Exogenous glutamine: The clinical evidence

Amino acid profiles: exploring their diagnostic and pathophysiological significance in hypertension

Hypertension, a major contributor to cardiovascular morbidity, is closely linked to amino acid metabolism. Amino acids, particularly branched-chain amino acids (BCAAs) and aromatic amino acids (AAAs), may play pivotal roles in the pathogenesis and potential management of hypertension. This review investigated the relationships between amino acid profiles, specifically BCAAs and AAAs, and hypertension, and examined their potential as diagnostic and therapeutic targets. An in-depth analysis was conducted on studies highlighting the associations of specific amino acids such as arginine, glycine, proline, glutamine, and the BCAAs and AAAs with hypertension. BCAAs and AAAs, alongside other amino acids like arginine, glycine, and proline, showed significant correlations with hypertension. These amino acids influence multiple pathways including nitric oxide synthesis, vascular remodeling, and neurotransmitter production, among others. Distinct amino acid profiles were discerned between hypertensive and non-hypertensive individuals. Amino acid profiling, particularly the levels of BCAAs and AAAs, offers promising avenues in the diagnostic and therapeutic strategies for hypertension. Future studies are crucial to confirm these findings and to delineate amino acid-based interventions for hypertension treatment.

Association of Glutamate Infusion With Risk of Acute Kidney Injury After Coronary Artery Bypass Surgery: A Pooled Analysis of 2 Randomized Clinical Trials

Importance

Acute kidney injury (AKI) after cardiac surgery is associated with increased morbidity and mortality, and measures to prevent AKI have had limited success. Glutamate has been reported to enhance natural postischemic recovery of the heart, but not among animals and humans with diabetes.

Objective

To summarize pooled results from the GLUTAMICS (Glutamate for Metabolic Intervention in Coronary Surgery) trials regarding the effect of glutamate on postoperative AKI among patients without diabetes undergoing coronary artery bypass graft (CABG) surgery.

Design, Setting, and Participants

Data on a total of 791 patients without diabetes from 2 prospective, randomized, double-blind multicenter trials performed at 5 cardiac surgery centers in Sweden between October 4, 2005, and November 12, 2009, and between November 15, 2015, and September 30, 2020, were pooled. Patients had acute coronary syndrome, left ventricular ejection fraction of 0.30 or less, or a European System for Cardiac Risk Evaluation II score of 3.0 or more and underwent CABG with or without additional valve procedure. Statistical analysis was performed from May to November 2023.

Interventions

Intravenous infusion of 0.125-M l-glutamic acid or saline at 1.65 mL/kg/h for 2 hours during reperfusion, after which the infusion rate was halved and an additional 50 mL was given.

Main Outcomes and Measures

The primary end point was AKI, defined as postoperative increase of plasma creatinine of 50% or more, corresponding to the Risk stage or higher in the Risk, Injury, Failure, Loss, and End-Stage kidney disease (RIFLE) criteria.

Results

A total of 791 patients without diabetes (391 who received glutamate [mean (SD) age, 69.3 (9.1) years; 62 women (15.9%)] and 400 controls [mean (SD) age, 69.6 (9.5) years; 73 women (18.3%)]) were randomized. Baseline data did not differ between groups. Glutamate was associated with a significantly lower risk of AKI (relative risk, 0.49 [95% CI, 0.29-0.83]). Dialysis was required for 2 patients in the glutamate group and 5 patients in the control group. In multivariable analysis, glutamate remained significantly associated with a protective effect against AKI (odds ratio, 0.47 [95% CI, 0.26-0.86]). In the glutamate and control groups, the rate of postoperative mortality at 30 days or less was 0.5% (2 of 391) vs 1.0% (4 of 400), and the rate of stroke at 24 hours or less was 0.8% (3 of 391) vs 1.8% (7 of 400).

Conclusions and Relevance

In this pooled analysis of 2 randomized clinical trials, infusion of glutamate was associated with a markedly lower risk of AKI after CABG among patients without diabetes. The findings are exploratory and need to be confirmed in prospective trials.

Trial Registration

ClinicalTrials.gov Identifiers: NCT00489827 and NCT02592824.

ESPEN guideline on chronic intestinal failure in adults - Update 2023

BACKGROUND & AIMS

In 2016, ESPEN published the guideline for Chronic Intestinal Failure (CIF) in adults. An updated version of ESPEN guidelines on CIF due to benign disease in adults was devised in order to incorporate new evidence since the publication of the previous ESPEN guidelines.

METHODS

The grading system of the Scottish Intercollegiate Guidelines Network (SIGN) was used to grade the literature. Recommendations were graded according to the levels of evidence available as A (strong), B (conditional), 0 (weak) and Good practice points (GPP). The recommendations of the 2016 guideline (graded using the GRADE system) which were still valid, because no studies supporting an update were retrieved, were reworded and re-graded accordingly.

RESULTS

The recommendations of the 2016 guideline were reviewed, particularly focusing on definitions, and new chapters were included to devise recommendations on IF centers, chronic enterocutaneous fistulas, costs of IF, caring for CIF patients during pregnancy, transition of patients from pediatric to adult centers. The new guideline consist of 149 recommendations and 16 statements which were voted for consensus by ESPEN members, online in July 2022 and at conference during the annual Congress in September 2022. The Grade of recommendation is GPP for 96 (64.4%) of the recommendations, 0 for 29 (19.5%), B for 19 (12.7%), and A for only five (3.4%). The grade of consensus is "strong consensus" for 148 (99.3%) and "consensus" for one (0.7%) recommendation. The grade of consensus for the statements is "strong consensus" for 14 (87.5%) and "consensus" for two (12.5%).

CONCLUSIONS

It is confirmed that CIF management requires complex technologies, multidisciplinary and multiprofessional activity, and expertise to care for the underlying gastrointestinal disease and to provide HPN support. Most of the recommendations were graded as GPP, but almost all received a strong consensus.

Exudative glutamine losses contribute to high needs after burn injury

Background

Burnpatients characteristically have increased energy, glucose, and protein requirements. Glutamine supplementation is strongly recommended during early‐phase treatment and is associated with improved immunity, wound healing, and reduced mortality. This study evaluated if early burn exudative losses might contribute to higher supplementation needs.

Methods

Patients admitted to the burn intensive care unit (ICU) had exudate collection from tight bandages applied to arms or legs during the first week (exudate aliquot twice daily). Seven amino acids (alanine, arginine, cystEine, glutamine, leucine, lysine, and methionine) were quantified by liquid chromatography–mass spectrometry. Descriptive analysis of all results is provided as median and interquartile range or in value ranges.

Results

Eleven patients aged 19–77 years, presenting with burns on 18%–70% of the body surface, with a median simplified acute physiology score II of 33 (range, 16–56) were included during the study period. The highest amino acid losses were observed during the first 3 days with an important interpatient and intrapatient variability. Glutamine and alanine losses were highest, followed by leucine and lysine in all patients; amino acid exudate concentrations were in the range of normal plasma concentrations and were stable over time. Total glutamine losses were correlated to the burned surface (r² = 0.552, P = .012), but not to enteral glutamine supplements.

