Glutamine: role in critical illness and ongoing clinical trials

Plasma and urine metabolomics for the identification of diagnostic biomarkers for sulfur mustard-induced lung injury

BACKGROUND

Sulfur mustard (SM) is a highly lethal chemical warfare agent that induces severe health complications in exposed individuals. Gaining insights into the metabolic changes caused by SM exposure is essential for understanding its underlying mechanisms and developing effective diagnostic and therapeutic interventions.

METHODS

In this investigation, we utilized proton nuclear magnetic resonance (H-NMR) spectroscopy to conduct metabolomic analysis in patients diagnosed with mustard lung disease (MLD) using a non-targeted approach. Metabolite measurements were conducted on plasma and urine samples collected from a total of 54 individuals, including 20 individuals with mild MLD, 20 individuals with moderate MLD, and 14 healthy individuals. Multivariate and univariate analyses were applied to identify metabolites that distinguish between the different groups, and enrichment analysis was performed to unveil the underlying biochemical pathways involved.

RESULTS

The obtained metabolic profile had the potential to differentiate moderate from healthy plasma, but not from mild patients using multivariate analysis. Sixteen metabolites from plasma were considered significantly different between the moderate and control groups (VIP > 1 and p < 0.05) that these metabolites involved in fatty acid and amino acid metabolism. Utilizing all 16 metabolites as a combined panel, we were able to distinguish between the moderate and control groups, achieving an area under the curve (AUC) of 0.854. Moreover, 6 and 8 urinary metabolites were detected between mild vs. control and moderate vs. control groups, respectively. Fourteen metabolites exhibited significant fold changes (FC) (FC < 0.66 or FC > 1.5; p < 0.05). These metabolites are involved in amino acid and nicotinate metabolism.

CONCLUSION

Our study provides novel insights into the metabolic changes associated with MLD and highlights potential pathways involved in the disease progression. These findings have implications for the development of targeted diagnostic and therapeutic strategies for MLD.

Nanovesicles for Sensitive Skin Care Developed via Self-Assembly of Glutamine Linoleate

BACKGROUND

L-glutamine and linoleic acid (LA) can suppress inflammatory cytokine expression; however, studies on their simultaneous application are limited due to polarity differences.

AIMS

To investigate the effect of glutamine linoleate vesicles (QLAsomes) on skin sensitization by assessing their impact on sensitization-related protein expression, bacterial growth, and clinical efficacy in relieving skin itchiness.

METHODS

After synthesizing and analyzing QLAsomes, their inhibitory effects on capsaicin-induced cytokine expression and Staphylococcus aureus growth were evaluated. In a double-blind clinical trial, 24 participants (ages 22-63) with sensitized skin applied 10 wt% QLAsome cream on one side and a vehicle or no cream on the other twice daily for 2 weeks. Itchiness in the elbow area was assessed using a visual analog scale and expert evaluation. Skin barrier changes were measured using transepidermal water loss (TEWL), skin erythema, and stratum corneum (SC) hydration.

RESULTS

QLAsomes, formed by L-glutamine and LA through hydrogen bonding, were spherical vesicles (164.6 ± 3.1 nm). Based on the inhibitory effects of L-glutamine and LA on inflammation-related factors, QLAsomes inhibited the capsaicin-induced expression of these factors more effectively than the individual components. IL-4 inhibition was improved by over 26%. Matrix metalloproteinase-1, which degrades collagen, showed 32% and 23% improvements compared to L-glutamine and LA, respectively. In a clinical evaluation, 10 wt% QLAsome cream reduced itching by 45% compared to before application, which is a 67% improvement compared to placebo. Skin evaluations revealed improvements in erythema (12%), TEWL (15%), and SC hydration (19%), suggesting that QLAsomes enhance the skin barrier function.

CONCLUSIONS

QLAsomes showed up to 32% higher expression inhibition of key skin sensitization-related factors than individual components, and based on this, improved pruritus by 67% more than placebo. As nanovesicles with skin-soothing properties, they are effective for drug encapsulation and managing skin sensitivity in pharmaceutical and cosmetic industries.

Glutamine sustains energy metabolism and alleviates liver injury in burn sepsis by promoting the assembly of mitochondrial HSP60-HSP10 complex via SIRT4 dependent protein deacetylation

Burns and burn sepsis, characterized by persistent and profound hypercatabolism, cause energy metabolism dysfunction that worsens organ injury and systemic disorders. Glutamine (Gln) is a key nutrient that remarkably replenishes energy metabolism in burn and sepsis patients, but its exact roles beyond substrate supply is unclear. In this study, we demonstrated that Gln alleviated liver injury by sustaining energy supply and restoring redox balance. Meanwhile, Gln also rescued the dysfunctional mitochondrial electron transport chain (ETC) complexes, improved ATP production, reduced oxidative stress, and protected hepatocytes from burn sepsis injury. Mechanistically, we revealed that Gln could activate SIRT4 by upregulating its protein synthesis and increasing the level of Nicotinamide adenine dinucleotide (NAD+), a co-enzyme that sustains the activity of SIRT4. This, in turn, reduced the acetylation of shock protein (HSP) 60 to facilitate the assembly of the HSP60-HSP10 complex, which maintains the activity of ETC complex II and III and thus sustain ATP generation and reduce reactive oxygen species release. Overall, our study uncovers a previously unknown pharmacological mechanism involving the regulation of HSP60-HSP10 assembly by which Gln recovers mitochondrial complex activity, sustains cellular energy metabolism and exerts a hepato-protective role in burn sepsis.

Glutamine stimulates the S6K/4E-BP branch of insulin signalling pathway to mitigate human poly(Q) disorders in Drosophila disease models

OBJECTIVE AND METHODS

Since, the S6K/4E-BP sub-pathway can be stimulated by various amino acids; we extended our investigation to examine if oral feeding of amino acids delivers rescue against human poly(Q) toxicity in Drosophila. We utilised Drosophila models of two different poly(Q) disorders to test our hypothesis. Glutamine was fed to the test flies orally mixed in the food. Control and treated flies were then tested for different parameters, such as formation of poly(Q) aggregates and neurodegeneration, to evaluate glutamine's proficiency in mitigating poly(Q) neurotoxicity.

RESULTS

Our study, for the first time, reports that glutamine feeding stimulates the growth promoting S6K/4E-BP branch of insulin signalling pathway and restricts pathogenesis of poly(Q) disorders in Drosophila disease models. We noted that glutamine treatment restricts the formation of neurotoxic poly(Q) aggregates and minimises neuronal deaths. Further, glutamine treatment re-establishes the chromatin architecture by improving the histone acetylation which is otherwise compromised in poly(Q) expressing neuronal cells.

DISCUSSION

Since, the insulin signalling pathway as well as mechanism of action of glutamine are fairly conserved between human and Drosophila, our finding strongly suggests that glutamine holds immense potential to be developed as an intervention therapy against the incurable human poly(Q) disorders.

