number of varied diseases, including sickle cell disease, thalassemia, malaria, acute asthma, cystic fibrosis, pulmonary hypertension, cardiovascular disease, certain cancers, and trauma, among others. Catabolism of arginine by arginase enzymes is the most common cause of an acquired arginine deficiency syndrome, frequently contributing to endothelial dysfunction and/or T-cell dysfunction, depending on the clinical scenario and disease state. Glutamine, an arginine precursor, is one of the most abundant amino acids in the body and, like arginine, becomes deficient in several conditions of stress, including critical illness, trauma, infection, cancer, and gastrointestinal disorders. At-risk populations are discussed together with therapeutic options that target these specific acquired amino acid deficiencies.

A novel carbon dots derived from reduced l-glutathione as fluorescent probe for the detection of the l-/d-arginine

Novel carbon dots (CDs) were fabricated by a hydro-thermal method, in which reduced l-glutathione was considered as the precursor and ethylenediamine as the passivating agent. Subsequently, the chemical structure and fluorescence stability of the CDs were thoroughly investigated.

Glutamine, fish oil and antioxidants in critical illness: MetaPlus trial post hoc safety analysis

BACKGROUND

The role of plasma glutamine, fish oil and antioxidants concentrations in the treatment effect of immune-modulating high-protein versus high-protein enteral nutrition on 6-month mortality in critically ill patients is explored, as unexpected negative outcomes of recent large randomized controlled trials on immune-modulating nutrients have raised questions about safety of these interventions.

METHODS

Post hoc analysis of the MetaPlus randomized controlled trial which was performed in a total of 301 medical, surgical and trauma critically ill patients in fourteen European intensive care units. Patients received either immune-modulating (glutamine, fish oil and antioxidant enriched) high-protein (IMHP) or isocaloric high-protein (HP) enteral nutrition. Six-month mortality and baseline, day 4 and day 8 plasma concentrations of glutamine, (eicosapentaenoicacid + decosahexaenoicacid)/long-chain fatty acid plasma level ratio ((epa + dha)/lcf ratio), selenium, vitamin c, vitamin e and zinc were measured.

RESULTS

The harmful treatment effect of the IMHP versus HP enteral nutrition on 6-month mortality was only demonstrated in the medical subgroup (HR 2.52, 95% CI 1.36-4.78, P = 0.004). Among medical patients, when corrected for age groups and APACHE-II scores, there were no statistically significant associations between baseline plasma levels and 6-month mortality, except for zinc (HR 1.06, 95% CI 1.00-1.12, P = 0.026). IMHP feeding resulted in statistically significant increase in plasma levels of glutamine, vitamin e, vitamin c and (epa + dha)/lcf ratio from baseline to day 4, while only the change from baseline to day 4 of (epa + dha)/lcf ratio was statistically significant associated with 6-month mortality (HR 1.18, 95% CI 1.02-1.35, P = 0.021) and identified as mediator for the harmful treatment effect of IMHP enteral nutrition among medical ICU patients.

CONCLUSION

We hypothesize that the harmful effect of IMHP compared to HP enteral nutrition in a heterogeneous group of critically ill patients is limited to the medical critically ill patients and mediated by an early increase in (epa + dha)/lcf ratio. Trial Registration Dutch Trial Register 26 January 2010 (NTR2181 http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=2181 ).

Argininemia and plasma arginine bioavailability - predictive factors of mortality in the severe trauma patients?

BACKGROUND

Arginine is an amino acid determinant in the metabolic, immune and reparative responses to severe trauma. The present study aims to determine argininemia and plasma arginine bioavailability (PAB) in critical trauma patients and to analyze its correlation with prognosis.

METHODS

A prospective study of 23 critical trauma patients was undertaken. Aminoacidemias were determined, by ion exchange chromatography, at admission and in the first and third days and compared with those of 11 healthy individuals. PAB was calculated. Severity indexes and outcome parameters were recorded.

RESULTS

Values of argininemia, citrullinemia and ornithinemia at the admission were significantly lower than those of the controls (arginine: 41.2 ± 20.6 versus 56.1 ± 11.9 μmol/L, P = 0.034). Hipoargininemia (<60 μmol/L) prevalence was 82.6 %. Mean PAB was 62.4 ± 25.6 %. Argininemia < 26 μmol/L constituted a significant predictive factor of in-hospital mortality [n = 4 (17.4 %); 75 versus 15.8 %, P = 0.04; odds ratio = 4.7; accuracy = 87 %] and lower actuarial survival (63.5 ± 43.9 versus 256.1 ± 33.3 days, P = 0.031). PAB <42 % [n = 6 (26.1 %)] was associated with higher lactacidemia levels (P = 0.033), higher in-hospital mortality (66.7 versus 11.8 %, P = 0.021; odds ratio = 5.7, accuracy = 82.6 %) and lower actuarial survival (87.2 ± 37.5 versus 261.4 ± 34.7 days, n.s.). Probability of in-hospital mortality was inversely and significantly related with PAB [61.8 ± 8.8 % (95 % CI 50.8-72.7) when PAB <41 % and 2.8 ± 1.9 % (95 % CI 1.9-8.3) when PAB > 81 %, P = 0.0001]. Charlson's index ≥1, APACHE II ≥19.5, SOFA ≥7.5, and glutaminemia < 320 μmol/L were also predictive factors of actuarial survival.

CONCLUSIONS

Those results confirm the high prevalence of arginine depletion in severe trauma patients and the relevance of argininemia and PAB as predictive factors of mortality in this context.