Conclusions

The study shows significant exudative losses during early‐stage burn recovery and particularly for glutamine and alanine. Glutamine loss generally decreased with wound closure, the subsequent decline of exudation, and the evolving size of burn surfaces.

Metabolomic profiling reveals amino acid and carnitine alterations as metabolic signatures in psoriasis

High-throughput metabolite profiling provides the opportunity to reveal metabolic mechanisms and identify biomarkers. Psoriasis is an immune-mediated chronic inflammatory disease. However, the role of metabolism in psoriasis pathogenesis remains unclear. Methods: Plasma samples of individuals (45 psoriasis and 45 sex-, age-, and BMI-matched healthy controls) were collected. Non-targeted metabolomics and amino acid- or carnitine-targeted metabolomics were conducted, then, plasma samples of mice induced by imiquimod (IMQ) were subjected to the amino acid- and carnitine-targeted metabolomic profiling. Flow cytometry was used to study the effect of L-carnitine (LC(C0)) on IMQ-induced psoriatic inflammation. Results: Through the non-targeted metabolomics approach, we detected significantly altered amino acids and carnitines in psoriasis patients. Amino acid-targeted metabolomic profiling identified 37 amino acids altered in psoriasis, of these 23 were markedly upregulated, including essential amino acids (EAAs), and branched-chain amino acids (BCAAs), whereas glutamine, cysteine, and asparagine were significantly down-regulated. Carnitine-targeted metabolomic profiling identified 40 significantly altered carnitines, 14 of which included palmitoylcarnitine (C16) and were markedly downregulated in psoriasis, whereas hexanoylcarnitine (C6) and 3-OH-octadecenoylcarnitine (C18:1-OH) were significantly upregulated. Interestingly, glutamine, asparagine, and C16 levels were negatively correlated with the PASI score. Moreover, a higher abundance of LC(C0) was associated with markedly reduced IMQ-induced epidermal thickening and infiltration of Th17 cells in skin lesions, indicating LC(C0) supplementation as a potential therapy for psoriasis treatment. Conclusion: Our results suggested the metabolism of amino acids and carnitines are significantly altered in psoriasis, especially the metabolism of EAAs, BCAAs, and LC(C0), which may play key roles in the pathogenesis of psoriasis.

Effects of glutamine supplementation on critically ill patients: Focus on efficacy and safety. An overview of systematic reviews

OBJECTIVES

The aim of this overview of systematic reviews was to synthesize, appraise, and present all systematic review (SR) evidence on the clinical efficacy of glutamine administration to severely ill patients.

METHODS

Medline, Scopus, the Cochrane Library, and Prospero were searched up to March 2020. Systematic reviews and meta-analyses of randomized controlled trials published in English, comparing immunomodulating diets-containing exclusively glutamine-with standard diets for critically ill adult patients were selected. Data were collected from each selected systematic review and all available primary studies. The primary outcome was overall mortality; secondary outcomes were rate of infectious complications, hospital and intensive care unit (ICU) length of stay (LOS).

RESULTS

Seventeen SRs were eligible for inclusion. Of the SRs, 16 included meta-analyses with moderate degree of overlap (corrected covered area = 10%). These included 117 randomized controlled trials with 9933 patients. Glutamine supplementation was not associated with overall mortality and ICU LOS. However, it may reduce the rate of infectious complications overall (N = 3666, risk ratio, 0.82; 95% confidence interval [CI], 0.73-0.92; I² = 33%: low quality of evidence). LOS was limited with the supplementation of glutamine (N = 4353 weighted mean difference, -2.90; 95% CI, -3.66 to -2.15; I² = 81%: very low quality of evidence), but this effect was diminished when only studies with low risk for bias were synthesized.

CONCLUSION

Glutamine could demonstrate a beneficial role in critical care patients of diminishing the rate of infectious complications and hospital and ICU LOS. However, future studies with better quality would confirm this finding.

The glutamine debate in surgery and critical care

PURPOSE OF REVIEW

Glutamine (GLN) is a versatile amino acid, long believed to have important implications in ICU and surgical patients. An extensive body of data examining GLN supplementation of TPN demonstrated a consistent signal of improved outcomes. However, recently signals of risk have come from two large-scale multicenter trials evaluating GLN (and other nutrients) at high dose and as primary pharmaconutrients, not as supplementation to complete nutrition. These trials indicate a risk of increased mortality when GLN is given to patients in shock, renal failure, and early in acute phase of critical care.

RECENT FINDINGS

Recent literature continues to confirm that low and high admission GLN levels are associated with increased ICU mortality and adverse outcomes. Further, a recent meta-analysis examined trials utilizing GLN-supplemented TPN in stabile ICU patients consistent with current clinical guidelines. This analysis showed GLN supplementation of TPN led to reduced infections, LOS and hospital mortality.

SUMMARY

Three recent meta-analyses have confirmed traditional GLN-supplemented (or 'GLN-Complemented' - providing GLN for completeness of amino acid content) TPN is safe, reduces mortality and improves outcome in surgical and ICU patients. Patients in need of TPN, burns, trauma or malignancies should continue to benefit from supplemental GLN, administered either intravenously at less than 0.35 g/kg/day or enterally at less than 0.5 g/kg/day. Further, a large trial of EN GLN supplementation in burns is ongoing. Thus, when used per guideline recommendations, the GLN story is likely still relevant to ICU outcomes and research.

Glutamine in Burn Injury

Burn injury is the most devastating of survivable injuries and is a worldwide public health crisis. Burn injury is among the most severe metabolic stresses a patient can sustain. A major burn leads to an inflammatory response and catabolism that, when compounded by burn wound nutrient losses, can lead to severe nutrition losses and deficiencies. These losses can impair immune function and wound healing and place burn patients at high risk for organ injury and mortality. Experimental data indicate glutamine (GLN) is well positioned mechanistically, perhaps above and beyond in any other intensive care unit setting, to improve outcome in burn-injured patients. Initial clinical trial data have also shown a consistent signal of reduced mortality and reduced hospital length of stay in burn-injured subjects, without signals of clinical risk. A number of GLN clinical trials demonstrate significant reductions of gram-negative bacteremia in burn injury, perhaps via maintenance of the gut barrier or gut immune function. Current societal recommendations continue to suggest the use of GLN in burn injury. The promising clinical data in burn-injured patients, with no signals of harm, have warranted study of GLN in the definitive RE-ENERGIZE trial, which is now ongoing.

Role of heat shock protein and cytokine expression as markers of clinical outcomes with glutamine-supplemented parenteral nutrition in surgical ICU patients

BACKGROUND

Nutrients, such as glutamine (GLN), have been shown to effect levels of a family of protective proteins termed heat shock proteins (HSPs) in experimental and clinical critical illness. HSPs are believed to serve as extracellular inflammatory messengers and intracellular cytoprotective molecules. Extracellular HSP70 (eHSP70) has been termed a chaperokine due to ability to modulate the immune response. Altered levels of eHSP70 are associated with various disease states. Larger clinical trial data on GLN effect on eHSP expression and eHSP70's association with inflammatory mediators and clinical outcomes in critical illness are limited.