Origin and Roles of Alanine and Glutamine in Gluconeogenesis in the Liver, Kidneys, and Small Intestine under Physiological and Pathological Conditions

Alanine and glutamine are the principal glucogenic amino acids. Most originate from muscles, where branched-chain amino acids (valine, leucine, and isoleucine) are nitrogen donors and, under exceptional circumstances, a source of carbons for glutamate synthesis. Glutamate is a nitrogen source for alanine synthesis from pyruvate and a substrate for glutamine synthesis by glutamine synthetase. The following differences between alanine and glutamine, which can play a role in their use in gluconeogenesis, are shown: (i) glutamine appearance in circulation is higher than that of alanine; (ii) the conversion to oxaloacetate, the starting substance for glucose synthesis, is an ATP-consuming reaction for alanine, which is energetically beneficial for glutamine; (iii) most alanine carbons, but not glutamine carbons, originate from glucose; and (iv) glutamine acts a substrate for gluconeogenesis in the liver, kidneys, and intestine, whereas alanine does so only in the liver. Alanine plays a significant role during early starvation, exposure to high-fat and high-protein diets, and diabetes. Glutamine plays a dominant role in gluconeogenesis in prolonged starvation, acidosis, liver cirrhosis, and severe illnesses like sepsis and acts as a substrate for alanine synthesis in the small intestine. Interactions among muscles and the liver, kidneys, and intestine ensuring optimal alanine and glutamine supply for gluconeogenesis are suggested.

Chemical composition, pharmacology and pharmacokinetic studies of GuHong injection in the treatment of ischemic stroke

GuHong injection is composed of safflower and N-acetyl-L-glutamine. It is widely used in clinical for cerebrovascular diseases, such as ischemic stroke and related diseases. The objective of this review is to comprehensively summarize the most recent information related to GuHong in the treatment of stroke, including chemical composition, clinical studies, potential pharmacological mechanisms and pharmacokinetics. Additionally, it examines possible scientific gaps in current study and aims to provide a reliable reference for future GuHong studies. The systematic review reveals that the chemical composition of safflower in GuHong is more than 300 chemical components in five categories. GuHong injection is primarily used in clinical applications for acute ischemic stroke and related diseases. Pharmacological investigations have indicated that GuHong acts in the early and recovery stages of ischemic stroke by anti-inflammatory, anti-oxidative stress, anti-coagulation, neuroprotective and anti-apoptotic mechanisms simultaneously. Pharmacokinetic studies found that the main exposed substances in rat plasma after GuHong administration are hydroxysafflor yellow A and N-acetyl-L-glutamine, and N-acetyl-L-glutamine could exert its pharmacological effect across the blood-brain barrier. As a combination of Chinese herb and chemical drug, GuHong injection has great value in drug research and clinical treatment, especially for ischemic stroke disease. This article represents a comprehensive and systematic review of existing studies on GuHong injection, including chemical composition, pharmacological mechanism, and pharmacokinetics, which provides reference significance for the clinical treatment of ischemic stroke with GuHong, as well as provides guidance for further study.

Role of Heme Oxygenase in Gastrointestinal Epithelial Cells

The gastrointestinal tract is a unique organ containing both vascular and luminal routes lined by epithelial cells forming the mucosa, which play an important role in the entry of nutrients and act as a selective barrier, excluding potentially harmful agents. Mucosal surfaces establish a selective barrier between hostile external environments and the internal milieu. Heme is a major nutritional source of iron and is a pro-oxidant that causes oxidative stress. Heme oxygenases (HOs) catalyze the rate-limiting step in heme degradation, resulting in the formation of iron, carbon monoxide, and biliverdin, which are subsequently converted to bilirubin by biliverdin reductase. In gastrointestinal pathogenesis, HO-1, an inducible isoform of HO, is markedly induced in epithelial cells and plays an important role in protecting mucosal cells. Recent studies have focused on the biological effects of the products of this enzymatic reaction, which have antioxidant, anti-inflammatory, and cytoprotective functions. In this review, the essential roles of HO in the gastrointestinal tract are summarized, focusing on nutrient absorption, protection against cellular stresses, and the maintenance and regulation of tight junction proteins, emphasizing the potential therapeutic implications. The biochemical basis of the potential therapeutic implications of glutamine for HO-1 induction in gastrointestinal injury is also discussed.

[Glutamine as a component of nutritional and metabolic therapy for surgical patients in ICU]

Glutamine is the most abundant amino acid in the human body that is involved in various metabolic processes. The development of hypermetabolic and hypercatabolic syndrome that accompanies critical conditions of ICU patients is associated with a decrease in the concentration of glutamine, especially in the blood plasma and muscles. This process may last for quite a long time and lead to a number of complications up to a fatal outcome. This review was aimed to analyze clinical studies conducted over the past 20 years that demonstrate the effect of intravenous infusion of glutamine dipeptide as part of balanced parenteral nutrition on the perioperative period: the severity of inflammatory response; the state of the intestinal mucosa; the incidence and severity of complications; mortality; the duration of stay in the ICU and hospital in general, etc. The analysis was performed using systematic reviews and meta-analyses based on randomized double-blind, placebo-controlled trials in different countries selected in the main databases (PubMed, EMBASE, Web of Science, The Cochrane Library, etc.). Most of the reports state that the inclusion of glutamine dipeptide in nutritional and metabolic therapy (NMT) in surgical patients reduces the frequency and severity of infectious complications and mortality, reduces the length of stay in ICU and in hospital in general, improves the biochemical parameters that reflect the condition of patients, and reduces the treatment costs. Thus, the conducted systematic reviews and meta-analyses confirm that the use of the parenteral form of glutamine dipeptide (Dipeptiven 20%) as part of balanced standard parenteral nutrition (PN) is a clinically and pharmacoeconomically justified strategy of NMT in surgical ICU patients.

Effects of parenteral glutamine in critically ill surgical patients: a systematic review and meta-analysis

Introduction

Introduction: glutamine (GLN), the most abundant non-essential amino acid in the plasma, tends to be rapidly depleted in cells in situations of metabolic stress. Some studies have demonstrated the benefits of GLN supplementation on mortality, infection, and length of hospital stay. The objective of this review was to analyze whether parenteral supplementation with GLN has any relevant effect in critically ill surgical patients. Methods: based on a systematic database search, randomized clinical trials (RCTs) published since 1985 were included if they had evaluated the effect of parenteral GLN supplementation in critical surgical patients. The statistical analysis was performed using the RevMan 5.3 software. Results: seven RCTs were eligible for the meta-analysis. Parenteral glutamine supplementation was associated with a non-significant 24 % reduction in mortality (RR = 0.76; 95 % CI: 0.50-1.15). Infections were significantly reduced (RR = 0.60; 95 % CI: 0.45-0.80), and length of hospital stay was 4.09 days shorter (95 % CI: -6.71 to -1.46). Conclusion: parenteral GLN usage in critical surgical patients seems to decrease infection and length of hospital stay, but we could not demonstrate a significant reduction in mortality.