A colorimetric and fluorometric dual-signal sensor for arginine detection by inhibiting the growth of gold nanoparticles/carbon quantum dots composite

A bidimensional optical sensing platform which combines the advantages of fluorescence and colorimetry has been designed for arginine (Arg) detection. The system was established by monitoring the influence of Arg on the growth of gold nanoparticles/carbon quantum dots (Au/CQDs) composite, and the CQDs synthesized by ethylene glycol were used as the reducing and stabilizing agent in this paper. Considering that Arg is the only amino acid with guanidine group and has the highest isoelectric point (pI) value at 10.76, Arg would carry positive charges at pH 7.4. Consequently, the positively charged guanidine group of Arg could attract AuCl₄^- and CQDs through electrostatic interaction, which inhibited the growth of Au/CQDs composite. Thereby, the color of the system almost did not change and the fluorescence quenching of CQDs was prevented in the presence of Arg. Based on the color change a low detection limit for Arg was 37nM, and a detection limit of 450nM was obtained by fluorescence spectroscopy. Moreover, this dual-signal sensor also revealed excellent selectivity toward Arg over other amino acids. Besides, Arg can be detected in urine samples with satisfactory results, which demonstrate the potential applications for real analysis.

Correlation of the L-Arginine Pathway with Thrombo-Inflammation May Contribute to the Outcome of Acute Ischemic Stroke

BACKGROUND

Immune responses contribute to secondary injury after acute ischemic stroke (AIS), and metabolites of the L-arginine pathway are associated with stroke outcome. Here, we analyzed the relationship of the L-arginine pathway with thrombo-inflammatory biomarkers in AIS and their additive and independent associations to outcome.

METHODS

Serial changes in P-selectin, tPA, MCP-1, sCD40L, IL-6, IL-8, L-arginine, and asymmetric and symmetric dimethylarginine (ADMA, SDMA) were investigated in 55 patients with AIS and without infection within 6 and 72 hours after stroke onset. Outcomes were assessed as National Institutes of Health Stroke Scale (NIHSS) worsening by 24 hours, poststroke infection, and death by 1 month.

RESULTS

Serum levels of L-arginine showed negative correlation, whereas ADMA and SDMA showed positive correlation with thrombo-inflammatory biomarkers in the hyperacute phase. Most of these correlations disappeared by 72 poststroke hours. Correlation of MCP-1 with both ADMA and SDMA levels at 6 hours was associated with both NIHSS worsening and poststroke infections, respectively; sCD40L and SDMA correlation at 6 hours was also associated with NIHSS worsening. Negative correlation between P-selectin and L-arginine concentrations in the hyperacute phase was associated with NIHSS worsening. Strong negative correlation was found between IL-6 and L-arginine levels in the hyperacute phase in patients with poststroke infection. Only L-arginine and SDMA at 72 hours were independently associated with poststroke infection respectively.

CONCLUSIONS

Concentration of L-arginine and ADMA/SDMA differentially correlates with thrombo-inflammation in the hyperacute phase of ischemic stroke. Such correlations are independently associated with poststroke infection but not with other outcomes.

Beneficial Effects of Early Enteral Nutrition After Major Rectal Surgery: A Possible Role for Conditionally Essential Amino Acids? Results of a Randomized Clinical Trial

OBJECTIVES

To investigate direct postoperative outcome and plasma amino acid concentrations in a study comparing early enteral nutrition versus early parenteral nutrition after major rectal surgery. Previously, it was shown that a low plasma glutamine concentration represents poor prognosis in ICU patients.

DESIGN

A preplanned substudy of a previous prospective, randomized, open-label, single-centre study, comparing early enteral nutrition versus early parenteral nutrition in patients at high risk of postoperative ileus after surgery for locally advanced or locally recurrent rectal cancer. Early enteral nutrition reduced postoperative ileus, anastomotic leakage, and hospital stay.

SETTING

Tertiary referral centre for locally advanced and recurrent rectal cancer.

PATIENTS

A total of 123 patients with locally advanced or recurrent rectal carcinoma requiring major rectal surgery.

INTERVENTIONS

Patients were randomized (ALEA web-based external randomization) preoperatively into two groups: early enteral nutrition (early enteral nutrition, intervention) by nasojejunal tube (n = 61) or early parenteral nutrition (early parenteral nutrition, control) by jugular vein catheter (n = 62). Eight hours after the surgical procedure artificial nutrition was started in hemodynamically stable patients, stimulating oral intake in both groups. Blood samples were collected to measure plasma glutamine, citrulline, and arginine concentrations using a validated ultra performance liquid chromatography-tandem mass spectrometric method.

MEASUREMENTS AND MAIN RESULTS

Baseline concentrations were comparable for both groups. Directly after rectal surgery, a decrease in plasma amino acids was observed. Plasma glutamine concentrations were higher in the parenteral group than in the enteral group on postoperative day 1 (p = 0.027) and day 5 (p = 0.008). Arginine concentrations were also significantly increased in the parenteral group at day 1 (p < 0.001) and day 5 (p = 0.001).

CONCLUSIONS

Lower plasma glutamine and arginine concentrations were measured in the enteral group, whereas a better clinical outcome was observed. We conclude that plasma amino acids do not provide a causal explanation for the observed beneficial effects of early enteral feeding after major rectal surgery.