OBJECTIVE

Explore effect of longitudinal change in serum eHSP70, eHSP27 and inflammatory cytokine levels on clinical outcomes such as pneumonia and mortality in adult surgical intensive care unit (SICU) patients. Further, evaluate effect of parenteral nutrition (PN) supplemented with GLN (GLN-PN) versus GLN-free, standard PN (STD-PN) on serum eHSP70 and eHSP27 concentrations.

METHODS

Secondary observational analysis of a multicenter clinical trial in 150 adults after cardiac, vascular, or gastrointestinal surgery requiring PN support and SICU care conducted at five academic medical centers. Patients received isocaloric, isonitrogenous PN, with or without GLN dipeptide. Serum eHSP70 and eHSP27, interleukin-6 (IL-6), and 8 (IL-8) concentrations were analyzed in patient serum at baseline (prior to study PN) and over 28 days of follow up.

RESULTS

eHSP70 declined over time in survivors during 28 days follow-up, but non-survivors had significantly higher eHSP70 concentrations compared to survivors. In patients developing pneumonia, eHSP70, eHSP27, IL-8, and IL-6 were significantly elevated. Adjusted relative risk for hospital mortality was reduced 75% (RR = 0.25, p = 0.001) for SICU patients with a faster decline in eHSP70. The area under the receiver operating characteristic curve was 0.85 (95% CI: 0.76 to 0.94) for the final model suggesting excellent discrimination between SICU survivors and non-survivors. GLN-PN did not alter eHSP70 or eHSP27 serum concentrations over time compared to STD-PN.

CONCLUSION

Our results suggest that serum HSP70 concentration may be an important marker for severity of illness and likelihood of recovery in the SICU. GLN-supplemented-PN did not increase eHSP70.

Exogenous glutamine impairs neutrophils migration into infections sites elicited by lipopolysaccharide by a multistep mechanism

Glutamine (GLN) is the most abundant free amino acid in the body, and is considered as a conditionally essential amino acid under stress conditions, acting as an important modulator of the immune response. We here investigated the role of exogenous GLN treatment on leukocyte migration after the onset of endotoxemia and the intracellular mechanisms of GLN actions on neutrophils. Two in vivo models of endotoxemia caused by lipopolysaccharide of Escherichia coli (LPS) injection were carried out in male outbred Balb/C mice 2-3 months old, as follow: (1) LPS (50 μg/kg) was intravenously injected 1 h prior to intravenous injection of GLN (0.75 mg/kg) and samples were collected 2 h later to investigate the role of GLN on the acute lung inflammation; (2) LPS (1 mg/kg) was intraperitoneally injected 1 h prior to intravenous injection of GLN (0.75 mg/kg) and samples were collected 18 h later to measure the effects of GLN on local and later phases of inflammation in the peritoneum. Results showed that GLN administration reduced the number of neutrophils in the inflamed lungs, partially recovery of the reduced number of leukocytes in the blood; reduced adhesion molecules on lung endothelium and on circulating neutrophils. Moreover, GLN treatment diminished the number of neutrophils, levels of chemotactic cytokine CXCL2 in the inflamed peritoneum, and neutrophils collected from the peritoneum of GLN-treated mice presented lower levels of Rho, Rac, and JNK. Together, our data show novel mechanisms involved in the actions of GLN on neutrophils migration.

Glutamine Administration Modulates Endothelial Progenitor Cell and Lung Injury in Septic Mice

This study investigated the effects of glutamine (GLN) administration on circulating endothelial progenitor cells (EPCs) and lung angiopoietin (Ang) gene expressions in polymicrobial sepsis. Mice were randomly assigned to a normal control group (NC), septic saline group (SS), and septic GLN group (SG). All mice were fed with a chow diet. Sepsis was induced by cecal ligation and puncture (CLP). The mice in SS group were injected with saline, whereas SG group administered 0.75 g GLN/kg body weight once via tail vein 1 h after CLP. Mice were killed 24 and 48 h after CLP. Their blood and lungs were collected for further analysis. The results showed that, compared with normal mice, sepsis resulted in higher C-X-C motif chemokine-12, vascular endothelial growth factor, nitric oxide levels, and a higher circulating EPC percentage. In addition, inflammatory cytokine concentrations and Ang-2 gene expression were upregulated in lung tissues. GLN administration enhanced the mobilization of EPC, and downregulated inflammatory cytokine production and the Ang-2 gene expressions in lungs. Histopathological findings showed that the extent of inflammatory lesions of the lung alveolar was less severe in the SG group than the SS group after CLP. Our results suggest that a single dose of intravenous GLN administration after initiation of sepsis promotes the mobilization of circulating EPC, and modulates the balance of Ang-Tie2 axis that may improve the vascular function, ameliorate inflammation, and protect lung injury against polymicrobial sepsis.

Nutrition Therapy in Sepsis

Sepsis is characterized by early massive catabolism, lean body mass (LBM) loss, and escalating hypermetabolism persisting for months to years. Early enteral nutrition should attempt to correct micronutrient/vitamin deficiencies, deliver adequate protein and moderated nonprotein calories, as well-nourished patients can generate reasonable endogenous energy. After resuscitation, increasing protein/calories are needed to attenuate LBM loss and promote recovery. Malnutrition screening is essential, and parenteral nutrition can be safely added when enteral nutrition is failing based on preillness malnutrition. Following discharge from intensive care unit, significantly increased protein/calorie delivery is required for months to years to facilitate functional and LBM recovery.

The Roles of Glutamine in the Intestine and Its Implication in Intestinal Diseases

Glutamine, the most abundant free amino acid in the human body, is a major substrate utilized by intestinal cells. The roles of glutamine in intestinal physiology and management of multiple intestinal diseases have been reported. In gut physiology, glutamine promotes enterocyte proliferation, regulates tight junction proteins, suppresses pro-inflammatory signaling pathways, and protects cells against apoptosis and cellular stresses during normal and pathologic conditions. As glutamine stores are depleted during severe metabolic stress including trauma, sepsis, and inflammatory bowel diseases, glutamine supplementation has been examined in patients to improve their clinical outcomes. In this review, we discuss the physiological roles of glutamine for intestinal health and its underlying mechanisms. In addition, we discuss the current evidence for the efficacy of glutamine supplementation in intestinal diseases.

Cardiovascular Risk Factors Associated With Blood Metabolite Concentrations and Their Alterations During a 4-Year Period in a Population-Based Cohort

Background—

The effects of lifestyle risk factors considered collectively on the human metabolism are to date unknown. We aim to investigate the association of these risk factors with metabolites and their changes during 4 years.

