Role of glutamine in bacterial transcytosis and epithelial cell injury

Nutrition and Nonalcoholic Fatty Liver Disease: Current Perspectives

Nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis are diseases in their own right as well as modifiable risk factors for cardiovascular disease and type 2 diabetes. With expanding knowledge on NAFLD pathogenesis, insights have been gleaned into molecular targets for pharmacologic and nonpharmacologic approaches. Lifestyle modifications constitute a cornerstone of NAFLD management. This article reviews roles of key dietary macronutrients and micronutrients in NAFLD pathogenesis and their effects on molecular targets shared with established or emerging pharmacotherapies. Based on current evidence, a recommendation for a dietary framework as part of the comprehensive management strategy for NAFLD is provided.

Enteric Pathogens and Their Toxin-Induced Disruption of the Intestinal Barrier through Alteration of Tight Junctions in Chickens

Maintaining a healthy gut environment is a prerequisite for sustainable animal production. The gut plays a key role in the digestion and absorption of nutrients and constitutes an initial organ exposed to external factors influencing bird’s health. The intestinal epithelial barrier serves as the first line of defense between the host and the luminal environment. It consists of a continuous monolayer of intestinal epithelial cells connected by intercellular junctional complexes which shrink the space between adjacent cells. Consequently, free passing of solutes and water via the paracellular pathway is prevented. Tight junctions (TJs) are multi-protein complexes which are crucial for the integrity and function of the epithelial barrier as they not only link cells but also form channels allowing permeation between cells, resulting in epithelial surfaces of different tightness. Tight junction’s molecular composition, ultrastructure, and function are regulated differently with regard to physiological and pathological stimuli. Both in vivo and in vitro studies suggest that reduced tight junction integrity greatly results in a condition commonly known as “leaky gut”. A loss of barrier integrity allows the translocation of luminal antigens (microbes, toxins) via the mucosa to access the whole body which are normally excluded and subsequently destroys the gut mucosal homeostasis, coinciding with an increased susceptibility to systemic infection, chronic inflammation and malabsorption. There is considerable evidence that the intestinal barrier dysfunction is an important factor contributing to the pathogenicity of some enteric bacteria. It has been shown that some enteric pathogens can induce permeability defects in gut epithelia by altering tight junction proteins, mediated by their toxins. Resolving the strategies that microorganisms use to hijack the functions of tight junctions is important for our understanding of microbial pathogenesis, because some pathogens can utilize tight junction proteins as receptors for attachment and subsequent internalization, while others modify or destroy the tight junction proteins by different pathways and thereby provide a gateway to the underlying tissue. This review aims to deliver an overview of the tight junction structures and function, and its role in enteric bacterial pathogenesis with a special focus on chickens. A main conclusion will be that the molecular mechanisms used by enteric pathogens to disrupt epithelial barrier function in chickens needs a much better understanding, explicitly highlighted for Campylobacter jejuni, Salmonella enterica and Clostridium perfringens. This is a requirement in order to assist in discovering new strategies to avoid damages of the intestinal barrier or to minimize consequences from infections.

Hepatic encephalopathy: Ever closer to its big bang

Hepatic encephalopathy (HE) is a neuropsychiatric disorder that commonly complicates the course of patients with liver disease. Despite the fact that the syndrome was probably first recognized hundreds of years ago, the exact pathogenesis still remains unclear. Minimal hepatic encephalopathy (MHE) is the earliest form of HE and is estimated to affect more that 75% of patients with liver cirrhosis. It is characterized by cognitive impairment predominantly attention, reactiveness and integrative function with very subtle clinical manifestations. The development of MHE is associated with worsen in driving skills, daily activities and the increase of overall mortality. Skeletal muscle has the ability to shift from ammonia producer to ammonia detoxifying organ. Due to its large size, becomes the main ammonia detoxifying organ in case of chronic liver failure and muscular glutamine-synthase becomes important due to the failing liver and brain metabolic activity. Gut is the major glutamine consumer and ammonia producer organ in the body. Hepatocellular dysfunction due to liver disease, results in an impaired clearance of ammonium and in its inter-organ trafficking. Intestinal bacteria, can also represent an extra source of ammonia production and in cirrhosis, small intestinal bacterial overgrowth and symbiosis can be observed. In the study of HE, to get close to MHE is to get closer to its big bang; and from here, to travel less transited roads such as skeletal muscle and intestine, is to go even closer. The aim of this editorial is to expose this road for further and deeper work.

Dietary supplementation of L-glutamine and L-glutamate in broiler chicks subjected to delayed placement

This study was conducted to investigate the effect of dietary glutamine (Gln) + glutamic acid (Glu) supplementation on growth performance and physiological stress response in broiler chickens subjected to 24 h delay in placement. Equal number of day-old broiler chicks were assigned to either immediate placement or with 24 h delay in placement with no access to feed and water. Chicks from each placement group were fed either standard starter diet (control) or standard starter diet +1% AminoGut (AG; mixture of 10% Gln and 10% Glu) from 1 to 21 d. Blood and duodenal samples were collected at 21 d for analysis of serum levels of ceruloplasmin (CER), ovotransferin (OVT) and α-1 acid glycoprotein (AGP), duodenal heat shock protein (HSP) 70 expression, and villi length and crypt depth. Results showed that delayed placement for 24 h was detrimental to weight gain during the starter phase (1 to 21 d) but not thereafter. AG supplementation was not able to eliminate that reduction in weight gain and feed intake during the starter stage. However, the observed enhancement in villi length and crypt depth at d 21 resulted in improvement of FCR and weight gain during the finisher stage (22 to 42 d) and consequently the overall period (1 to 42 d). Broiler chickens supplemented with AG also showed lower mortality rate, and higher AGP, OVT, CER, and HSP 70 expression compared to their control counterparts. Based on AGP, OVT, CER, and HSP 70 expression, there is no indication that delayed placement was physiologically stressful to the broiler chickens at 21 d of age.