The Impact of Perioperative Glutamine-supplemented Parenteral Nutrition on Outcomes of Patients Undergoing Abdominal Surgery: A Meta-analysis of Randomized Clinical Trials

The objective of this study was to evaluate the impact of perioperative glutamine-supplemented parenteral nutrition (GLN-PN) on clinical outcomes in patients undergoing abdominal surgery. MEDLINE, EMBASE, and the Cochrane Controlled Clinical Trials Register were searched to retrieve the eligible studies. Eligible studies were randomized controlled trials (RCTs) that compared the effect of GLN-PN and standard PN on clinical outcomes in patients undergoing abdominal surgery. Clinical outcomes of interest were postoperative mortality, length of hospital stay, morbidity of infectious complication, and cumulative nitrogen balance. Statistical analysis was conducted by RevMan 5.0 software from the Cochrane Collaboration. Sixteen RCTs with 773 patients were included in this meta-analysis. The results showed a significant decrease in the infectious complication rates of patients undergoing abdominal surgery receiving GLN-PN (risk ratio [RR], 0.48; 95% confidence interval [CI], 0.32 to 0.72; P = 0.0004). The overall effect indicated glutamine significantly reduced the length of hospital stay in the form of alanyl-glutamine (weighted mean difference [WMD], -3.17; 95% CI, -5.51 to -0.82; P = 0.008) and in the form of glycyl-glutamine (WMD, -3.40; 95% CI, -5.82 to -0.97; P = 0.006). A positive effect in improving postoperative cumulative nitrogen balance was observed between groups (WMD, 7.40; 95% CI, 3.16 to 11.63; P = 0.0006), but no mortality (RR, 1.52; 95% CI, 0.21 to 11.9; P = 0.68). Perioperative GLN-PN is effective and safe to shorten the length of hospital stay, reduce the morbidity of postoperative infectious complications, and improve nitrogen balance in patients undergoing abdominal surgery.

Antecedent Dietary Glutamine Supplementation Benefits Modulation of Liver Pyroptosis in Mice with Polymicrobial Sepsis

The liver is the main organ responsible for bacterial and endotoxin clearance. Pyroptosis is a form of proinflammatory programmed cell death activated by caspase-1/11 and gasdermin D (GadD). Pyroptosis protects the host against bacterial infection; however, overactive pyroptosis can lead to organ injury. Glutamine (GLN) is a specific amino acid with anti-inflammatory and immunomodulatory properties. This study investigated the effects of GLN pretreatment on liver pyroptosis in a mouse model of polymicrobial sepsis. Mice were assigned to sham, sepsis control (Sepsis-C), and sepsis GLN (Sepsis-G) groups. The sham and Sepsis-C groups were fed the AIN-93G diet. The Sepsis-G group was provided with identical diet components except that part of the casein was replaced by GLN. After feeding the respective diets for 2 weeks, a cecal ligation and puncture (CLP) procedure was performed in the sepsis groups. An antibiotic was administered after CLP. Mice were sacrificed at either 24 or 72 h after CLP. The results showed that sepsis resulted in upregulated liver caspase-1/11 expression. Compared to the Sepsis-C group, the Sepsis-G group had higher liver caspase-11 and NLRP3 gene expressions at 24 h and lower active caspase-1/11 and cleaved GadD protein levels at 72 h after sepsis. Additionally, liver inflammatory cytokine gene expressions had decreased by 72 h post-CLP. The findings suggest that prophylactic administration of GLN initially upregulated liver pyroptosis to eradicate pathogens, yet the process of pyroptosis was suppressed in the late phase of sepsis. This may have beneficially attenuated liver inflammation and injury in an antibiotic-treated septic condition.

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.

The relationship between plasma amino acids and circulating albumin and haemoglobin in postabsorptive stroke patients

Background

This retrospective study had two main aims: (1) to document possible correlations between plasma Amino Acids (AAs) and circulating Albumin (Alb) and Haemoglobin (Hb); and (2) to identify which AAs were predictors of Alb and Hb.

Methods

The study considered 125 stroke subjects (ST) (61.6% males; 65.6 +/- 14.9 years) who met the eligibility criteria (absence of co morbidities associated with altered plasma AAs and presence of plasma AAs determined after overnight fasting). Fifteen matched healthy subjects with measured plasma AAs served as controls.

Results

The best correlations of Alb were with tryptophan (Trp) and histidine (His) (r = + 0.53; p < 0.0001), and those of Hb were with histidine (r = +0.47) and Essential AAs (r = +0.47) (both p<0.0001). In multivariate analysis, Trp (p< 0.0001) and His (p = 0.01) were shown to be the best positive predictors of Alb, whereas glutamine (p = 0.006) was the best positive predictor of Hb.

Conclusions

The study shows that the majority of plasma AAs were positively correlated with Alb and Hb. The best predictors of circulating Alb and Hb were the levels of tryptophan and glutamine, respectively.

Capillary Electrophoresis of Free Amino Acids in Physiological Fluids Without Derivatization Employing Direct or Indirect Absorbance Detection

Whole blood and/or plasma amino acids are useful for monitoring whole-body protein and amino acid metabolism in an organism under various physiological and pathophysiological conditions. Various methodological procedures are in use for their measurement in biological fluids. From the time when capillary electrophoresis was introduced as a technology offering rapid separation of various ionic and/or ionizable compounds with low sample and solvent consumption, there were many attempts to use it for the measurement of amino acids present in physiological fluids. As a rule, these methods require derivatization procedures for detection purposes.Here, we present two protocols for the analysis of free amino acids employing free zone capillary electrophoresis. Main advantage of both methods is an absence of any derivatization procedures that permits the analysis of free amino acid in physiological fluids. The method using direct detection and carrier electrolyte consisting of disodium monophosphate (10 mM at pH 2.90) permits determination of compounds that absorb in UV region (aromatic and sulfur containing amino acids, as well as some peptides such as carnosine, reduced, and oxidized glutathione). The other method use indirect absorbance detection, employing 8 mM p-amino salicylic acid buffered with sodium carbonate at pH 10.2 as running electrolyte. It permits quantification of 30 underivatized physiological amino acids and peptides. In our experience factorial design represents a useful tool for final optimization of the electrophoretic conditions if it is necessary.

Clinical Nutrition in Critical Care Medicine - Guideline of the German Society for Nutritional Medicine (DGEM)

PURPOSE

Enteral and parenteral nutrition of adult critically ill patients varies in terms of the route of nutrient delivery, the amount and composition of macro- and micronutrients, and the choice of specific, immune-modulating substrates. Variations of clinical nutrition may affect clinical outcomes. The present guideline provides clinicians with updated consensus-based recommendations for clinical nutrition in adult critically ill patients who suffer from at least one acute organ dysfunction requiring specific drug therapy and/or a mechanical support device (e.g., mechanical ventilation) to maintain organ function.