Perioperative glutamine supplementation restores disturbed renal arginine synthesis after open aortic surgery: a randomized controlled clinical trial

Postoperative renal failure is a common complication after open repair of an abdominal aortic aneurysm. The amino acid arginine is formed in the kidneys from its precursor citrulline, and citrulline is formed from glutamine in the intestines. Arginine enhances the function of the immune and cardiovascular systems, which is important for recovery after surgery. We hypothesized that renal arginine production is diminished after ischemia-reperfusion injury caused by clamping of the aorta during open abdominal aortic surgery and that parenteral glutamine supplementation might compensate for this impaired arginine synthesis. This open-label clinical trial randomized patients who underwent clamping of the aorta during open abdominal aortic surgery to receive a perioperative supplement of intravenous alanyl-glutamine (0.5 g·kg(-1)·day(-1); group A, n = 5) or no supplement (group B, n = 5). One day after surgery, stable isotopes and tracer methods were used to analyze the metabolism and conversion of glutamine, citrulline, and arginine. Whole body plasma flux of glutamine, citrulline, and arginine was significantly higher in group A than in group B (glutamine: 391 ± 34 vs. 258 ± 19 μmol·kg(-1)·h(-1), citrulline: 5.7 ± 0.4 vs. 2.8 ± 0.4 μmol·kg(-1)·h(-1), and arginine: 50 ± 4 vs. 26 ± 2 μmol·kg(-1)·h(-1), P < 0.01), as was the synthesis of citrulline from glutamine (4.8 ± 0.7 vs. 1.6 ± 0.3 μmol·kg(-1)·h(-1)), citrulline from arginine (2.3 ± 0.3 vs. 0.96 ± 0.1 μmol·kg(-1)·h(-1)), and arginine from glutamine (7.7 ± 0.4 vs. 2.8 ± 0.2 μmol·kg(-1)·h(-1)), respectively (P < 0.001 for all). In conclusion, the production of citrulline and arginine is severely reduced after clamping during aortic surgery. This study shows that an intravenous supplement of glutamine increases the production of citrulline and arginine and compensates for the inhibitory effect of ischemia-reperfusion injury.

Neuromuscular Dysfunction in Experimental Sepsis and Glutamine

BACKGROUND

Electrophysiological studies show that critical illness polyneuromyopathy appears in the early stage of sepsis before the manifestation of clinical findings. The metabolic response observed during sepsis causes glutamine to become a relative essential amino acid.

AIMS

We aimed to assess the changes in neuromuscular transmission in the early stage of sepsis after glutamine supplementation.

STUDY DESIGN

Animal experimentation.

METHODS

Twenty male Sprague-Dawley rats were randomized into two groups. Rats in both groups were given normal feeding for one week. In the study group, 1 g/kg/day glutamine was added to normal feeding by feeding tube for one week. Cecal ligation and perforation (CLP) surgery was performed at the end of one week. Before and 24 hours after CLP, compound muscle action potentials were recorded from the gastrocnemius muscle.

RESULTS

Latency measurements before and 24 hours after CLP were 0.68±0.05 ms and 0.80±0.09 ms in the control group and 0.69±0.07 ms and 0.73±0.07 ms in the study group (p<0.05).

CONCLUSION

Since enteral glutamine prevented compound muscle action potentials (CMAP) latency prolongation in the early phase of sepsis, it was concluded that enteral glutamine replacement might be promising in the prevention of neuromuscular dysfunction in sepsis; however, further studies are required.

Enteral Glutamine Administration in Critically Ill Nonseptic Patients Does Not Trigger Arginine Synthesis

Glutamine supplementation in specific groups of critically ill patients results in favourable clinical outcome. Enhancement of citrulline and arginine synthesis by glutamine could serve as a potential mechanism. However, while receiving optimal enteral nutrition, uptake and enteral metabolism of glutamine in critically ill patients remain unknown. Therefore we investigated the effect of a therapeutically relevant dose of L-glutamine on synthesis of L-citrulline and subsequent L-arginine in this group. Ten versus ten critically ill patients receiving full enteral nutrition, or isocaloric isonitrogenous enteral nutrition including 0.5 g/kg L-alanyl-L-glutamine, were studied using stable isotopes. A cross-over design using intravenous and enteral tracers enabled splanchnic extraction (SE) calculations. Endogenous rate of appearance and SE of glutamine citrulline and arginine was not different (SE controls versus alanyl-glutamine: glutamine 48 and 48%, citrulline 33 versus 45%, and arginine 45 versus 42%). Turnover from glutamine to citrulline and arginine was not higher in glutamine-administered patients. In critically ill nonseptic patients receiving adequate nutrition and a relevant dose of glutamine there was no extra citrulline or arginine synthesis and glutamine SE was not increased. This suggests that for arginine synthesis enhancement there is no need for an additional dose of glutamine when this population is adequately fed. This trial is registered with NTR2285.

The impact of nutritional status on treatment outcomes of patients with limb-threatening diabetic foot ulcers

AIM

This study aimed to investigate the nutritional status of patients with limb-threatening diabetic foot ulcers (DFUs) and its impact on treatment outcomes.

METHODS

A total of 478 consecutive patients (mean age, 65.4years) treated for limb-threatening DFUs were enrolled. Nutritional status assessment using the Mini Nutritional Assessment (MNA) and Geriatric Nutritional Risk Index (GNRI) was performed by three qualified dieticians within 48hours of admission. Limb-preservation outcomes were stratified into major lower extremity amputation (LEA) (above the ankle, n=33), minor LEA (distal to ankle, n=117) and no amputation (non-LEA, n=328).

RESULTS

Most patients were identified as being at risk of malnutrition (70.5%) or malnourished (14.6%) (mean MNA score, 20.6±3.4). MNA scores decreased with increasing severity of LEA (mean, 21.1, 20.0, and 17.9, respectively; P for linear trend <0.001), associated inversely with the tendency to require LEA (P for linear trend was 0.001), and associated independently with both major and minor LEA outcomes (adjusted odds ratio [aOR]=0.80, 95% confidence interval [CI], 0.65-0.99, P=0.042 and aOR=0.89, 95% CI, 0.80-0.99, P=0.032, respectively). The predictive value was sustained in patients younger than age 65years. Though GNRI results had similar associations with outcomes, its predictive value was limited in minor LEA and younger population.