Methods and Results—

One hundred and sixty-three metabolites were measured in serum samples with the AbsoluteIDQ kit p150 (Biocrates) following a targeted metabolomics approach, in a population-based cohort of 1030 individuals, aged 45 to 83 years at baseline. We evaluated associations between metabolite concentrations (28 acylcarnitines, 14 amino acids, 9 lysophosphocholines, 72 phosphocholines, 10 sphingomyelins and sum of hexoses) and 5 lifestyle risk factors (body mass index [BMI], alcohol consumption, smoking, diet, and exercise). Multilevel or simple linear regression modeling adjusted for relevant covariates was used for the evaluation of cross-sectional or longitudinal associations, respectively; multiple testing correction was based on false discovery rate. BMI, alcohol consumption, and smoking were associated with lipid metabolism (reduced lyso- and acyl-alkyl-phosphatidylcholines and increased diacylphosphatidylcholines concentrations). Smoking showed positive associations with acylcarnitines, and BMI correlated inversely with nonessential amino acids. Fewer metabolites showed relative changes that were associated with baseline risk factors: increases in 5 different acyl-alkyl phosphatidylcholines were associated with lower alcohol consumption and BMI and with a healthier diet. Increased levels of tyrosine were associated with BMI. Sex-specific effects of smoking and BMI were found specifically related to acylcarnitine metabolism: in women higher BMI and in men more pack-years were associated with increases in acylcarnitines.

Conclusions—

This study showed sex-specific effects of lifestyle risks factors on human metabolism and highlighted their long-term metabolic consequences.

Nutritional Alterations Associated with Neurological and Neurosurgical Diseases

Neurological and neurosurgical diseases lead to complications producing malnutrition increasing pathology and mortality. In order to avoid complications because of malnutrition or overcome deficiencies in nutrients supplements are often used for these subjects. The physiopathological mechanisms of malnutrition, methods of nutritional assessment and the supplemental support are reviewed in this paper based on the assumption that patients need to receive adequate nutrition to promote optimal recovery, placing nutrition as a first line treatment and not an afterthought in the rehabilitation.

ESPEN guidelines on chronic intestinal failure in adults

BACKGROUND & AIMS

Chronic Intestinal Failure (CIF) is the long-lasting reduction of gut function, below the minimum necessary for the absorption of macronutrients and/or water and electrolytes, such that intravenous supplementation is required to maintain health and/or growth. CIF is the rarest organ failure. Home parenteral nutrition (HPN) is the primary treatment for CIF. No guidelines (GLs) have been developed that address the global management of CIF. These GLs have been devised to generate comprehensive recommendations for safe and effective management of adult patients with CIF.

METHODS

The GLs were developed by the Home Artificial Nutrition & Chronic Intestinal Failure Special Interest Group of ESPEN. The GRADE system was used for assigning strength of evidence. Recommendations were discussed, submitted to Delphi rounds, and accepted in an online survey of ESPEN members.

RESULTS

The following topics were addressed: management of HPN; parenteral nutrition formulation; intestinal rehabilitation, medical therapies, and non-transplant surgery, for short bowel syndrome, chronic intestinal pseudo-obstruction, and radiation enteritis; intestinal transplantation; prevention/treatment of CVC-related infection, CVC-related occlusion/thrombosis; intestinal failure-associated liver disease, gallbladder sludge and stones, renal failure and metabolic bone disease. Literature search provided 623 full papers. Only 12% were controlled studies or meta-analyses. A total of 112 recommendations are given: grade of evidence, very low for 51%, low for 39%, moderate for 8%, and high for 2%; strength of recommendation: strong for 63%, weak for 37%.

CONCLUSIONS

CIF management requires complex technologies, multidisciplinary and multiprofessional activity, and expertise to care for both the underlying gastrointestinal disease and to provide HPN support. The rarity of the condition impairs the development of RCTs. As a consequence, most of the recommendations have a low or very low grade of evidence. However, two-thirds of the recommendations are considered strong. Specialized management and organization underpin these recommendations.

Improving rehabilitation after critical illness through outpatient physiotherapy classes and essential amino acid supplement: A randomized controlled trial

PURPOSE

Patients recovering from critical illness may be left with significant muscle mass loss. This study aimed to evaluate whether a 6-week program of enhanced physiotherapy and structured exercise (PEPSE) and an essential amino acid supplement drink (glutamine and essential amino acid mixture [GEAA]) improves physical and psychological recovery.

MATERIALS AND METHODS

Intensive care patients aged 45 years or older, with a combined intensive care unit stay/pre-intensive care unit stay of 5 days or more were recruited to a randomized controlled trial examining the effect of PEPSE and GEAA on recovery. The 2 factors were tested in a 2 × 2 factorial design: (1) GEAA drink twice daily for 3 months and (2) 6-week PEPSE in first 3 months. Primary efficacy outcome was an improvement in the 6-minute walking test at 3 months.

RESULTS

A total of 93 patients were randomized to the study. Patients receiving the PEPSE and GEA had the biggest gains in distance walked in 6-minute walking test (P < .0001). There were also significant reductions in rates of anxiety in study groups control supplement/PEPSE (P = .047) and GEAA supplement/PEPSE (P = .036) and for GEAA supplement/PEPSE in depression (P = .0009).

CONCLUSION

Enhanced rehabilitation combined with GEAA supplement may enhance physical recovery and reduce anxiety and depression.

The effects of acute oral glutamine supplementation on exercise-induced gastrointestinal permeability and heat shock protein expression in peripheral blood mononuclear cells

Chronic glutamine supplementation reduces exercise-induced intestinal permeability and inhibits the NF-κB pro-inflammatory pathway in human peripheral blood mononuclear cells. These effects were correlated with activation of HSP70. The purpose of this paper is to test if an acute dose of oral glutamine prior to exercise reduces intestinal permeability along with activation of the heat shock response leading to inhibition of pro-inflammatory markers. Physically active subjects (N = 7) completed baseline and exercise intestinal permeability tests, determined by the percent ratio of urinary lactulose (5 g) to rhamnose (2 g). Exercise included two 60-min treadmill runs at 70 % of VO2max at 30 °C after ingestion of glutamine (Gln) or placebo (Pla). Plasma levels of endotoxin and TNF-α, along with peripheral blood mononuclear cell (PBMC) protein expression of HSP70 and IκBα, were measured pre- and post-exercise and 2 and 4 h post-exercise. Permeability increased in the Pla trial compared to that at rest (0.06 ± 0.01 vs. 0.02 ± 0.018) and did not increase in the Gln trial. Plasma endotoxin was lower at the 4-h time point in the Gln vs. 4 h in the Pla (6.715 ± 0.046 pg/ml vs. 7.952 ± 1.11 pg/ml). TNF-α was lower 4 h post-exercise in the Gln vs. Pla (1.64 ± 0.09 pg/ml vs. 1.87 ± 0.12 pg/ml). PBMC expression of IkBα was higher 4 h post-exercise in the Gln vs. 4 h in the Pla (1.29 ± 0.43 vs. 0.8892 ± 0.040). HSP70 was higher pre-exercise and 2 h post-exercise in the Gln vs. Pla (1.35 ± 0.21 vs. 1.000 ± 0.000 and 1.65 ± 0.21 vs. 1.27 ± 0.40). Acute oral glutamine supplementation prevents an exercise-induced rise in intestinal permeability and suppresses NF-κB activation in peripheral blood mononuclear cells.

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.