METHODS

The former guidelines of the German Society for Nutritional Medicine (DGEM) were updated according to the current instructions of the Association of the Scientific Medical Societies in Germany (AWMF) valid for a S2k-guideline. According to the S2k-guideline classification, no systematic review of the available evidence was required to make recommendations, which, therefore, do not state evidence- or recommendation grades. Nevertheless, we considered and commented the evidence from randomized-controlled trials, meta-analyses and observational studies with adequate sample size and high methodological quality (until May 2018) as well as from currently valid guidelines of other societies. The liability of each recommendation was described linguistically. Each recommendation was finally validated and consented through a Delphi process.

RESULTS

In the introduction the guideline describes a) the pathophysiological consequences of critical illness possibly affecting metabolism and nutrition of critically ill patients, b) potential definitions for different disease phases during the course of illness, and c) methodological shortcomings of clinical trials on nutrition. Then, we make 69 consented recommendations for essential, practice-relevant elements of clinical nutrition in critically ill patients. Among others, recommendations include the assessment of nutrition status, the indication for clinical nutrition, the timing and route of nutrient delivery, and the amount and composition of substrates (macro- and micronutrients); furthermore, we discuss distinctive aspects of nutrition therapy in obese critically ill patients and those treated with extracorporeal support devices.

CONCLUSION

The current guideline provides clinicians with up-to-date recommendations for enteral and parenteral nutrition of adult critically ill patients who suffer from at least one acute organ dysfunction requiring specific drug therapy and/or a mechanical support device (e.g., mechanical ventilation) to maintain organ function. The period of validity of the guideline is approximately fixed at five years (2018-2023).

Glutamine Administration in Early or Late Septic Phase Downregulates Lymphocyte PD-1/PD-L1 Expression and the Inflammatory Response in Mice With Polymicrobial Sepsis

BACKGROUND

Sepsis is a severe inflammatory response to infection. Excessive compensation to inflammation leads to dysregulated immune response that ultimately results in organ damage and lethality of sepsis. This study administered glutamine (GLN) in the early or late phase of sepsis to investigate its effects on regulating leukocyte programmed cell death 1 (PD-1) and its ligand (programmed cell death ligand 1 [PD-L1]) expression, macrophage function, inflammation, and acute kidney injury in sepsis.

METHODS

Mice were randomly assigned to cecal ligation and puncture (CLP) or sham-operated groups. Septic mice were respectively injected once with saline or 0.75 g GLN/kg body weight at 3 or 10 hours post-CLP via tail vein. All mice were sacrificed 24 hours after CLP.

RESULTS

Sepsis enhanced the percentage of interferon-γ-expressing and interleukin (IL)-17A-expressing CD4⁺ T cells, expression of PD-1 on T cells, and PD-L1 on B cells and monocytes. Inflammatory mediator messenger RNA (mRNA) expression in kidney tissues and proapoptotic caspase-3 mRNA expression in mesenteric lymph nodes were also upregulated. GLN administration decreased plasma IL-6 level, downregulated the percentage of IL-17A-expressing CD4⁺ T cells, attenuated macrophage dysfunction, decreased caspase-3 mRNA expression, and reduced PD-1/PD-L1 expression by T and B cells. Histological findings also showed that kidney damage was attenuated. GLN administered at 3 and 10 hours after CLP offered nearly equal effects on PD-1/PD-L1 and inflammatory mediator expression after CLP.

CONCLUSIONS

These findings suggest that a single dose of GLN administration in either the early or late phase during sepsis promotes a more balanced immune regulation and reduced systemic and kidney inflammatory responses in mice.

A RandomizEd trial of ENtERal Glutamine to minimIZE thermal injury (The RE-ENERGIZE Trial): a clinical trial protocol

Background:

Burn injury represents a significant public health problem worldwide. More than in any other injury, the inflammation and catabolism associated with severe burns can exacerbate nutrient deficiencies resulting in impaired immune function and increased risk of developing infection, organ dysfunction and death. Consequently, over the last few decades numerous trials have evaluated the impact of different nutritional strategies in severe burn injury. Glutamine is of particular interest, as it appears vital for a number of key stress-response pathways in serious illness. The purpose of the current manuscript is to provide the rationale and protocol for a large clinical trial of supplemental enteral glutamine in 2700 severe burn-injured patients.

Methods:

We propose a multicentre, double-blind, pragmatic, randomized, clinical trial involving 80 tertiary intensive care unit (ICU) burn centres worldwide. We aim to enrol patients with deep second- and/or third-degree burns at moderate or high risk for death. We will exclude patients admitted > 72 h before screening and patients with advanced liver and kidney disease. The study intervention consists of enteral glutamine 0.5 g/kg/day vs. isocaloric maltodextran control delivered enterally. Primary outcome will be six-month mortality. Key secondary outcomes include time to discharge alive from hospital, ICU and hospital mortality, length of stay and health-related quality of life at six months.

Significance:

This study will be the first large international multicentre trial examining the effects of glutamine in burn patients. Negative or positive, the results of this trial will inform the clinical practice of burns care worldwide.

Clinicaltrials.gov ID #NCT00985205

Patients with severe burns need to recover in a hospital burn unit for a long time and are at high risk of developing infections and dying. Proper nutrition and certain nutrients may improve survival in these patients and shorten their stay in the burn unit. Glutamine is a building block of protein that is normally made in the body and is found in different foods we eat. It is of great interest because it has several beneficial effects on the body during serious illness, such as with burn injury. In this study, we will look at the effect of glutamine supplementation on survival and time spent in hospital. A total of 80 burn units around the world will enrol 2700 patients with 2nd or 3rd degree burns over 4 years. Patients will receive either glutamine powder or a placebo through a feeding tube or mixed with food, from admission to the burn unit, until a week after the burn wound has healed. The main outcome for this study is survival at 6 months. Other outcomes include the time taken to be discharged from hospital alive and duration of stay in the burn unit. This study will be the first large international multicentre trial examining the effects of glutamine in burn patients. Glutamine may lead to better survival and less complications in burn patients, who have a devastating and disabling burn injury. If the trial is positive, the results will be used to inform how nutrition should be given to such patients worldwide.