CONCLUSIONS

Patients' nutritional status was shown to have significant influence on limb-preservation outcomes for limb-threatening DFUs. Nutritional assessment of this patient population using the MNA is recommended.

A new Schiff base and its metal complex as colorimetric and fluorescent–colorimetric sensors for rapid detection of arginine

A new Schiff base (L) and its Pb²⁺-complex have been utilized for rapid detection of arginine in aqueous medium.Lexhibits an excellent selective colorimetric response whereas its Pb²⁺-complex exploits fluorescent-colorimetric response towards arginine with very low detection limits.

Preventive effects of amino-acid-rich elemental diet Elental® on chemotherapy-induced oral mucositis in patients with colorectal cancer: a prospective pilot study

Purpose

The prospective pilot study was designed to evaluate the preventive effects of amino-acid-rich elemental diet (ED), Elental^®, on chemotherapy-induced oral mucositis in patients with colorectal cancer. The factors influencing its efficacy are also investigated.

Methods

A total of 22 eligible patients with colorectal cancer experiencing grade 1–3 oral mucositis during treatment with fluorouracil-based chemotherapy entered the current study. Their average age was 67 years. There were 10 male and 12 female. The PS was 0 in the majority of patients. Patients received two courses of the same chemotherapy regimen and Elental^® concurrently after recovery to grade 0 or 1 oral mucositis.

Results

FOLFOX6 + bevacizumab in 8 patients, FOLFIRI + bevacizumab in 8 patients, FOLFIRI + panitumumab in 1 patient, FOLFIRI in 1 patient, XELOX + bevacizumab in 2 patients, and S-1 + cetuximab in 2 patients were used as first-line (16 cases) or as second-line (6 cases) chemotherapy. Dose reduction of 5-fluorouracil (5-FU) or oral fluoropyrimidine was performed in the 2 patients achieving grade 3 oral mucositis and in the 3 patients achieving grade 2 oral mucositis. The maximum grade of oral mucositis decreased in 18 of the 22 patients during the first treatment course with Elental^® (p = 0.0002) and in 20 of the 22 patients in the second course (p < 0.0001). Multivariate analyses found that the dose reduction in 5-FU or oral fluoropyrimidine, ED intake, and the prior administration of ED were each a significant factor for the preventive efficacy on oral mucositis.

Conclusion

The amino-acid-rich elemental diet Elental^® may be useful as a countermeasure for 5-FU-based chemotherapy-induced oral mucositis in patients with colorectal cancer.

Adaptations of Arginine's Intestinal-Renal Axis in Cachectic Tumor-Bearing Rats

Malignancies induce disposal of arginine, an important substrate for the immune system. To sustain immune function, the tumor-bearing host accelerates arginine's intestinal-renal axis by glutamine mobilization from skeletal muscle and this may promote cachexia. Glutamine supplementation stimulates argi-nine production in healthy subjects. Arginine's intestinal-renal axis and the effect of glutamine supplementation in cancer cach-exia have not been investigated. This study evaluated the long-term adaptations of the interorgan pathway for arginine production following the onset of cachexia and the metabolic effect of glutamine supplementation in the cachectic state. Fischer-344 rats were randomly divided into a tumor-bearing group (n = 12), control group (n = 7) and tumor-bearing group receiving a glutamine-enriched diet (n = 9). Amino acid fluxes and net fractional extractions across intestine, kidneys, and liver were studied. Compared to controls, the portal-drained viscera of tumor-bearing rats took up significantly more glutamine and released significantly less citrulline. Renal metabolism was unchanged in the cachectic tumor-bearing rats compared with controls. Glutamine supplementation had no effects on intestinal and renal adaptations. In conclusion, in the cachectic state, an increase in intestinal glutamine uptake is not accompanied by an increase in renal arginine production. The adaptations found in the cachectic, tumor-bearing rat do not depend on glutamine availability.

Taurine Concentrations Decrease in Critically Ill Patients With Shock Given Enteral Nutrition

BACKGROUND

Nutrition studies in the intensive care unit (ICU) have shown that adequate enteral nutrition (EN) support has clinical benefits. However, the course of amino acid concentrations in plasma has never been investigated in patients admitted with shock receiving EN. We hypothesized that plasma concentrations, when deficit, increase during EN and that persistent deficiency is associated with poor outcome.

METHODS

In 33 septic or cardiogenic shock patients receiving EN, plasma amino acid concentrations were measured during 5 days. Changes in amino acid concentrations, correlations with clinical outcome variables, and regression analyses were studied.

RESULTS

On ICU admission, several plasma concentrations were deficient. Plasma concentrations of almost all amino acids increased. In contrast, taurine decreased by >50%, from 47.6 µmol/L on admission to 20.0 µmol/L at day 1, and remained low at day 5. Taurine (admission) correlated with time on mechanical ventilation (R = -0.42, P = .015). Taurine decrease within 24 hours correlated with Acute Physiology and Chronic Health Evaluation II predicted mortality (R = 0.43, P = .017) and Sequential Organ Failure Assessment score (R = 0.36, P = .05). Regression analyses confirmed correlations.

CONCLUSIONS

Several amino acids were deficient in plasma on ICU admission but increased during EN. Taurine concentrations declined and were associated with longer periods of mechanical ventilation and ICU support. Fast taurine decline correlated with severity of organ failure. These findings support the role of taurine during ischemia, reperfusion, and inflammation. Taurine may be an essential candidate to enrich nutrition support for critically ill patients, although more research is required.