Glutamine administration modulates lung γδ T lymphocyte expression in mice with polymicrobial sepsis

This study investigated the effects of glutamine (GLN) administration on regulating lung γδ T cells in polymicrobial sepsis. Mice were randomly assigned to normal group (NC), septic saline group (SS), and septic GLN group (SG). All mice were fed with chow diet. Sepsis was induced by cecal ligation and puncture (CLP). The SS and SG groups were, respectively, injected with saline and 0.75 g GLN/kg body weight once via tail vein 1 h after CLP. Mice were killed 12 and 24 h after CLP. Their lungs were collected for further analysis. The results showed that, compared with normal mice, sepsis resulted in higher lung γδ T cell and neutrophil percentages and higher cytokine expressed by γδ T cells. Histopathologic findings showed that the extent of inflammatory lesions of the lung alveolar was less severe in the SG group than the SS group after CLP. The SG group had a higher γδ T cell percentage and lower γδ T cell apoptotic rates as well as lower neutrophil numbers in the lungs. Also, interleukin 17A (IL-17A), interferon γ, and IL-10 expressed by γδ T cells and CXC receptor 2 expressed by neutrophils decreased in the SG group. Moreover, GLN reduced IL-17A, IL-1β, and IL-23 concentrations and myeloperoxidase activity in lung tissues. Our results suggest that GLN administration after initiation of sepsis affects lung γδ T cell percentage and cytokine secretion and prevented apoptosis of γδ T cells and neutrophil infiltration to the lungs, which may partly be responsible for ameliorating acute lung injury induced by sepsis.

Glutamine supplementation for critically ill adults

BACKGROUND

Glutamine is a non-essential amino acid which is abundant in the healthy human body. There are studies reporting that plasma glutamine levels are reduced in patients with critical illness or following major surgery, suggesting that glutamine may be a conditionally essential amino acid in situations of extreme stress. In the past decade, several clinical trials examining the effects of glutamine supplementation in patients with critical illness or receiving surgery have been done, and the systematic review of this clinical evidence has suggested that glutamine supplementation may reduce infection and mortality rates in patients with critical illness. However, two recent large-scale randomized clinical trials did not find any beneficial effects of glutamine supplementation in patients with critical illness.

OBJECTIVES

The objective of this review was to:1. assess the effects of glutamine supplementation in critically ill adults and in adults after major surgery on infection rate, mortality and other clinically relevant outcomes;2. investigate potential heterogeneity across different patient groups and different routes for providing nutrition.

SEARCH METHODS

We searched the Cochrane Anaesthesia Review Group (CARG) Specialized Register; Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (2013, Issue 5); MEDLINE (1950 to May 2013); EMBASE (1980 to May 2013) and Web of Science (1945 to May 2013).

SELECTION CRITERIA

We included controlled clinical trials with random or quasi-random allocation that examined glutamine supplementation versus no supplementation or placebo in adults with a critical illness or undergoing elective major surgery. We excluded cross-over trials.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted the relevant information from each included study using a standardized data extraction form. For infectious complications and mortality and morbidity outcomes we used risk ratio (RR) as the summary measure with the 95% confidence interval (CI). We calculated, where appropriate, the number needed to treat to benefit (NNTB) and the number needed to treat to harm (NNTH). We presented continuous data as the difference between means (MD) with the 95% CI.

MAIN RESULTS

Our search identified 1999 titles, of which 53 trials (57 articles) fulfilled our inclusion criteria. The 53 included studies enrolled a total of 4671 participants with critical illness or undergoing elective major surgery. We analysed seven domains of potential risk of bias. In 10 studies the risk of bias was evaluated as low in all of the domains. Thirty-three trials (2303 patients) provided data on nosocomial infectious complications; pooling of these data suggested that glutamine supplementation reduced the infectious complications rate in adults with critical illness or undergoing elective major surgery (RR 0.79, 95% CI 0.71 to 0.87, P ＜ 0.00001, I² = 8%, moderate quality evidence). Thirty-six studies reported short-term (hospital or less than one month) mortality. The combined rate of mortality from these studies was not statistically different between the groups receiving glutamine supplement and those receiving no supplement (RR 0.89, 95% CI 0.78 to 1.02, P = 0.10, I² = 22%, low quality evidence). Eleven studies reported long-term (more than six months) mortality; meta-analysis of these studies (2277 participants) yielded a RR of 1.00 (95% CI 0.89 to 1.12, P = 0.94, I² = 30%, moderate quality evidence). Subgroup analysis of infectious complications and mortality outcomes did not find any statistically significant differences between the predefined groups. Hospital length of stay was reported in 36 studies. We found that the length of hospital stay was shorter in the intervention group than in the control group (MD -3.46 days, 95% CI -4.61 to -2.32, P < 0.0001, I² = 63%, low quality evidence). Slightly prolonged intensive care unit (ICU) stay was found in the glutamine supplemented group from 22 studies (2285 participants) (MD 0.18 days, 95% CI 0.07 to 0.29, P = 0.002, I² = 11%, moderate quality evidence). Days on mechanical ventilation (14 studies, 1297 participants) was found to be slightly shorter in the intervention group than in the control group (MD - 0.69 days, 95% CI -1.37 to -0.02, P = 0.04, I² = 18%, moderate quality evidence). There was no clear evidence of a difference between the groups for side effects and quality of life, however results were imprecise for serious adverse events and few studies reported on quality of life. Sensitivity analysis including only low risk of bias studies found that glutamine supplementation had beneficial effects in reducing the length of hospital stay (MD -2.9 days, 95% CI -5.3 to -0.5, P = 0.02, I² = 58%, eight studies) while there was no statistically significant difference between the groups for all of the other outcomes.

AUTHORS' CONCLUSIONS

This review found moderate evidence that glutamine supplementation reduced the infection rate and days on mechanical ventilation, and low quality evidence that glutamine supplementation reduced length of hospital stay in critically ill or surgical patients. It seems to have little or no effect on the risk of mortality and length of ICU stay, however. The effects on the risk of serious side effects were imprecise. The strength of evidence in this review was impaired by a high risk of overall bias, suspected publication bias, and moderate to substantial heterogeneity within the included studies.

Parenteral glutamine supplementation in critical illness: a systematic review

Introduction

The potential benefit of parenteral glutamine (GLN) supplementation has been one of the most commonly studied nutritional interventions in the critical care setting. The aim of this systematic review was to incorporate recent trials of traditional parenteral GLN supplementation in critical illness with previously existing data.

Methods

All randomized controlled trials of parenterally administered GLN in critically ill patients conducted from 1997 to 2013 were identified. Studies of enteral GLN only or combined enteral/parenteral GLN were excluded. Methodological quality of studies was scored and data was abstracted by independent reviewers.