Effects of early enteral nutrition supplemented with collagen peptides on post-burn inflammatory responses in a mouse model

The effect of early enteral nutrition (EN) supplemented with Alaska pollock skin-derived collagen peptides (CPs) on post-burn inflammatory responses was investigated in a mouse model. Male blab/c mice were randomly assigned to four groups: a sham burn (SB) group, a control group (burn + EN + glycine, BE), a positive control group (burn + EN + glutamine, BEG) and a treatment group (burn + EN + CPs, BEC). Burn-induced increases of serum endotoxin level, and systemic and intestinal concentration of TNF-α and IL-6 were attenuated in BEG and BEC at post-burn day (PBD) 1, 3 and 7 (p < 0.05 vs. BE). Notably, BEC revealed a prominent decrease of the serum endotoxin level, TNF-α and IL-6 as compared to BEG at PBD 7 (p < 0.05). Furthermore, EN supplemented with CPs diminished the phosphorylation of intestinal NF-κB p65 and simultaneously down-regulated the mRNA expression of TNF-α and IL-6 in small intestine (p < 0.05 vs. BE). Also, it demonstrated a comparable effect with glutamine in ameliorating post-burn inflammatory responses in mice with burns. Therefore, CPs could be considered as a potential immunonutrient supplement in EN to improve post-burn outcomes in burn patients.

Therapeutic benefits of glutamine: An umbrella review of meta-analyses

Glutamine may be an essential amino acid in patients with catabolic disease, as it has been demonstrated that circulating glutamine levels drop during critical illness and following major surgery; this may result in an increase in secondary infection risk, recovery time and mortality rates. However, there is much discrepancy in the literature with regards to randomized controlled studies, and therefore, the present study is an umbrella review of published meta-analyses, conducted to examine the effectiveness of glutamine's role as a therapeutic agent. A search using PubMed, Cochrane Library and CINAHL from January 1st, 1980 to December 31st, 2016 was conducted using the following strategy: 'Glutamine AND (meta-analysis OR systematic review)' and publications were retrieved, which provided quantitative statistical analysis of pooled treatment effects on the relative risks of infectious complications, mortality and length of stay in hospital. A total of 22 meta-analyses were entered into the current umbrella review. As displayed in Tables I, II and III, these analyses are split into three groups, based on different parameters. Of the 19 meta-analyses investigating the effects of infectious complications, 15 identified statistically significant reductions in complications, with relative risks ranging between 0.42 and 0.93. In addition, 12 of the 18 meta-analyses analyzing the length of hospital stays presented statistically significant reductions in the length of stay, with reductions ranging between 0.19 to 4.73 days. Only 4 of the 15 meta-analyses studying mortality effects identified statistically significant reductions in mortality with relative risks ranging between 0.64 and 1.28. Statistically significant heterogeneity was observed in 16 of 22 meta-analyses, and publication bias was observed in five of 11 meta-analyses. Glutamine supplementation for critically ill or surgical patients through parenteral or enteral routes appears to reduce the rate of hospital acquired infectious complications and shortening of the length of stay in hospital. Furthermore, glutamine supplementation appeared to reduce the rate of in-patient mortality, but the majority of meta-analyses did not reach statistical significance. However, researchers must appreciate the positive results with caution in light of the fact that there exists statistically significant heterogeneity for the majority of meta-analyses, and statistically significant publication bias in almost half.

Gastrointestinal immune and microbiome changes during parenteral nutrition

Parenteral nutrition (PN) is a lifesaving therapy that provides intravenous nutrition support to patients who cannot, or should not, feed via the gastrointestinal (GI) tract. Unfortunately, PN also carries certain risks related to infection and metabolic complications compared with enteral nutrition. In this review, an overview of PN and GI immune and microbiome changes is provided. PN impacts the gut-associated lymphoid tissue functions, especially adaptive immune cells, changes the intestinal epithelium and chemical secretions, and significantly alters the intestinal microbiome. Collectively, these changes functionally result in increased susceptibility to infectious and injurious challenge. Since PN remains necessary in large numbers of patients, the search to improve outcomes by stimulating GI immune function during PN remains of interest. This review closes by describing recent advances in using enteric nervous system neuropeptides or microbially derived products during PN, which may improve GI parameters by maintaining immunity and physiology.

When Is It Appropriate to Use Glutamine in Critical Illness?

Glutamine is a nonessential amino acid, which under trauma or critical illness can become essential. A number of historic small single-center randomized controlled trials (RCTs) have demonstrated positive treatment effects on clinical outcomes with glutamine supplementation. Meta-analyses based on these trials demonstrated a significant reduction in hospital mortality, intensive care unit (ICU) length of stay (LOS), and hospital LOS with intravenous (IV) glutamine. Similar results were not noted in 2 large multicenter RCTs (REDOXS and MetaPlus) assessing the efficacy of glutamine supplementation in ventilated ICU patients. The REDOXS trial of 40 ICUs randomized 1223 ventilated ICU patients to glutamine (IV and enteral), antioxidants, both glutamine and antioxidants, or placebo. The main conclusions were a trend toward increased 28-day mortality and significant increased hospital and 6-month mortality in those who received glutamine. The MetaPlus trial of 14 ICUs, which randomized 301 ventilated ICU patients to glutamine-enriched enteral vs an isocaloric diet, noted increased 6-month mortality in the glutamine-supplemented group. Newer RCTs have focused on specific populations and have demonstrated benefits in burn and elective surgery patients with glutamine supplementation. Whether larger studies will confirm these findings is yet to be determined. Recent American Society for Parenteral and Enteral Nutrition guidelines recommend that IV and enteral glutamine should not be used in the critical care setting based on the moderate quality of evidence available. We agree with these recommendations and would encourage larger multicenter studies to evaluate the risks and benefits of glutamine in burn and elective surgery patients.

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.

Glutamine supplementation to prevent morbidity and mortality in preterm infants

BACKGROUND

Glutamine is a conditionally essential amino acid. Endogenous biosynthesis may be insufficient for tissue needs in states of metabolic stress. Evidence exists that glutamine supplementation improves clinical outcomes in critically ill adults. It has been suggested that glutamine supplementation may also benefit preterm infants.

OBJECTIVES

To determine the effects of glutamine supplementation on mortality and morbidity in preterm infants.

SEARCH METHODS

We used the standard search strategy of the Cochrane Neonatal Review Group. This included searches of the Cochrane Central Register of Controlled Trials (CENTRAL, 2015, Issue 12), MEDLINE, EMBASE and Maternity and Infant Care (to December 2015), conference proceedings and previous reviews.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials that compared glutamine supplementation versus no glutamine supplementation in preterm infants at any time from birth to discharge from hospital.

DATA COLLECTION AND ANALYSIS

We extracted data using the standard methods of the Cochrane Neonatal Review Group, with separate evaluation of trial quality and data extraction by two review authors. We synthesised data using a fixed-effect model and reported typical relative risk, typical risk difference and weighted mean difference.

MAIN RESULTS

We identified 12 randomised controlled trials in which a total of 2877 preterm infants participated. Six trials assessed enteral glutamine supplementation and six trials assessed parenteral glutamine supplementation. The trials were generally of good methodological quality. Meta-analysis did not find an effect of glutamine supplementation on mortality (typical relative risk 0.97, 95% confidence interval 0.80 to 1.17; risk difference 0.00, 95% confidence interval -0.03 to 0.02) or major neonatal morbidities including the incidence of invasive infection or necrotising enterocolitis. Three trials that assessed neurodevelopmental outcomes in children aged 18 to 24 months and beyond did not find any effects.