Prophylactic inhalation of L-alanyl-L-glutamine enhances heat shock protein 72 and attenuates endotoxin-induced lung injury in rats

Studies have demonstrated that heat shock protein 70 (HSP70) plays an important role in the protection of stressed organisms. The development of strategies for enhancing HSPs expression may provide novel means of minimizing inflammatory lung conditions, such as acute lung injury. This study aimed to examine the effect of L-alanyl-L-glutamine (GLN) inhalation in enhancing pulmonary HSP72 (inducible HSP70) expression and attenuating lung damage in a model of acute lung injury induced by lipopolysaccharide (LPS) inhalation. The experimental rats were randomly assigned to one of four experimental groups: (1) NS: saline inhalation; (2) NS-LPS: pretreatment by saline inhalation 12 h before LPS inhalation; (3) GLN: glutamine inhalation; (4) GLN-LPS: pretreatment by glutamine inhalation 12 h before LPS inhalation. The results show that GLN compared with saline administration, led to significant increase in lung HSP72 both in non LPS-treated rats and LPS-treated rats. In LPS-treated rats, pretreatment by GLN inhalation produced less lung injury as evidenced by the decrease in lung injury score and dramatic decrease in lactate dehydrogenase (LDH) activity and polymorphonuclear leukocyte cell differentiation counts (PMN %) in the bronchoalveolar lavage fluid. The study indicates that prophylactic glutamine inhalation associated with the enhancement of HSP72 synthesis attenuates tissue damage in experimental lung injury.

Intravenous glutamine supplementation enhances renal de novo arginine synthesis in humans: a stable isotope study

BACKGROUND

Arginine plays a role in many different pathways in multiple cell types. Consequently, a shortage of arginine, caused by pathologic conditions such as cancer or injury, has the potential to disturb many cellular and organ functions. Glutamine is the ultimate source for de novo synthesis of arginine in humans via the intestinal-renal axis. Therefore, we hypothesized that parenteral glutamine supplementation may stimulate the interorgan pathway of arginine production.

OBJECTIVES

The objectives were to quantify arginine production from its precursor glutamine and to establish the contribution of the kidneys to de novo synthesis of arginine in patients receiving intravenous supplementation of glutamine dipeptide during major abdominal surgery.

DESIGN

Whole-body and renal metabolism of glutamine, citrulline, and arginine was assessed by stable isotope techniques in 7 patients receiving a perioperative supplement of intravenous alanyl-glutamine (0.5 g · kg(-1) · d(-1)).

RESULTS

Plasma glutamine, citrulline, and arginine concentrations increased significantly in patients receiving intravenous glutamine dipeptide. At whole-body level, 91% of total citrulline turnover was derived from glutamine, whereas 49% of whole-body citrulline turnover was used for de novo synthesis of arginine. The kidneys were responsible for 75% of whole-body arginine production from citrulline.

CONCLUSIONS

Glutamine and citrulline are important sources for de novo arginine synthesis. The kidneys are the main production site for endogenous arginine. After comparison of these results with previous similar studies, our data suggest that an intravenous glutamine supplement doubles renal arginine production from citrulline. This trial was registered at www.trialregister.nl as NTR2914.

Effect of glutamine supplementation on cardiovascular risk factors in patients with type 2 diabetes

OBJECTIVE

The aim of this study was to assess clinical relevance of long-term oral glutamine supplementation on lipid profile and inflammatory and metabolic factors in patients with diabetes.

METHOD

Sixty-six patients with type 2 diabetes between the ages of 18 and 65 y were randomized to receive glutamine 30 g/d (10 g powder, three times a day) or placebo, in a double-blind, placebo-controlled trial during a 6-wk treatment period. Fifty-three patients completed the trial. Independent samples t test and analysis of covariance were used.

RESULTS

After a 6-wk treatment period, a significant difference was observed between the two groups in body fat mass (P = 0.01) and percentage of body fat (P = 0.008). Moreover, a significant reduction in waist circumference (P < 0.001) and a tendency for an increase in fat-free mass (P = 0.03), with no change in body weight and body mass index (BMI) was found. Enhancement in body fat-free mass was mainly attributed to trunk (P = 0.03). There was a downward trend in systolic blood pressure (P = 0.005) but not diastolic. Fasting blood glucose (mmol/L) concentration significantly decreased after the 6-wk intervention (P = 0.04). Mean hemoglobin A1c was significantly different between the groups at week 6 (P = 0.04). No significant difference was detected for fasting insulin, homeostasis model assessment for insulin resistance and quantitative insulin sensitivity index between groups (P > 0.05). No significant difference was observed between groups in total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol and triglyceride. No treatment effect on C-reactive protein was found (P = 0.44).

CONCLUSION

We demonstrated that the 6-wk supplementation with 30 g/d glutamine markedly improved some cardiovascular risk factors, as well as body composition, in patients with type 2 diabetes. Future glutamine dose-response studies are warranted in these areas.

Increased hepatic blood flow during enteral immune-enhancing diet gavage requires intact enterohepatic bile cycling

OBJECTIVES

Total hepatic blood flow (HBF) via the hepatic artery and portal vein is highly dependent on gastrointestinal perfusion. During postprandial hyperemia, intestinal blood flow depends on nutrient composition, gastrointestinal location, and time. Immune-enhancing diets (IEDs) containing n-3 polyunsaturated fatty acids (PUFAs) selectively augment blood flow in the ileum at 60-120 min via a bile-dependent mechanism. My colleagues and I hypothesized that liver blood flow would be similarly affected by IEDs containing n-3 PUFAs.

METHODS

Mean arterial blood pressure, heart rate, and effective HBF (galactose clearance) were measured in anesthetized male Sprague-Dawley rats after gastric gavage of either a control diet (CD, Boost, Novartis) or an IED (Impact, Nestle Nutrition), with or without bile-duct ligation (BDL), and with or without supplemental bile (bovine, dried, unfractionated). Significance was assessed by 2-way ANOVA for repeated measures with the Tukey-Kramer honestly significant difference test.