Results

A total of 26 studies involving 2,484 patients examining only parenteral GLN supplementation of nutrition support were identified in ICU patients. Parenteral GLN supplementation was associated with a trend towards a reduction of overall mortality (relative risk (RR) 0.88, 95% confidence interval (CI) 0.75, 1.03, P = 0.10) and a significant reduction in hospital mortality (RR 0.68, 95% CI 0.51, 0.90, P = 0.008). In addition, parenteral GLN was associated with a strong trend towards a reduction in infectious complications (RR 0.86, 95% CI 0.73, 1.02, P = 0.09) and ICU length of stay (LOS) (WMD –1.91, (95% CI -4.10, 0.28, P = 0.09) and significant reduction in hospital LOS (WMD -2.56, 95% CI -4.71, -0.42, P = 0.02). In the subset of studies examining patients receiving parenteral nutrition (PN), parenteral GLN supplementation was associated with a trend towards reduced overall mortality (RR 0.84, 95% CI 0.71, 1.01, P = 0.07).

Conclusions

Parenteral GLN supplementation given in conjunction with nutrition support continues to be associated with a significant reduction in hospital mortality and hospital LOS. Parenteral GLN supplementation as a component of nutrition support should continue to be considered to improve outcomes in critically ill patients.

Glutamine and alanine-induced differential expression of intracellular IL-6, IL-8, and TNF-α in LPS-stimulated monocytes in human whole-blood

To investigate the effects of the commonly-used immunomodulators l-glutamine, l-alanine, and the combination of both l-alanyl-l-glutamine (Dipeptamin(®)) on intracellular expression of IL-6, IL-8, and TNF-α during endotoxemia, lipopolysaccharide (LPS)-stimulated human monocytes in a whole blood system were investigated by flow cytometry. Whole blood of twenty-seven healthy volunteers was stimulated with LPS and incubated with three different amino acid solutions (1. l-glutamine, 2. l-alanine, 3. l-alanyl-l-glutamine, each concentration 2 mM, 5 mM, incubation time 3 h). CD14(+) monocytes were phenotyped in whole-blood and intracellular expression of cytokines was assessed by flow cytometry. Our investigations showed for the first time in whole blood probes, imitating best physiologically present cellular interactions, that l-glutamine caused a dose-independent inhibitory effect on IL-6 and TNF-α production in human monocytes stimulated with LPS. However, l-alanine had contrary effects on IL-6 expression, significantly upregulating expression of IL-6 in LPS-treated monocytes. The impact of l-alanine on the expression of TNF-α was comparable with glutamine. Neither amino acid was able to affect IL-8 production in LPS-stimulated monocytes. The combination of both did not influence significantly IL-6 and IL-8 expression in monocytes during endotoxemia, however strongly reduced TNF-α production. For the regulation of TNF-α, l-glutamine, l-alanine and the combination of both show a congruent and exponentiated downregulating effect during endotoxemia, for the modulation of IL-6, l-glutamine and l-alanine featured opposite regulation leading to a canceling impact of each other when recombining both amino acids.

Glutamine supplemented parenteral nutrition to prevent ventilator-associated pneumonia in the intensive care unit

OBJECTIVE

Ventilator-associated pneumonia (VAP) is a form of nosocomial pneumonia that increases patient morbidity and mortality, length of hospital stay, and healthcare costs. Glutamine preserves the intestinal mucosal structure, increases immune function, and reduces harmful changes in gut permeability in patients receiving total parenteral nutrition (TPN). We hypothesized that TPN supplemented by glutamine might prevent the development of VAP in patients on mechanical ventilator support in the intensive care unit (ICU).

MATERIAL AND METHODS

With the approval of the ethics committee and informed consent from relatives, 60 patients who were followed in the ICU with mechanical ventilator support were included in our study. Patients were divided into three groups. The first group received enteral nutrition (n=20), and the second was prescribed TPN (n=20) while the third group was given glutamine-supplemented TPN (n=20). C-reactive protein (CRP), sedimentation rate, body temperature, development of purulent secretions, increase in the amount of secretions, changes in the characteristics of secretions and an increase in requirement of deep tracheal aspiration were monitored for seven days by daily examination and radiographs.

RESULTS

No statistically significant difference was found among groups in terms of development of VAP (p=0.622).

CONCLUSION

Although VAP developed at a lower rate in the glutamine-supplemented TPN group, no statistically significant difference was found among any of the groups. Glutamine-supplemented TPN may have no superiority over unsupplemented enteral and TPN in preventing VAP.

Effects of glutamine supplementation on muscle function and stress responses in a mouse model of spinal cord injury

Spinal cord injury (SCI) results in loss of muscle function due to rapid breakdown of contractile proteins. Glutamine supplementation improves clinical outcomes, but its effects on muscle function after SCI are unknown. The benefits of glutamine in non-skeletal muscle tissues involve elevated heat shock protein (Hsp)70 and Hsp25, but the muscle response may differ because it is the largest contributor to plasma glutamine. We tested the hypothesis that glutamine preserves muscle function after SCI and that this is associated with increased heat shock protein and reduced inflammatory factors, interleukin-6 (IL-6) and tumour necrosis factor-α (TNFα). Changes in plantarflexor force, fatigability and total myofibrillar, Hsp70, Hsp25, IL-6 and TNFα muscle protein levels were measured 7 days after sham or spinal cord transection surgery in mice receiving daily placebo or glutamine. Compared with placebo, after SCI glutamine significantly attenuated the reductions in maximal isometric force (0.22 ± 0.01 versus 0.31 ± 0.03 N, respectively) and fatigue resistance (34 ± 4 versus 59 ± 4% of initial force, respectively). Glutamine significantly ameliorated the loss of myofibrillar protein with spinal cord transection. Spinal cord transection was associated with decreased Hsp70 and Hsp25 with glutamine only (45 ± 3 and 44 ± 5% of placebo, respectively). Glutamine significantly reduced spinal cord transection-associated increases in IL-6 and TNFα compared with placebo (38 ± 6 and 37 ± 8% of placebo, respectively). Functionally, early reductions in contractile protein, force and fatigue resistance after SCI were reversed with glutamine. Spinal cord transection-associated reductions in Hsp70, Hsp25, IL-6 and TNFα with glutamine versus placebo suggest lower stress in the muscle, possibly related to a reduced need to produce glutamine. These findings support glutamine as a therapeutic intervention to accelerate recovery of muscle function after SCI.

Glutamine randomized studies in early life: the unsolved riddle of experimental and clinical studies

Glutamine may have benefits during immaturity or critical illness in early life but its effects on outcome end hardpoints are controversial. Our aim was to review randomized studies on glutamine supplementation in pups, infants, and children examining whether glutamine affects outcome. Experimental work has proposed various mechanisms of glutamine action but none of the randomized studies in early life showed any effect on mortality and only a few showed some effect on inflammatory response, organ function, and a trend for infection control. Although apparently safe in animal models (pups), premature infants, and critically ill children, glutamine supplementation does not reduce mortality or late onset sepsis, and its routine use cannot be recommended in these sensitive populations. Large prospectively stratified trials are needed to better define the crucial interrelations of “glutamine-heat shock proteins-stress response” in critical illness and to identify the specific subgroups of premature neonates and critically ill infants or children who may have a greater need for glutamine and who may eventually benefit from its supplementation. The methodological problems noted in the reviewed randomized experimental and clinical trials should be seriously considered in any future well-designed large blinded randomized controlled trial involving glutamine supplementation in critical illness.