AUTHORS' CONCLUSIONS

The available trial data do not provide evidence that glutamine supplementation confers important benefits for preterm infants.

Glutamine supplementation to prevent morbidity and mortality in preterm infants

BACKGROUND

Glutamine is a conditionally essential amino acid. Endogenous biosynthesis may be insufficient for tissue needs in states of metabolic stress. Evidence exists that glutamine supplementation improves clinical outcomes in critically ill adults. It has been suggested that glutamine supplementation may also benefit preterm infants.

OBJECTIVES

To determine the effects of glutamine supplementation on mortality and morbidity in preterm infants.

SEARCH METHODS

We used the standard search strategy of the Cochrane Neonatal Review Group. This included searches of the Cochrane Central Register of Controlled Trials (CENTRAL, 2015, Issue 12), MEDLINE, EMBASE and Maternity and Infant Care (to December 2015), conference proceedings and previous reviews.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials that compared glutamine supplementation versus no glutamine supplementation in preterm infants at any time from birth to discharge from hospital.

DATA COLLECTION AND ANALYSIS

We extracted data using the standard methods of the Cochrane Neonatal Review Group, with separate evaluation of trial quality and data extraction by two review authors. We synthesised data using a fixed-effect model and reported typical relative risk, typical risk difference and weighted mean difference.

MAIN RESULTS

We identified 12 randomised controlled trials in which a total of 2877 preterm infants participated. Six trials assessed enteral glutamine supplementation and six trials assessed parenteral glutamine supplementation. The trials were generally of good methodological quality. Meta-analysis did not find an effect of glutamine supplementation on mortality (typical relative risk 0.97, 95% confidence interval 0.80 to 1.17; risk difference 0.00, 95% confidence interval -0.03 to 0.02) or major neonatal morbidities including the incidence of invasive infection or necrotising enterocolitis. Three trials that assessed neurodevelopmental outcomes in children aged 18 to 24 months and beyond did not find any effects.

AUTHORS' CONCLUSIONS

The available trial data do not provide evidence that glutamine supplementation confers important benefits for preterm infants.

Glutamine Supplementation in Intensive Care Patients: A Meta-Analysis of Randomized Clinical Trials

The role of glutamine (GLN) supplementation in critically ill patients is controversial. Our aim was to analyze its potential effect in patients admitted to intensive care unit (ICU).We performed a systematic literature review through Medline, Embase, Pubmed, Scopus, Ovid, ISI Web of Science, and the Cochrane-Controlled Trials Register searching for randomized clinical trials (RCTs) published from 1983 to 2014 and comparing GLN supplementation to no supplementation in patients admitted to ICU. A random-effect meta-analysis for each outcome (hospital and ICU mortality and rate of infections) of interest was carried out. The effect size was estimated by the risk ratio (RR).Thirty RCTs were analyzed with a total of 3696 patients, 1825 (49.4%) receiving GLN and 1859 (50.6%) no GLN (control groups). Hospital mortality rate was 27.6% in the GLN patients and 28.6% in controls with an RR of 0.93 (95% CI = 0.81-1.07; P = 0.325, I = 10.7%). ICU mortality was 18.0 % in the patients receiving GLN and 17.6% in controls with an RR of 1.01 (95% CI = 0.86-1.19; P = 0.932, I = 0%). The incidence of infections was 39.7% in GLN group versus 41.7% in controls. The effect of GLN was not significant (RR = 0.88; 95% CI = 0.76-1.03; P = 0.108, I = 56.1%).These results do not allow to recommend GLN supplementation in a generic population of critically ills. Further RCTs are needed to explore the effect of GLN in more specific cohort of patients.

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.

The protective effects of glutamine in a rat model of ventilator-induced lung injury

BACKGROUND

The mortality rate of patients with acute respiratory distress syndrome (ARDS) is still high despite the use of protective ventilatory strategies. We sought to examine the pharmacological effects of glutamine (GLN) in a two-hit model of endotoxin-induced inflammation followed by ventilator-induced lung injury (VILI). We hypothesized that the administration of GLN ameliorates the VILI.

METHODS

Sprague-Dawley rats were anesthetized and given lipopolysaccharide (LPS) intratracheally as a first hit to induce lung inflammation, followed 24 h later by a second hit of mechanical ventilation (MV) with either low tidal volume (6 mL/kg) with 5 cmH2O of positive end-expiratory pressure (PEEP) or high tidal volume (22 mL/kg) with zero PEEP for 4 h. GLN or lactated Ringer's solution as the placebo was administered intravenously 15 min prior to MV.

RESULTS

In the LPS-challenged rats ventilated with high tidal volume, the treatment with GLN improved lung injury indices, lung mechanics and cytokine responses compared with the placebo group.

CONCLUSIONS

The administration of GLN given immediately prior to MV may be beneficial in the context of reducing VILI.

Protective effect of glutamine in critical patients with acute liver injury

BACKGROUND

Glutamine (Gln) supplementation is known to decrease oxidative stress and inflammatory response, enhance resistance to infectious pathogens, shorten hospital stay, and decrease medical costs of patients. This study was undertaken to evaluate the relationship between the effect of early parenteral glutamine (Gln) supplement on acute liver injury (ALI) and heat shock protein 70 (HSP-70) expression in critical patients.

METHODS

Forty-four patients who had been admitted to the emergency intensive care unit (EICU) of Nanjing First Hospital Affiliated to Nanjing Medical University were randomly divided into a control group (n=22) and a Gln group (n=22). The patients of the two groups received enteral and parenteral nutrition. In addition, parenteral Gln 0.4 g/kg per day was given for 7 days in the Gln group. Serum HSP-70 and Gln were measured at admission and at 7 days after admission. Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), and total bilirubin (TBiL), serum levels of HSP-70 and Gln, mechanical ventilation (MV) time, ICU stay, peripheral blood of TNF-α, IL-6, CD3, CD4 and CD4/CD8 levels were also measured in the two groups.

RESULTS

In the Gln group, the levels of serum HSP-70 and Gln were significantly higher after Gln treatment than those before the treatment (P<0.01). HSP-70 level was positively correlated with the Gln level in the Gln group after administration of parenteral Gln (P<0.01). The levels of serum ALT, AST, TBiL and TNF-α, IL-6 were lower in the Gln group than in the non-Gln group (P<0.01). MV time and ICU stay were significantly different between the two groups (P<0.05). The levels of CD3, CD4 and CD4/CD8 were significantly higher in the Gln group than in the control group after treatment (P<0.05).

CONCLUSION

Parenteral Gln significantly increases the level of serum HSP70 in critically ill patients. The enhanced expression of HSP70 is correlated with improved outcomes of Gln-treated patients with acute liver injury.