L-Glutamine Supplementation Improves Nelfinavir-Associated Diarrhea in HIV-Infected Individuals

PURPOSE

To determine whether L-glutamine decreases the severity of nelfinavir-associated diarrhea in HIV-infected individuals. Other endpoints include the effect on quality of life, muscle-wasting syndrome, CD4 counts, and viral load.

METHOD

HIV-infected patients with nelfinavir-associated diarrhea for >1 month were randomized to receive L-glutamine 30 g/day or placebo for 10 days in a prospective, double-blind, crossover study. Diarrhea was measured on a scale ranging from grade 0 (no diarrhea) to grade 4 (severe diarrhea, > 7 stools/day). Quality of life was assessed by the Medical Outcome Study (MOS) HIV questionnaire.

RESULTS

Twenty-five participants completed the study. There was a significant difference between the L-glutamine and placebo arms on the mean grade of diarrhea (0.762 vs. 1.850, p <.01) when placebo was administered first. When L-glutamine was administered first, there was a significant crossover effect (p <.02), with similar mean grades of diarrhea in the two groups. There was also a significant difference between L-glutamine and placebo in the mean change in MOS scores from baseline (1.48 vs. -2.19, p <.017). There were no significant differences between treatment groups for the other endpoints.

CONCLUSIONS

In this population of HIV-positive participants, L-glutamine 30 g/day significantly (p <.01) reduced the severity of nelfinavir-associated diarrhea and produced improved quality of life compared with placebo.

Glutamine supplementation for young infants with severe gastrointestinal disease

BACKGROUND

Endogenous glutamine biosynthesis may be insufficient to meet the needs of people with severe gastrointestinal disease. Results from studies using experimental animal models of gastrointestinal disease have suggested that glutamine supplementation improves clinical outcomes. This review examines evidence on the effect of glutamine supplementation in young infants with severe gastrointestinal disease.

OBJECTIVES

To assess the effect of supplemental glutamine on mortality and morbidity in young infants with severe gastrointestinal disease.

SEARCH METHODS

We searcheed the Cochrane Central Register of Controlled Trials (The Cochrane Library, 2014, Issue 8), MEDLINE, EMBASE, and CINAHL (from inception to September 2014), conference proceedings, and reference lists from previous reviews.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials that compared glutamine supplementation versus no glutamine supplementation in infants up to three months old (corrected for preterm birth if necessary) with severe gastrointestinal disease defined as a congenital or acquired gastrointestinal condition that is likely to necessitate providing parenteral nutrition for at least 24 hours.

DATA COLLECTION AND ANALYSIS

Two review authors assessed trial eligibility and risk of bias and undertook data extraction independently. We analysed the treatment effects in the individual trials and reported the risk ratio (RR) and risk difference (RD) for dichotomous data and mean difference for continuous data, with 95% confidence intervals (CI). We used a fixed-effect model in meta-analyses and explored the potential causes of heterogeneity in sensitivity analyses.

MAIN RESULTS

We found three trials in which a total of 274 infants participated. The trials were of good methodological quality but were too small to detect clinically important effects of glutamine supplementation. Meta-analyses did not reveal a statistically significant difference in the risk of death before hospital discharge (typical RR 0.79, 95% CI 0.19 to 3.20; typical RD -0.01, 95% CI -0.05 to 0.03) or in the rate of invasive infection (typical RR 1.37, 95% CI 0.89 to 2.11; typical RD 0.08, 95% CI -0.03 to 0.18]).

AUTHORS' CONCLUSIONS

The available data from randomised controlled trials do not suggest that glutamine supplementation has any important benefits for young infants with severe gastrointestinal disease.

Helicobacter bilis gamma-glutamyltranspeptidase enhances inflammatory stress response via oxidative stress in colon epithelial cells

Helicobacter bilis (H. bilis) infection is associated with cases of inflammatory bowel Disease, thyphlocolitis, hepatitis and cholecystitis. However, little is known about the bacterial virulence determinants or the molecular mechanisms involved. Recently, H. bilis γ-glutamyltranspeptidase (HBgGT) was shown to be a virulence factor decreasing host cell viability. Bacterial gGTs play a key role in synthesis and degradation of glutathione and enables the bacteria to utilize extracellular glutamine and glutathione as sources of glutamate. gGT-mediated loss of cell viability has so far been linked to DNA damage via oxidative stress, but the signaling cascades involved herein have not been described. In this study, we identified enhanced ROS production induced by HBgGT as a central factor involved in the activation of the oxidative stress response cascades, which finally activate CREB, AP-1 and NF-κB in H. bilis infected colon cancer cells. IL-8, an important pro-inflammatory chemokine that is a common downstream target of these transcription factors, was up-regulated upon H. bilis infection in an HBgGT dependent manner. Moreover, the induction of these signaling responses and inflammatory cytokine production in host cells could be linked to HBgGT-mediated glutamine deprivation. This study implicates for the first time HBgGT as an important regulator of signaling cascades regulating inflammation in H. bilis infected host epithelial cells that could be responsible for induction of inflammatory disorders by the bacterium.