RESULTS

Compared with baseline levels, a CD increased HBF (peak at 40 min , *P < 0.05) whereas an IED increased HBF in two distinct peaks at 40 min (*P < 0.05) and 120 min (*P < 0.05), but BDL prevented both the early (CD and IED, †P < 0.05) and late peaks (IED, †P < 0.05). Bile supplementation in the CD + BDL or IED + BDL groups restored neither the CD peak nor the early or late IED peaks.

CONCLUSIONS

HBF during absorptive intestinal hyperemia is modulated by a mechanism that requires an intact enterohepatic circulation. The early peaks at 40 min (CD or IED) were prevented by BDL, even though fat absorption in the proximal gut occurs by bile-independent direct absorption. Bile supplementation with the diet (CD + BDL or IED + BDL) was insufficient to restore HBF hyperemia, which implies that a relationship exists between intestinal and hepatic blood flow that is not solely dependent on bile-mediated intestinal fat absorption and bile recirculation.

Alterations in glutamine metabolism and its conversion to citrulline in sepsis

In enterocytes, glutamine serves as the major source of energy; another metabolic fate of glutamine is conversion to citrulline. Because sepsis can affect gut function and integrity, alterations in glutamine metabolism may exist and lead to decreased citrulline production. This study aimed to investigate how sepsis affects glutamine metabolism, including its conversion to citrulline, by measuring glutamine and citrulline flux, fractional splanchnic extraction of glutamine and leucine, and the contribution of glutamine nitrogen to citrulline in septic patients and healthy controls. Eight patients with severe sepsis and 10 healthy controls were given primed, constant intravenous infusion of [(2)H2]citrulline and sequential administration of intravenous and enteral [α-(15)N]glutamine and [(13)C]leucine in the postabsorptive state. The results showed that, compared with healthy controls, septic patients had a significantly lower whole body citrulline flux and plasma concentration, higher endogenous leucine flux, and higher glutamine clearance. Fractional splanchnic extraction of leucine was higher in septic patients than in controls, but fractional extraction of glutamine was not different. The majority of the (15)N label transferred from glutamine to citrulline was found at the α-position. These results demonstrate that lower glutamine plasma concentrations in sepsis were a result of increased glutamine clearance. Despite adequate splanchnic uptake of glutamine, there is decreased production of citrulline, suggesting a defect in the metabolic conversion of glutamine to citrulline, decreased uptake of glutamine by the enterocyte but increased uptake by the liver, and/or shunting of glutamine to other metabolic pathways.

Branched-chain amino acid supplementation: impact on signaling and relevance to critical illness

The changes that occur in mammalian systems following trauma and sepsis, termed systemic inflammatory response syndrome, elicit major changes in carbohydrate, protein, and energy metabolism. When these events persist for too long they result in a severe depletion of lean body mass, multiple organ dysfunction, and eventually death. Nutritional supplementation has been investigated to offset the severe loss of protein, and recent evidence suggests that diets enriched in branched-chain amino acids (BCAAs) may be especially beneficial. BCAAs are metabolized in two major steps that are differentially expressed in muscle and liver. In muscle, BCAAs are reversibly transaminated to the corresponding α-keto acids. For the complete degradation of BCAAs, the α-keto acids must travel to the liver to undergo oxidation. The liver, in contrast to muscle, does not significantly express the branched-chain aminotransferase. Thus, BCAA degradation is under the joint control of both liver and muscle. Recent evidence suggests that in liver, BCAAs may perform signaling functions, more specifically via activation of mTOR (mammalian target of rapamycin) signaling pathway, influencing a wide variety of metabolic and synthetic functions, including protein translation, insulin signaling, and oxidative stress following severe injury and infection. However, understanding of the system-wide effects of BCAAs that integrate both metabolic and signaling aspects is currently lacking. Further investigation in this respect will help rationalize the design and optimization of nutritional supplements containing BCAAs for critically ill patients.

Novel nutritional substrates in surgery

Pharmaco-nutrients have beneficial effects on protective and immunological mechanisms in patients undergoing surgery, which are important for recovery after injury and in combating infectious agents. The aim of this review article was to outline the potential of the administration of nutritional substrates to surgical patients and the underlying mechanisms that make them particularly important in peri-operative care. Surgery causes a stress response, which has catabolic effects on the body's substrate stores. The amino acid glutamine is a stimulating agent for immune cells. It activates protective mechanisms through its role as a precursor for antioxidants and it improves the barrier function of the gut. Arginine also enhances the function of the immune system, since it is the substrate for T-lymphocytes. Furthermore, n-3 PUFA stabilise surgery-induced hyper-inflammation. Taurine is another substrate that may counteract the negative effects of surgical injury on acid–base balance and osmotic balance. These pharmaco-nutrients rapidly become deficient under the influence of surgical stress. Supplementation of these nutrients in surgical patients may restore their protective and immune-enhancing actions and improve clinical outcome. Moreover, pre-operative fasting is still common practice in the Western world, although fasting has a negative effect on the patient's condition and the recovery after surgery. This may be counteracted by a simple intervention such as administering a carbohydrate-rich supplement just before surgery. In conclusion, there are various nutritional substrates that may be of great value in improving the condition of the surgical patient, which may be beneficial for post-operative recovery.