Development and current use of parenteral nutrition in critical care - an opinion paper

Critically ill patients depend on artificial nutrition for the maintenance of their metabolic functions and lean body mass, as well as for limiting underfeeding-related complications. Current guidelines recommend enteral nutrition (EN), possibly within the first 48 hours, as the best way to provide the nutrients and prevent infections. EN may be difficult to realize or may be contraindicated in some patients, such as those presenting anatomic intestinal continuity problems or splanchnic ischemia. A series of contradictory trials regarding the best route and timing for feeding have left the medical community with great uncertainty regarding the place of parenteral nutrition (PN) in critically ill patients. Many of the deleterious effects attributed to PN result from inadequate indications, or from overfeeding. The latter is due firstly to the easier delivery of nutrients by PN compared with EN increasing the risk of overfeeding, and secondly to the use of approximate energy targets, generally based on predictive equations: these equations are static and inaccurate in about 70% of patients. Such high uncertainty about requirements compromises attempts at conducting nutrition trials without indirect calorimetry support because the results cannot be trusted; indeed, both underfeeding and overfeeding are equally deleterious. An individualized therapy is required. A pragmatic approach to feeding is proposed: at first to attempt EN whenever and as early as possible, then to use indirect calorimetry if available, and to monitor delivery and response to feeding, and finally to consider the option of combining EN with PN in case of insufficient EN from day 4 onwards.

Glutamine attenuates acute lung injury caused by acid aspiration

Inadequate ventilator settings may cause overwhelming inflammatory responses associated with ventilator-induced lung injury (VILI) in patients with acute respiratory distress syndrome (ARDS). Here, we examined potential benefits of glutamine (GLN) on a two-hit model for VILI after acid aspiration-induced lung injury in rats. Rats were intratracheally challenged with hydrochloric acid as a first hit to induce lung inflammation, then randomly received intravenous GLN or lactated Ringer's solution (vehicle control) thirty min before different ventilator strategies. Rats were then randomized to receive mechanical ventilation as a second hit with a high tidal volume (TV) of 15 mL/kg and zero positive end-expiratory pressure (PEEP) or a low TV of 6 mL/kg with PEEP of 5 cm H2O. We evaluated lung oxygenation, inflammation, mechanics, and histology. After ventilator use for 4 h, high TV resulted in greater lung injury physiologic and biologic indices. Compared with vehicle treated rats, GLN administration attenuated lung injury, with improved oxygenation and static compliance, and decreased respiratory elastance, lung edema, extended lung destruction (lung injury scores and lung histology), neutrophil recruitment in the lung, and cytokine production. Thus, GLN administration improved the physiologic and biologic profiles of this experimental model of VILI based on the two-hit theory.

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.

Oral L-glutamine administration attenuated cutaneous wound healing in Wistar rats

The objective of this study was to evaluate the wound healing potential of L-glutamine in laboratory rats using excision and incision wound models. Excision wounds of size 500 mm(2) and depth 2 mm were made on the dorsal portion of male Wistar rats (230-250 g) and were used for the study of oral L-glutamine (1 g/kg) treatment on the rate of contraction of wound and epithelisation. Histological evaluation of wound tissue was also performed. Six-centimetre-long two linear-paravertebral incisions in male Wistar rats (230-250 g) were used to study the effect of L-glutamine (1 g/kg, p.o.) treatment on tensile strength, total protein and hydroxyproline content in the incision model. Oral administration of L-glutamine (1 g/kg) significantly decreased wound area, epithelisation period and wound index, whereas the rate of wound contraction significantly increased (P < 0·001) when compared with vehicle control rats in the excision wound model. Tensile strength, hydroxyproline content and protein level were significantly increased (P < 0·001) in L-glutamine (1 g/kg, p.o.)-treated rats when compared with vehicle control rats in the incision wound model. Histological evaluation of wound tissue from L-glutamine (1 g/kg, p.o.)-treated rats showed complete epithelialisation with new blood vessel formation and high fibrous tissues in the excision wound model. In conclusion, oral administration of l-glutamine (1 g/kg) promotes wound healing by acting on various stages of wound healing such as collagen synthesis, wound contraction and epithelialisation.

Glutamine modulates CD8αα(+) TCRαβ(+) intestinal intraepithelial lymphocyte expression in mice with polymicrobial sepsis

OBJECTIVES

CD8αα(+) T-cell receptor (TCR) αβ(+) intestinal intraepithelial lymphocytes (IELs) were found to have a regulatory function in the mucosal immune system. Glutamine (GLN) is an amino acid with immunomodulatory effects. The aim of this study was to investigate the influences of GLN on the proportion of CD8αα(+) TCRαβ(+) IELs and associated inflammatory mediator gene expression in polymicrobial sepsis.

METHODS

Mice were randomly assigned to a normal (NC) group, a sepsis with saline (SS) group, or a sepsis with GLN (SG) group. The NC group was fed a chow diet. Sepsis was induced by cecal ligation and puncture (CLP). The SS group was administered saline, and the SG group was given 0.75 g GLN/kg body weight via a tail vein after CLP. Mice were sacrificed 12 h after CLP, and CD8αα(+) TCRαβ(+) IELs were isolated for further analysis.

RESULTS

Sepsis resulted in a lower percentage of CD8αα(+) TCRαβ(+) IELs, and higher messenger (m)RNA expression of complement 5a receptor, interleukin (IL)-2 receptor β, IL-15 receptor α, and interferon-γ by CD8αα(+) TCRαβ(+) IELs. These immunomodulatory mediator genes decreased, whereas IL-7 receptor and transforming growth factor-β expressions increased in CD8αα(+) TCRαβ(+) IELs in septic mice with GLN administration. Annexin V⁄7-AAD staining revealed significantly lower apoptotic rates of CD8αα(+) TCRαβ(+) IELs in the SG group.

CONCLUSION

A single dose of GLN administered after the initiation of sepsis increased the percentage of CD8αα(+) TCRαβ(+) IELs, prevented apoptosis of CD8αα(+) TCRαβ(+) IELs, and downregulated CD8αα(+) TCRαβ(+) IEL-expressed inflammatory mediators. These results suggest that GLN influenced the distribution and cytokine secretion of the CD8αα(+) TCRαβ(+) IEL subset, which may ameliorate sepsis-induced inflammatory reactions and thus mitigate the severity of intestinal epithelial injury.

A systematic literature review and meta-analysis of randomized clinical trials of parenteral glutamine supplementation

BACKGROUND & AIMS

Glutamine supplementation has been associated with reduced mortality, infections and hospital length of stay in critically ill patients and patients undergoing major surgery. We carried out a meta-analysis to examine randomized clinical trial (RCT)-based evidence of these effects.