Metabolite profiling identifies pathways associated with metabolic risk in humans

BACKGROUND

Although metabolic risk factors are known to cluster in individuals who are prone to developing diabetes mellitus and cardiovascular disease, the underlying biological mechanisms remain poorly understood.

METHODS AND RESULTS

To identify pathways associated with cardiometabolic risk, we used liquid chromatography/mass spectrometry to determine the plasma concentrations of 45 distinct metabolites and to examine their relation to cardiometabolic risk in the Framingham Heart Study (FHS; n=1015) and the Malmö Diet and Cancer Study (MDC; n=746). We then interrogated significant findings in experimental models of cardiovascular and metabolic disease. We observed that metabolic risk factors (obesity, insulin resistance, high blood pressure, and dyslipidemia) were associated with multiple metabolites, including branched-chain amino acids, other hydrophobic amino acids, tryptophan breakdown products, and nucleotide metabolites. We observed strong associations of insulin resistance traits with glutamine (standardized regression coefficients, -0.04 to -0.22 per 1-SD change in log-glutamine; P<0.001), glutamate (0.05 to 0.14; P<0.001), and the glutamine-to-glutamate ratio (-0.05 to -0.20; P<0.001) in the discovery sample (FHS); similar associations were observed in the replication sample (MDC). High glutamine-to-glutamate ratio was associated with lower risk of incident diabetes mellitus in FHS (odds ratio, 0.79; adjusted P=0.03) but not in MDC. In experimental models, administration of glutamine in mice led to both increased glucose tolerance (P=0.01) and decreased blood pressure (P<0.05).

CONCLUSIONS

Biochemical profiling identified circulating metabolites not previously associated with metabolic traits. Experimentally interrogating one of these pathways demonstrated that excess glutamine relative to glutamate, resulting from exogenous administration, is associated with reduced metabolic risk in mice.

Glutamine supplementation in sick children: is it beneficial?

The purpose of this review is to provide a critical appraisal of the literature on Glutamine (Gln) supplementation in various conditions or illnesses that affect children, from neonates to adolescents. First, a general overview of the proposed mechanisms for the beneficial effects of Gln is provided, and subsequently clinical studies are discussed. Despite safety, studies are conflicting, partly due to different effects of enteral and parenteral Gln supplementation. Further insufficient evidence is available on the benefits of Gln supplementation in pediatric patients. This includes premature infants, infants with gastrointestinal disease, children with Crohn's disease, short bowel syndrome, malnutrition/diarrhea, cancer, severe burns/trauma, Duchenne muscular dystrophy, sickle cell anemia, cystic fibrosis, and type 1 diabetes. Moreover, methodological issues have been noted in some studies. Further mechanistic data is needed along with large randomized controlled trials in select populations of sick children, who may eventually benefit from supplemental Gln.

Metabolic considerations in management of surgical patients

Metabolic changes after surgery, trauma, or serious illness have a complex pathophysiology. The early posttraumatic stress response is physiologic and associated with a state of hyperinflammation, increased oxygen consumption, and increased energy expenditure. These are part of a systemic reaction that encompasses a wide range of endocrinological, immunologic, and hematological effects. Surgery initiates changes in metabolism that can affect virtually all organs and tissues; the metabolic response results in hormone-mediated mobilization of endogenous substrates that leads to stress catabolism. Hypercatabolism has been associated with severe complications related to hyperglycemia, hypoproteinemia, and immunosuppression. Proper metabolic support is essential to restore homeostasis and ensure survival.

Amino acid composition in parenteral nutrition: what is the evidence?

PURPOSE OF REVIEW

Complete parenteral nutrition solutions contain mixed amino acid products providing all nine essential amino acids and a varying composition of nonessential amino acids. Relatively little rigorous comparative efficacy research on altered parenteral nutrition amino acid composition has been published in recent years.

RECENT FINDINGS

Limited data from randomized, double-blind, adequately powered clinical trials to define optimal doses of total or individual amino acids in parenteral nutrition are available. An exception is the growing number of studies on the efficacy of glutamine supplementation of parenteral nutrition or given as a single parenteral agent. Parenteral glutamine appears to confer benefit in selected patients; however, additional data to define optimal glutamine dosing and the patient subgroups who may most benefit from this amino acid are needed. Although some promising studies have been published, little data are available in the current era of nutrition support on the clinical efficacy of altered doses of arginine, branched chain amino acids, cysteine, or taurine supplementation of parenteral nutrition.

SUMMARY

Despite routine use of parenteral nutrition, surprisingly little clinical efficacy data are available to guide total or specific amino acid dosing in adult and pediatric patients requiring this therapy. This warrants increased attention by the research community and funding agencies to better define optimal amino acid administration strategies in patient subgroups requiring parenteral nutrition.

Berberine attenuates lipopolysaccharide-induced impairments of intestinal glutamine transport and glutaminase activity in rat

Berberine was reported to protect against the intestinal injury and improve the survival rate in sepsis, and glutamine deficiency was considered to be correlated with mortality in sepsis. We found that berberine pretreatment ameliorated lipopolysaccharide-induced direct intestinal injury and mucosal hypoplasia and attenuated impairments of intestinal glutamine transport and glutaminase activity, B(0)AT1 mRNA and protein expressions, and glutaminase protein expression. These findings showed the first time that berberine pretreatment could improve intestinal recovery and attenuate the impairment of glutamine transport and glutaminase activity in rat sepsis. This might be one of the mechanisms for the beneficial effect of berberine on sepsis.

"Metabolic staging" after major trauma - a guide for clinical decision making?

Metabolic changes after major trauma have a complex underlying pathophysiology. The early posttraumatic stress response is associated with a state of hyperinflammation, with increased oxygen consumption and energy expenditure. This hypercatabolic state must be recognized early and mandates an early nutritional management strategy. A proactive concept of early enteral "immunonutrition" in severely injured patients, is aimed at counterbalancing the negative aspects of hyperinflammation and hypercatabolism in order to reduce the risk of late complications, including infections and posttraumatic organ failure. Recently, the concept of "metabolic staging" has been advocated, which takes into account the distinct inflammatory phases and metabolic phenotypes after major trauma, including the "ischemia/reperfusion phenotype", the "leukocytic phenotype", and the "angiogenic phenotype". The potential clinical impact of metabolic staging, and of an appropriately adapted "metabolic control" and nutritional support, remains to be determined.