Fish oil increases blood flow in the ileum during chronic feeding in rats

Benefits of enteral feeding with immune-enhancing diets (IEDs) depend on route, timing, and composition. We hypothesized that chronic enteral feeding with certain individual immunonutrients would enhance gastrointestinal blood flow. Male rats were fed a standard enteral diet supplemented with immunonutrients for 5 days before study. Groups were (1) standard rat chow, (2) liquid control diet (CD) alone (CD), (3) CD + fish oil, (4) CD + L-arginine, and (5) CD + RNA fragments. Whole organ blood flow distribution was measured by colorimetric microsphere technique in antrum, small intestine (in thirds), colon, liver, spleen, pancreas, and kidneys. Chronic feeding for 5 days with CD + fish oil increased blood flow in the distal third of the small intestine compared with CD alone, whereas feeding with CD + L-arginine decreased blood flow in the small intestine (all segments) compared with CD alone. Acute gavage of CD + L-arginine or CD + fish oil increased blood flow in the proximal and middle third of the small intestine compared with CD alone. Control diet + RNA increased blood flow in the proximal small intestine compared with CD alone. These findings support prior acute feeding studies with CD, CD + individual immunonutrients, or IED. Our current data suggest that blood flow benefits associated with fish oil persist during chronic feeding in rats. Enhanced gastrointestinal perfusion might partially explain the benefits of early enteral feeding with IEDs not seen with regular enteral diets and parenteral immunonutrient delivery.

Nutritional and metabolic abnormalities and nutrition support therapy in patients with liver failure

Nutritional and metabolic damage is an important manifestation of severe liver disease and is significantly associated with prognosis. In this paper, we review nutritional and metabolic abnormalities and nutritional support therapy in patients with liver failure by summarizing the indicators for evaluating the nutritional and metabolic status and the features of nutrients and energy metabolism. We point out that resting energy expenditure can be measured using CCM-D nutrition metabolism test system in liver failure patients. Energy supply is primarily contributed by fat oxidation in patients with chronic liver failure, and their respiratory quotient is significantly lower than the predicted values. In addition, we discuss nutritional support intervention methods and intake for different stages of liver failure. Our aim is to raise the awareness of clinicians for malnutrition in patients with liver failure to formulate individualized nutrition support therapy.

Physiology and pathophysiology of splanchnic hypoperfusion and intestinal injury during exercise: strategies for evaluation and prevention

Physical exercise places high demands on the adaptive capacity of the human body. Strenuous physical performance increases the blood supply to active muscles, cardiopulmonary system, and skin to meet the altered demands for oxygen and nutrients. The redistribution of blood flow, necessary for such an increased blood supply to the periphery, significantly reduces blood flow to the gut, leading to hypoperfusion and gastrointestinal (GI) compromise. A compromised GI system can have a negative impact on exercise performance and subsequent postexercise recovery due to abdominal distress and impairments in the uptake of fluid, electrolytes, and nutrients. In addition, strenuous physical exercise leads to loss of epithelial integrity, which may give rise to increased intestinal permeability with bacterial translocation and inflammation. Ultimately, these effects can deteriorate postexercise recovery and disrupt exercise training routine. This review provides an overview on the recent advances in our understanding of GI physiology and pathophysiology in relation to strenuous exercise. Various approaches to determine the impact of exercise on the individual athlete's GI tract are discussed. In addition, we elaborate on several promising components that could be exploited for preventive interventions.

Perioperative arginine-supplemented nutrition in malnourished patients with head and neck cancer improves long-term survival

BACKGROUND

Plasma arginine concentrations are lower in patients with cancer, which indicates that arginine metabolism may be disturbed in these patients. Arginine supplementation has been associated with positive effects on antitumor mechanisms and has been shown to reduce tumor growth and to prolong survival. Furthermore, the prognosis of patients with head and neck cancer remains disappointing. Insufficient intake frequently leads to malnutrition, which contributes to high morbidity and mortality rates.

OBJECTIVE

The aim of this study was to assess the long-term effects of perioperative arginine supplementation in severely malnourished patients with head and neck cancer.

DESIGN

In this double-blind, randomized, controlled trial, we randomly assigned 32 severely malnourished patients with head and neck cancer to receive 1) standard perioperative enteral nutrition (n = 15) or 2) arginine-supplemented perioperative enteral nutrition (n = 17). The primary outcome was long-term (≥10 y) survival. Secondary outcomes included the long-term appearance of locoregional recurrence, distant metastases, and second primary tumors.

RESULTS

No significant differences in baseline characteristics were observed between groups. The group receiving arginine-enriched nutrition had a significantly better overall survival (P = 0.019) and better disease-specific survival (P = 0.022). Furthermore, the arginine-supplemented group had a significantly better locoregional recurrence-free survival (P = 0.027). No significant difference in the occurrence of distant metastases or occurrence of a second primary tumor was observed between the groups.

CONCLUSION

Perioperative arginine-enriched enteral nutrition significantly improved the long-term overall survival and long-term disease-specific survival in malnourished patients with head and neck cancer.

The role of asymmetric dimethylarginine and arginine in the failing heart and its vasculature

Nitric oxide (NO) is formed from arginine by the enzyme nitric oxide synthase (NOS). Asymmetric dimethylarginine (ADMA) can inhibit NO production by competing with arginine for NOS binding. Therefore, the net amount of NO might be indicated by the arginine/ADMA ratio. In turn, arginine can be metabolized by the enzyme arginase, and ADMA by the enzyme dimethylarginine dimethylaminohydrolase (DDAH). While ADMA has been implicated as a cardiovascular risk factor, arginine supplementation has been indicated as a treatment in cardiac diseases. This review discusses the roles of ADMA and arginine in the failing heart and its vasculature. Furthermore, it proposes nutritional therapies to improve NO availability.

Glutamine: precursor or nitrogen donor for citrulline synthesis?