The protective effects of glutamine on radiation-induced diarrhea

INTRODUCTION

Glutamine is a neutral amino acid that is used by rapidly dividing cells such as erythrocytes, lymphocytes, and fibroblasts. It is also the substrate of glutathione synthesis. In normal metabolic rates, glutamine is an amino acid synthesized endogenously, but in high metabolic conditions such as cancer, it must be taken exogenously. Animal studies strongly demonstrate that glutamine protects both the upper and lower gastrointestinal tract mucosa from the effects of chemotherapy, radiotherapy, or other causes of injury. In this study, we investigated the protective effect of glutamine on radiation-induced diarrhea.

PATIENTS AND METHOD

The patients were divided into glutamine-treated and placebo groups. In the glutamine-treated group, 15 g of oral glutamine was administered three times daily. The patients were evaluated for diarrhea grade according to the National Cancer Institute Common Toxicity Criteria version 3.0, (Table 1), need for loperamide use, need for supportive parenteral therapy, and treatment breaks due to diarrhea.

RESULTS

There was no difference in overall diarrhea incidence when the two groups were compared. When diarrhea grade was evaluated, none of the patients in the glutamine-treated group had grade 3-4 diarrhea, but in the placebo group, grade 3-4 diarrhea was seen in 69 % of the patients. In the placebo-treated group, patients requiring loperamide and parenteral supportive therapy were 39 and 92 %, respectively. There was no treatment break in glutamine-treated patients.

CONCLUSION

Glutamine may have protective effect on radiation-induced severe diarrhea.

Effect of parenteral administration of glutamine on autophagy of liver cell and immune responses in weaned calves

The objectives of this study were to determine the effects of an increased jugular supply of L-Gln on post-weaning growth, immune responses, intestinal morphology and autophagy of weaned calves. At 35 days of age, 24 Holstein calves (initial 50 ± 1.5 kg; 35 ± 2 day of age) were randomly allocated to four treatments, and each treatment included five male and one female calves. Holstein calves were assigned to treatments of (i) i.v. infusion of 2 l of 0.85% NaCl, Control group [C]; (ii) i.v. infusion of 8 g/day of L-Gln mixed with 2 l of 0.85% NaCl solution [L]; (iii) i.v. infusion of 16 g/day of L-Gln mixed with 2 l of 0.85% NaCl solution [M]; and (iv) i.v. infusion of 32 g/day of L-Gln mixed with 2 l of 0.85% NaCl [H]; The infusion was 2 h/day for each of 14 consecutive days starting on day 1 after weaning. Feed and water were freely available to all calves. All calves were killed on the 14th day post-weaning for measurements of autophagy of liver cell and intestinal morphology. Gln has no effect on dry matter intake (DMI) and average daily gain (ADG). Gln infusion increased quadratically the abundance of CD4+, monocyte and the ratio of CD4+/CD8+. The urea N, Gln and Glucose in plasma increased linearly with increasing Gln loads. Gln infusion increased quadratically villus height and crypt depth of intestine. The autophagy level of liver cell was improved with the Gln infusion dose increased.

Amelioration of radiation-induced acute inflammation and mucosal atrophy by beta-hydroxy-beta-methylbutyrate, L-glutamıne, and L-argınıne: results of an experimental study

PURPOSE

We aimed to evaluate the effects of β-hydroxy-β-methylbutyrate, L-glutamine, and L-arginine (HMB/Glu/Arg) on radiation-induced acute inflammation and mucosal atrophy in the oral mucosa.

METHODS

Twenty-eight rats were divided into four groups. group (G) 1 was defined as control group, and G2 was the radiation therapy (RT) group. G3 and G4 were HMB/Glu/Arg control and 17 Gy RT plus HMB/Glu/Arg groups, respectively. A single dose of 17 Gy RT was given to the head and neck area, and the active supplement consisting of 5.2 g of HMB, 29.6 g arginine, and 29.6 g of glutamine which was equivalent to 60 kg adult dose was calculated for each rat and administrated orally. HMB/Glu/Arg started from the day of RT and continued until the animals were sacrificed 7 days after the RT. The extent of acute inflammation and mucosal atrophy for each rat was quantified with image analysis of histological sections of the oral mucosa.

RESULTS

There were significant differences in terms of epithelial thickness, subepithelial edema, inflammation, and congestion between all groups (p values were <0.001, 0.003, <0.001, and 0.001 for each parameter, respectively). Using HMB/Glu/Arg alone led to hypertrophic changes in the epithelial layer. Moreover, when used with RT, HMB/Glu/Arg reversed radiation-induced epithelial atrophy (p, 0.006) and decreased radiation-induced inflammation at a significant level (p, 0.007).

CONCLUSION

Concomitant use of HMB/Glu/Arg appears to ameliorate the radiation-induced acute inflammation and mucosal atrophy which represent the early phase of acute oral mucositis; however, this finding should be clarified with further clinical studies.

Glutamine supplementation for young infants with severe gastrointestinal disease

BACKGROUND

Endogenous glutamine biosynthesis may be insufficient to meet the needs of people with severe gastrointestinal disease. Studies using experimental animal models and controlled trials in adult patients with severe gastrointestinal disease have suggested that glutamine supplementation improves clinical outcomes. This review examines evidence for the effect of glutamine supplementation in young infants with severe gastrointestinal disease.

OBJECTIVES

To assess the evidence from randomised controlled trials that providing supplemental glutamine reduces mortality and morbidity in young infants with severe gastrointestinal disease.

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, 2012, Issue 1), 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 infants up to three months old (corrected for preterm birth if necessary) with severe gastrointestinal disease defined as a congenital or acquired gastrointestinal condition that is likely to necessitate providing parenteral nutrition for at least 24 hours.

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 risk ratio (RR), typical risk difference (RD), and weighted mean difference (WMD).