METHODS

Based on a systematic database search, RCTs published since 1990 were included if they evaluated the effect of parenteral glutamine supplementation against a background of parenteral nutrition. Enteral (tube) feeding in a proportion of patients was allowable. Information on RCT methodology, quality and outcomes was extracted. Random effects meta-analysis followed the DerSimonian-Laird approach.

RESULTS

Forty RCTs were eligible for meta-analysis. Parenteral glutamine supplementation was associated with a non-significant 11% reduction in short-term mortality (RR = 0.89; 95% CI, 0.77-1.04). Infections were significantly reduced (RR = 0.83; 95% CI, 0.72-0.95) and length of stay was 2.35 days shorter (95% CI, -3.68 to -1.02) in the glutamine arms. Meta-analysis results were strongly influenced by one recent trial. An element of publication bias could not be excluded.

CONCLUSION

Parenteral glutamine supplementation in severely ill patients may reduce infections, length of stay and mortality, but substantial uncertainty remains. Unlike previous meta-analyses, we could not demonstrate a significant reduction in mortality.

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.

Glutamine supplementation to prevent morbidity and mortality in preterm infants

BACKGROUND

Glutamine is a conditionally essential amino acid. Endogenous biosynthesis may be insufficient for tissue needs in states of metabolic stress. Evidence exists that glutamine supplementation improves clinical outcomes in critically ill adults. It has been suggested that glutamine supplementation may also benefit preterm infants.

OBJECTIVES

To determine the effects of glutamine supplementation on mortality and morbidity in preterm infants.

SEARCH METHODS

We used the standard search strategy of the Cochrane Neonatal Review Group. This included searches of the Cochrane Central Register of Controlled Trials (The Cochrane Library, 2011, Issue 4), MEDLINE, EMBASE and CINAHL (to November 2011), conference proceedings and previous reviews.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials that compared glutamine supplementation versus no glutamine supplementation in preterm infants at any time from birth to discharge from hospital.

DATA COLLECTION AND ANALYSIS

We extracted data using the standard methods of the Cochrane Neonatal Review Group, with separate evaluation of trial quality and data extraction by two review authors. We synthesised data using a fixed-effect model and reported typical relative risk, typical risk difference and weighted mean difference.

MAIN RESULTS

We identified 11 randomised controlled trials in which a total of 2771 preterm infants participated. Five trials assessed enteral glutamine supplementation and six trials assessed parenteral glutamine supplementation. The trials were generally of good methodological quality. Meta-analysis did not detect a statistically significant effect of glutamine supplementation on mortality [typical relative risk 0.98 (95% confidence interval 0.80 to 1.18); risk difference 0.00 (95% confidence interval -0.03 to 0.02)] or major neonatal morbidities including the incidence of invasive infection or necrotising enterocolitis. Two trials that assessed neurodevelopmental outcomes at 18 to 24 months did not find any statistically significant differences in various assessments.

AUTHORS' CONCLUSIONS

The available trial data do not provide evidence that glutamine supplementation confers important benefits for preterm infants.

Nutrition delivery for obese ICU patients: delivery issues, lack of guidelines, and missed opportunities

The most appropriate enteral formula for the severely obese population has yet to be determined. The obese patient in the intensive care unit (ICU) creates numerous difficulties for managing care, one being the ability to deliver appropriate and timely nutrition. Access for nutrition therapy, either enteral or parenteral, can also create a challenge. Currently, no specific guidelines are available on a national or international scale to address the issues of how and when to feed the obese patient in the ICU. A bias against feeding these patients exists, secondary to the perception that an enormous quantity of calories is stored in adipose tissue. Making a specialty enteral formula for obesity from existing commercial formulas and other modular nutrient components is not practical, secondary to difficulty with solubility issues, dilution of the formula, and safety concerns. Using today's concepts and current metabolic data, a formula could be produced that would address many of the specific metabolic derangements noted in obesity. This formula should have a high-protein, low-carbohydrate content with at least a portion of the lipid source coming from fish oil. Specific nutrients that may be beneficial in obesity include arginine, glutamine, leucine, L-carnitine, lipoic acid, S-adenosylmethionine, and betaine. Certain trace minerals such as magnesium, zinc, and selenium may also be of value in the obese population. The concept of a specific bariatric formulation for the ICU setting is theoretically sound, is scientifically based, and could be delivered to patients safely.

Capillary electrophoresis of free amino acids in physiological fluids without derivatization employing direct or indirect absorbance detection

Whole blood and/or plasma amino acids are useful for monitoring whole body protein and amino acid metabolism in an organism under various physiological and pathophysiological conditions. Various methodological procedures are in use for their measurement in biological fluids. From the time when capillary electrophoresis was introduced as a technology offering rapid separation of various ionic and/or ionizable compounds with low sample and solvent consumption, there were many attempts to use it for the measurement of amino acids present in physiological fluids. As a rule, these methods require derivatization procedures for detection purposes.Here, we present two protocols for the analysis of free amino acids employing free zone capillary electrophoresis. Main advantage of both methods is an absence of any derivatization procedures that permits the analysis of free amino acid in physiological fluids. The method using direct detection and carrier electrolyte consisting of disodium monophosphate (10 mM at pH 2.90) permits determination of compounds that absorb in UV region (aromatic and sulfur containing amino acids, as well as some peptides, such as carnosine, reduced and oxidized glutathione). The other method uses indirect absorbance detection, employing 8 mM p-amino salicylic acid buffered with sodium carbonate at pH 10.2 as running electrolyte. It permits quantification of 30 underivatized physiological amino acids and peptides. In our experience, factorial design represents a useful tool for final optimization of the electrophoretic conditions if it is necessary.

Clinical review: Optimizing enteral nutrition for critically ill patients--a simple data-driven formula

In modern critical care, the paradigm of 'therapeutic nutrition' is replacing traditional 'supportive nutrition'. Standard enteral formulas meet basic macro- and micronutrient needs; therapeutic enteral formulas meet these basic needs and also contain specific pharmaconutrients that may attenuate hyperinflammatory responses, enhance the immune responses to infection, or improve gastrointestinal tolerance. Choosing the right enteral feeding formula may positively affect a patient's outcome; targeted use of therapeutic formulas can reduce the incidence of infectious complications, shorten lengths of stay in the ICU and in the hospital, and lower risk for mortality. In this paper, we review principles of how to feed (enteral, parenteral, or both) and when to feed (early versus delayed start) patients who are critically ill. We discuss what to feed these patients in the context of specific pharmaconutrients in specialized feeding formulations, that is, arginine, glutamine, antioxidants, certain ω-3 and ω-6 fatty acids, hydrolyzed proteins, and medium-chain triglycerides. We summarize current expert guidelines for nutrition in patients with critical illness, and we present specific clinical evidence on the use of enteral formulas supplemented with anti-inflammatory or immune-modulating nutrients, and gastrointestinal tolerance-promoting nutritional formulas. Finally, we introduce an algorithm to help bedside clinicians make data-driven feeding decisions for patients with critical illness.