Although glutamine is considered the main precursor for citrulline synthesis, the current literature does not differentiate between the contribution of glutamine carbon skeleton vs. nonspecific nitrogen (i.e., ammonia) and carbon derived from glutamine oxidation. To elucidate the role of glutamine and nonspecific nitrogen in the synthesis of citrulline, l-[2-(15)N]- and l-[5-(15)N]glutamine and (15)N-ammonium acetate were infused intragastrically in mice. The amino group of glutamine labeled the three nitrogen groups of citrulline almost equally. The amido group and ammonium acetate labeled the ureido and amino groups of citrulline, but not the delta-nitrogen. D(5)-glutamine also infused in this arm of the study, which traces the carbon skeleton of glutamine, was utilized poorly, accounting for only 0.2-0.4% of the circulating citrulline. Dietary glutamine nitrogen (both N groups) incorporation was 25-fold higher than the incorporation of its carbon skeleton into citrulline. To investigate the relative contributions of the carbon skeleton and nonspecific carbon of glutamine, arginine, and proline to citrulline synthesis, U-(13)C(n) tracers of these amino acids were infused intragastrically. Dietary arginine was the main precursor for citrulline synthesis, accounting for approximately 40% of the circulating citrulline. Proline contribution was minor (3.4%), and glutamine was negligible (0.4%). However, the glutamine tracer resulted in a higher enrichment in the ureido group, indicating incorporation of nonspecific carbon from glutamine oxidation into carbamylphosphate used for citrulline synthesis. In conclusion, dietary glutamine is a poor carbon skeleton precursor for the synthesis of citrulline, although it contributes both nonspecific nitrogen and carbon to citrulline synthesis.

Advancing from immunonutrition to a pharmaconutrition: a gigantic challenge

PURPOSE OF REVIEW

This review presents some difficulties encountered to develop and translate immunonutrition into clinical practice, and suggests moving forward to a pharmaconutrition approach.

RECENT FINDINGS

Immunonutrition suffers from inconclusive and contradictory data due to the design of many of experiments and clinical studies conducted so far. The concept of a single immunonutrient formula applicable to various types of patients has also contributed to leave the medical world in a state of uncertainty. We propose to move forward to the concept of pharmaconutrition where a disease-dedicated nutrition therapy is developed following a rigorous step-by-step procedure. Nutrients are selected according to their pharmacological properties and after an in-depth evaluation of their biological interactions when mixed together. The optimum administration schedule (i.e. dose, route, timing and duration) of the new formulae is then determined in well conducted projective clinical trials where it is administered apart from the standard nutrition to ensure full delivery of the expected doses.

SUMMARY

This review suggests moving forward to a pharmaconutrition approach where a rigorous step-by-step procedure would allow overcoming of the difficulties encountered to translate immunonutrition into clinical practice.

ESPEN Guidelines on Parenteral Nutrition: intensive care

Nutritional support in the intensive care setting represents a challenge but it is fortunate that its delivery and monitoring can be followed closely. Enteral feeding guidelines have shown the evidence in favor of early delivery and the efficacy of use of the gastrointestinal tract. Parenteral nutrition (PN) represents an alternative or additional approach when other routes are not succeeding (not necessarily having failed completely) or when it is not possible or would be unsafe to use other routes. The main goal of PN is to deliver a nutrient mixture closely related to requirements safely and to avoid complications. This nutritional approach has been a subject of debate over the past decades. PN carries the considerable risk of overfeeding which can be as deleterious as underfeeding. Therefore the authors will present not only the evidence available regarding the indications for PN, its implementation, the energy required, its possible complementary use with enteral nutrition, but also the relative importance of the macro- and micronutrients in the formula proposed for the critically ill patient. Data on long-term survival (expressed as 6 month survival) will also be considered a relevant outcome measure. Since there is a wide range of interpretations regarding the content of PN and great diversity in its practice, our guidance will necessarily reflect these different views. The papers available are very heterogeneous in quality and methodology (amount of calories, nutrients, proportion of nutrients, patients, etc.) and the different meta-analyses have not always taken this into account. Use of exclusive PN or complementary PN can lead to confusion, calorie targets are rarely achieved, and different nutrients continue to be used in different proportions. The present guidelines are the result of the analysis of the available literature, and acknowledging these limitations, our recommendations are intentionally largely expressed as expert opinions.

Arginine, citrulline and nitric oxide metabolism in sepsis

Arginine has vasodilatory effects, via its conversion by NO synthase into NO, and immunomodulatory actions which play important roles in sepsis. Protein breakdown affects arginine availability and the release of asymmetric dimethylarginine, an inhibitor of NO synthase, may therefore affect NO synthesis in patients with sepsis. The objective of the present study was to investigate whole-body in vivo arginine and citrulline metabolism and NO synthesis rates, and their relationship to protein breakdown in patients with sepsis or septic shock and in healthy volunteers. Endogenous leucine flux, an index of whole-body protein breakdown rate, was measured in 13 critically ill patients with sepsis or septic shock and seven healthy controls using an intravenous infusion of [1-13C]leucine. Arginine flux, citrulline flux and the rate of conversion of arginine into citrulline (an index of NO synthesis) were measured with intravenous infusions of [15N2]guanidino-arginine and [5,5-2H2]citrulline. Plasma concentrations of nitrite plus nitrate, arginine, citrulline and asymmetric dimethylarginine were measured. Compared with controls, patients had a higher leucine flux and higher NO metabolites, but arginine flux, plasma asymmetric dimethylarginine concentration and the rate of NO synthesis were not different. Citrulline flux and plasma arginine and citrulline were lower in patients than in controls. Arginine production was positively correlated with the protein breakdown rate. Whole-body arginine production and NO synthesis were similar in patients with sepsis and septic shock and healthy controls. Despite increased proteolysis in sepsis, there is a decreased arginine plasma concentration, suggesting inadequate de novo synthesis secondary to decreased citrulline production.