MAIN RESULTS

We found two trials in which a total of 100 infants participated. The trials were of good methodological quality but were too small to detect clinically important effects of glutamine supplementation. Meta-analysis did not reveal a statistically significant difference in the risk of death before hospital discharge (typical RR 1.57; 95% confidence interval (95% CI) 0.25 to 9.66; RD 0.02; 95% CI -0.06 to 0.10) or in the rate of invasive infection [typical RR 1.22; 95% CI 0.55 to 2.70; RD 0.04; 95% CI -0.12 to 0.20).

AUTHORS' CONCLUSIONS

The available data from randomised controlled trials are insufficient to determine whether glutamine supplementation has any important benefits for young infants with severe gastrointestinal disease.

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.

Preventive oral supplementation with glutamine and arginine has beneficial effects on the intestinal mucosa and inflammatory cytokines in endotoxemic rats

The objective of this study was to evaluate the effect of oral supplementation with a combination of arginine and glutamine on the intestinal mucosa and inflammatory cytokines of lipopolysaccharide (LPS)-induced adult rats. Fifty Sprague-Dawley rats (average weight of 185 ± 15 g) were randomly divided into five groups: control group A (CA) and control group B (CB), both orally supplemented with 0.9% saline; group Arg, supplemented with 300 mg/kg day(-1) arginine; group Gln, supplemented with 300 mg/kg day(-1) glutamine; group AG, supplemented with 150 mg/kg day(-1) arginine and 150 mg/kg day(-1) glutamine. The experiment lasted for 2 weeks. Food intake and body weight were measured during the experiment. At 10.00 h of day 15, animals were injected with 4 mg/kg LPS (group CB, Arg, Gln, and AG) or sterile saline (group CA) after supplementation. Then at 14.00 h, all animals were killed and blood and tissue collected. The results showed that compared with group CB, arginine concentration tended to be increased (P > 0.05) in group Arg and AG, while there was no significant difference in glutamine concentration among the groups challenged with LPS. Oral supplementation with arginine or/and glutamine mitigated morphology impairment (lower villus height, P < 0.05) in the jejunum and ileum induced by LPS challenge. LPS administration resulted in a significant increase in TNF-α, IL-1β, IL-6 and IL-10 mRNA abundance. Arginine only significantly decreased TNF-α mRNA abundance in the ileum, while glutamine significantly decreased both TNF-α and IL-10 mRNA in the ileum. A combination of arginine and glutamine significantly decreased TNF-α and IL-1β mRNA abundance in both the jejunum and ileum, while they also significantly decreased anti-inflammatory IL-10 in the ileum. These results revealed that an oral supply of combined arginine and glutamine had more favorable effects on the intestinal mucosa and inflammatory cytokines than a supply of arginine or glutamine alone.

Enteral supplementation with glycyl-glutamine improves intestinal barrier function after liver transplantation in rats

BACKGROUND

Most patients after liver transplantation (LT) suffer from intestinal barrier dysfunction. Glycyl-glutamine (Gly-Gln) by parenteral supplementation is hydrolyzed to release glutamine, which improves intestinal barrier function in intestinal injury. This study aimed to investigate the effect of Gly-Gln by enteral supplementation on intestinal barrier function in rats after allogenetic LT under immunosuppressive therapy.

METHODS

Twelve inbred Lewis rats were selected randomly as donors, and 24 inbred Brown Norway (BN) rats as recipients of allogenetic LT. The recipients were divided into a control group (Ala, n=12) and an experimental group (Gly-Gln, n=12). In each group, 6 normal BN rats were sampled for normal parameters on preoperative day 3. The 6 recipients in the control group received alanine (Ala) daily by gastric perfusion for 3 preoperative days and 7 postoperative days, and the 6 recipients in the experimental group were given Gly-Gln in the same manner. The 12 BN recipients underwent orthotopic LT under sterile conditions after a 3-day fast and were given immunosuppressive therapy for 7 days. They were harvested for sampling on postoperative day 8. The following parameters were assessed: intestinal mucosal protein content, mucosal ultrastructure, ileocecal sIgA content, portal plasma levels of endotoxin and TNF-alpha, and bacterial translocation.

RESULTS

All recipients were alive after LT. On preoperative day 3, all parameters were similar in the two groups. On postoperative day 8, all parameters in the two groups were remarkably changed from those on preoperative day 3. However, compared to the Ala group, supplementation with Gly-Gln increased the levels of intestinal mucosal protein and ileocecal sIgA, improved mucosal microvilli, and decreased portal plasma levels of endotoxin and TNF-alpha as well as bacterial translocation.

CONCLUSION

Enteral supplementation with Gly-Gln improved intestinal barrier function after allogenetic LT in rats.

Intestinal growth and morphology is associated with the increase in heat shock protein 70 expression in weaning piglets through supplementation with glutamine