Oral glutamine protects against acute doxorubicin-induced cardiotoxicity of tumor-bearing rats

Doxorubicin (DOX), a widely used anticancer drug, has a dose-dependent cardiotoxicity, attributed mainly to free radical formation. The cardiomyocyte oxidative stress occurs rapidly after DOX treatment, resulting in harmful modifications to proteins, lipids, and DNA. Previous data showed that oral l-glutamine (Gln) prevented cardiac lipid peroxidation and maintained normal cardiac glutathione (GSH) levels in DOX-treated rats. Our aim in this study was to examine the effect of Gln on DOX-induced cardiac oxidative stress in a tumor-bearing host. Female Fisher344 rats with implanted MatBIII mammary tumors were randomized into 2 groups: a Gln group that received l-Gln (1 g.kg(-1).d(-1)) (n = 10) via a Gln-enriched diet and/or gavage with 50% Gln suspension during the whole experiment and a control group that was fed the same diet formulation without Gln and/or were gavaged with water. All rats received a single injection of 12 mg/kg DOX and were killed 3 d later. GSH levels of hearts, livers, tumors, and blood, as well as cardiac histological alterations, lipid peroxidation, peroxinitrite levels, and caspase-3 activation were determined. Cardiac physiologic alterations were assessed by ultrasound imaging before and 3 d after DOX administration. The Gln supplementation resulted in lower cardiac lipid peroxidation and peroxintrite levels and elevated cardiac catalase enzyme activity and GSH compared with the controls, without affecting those of the tumors. DOX-induced alterations of the echocardiographic parameters were significantly reduced in the Gln-supplemented rats. These data indicate that Gln is able to reduce the oxidative damage of cardiomyocytes that occurs soon after DOX administration and thus protects the heart of a tumor-bearing host from DOX-induced cardiomyopathy.

Different alterations in rat intestinal glutamine transport during the progression of CLP- and LPS-induced sepsis

BACKGROUND

A marked deficiency of glutamine in clinical critical illness is correlated with mortality in the intensive care unit. Though intestinal glutamine transport was reported to be impaired in late sepsis, we hypothesized that there might be a different alteration in the early stage, with differential effects on the Na(+)-dependent glutamine transporters B(0)AT1, ATB(0,+), and ATA2.

MATERIALS AND METHODS

Sepsis was induced by cecal ligation and puncture or lipopolysaccharide intraperitoneal injection in Sprague Dawley rats, and the samples were collected at 0, 2, 6, 12, 24h. Small intestinal brush border glutamine transport was studied by a rapid filtration technique. The relative contributions of the three main transporter, B(0)AT1, ATB(0,+), and ATA2, were determined by competitive inhibition. The mRNA level of each transporter was analyzed by RT-PCR, and an extra immunohistochemistry analysis was performed to detect the localization of ATA2 protein in small intestine. Serum TNF-α and IL-10 concentrations were quantitated by ELISA.

RESULTS

Intestinal glutamine transport showed a biphasic change with an early increase and a late decrease in both CLP and LPS group. The early increase of glutamine transport was mainly attributable to the increased contributions of ATA2 and ATB(0,+). The transport activities of B(0)AT1, ATB(0,+) altered mainly because of the number of transporters (mRNA level as an indicator), while turned to ATA2, the redistribution was also found to be involved. The plasma TNF-α and IL-10 levels, especially the former, showed similar changing profiles to glutamine transport and, thus, may have relevance to it.

CONCLUSION

Rat intestinal glutamine transport showed an early increase and a late decrease in sepsis, and may provide some information for sepsis treatment.

Parenteral nutrition in the critically ill patient

A 67-year-old woman with type 2 diabetes mellitus undergoes extensive resection of the small bowel and right colon with a jejunostomy and colostomy because of mesenteric ischemia. In the surgical intensive care unit, severe systemic inflammatory response syndrome with possible sepsis develops. The patient is treated with volume resuscitation, vasopressor support, mechanical ventilation, broad-spectrum antibiotics, and intravenous insulin infusion. Low-dose tube feedings are initiated postoperatively through a nasogastric tube. However, these feedings are discontinued after the development of escalating vasopressor requirements, worsening abdominal distention, and increased gastric residual volume, along with an episode of emesis. The hospital nutritional-support service is consulted for feeding recommendations. A discussion with the patient's family reveals that during the previous 6 months, she lost approximately 15% of her usual body weight and decreased her food intake because of abdominal pain associated with eating. Her preoperative body weight was 51 kg (112 lb), or 90% of her ideal body weight. The physical examination reveals mild wasting of skeletal muscle and fat. Blood tests show hypomagnesemia, hypophosphatemia, and normal hepatic and renal function. Central venous parenteral nutrition is recommended.

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.

The effect of glutamine infusion on the inflammatory response and HSP70 during human experimental endotoxaemia

INTRODUCTION

Glutamine supplementation has beneficial effects on morbidity and mortality in critically ill patients, possibly in part through an attenuation of the proinflammatory cytokine response and a stimulation of heat shock protein (HSP)70. We infused either alanine-glutamine or saline during endotoxin challenge and measured plasma cytokines and HSP70 protein expression.

METHODS

This crossover study, conducted in eight healthy young men, was double-blind, randomized and placebo-controlled. It was performed on 2 trial days, separated by a 4-week washout period. The volunteers received an infusion of alanine-glutamine at a rate of 0.025 g/(kg body weight x hour) or saline for 10 hours. After 2 hours, an intravenous bolus of Escherichia coli endotoxin (0.3 ng/kg) was administered. Blood samples were collected hourly for the following 8 hours. HSP70 protein content in isolated blood mononuclear cells (BMNCs) was measured by Western blotting.

RESULTS

Plasma glutamine increased during alanine-glutamine infusion. Endotoxin reduced plasma glutamine during both trials, but plasma glutamine levels remained above baseline with alanine-glutamine supplementation. Endotoxin injection was associated with alterations in white blood cell and differential counts, tumour necrosis factor-alpha, IL-6, temperature and heart rate, but glutamine affected neither the endotoxin-induced change in these variables nor the expression of HSP70 in BMNCs.

CONCLUSIONS

Endotoxin reduced plasma glutamine independently of alanine-glutamine infusion, but supplementation allows plasma levels to be maintained above baseline. Glutamine alters neither endotoxin-induced systemic inflammation nor early expression of HSP70 in BMNCs.

TRIAL REGISTRATION

ClinicalTrials.gov ID: NCT 00780520.

Glutamine metabolism and function in relation to proline synthesis and the safety of glutamine and proline supplementation

At normal intakes, dietary glutamine and glutamate are metabolized by the small intestine and essentially all glutamine within the body is synthesized de novo through the action of glutamine synthetase. The major sites of net glutamine synthesis are skeletal muscle, lung, and adipose tissue and, under some conditions, the liver. In addition to the small intestine, where glutamine is the major respiratory fuel, other sites of net glutamine utilization include the cells of the immune system, the kidneys, and the liver. The intestine expresses pyrroline 5-carboxylate (P5C) synthase, which means that proline is an end product of intestinal glutamine catabolism. Proline can also be synthesized from ornithine and the exact contribution of the 2 pathways is not certain. Infusion of proline i.v. to increase circulating concentrations is associated with increased proline oxidation and decreased proline synthesis. In contrast, conditions of proline insufficiency, after feeding low-proline diets or in response to high rates of proline catabolism in burn patients, do not result in increased proline synthesis. Glutamine supplementation is widespread and up to 0.57-0.75 g.kg(-1).d(-1) is well tolerated. Similarly, the only study of proline supplementation, in which patients with gyrate atrophy were given 488 mg.kg(-1).d(-1), reported no deleterious side effects. In the absence of controlled trials, it is currently not possible to estimate a safe upper limit for either of these 2 amino acids.