The objectives of this study were to determine the effects of oral Gln supplementation on growth performance, intestinal morphology, and expression of heat shock protein (Hsp) 70 in weaning piglets. A total of 65 piglets after weaning at 21 d of age (d 0) were used in this experiment. Five piglets were randomly selected and euthanized initially at d 0 to determine baseline values for the expression of Hsp70 in the small intestine. The remaining piglets were randomly assigned to 1 of 2 treatments and received 0 or 1 g of oral Gln/kg of BW every 12 h. After piglets were humanely killed at d 3, 7, and 14 postweaning, the duodenum, jejunum, and ileum of piglets were sampled to evaluate intestinal morphology and the expression and localization of Hsp70. The results indicated that oral Gln supplementation increased plasma concentrations of Gln compared with those in control piglets (P < 0.05). Average daily gain and ADFI were greater in piglets orally supplemented with Gln than in control piglets during the whole period (P < 0.05). The incidence of diarrhea in piglets orally supplemented with Gln was 24% less than (P = 0.064) that in control piglets at 8 to 14 d after weaning. The weights of the jejunum and ileum were greater in piglets orally supplemented with Gln compared with those of control piglets relative to BW on d 14 postweaning (P < 0.05). The villus height and the villus height:crypt depth ratio in the jejunum and the ileum were greater in piglets receiving oral Gln on d 14 postweaning (P < 0.05) than in control piglets. These results indicate that Gln supplementation can influence the intestinal morphology of weaned piglets. The expression of hsp70 mRNA and Hsp70 proteins in the duodenum and jejunum was greater in piglets supplemented with Gln than in control piglets (P < 0.05). However, Gln supplementation had no effect on the expression of hsp70 mRNA and Hsp70 proteins in the ileum. Moreover, the localization of Hsp70 in the cytoplasm indicated that Hsp70 has a cytoprotective role in epithelial cell function and structure. These results indicate that Gln supplementation may be beneficial for intestinal health and development and may thus mitigate diarrhea and improve growth performance. The protective mechanisms of Gln in the intestine may be associated with the increase in Hsp70 expression.

Plasma glutamine concentrations in the horse following feeding and oral glutamine supplementation

REASONS FOR PERFORMING STUDY

Pharmacological benefits of glutamine supplementation have been shown in athletically and clinically stressed human subjects. In the horse, infection and intense exercise have also been shown to significantly decrease plasma glutamine concentrations, but little is known on how best to supplement.

OBJECTIVE

To evaluate whether ingestion of different foodstuffs, with or without L-glutamine (G) or a peptide (Pep) containing 31.5% w/w G in a water-stable form, could affect plasma glutamine concentrations (P-GC).

MATERIALS AND METHODS

Nine feeds (molassed sugar beet-pulp (mSB); naked oats (nO); commercial mix (CM); mSB with 30 or 60 mg/kg bwt G or the G-molar equivalent of Pep; and CM with 60 mg/kg bwt G or equivalent Pep) were offered to 6 healthy mature horses on different days following overnight food restriction. The changes in P-GC were monitored for 8 h post feeding.

RESULTS

After 1.5 h mean +/- s.d. AP-GC were -0.9 +/- 10.2% (mSB), +12.5 +/- 7.1% (nO) and +44.7 +/- 15.9% (CM; P<0.05). deltaP-GC with mSB supplemented with G was +60.9 +/- 30.0% (30 mg; P<0.05) and +156.8 +/- 34.6% (60 mg; P<0.05) at 1 h; deltaP-GC with Pep was 51.0 +/- 31.0% (30 mg equivalent, P<0.05) and +91.1 +/- 9.5% (60 mg equivalent, P<0.05) at 1 h. After 10 days of supplementation with 60 mg/kg bwt G, AP-GC following a further 60 mg/kg bwt G challenge showed a similar increase at 1 h of +154.3 +/- 37.9%; prevalues were unchanged. G and Pep added to CM, increased P-GC by 246.3 +/- 55.3 (+99.2%) and 252.3 +/- 94.2 micromol/l (96.7%) at 1.5 h with concentrations still above prevalues at 8 h (P<0.05). Apart from the CM (with or without supplement), pre P-GC was always regained by 4 h. Plasma NH3 and plasma protein concentrations were unaffected by supplementation with G or Pep.

CONCLUSION

P-GC may be modified by appropriate supplementation with no apparent adverse effects.

POTENTIAL RELEVANCE

Increasing P-GC through appropriate supplementation may be of benefit in the athletically or clinically stressed horse with lowered plasma glutamine concentrations.

L-Glutamine Use in the Treatment and Prevention of Mucositis and Cachexia: A Naturopathic Perspective

L-Glutamine (L-GLN) is considered a nonessential amino acid that has a variety of applications in naturopathic medicine. It has been postulated that in the critically ill patient, GLN becomes an essential amino acid for recovery, restoration, and repair at a cellular level. Mucositis is an intestinal mucosal damage of the gastrointestinal tract—mouth, throat, stomach, intestines, rectum, and anus—that is caused directly by chemotherapies and radiotherapies. Cancer cachexia is a significant biochemical event, which is characterized by weight loss, fatigue, and indicative of depletion of skeletal muscle GLN—a hypercatabolic state. There has been some question as to the use of GLN in this patient population because of its role as a preferred energy source not only for enterocytes and lymphocytes but for malignant cells as well.This article will address the questions of safety, efficacy, dosing, and toxicity of GLN used as an integrative therapeutic in ongoing integrative cancer treatment.

Glutamine supplementation for young infants with severe gastrointestinal disease

BACKGROUND

Endogenous glutamine biosynthesis may be insufficient to meet the needs of infants with severe gastrointestinal disease. Studies using animal models of gastrointestinal disease and controlled trials in adult patients have suggested that glutamine supplementation improves clinical outcomes.

OBJECTIVES

To assess the evidence from randomised controlled trials that providing supplemental glutamine reduces mortality and morbidity in infants with severe gastrointestinal disease.

SEARCH STRATEGY

The standard search strategy of the Cochrane Neonatal Review Group was used. This included searches of the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 3, 2006), MEDLINE (1966 - August 2006), EMBASE (1980 - August 2006), conference proceedings, and previous reviews.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials that compared glutamine supplementation versus no glutamine supplementation in infants (up to three months old, corrected for preterm birth) with severe gastrointestinal disease (defined as a congenital or acquired gastrointestinal condition that is likely to necessitate providing parenteral nutrition for at least 24 hours).

DATA COLLECTION AND ANALYSIS

Data were extracted using the standard methods of the Cochrane Neonatal Review Group, with separate evaluation of trial quality and data extraction by two reviewer authors, and synthesis of data using relative risk, risk difference and weighted mean difference.

MAIN RESULTS

Two trials in which a total of 100 infants participated were identified. In one trial, a minority of participants were infants older than three months. These studies were generally of good methodological quality but were underpowered to detect clinically important effects of glutamine supplementation. Meta-analysis did not reveal a statistically significant difference in the risk of death before hospital discharge [typical relative risk 1.57 (95% confidence interval 0.25 to 9.66); typical risk difference 0.02 (95% confidence interval -0.06 to 0.10)], nor in the rate of invasive infection [typical relative risk 1.22 (95% confidence interval 0.55 to 2.70); typical risk difference: 0.04 (95% confidence interval -0.12 to 0.20)].

AUTHORS' CONCLUSIONS

The available data from randomised controlled trials are not sufficient to determine whether glutamine supplementation confers clinically significant benefits for infants with severe gastrointestinal disease. Further trials are needed.

Necrotizing enterocolitis: a practical guide to its prevention and management

Neonatal necrotizing enterocolitis is the second most common cause of morbidity in premature infants and requires intensive care over an extended period. Despite advances in medical and surgical techniques, the mortality and long-term morbidity due to necrotizing enterocolitis remain very high. Recent advances have shifted the attention of researchers from the classic triad (ischemia, bacteria, and the introduction of a metabolic substrate into the intestine) of necrotizing enterocolitis, to gut maturation, feeding practices, and inflammation. The focus on inflammation includes proinflammatory cytokines such as tumor necrosis factor-alpha, interleukin (IL)-6, IL-18, and platelet-activating factor. Research related to the etiology of necrotizing enterocolitis has moved quickly from clostridial toxin to bacterial and other infectious agents. More recently, the pattern of bacterial colonization has been given emphasis rather than the particular species or strain of bacteria or their virulence. Gram-negative bacteria that form part of the normal flora are now speculated as important factors in triggering the injury process in a setting where there is a severe paucity of bacterial species and possible lack of protective Gram-positive organisms. Although the incidence of necrotizing enterocolitis has increased because of the survival of low birthweight infants, clinicians are more vigilant in their detection of the early gastrointestinal symptoms of necrotizing enterocolitis; however, radiographic demonstration of pneumatosis intestinalis remains the hallmark of necrotizing enterocolitis. With prompt diagnosis, a large proportion of infants with necrotizing enterocolitis are now able to be managed medically with intravenous fluid and nutrition, nasogastric suction, antibacterials, and close monitoring of physiologic parameters. In the advanced cases that require surgery, clinicians tend to opt for either simple peritoneal drainage (for very small and sick infants) or laparotomy and resection of the affected part. Intestinal transplantation later in life is available as a viable option for those who undergo resection of large segments of the intestine. It is becoming more evident that treatment of this devastating disease is expensive and comes with the toll of significant long-term sequelae. This has resulted in renewed interest in designing alternative strategies to prevent this serious gastrointestinal disease. Simple trophic feeding and the use of L-glutamine and arginine are novel avenues that have been examined. The use of probiotics ('friendly' bacterial flora) has been introduced as a promising tool for establishing healthy bacterial flora in the newborn gut to block the injury process that may ultimately lead to necrotizing enterocolitis.

Effects of enteral glutamine supplement on endotoxin translocation and mucosal immune barrier in starved rats

AIM: To investigate the changes in intestinal structure and function as well as the effect of enteral glutamine (GLN) supplement on the endotoxin translocation and immunological function in starved rats.

METHODS: Ninety male Sprague Dawley rats were randomly divided into 3 groups: normal control group (n = 10), starved group (group A, n = 40) and GLN group (group B, n = 40). The rats were sacrificed 3, 5, 7 and 9 d after starvation, respectively. Blood samples were collected from portal vein for the detection of plasma endotoxin and tissue samples removed from ileocecum were observed under light microscope for morphological changes. A contrasting study on the expression of secretary immunoglobulin A (sIgA) and the numbers of CD4⁺, CD8⁺ T lymphocytes were also performed between control group and other groups by immunohistochemical staining method.

RESULTS: The atrophy of intestinal mucosa and villa were observed 3 d after starvation in group A, with the degeneration, necrosis, and shedding of partial mucosal epithelial cells. The changes were gradually deteriorated till the 9^th day after starvation. Those pathological changes were lighter in group B than those in group A on the 3^rd day after starvation and restored to normal on the 5^th day. As the starvation time prolonged, the atrophy, degeneration and necrosis of the mucosal epithelial cells appeared again in group B, but were still lighter than those in group A. The levels of endotoxin were significantly higher 3, 5, 7 and 9 d after starvation in both group A and B than those in the controls, and there were also marked differences between group B and A (322.4 ± 65.1, 389.4 ± 32.6, 464.4 ± 76.6, 413.7 ± 67.2 EU/L vs 527.1 ± 74.9, 546.3 ± 65.7, 623.9 ± 85.9, 587.5 ± 140.8 EU/L, all P < 0.01). The expression of sIgA and the numbers CD4⁺ and CD8⁺ T lymphocytes in intestinal mucosa were reduced significantly in group A and B, in compared with those in the controls (P < 0.05 or P < 0.01), and there were higher levels of sIgA and CD4⁺ and CD8⁺ T lymphocytes in group B than those in group A (P < 0.01).

CONCLUSION: The structure of intestinal mucosa is damaged in the earlier stage of starvation in rats, accompanied by endotoxin translocation and dysfunction of intestinal mucosal immune barrier. Early enteral nourishment of glutamine is helpful for inhibiting endotoxin translocation and improve immune function of intestinal mucosa.

Supplementation of 1% l-Glutamine to Milk Replacer Does Not Overcome the Growth Depression in Calves Caused by Soy Protein Concentrate

Glutamine, an important fuel and biosynthetic precursor in intestinal epithelial cells, helps maintain intestinal integrity and function when supplemented to the diet of many species. The hypothesis tested here was that glutamine supplementation would overcome the decreased average daily gain (ADG) and altered intestinal morphology caused by milk replacer containing soy protein concentrate (SPC). Holstein calves (9 male and 1 freemartin female per treatment) were assigned to diets of 1) all-milk-protein (from whey proteins) milk replacer, 2) milk replacer with 60% milk protein replacement from SPC, and 3) SPC milk replacer as in diet 2 plus 1% (dry basis) l-glutamine. Milk replacers were reconstituted to 12.5% solids and were fed at 10% of body weight from d 3 to 10 of age, and at 12% of body weight (adjusted weekly) from d 10 through 4 wk of age. No dry feed (starter) was fed, but water was freely available. Glutamine was added at each feeding to reconstituted milk replacer. Five calves from each treatment were slaughtered at the end of wk 4 for measurements of intestinal morphology. The ADG was greater for calves fed the all-milk control than for those fed SPC; glutamine did not improve ADG (0.344, 0.281, and 0.282 kg/d for diets 1 to 3, respectively). Intake of protein was adequate for all groups and did not explain the lower growth for calves fed SPC. Villus height and crypt depth did not differ among treatments in the duodenum. In the jejunum, villus height (713, 506, and 464 mum, for diets 1 to 3, respectively) and crypt depth (300, 209, and 229 mum, respectively) were greater for calves fed all milk protein than for either SPC group. In the ileum, villus height was greater for calves fed all milk than for either soy group (532, 458, and 456 mum), whereas crypt depth tended to be greater (352, 301, and 383 mum for diets 1 to 3, respectively), and the villus to crypt ratio was lower for calves supplemented with glutamine than for those fed SPC alone. Urea N concentration in plasma was greater for calves supplemented with glutamine than for those fed SPC alone, indicating that glutamine was at least partially catabolized. Supplemental l-glutamine did not improve growth or intestinal morphology of calves fed milk replacer containing SPC.

Prevention of bacterial translocation using glutamine: a new strategy of investigation

OBJECTIVE

This study investigated the role of glutamine (Gln) on bacterial translocation in an intestinal obstruction model by using Escherichia coli labeled with technetium 99m (99mTc-E. coli).

METHODS

Intestinal obstruction was performed by a single ligature of the terminal ileum in rats. Animals in the control group (group 1) were sham operated (not obstructed). Experimental group 2 had intestinal obstruction. Groups 1 and 2 were not treated with Gln. Groups 3 and 4 were treated with Gln for 7 d before surgery with 250 and 500 mg x kg(-1) x d(-1), respectively. A suspension containing 100 million colony-forming units/mL of (99m)Tc-E. coli was injected into the lumen of the ileum. Twenty-four hours after surgery, blood, mesenteric lymph nodes, livers, spleens, and lungs were collected for determination of radioactivity. The Mann-Whitney U test was performed for statistical analysis. P <or= 0.05 was considered statistically significant.

RESULTS

Rats that had an intestinal obstruction showed a significant increase in 99mTc-E. coli translocation from the lumen to all organs investigated compared with the sham-operated group (P <or= 0.01). There was a significant difference between the intestinally obstructed group and Group 4 treated with Gln at 500 mg x kg(-1) x d(-1) (P <or= 0.05), which did not occur in Group 3 treated with Gln at 250 mg x kg(-1) x d(-1).

CONCLUSIONS

The new method using 99mTc-E. coli was found to be suitable for studies of bacterial translocation. Gln did not prevent bacterial translocation but did significantly decrease the spread of 99mTc-E. coli among organs such as the liver, lung, and spleen. The effect of Gln in cases of intestinal obstruction was found to be dose dependent.

Does the addition of glutamine to enteral feeds affect patient mortality?

OBJECTIVE

Studies have failed to consistently demonstrate improved survival in intensive care unit (ICU) patients receiving immune-modulating nutrient-enhanced enteral feeds when compared with standard enteral feeds. The objective was to study in a prospective fashion the effects of adding glutamine to standard or immune-modulated (supplemented with omega-3 fatty acids, beta-carotene, and amino acids such as glutamine and arginine) tube feeds.

DESIGN

Prospective, unblinded study using sequential allocation.

SETTING

A university surgical trauma ICU.

PATIENTS

All surgical and trauma patients admitted to the surgical trauma ICU at a university hospital over a 3-yr period who were to receive enteral feeds (n = 185).

INTERVENTIONS

Sequential assignment to three isocaloric, isonitrogenous diets was performed as follows: standard 1-kcal/mL feeds with added protein (group 1), standard feeds with the addition of 20-40 g/day (0.6 g/kg/day) glutamine (group 2), or an immune-modulated formula with similar addition of glutamine (group 3). The goal for all patients was 25-30 kcal/kg/day and 2 g/kg/day protein.

MEASUREMENTS AND MAIN RESULTS

Patients were followed until discharge from the hospital. The primary end point was in-hospital mortality, and multiple secondary end points were recorded. In-hospital mortality for group 1 was 6.3% (four of 64) vs. 16.9% (ten of 59, p = .09) for group 2 and 16.1% (ten of 62, p = .09) for group 3. After controlling for age and severity of illness, the difference in mortality between patients receiving standard tube feeds and all patients receiving glutamine was not significant (p < or = .11). There were no statistically significant differences between the groups for secondary end points.

CONCLUSIONS

The addition of glutamine to standard enteral feeds or to an immunomodulatory formula did not improve outcomes. These findings suggest that enteral glutamine should not be routinely administered to patients with surgical critical illness.

Differentiation stage-dependent preferred uptake of basolateral (systemic) glutamine into Caco-2 cells results in its accumulation in proteins with a role in cell-cell interaction

Glutamine is an essential amino acid for enterocytes, especially in states of critical illness and injury. In several studies it has been speculated that the beneficial effects of glutamine are dependent on the route of supply (luminal or systemic). The aim of this study was to investigate the relevance of both routes of glutamine delivery to in vitro intestinal cells and to explore the molecular basis for proposed beneficial glutamine effects: (a) by determining the relative uptake of radiolabelled glutamine in Caco-2 cells; (b) by assessing the effect of glutamine on the proteome of Caco-2 cells using a 2D gel electrophoresis approach; and (c) by examining glutamine incorporation into cellular proteins using a new mass spectrometry-based method with stable isotope labelled glutamine. Results of this study show that exogenous glutamine is taken up by Caco-2 cells from both the apical and the basolateral side. Basolateral uptake consistently exceeds apical uptake and this phenomenon is more pronounced in 5-day-differentiated cells than in 15-day-differentiated cells. No effect of exogenous glutamine supply on the proteome was detected. However, we demonstrated that exogenous glutamine is incorporated into newly synthesized proteins and this occurred at a faster rate from basolateral glutamine, which is in line with the uptake rates. Interestingly, a large number of rapidly labelled proteins is involved in establishing cell-cell interactions. In this respect, our data may point to a molecular basis for observed beneficial effects of glutamine on intestinal cells and support results from studies with critically ill patients where parenteral glutamine supplementation is preferred over luminal supplementation.

A randomized controlled trial of enteral glutamine supplementation in very low birth weight infants: plasma amino acid concentrations

OBJECTIVE

Glutamine depletion has negative effects on the functional integrity of the gut and leads to immunosuppression. Very low birth weight (VLBW) infants are susceptible to glutamine depletion, as enteral nutrition is limited in the first weeks of life. Enteral glutamine supplementation may have a positive effect on feeding tolerance, infectious morbidity and short-term outcome. The aim of the study was to determine the effect of enteral glutamine supplementation on plasma amino acid concentrations, reflecting one aspect of safety of enteral glutamine supplementation in VLBW infants.

METHODS

In a double-blind placebo-controlled randomized controlled trial, VLBW infants (gestational age <32 weeks or birth weight <1500 g) received enteral glutamine supplementation (0.3 g/kg per day) or isonitrogenous placebo supplementation (alanine) between day 3 and day 30 of life. Supplementation was added to breast milk or to preterm formula. Plasma amino acid concentrations were measured at four time points: before the start of the study and at days 7, 14 and 30 of life.

RESULTS

Baseline patient and nutritional characteristics were not different in glutamine (n = 52) and control (n = 50) groups. Plasma concentrations of most essential and non-essential amino acids increased throughout the study period. There was no effect of enteral glutamine supplementation. In particular, the increase of plasma glutamine and glutamate concentrations was not different between the treatment groups (P = 0.49 and P = 0.34 respectively, day 30).

CONCLUSIONS

Enteral glutamine supplementation in VLBW infants does not alter plasma concentrations of glutamine, glutamate or other amino acids. Enteral supplementation in a dose of 0.3 g/kg per day seems safe in VLBW infants.

Glutamine-enriched enteral nutrition in very-low-birth-weight infants and effects on feeding tolerance and infectious morbidity: a randomized controlled trial

BACKGROUND

Glutamine depletion has negative effects on the functional integrity of the gut and leads to immunosuppression. Very-low-birth-weight (VLBW) infants are susceptible to glutamine depletion because nutrition is limited in the first weeks of life.

OBJECTIVE

The objective was to determine the effect of glutamine-enriched enteral nutrition on feeding tolerance, infectious morbidity, and short-term outcome in VLBW infants.

DESIGN

In a double-blind randomized controlled trial, VLBW infants (gestational age <32 wk or birth weight <1500 g) were allocated to receive enteral glutamine supplementation (0.3 g . kg(-1) . d(-1)) or isonitrogenous control supplementation (alanine) between days 3 and 30 of life. The supplementations were added to breast milk or to preterm formula. The primary endpoint for the study was time to full enteral feeding. Secondary endpoints were other variables of feeding tolerance, infectious morbidity, and short-term outcome.

RESULTS

Baseline patient and nutritional characteristics were not significantly different in the glutamine-supplemented (n = 52) and the control (n = 50) groups. The median time to full enteral feeding was 13 d (range: 7-31 d) in the glutamine-supplemented group and 13 d (range: 6-35 d) in the control group (hazard ratio: 1.19; 95% CI: 0.79, 1.79; P = 0.40). In the glutamine-supplemented group, 26 of 52 infants (50%) had >/=1 serious infection compared with 38 of 50 (76%) in the control group (odds ratio: 0.32; 95% CI: 0.14, 0.74; P = 0.008). Other variables of feeding tolerance and short-term outcome were not significantly different between groups.

CONCLUSIONS

Glutamine-enriched enteral nutrition did not improve feeding tolerance or short-term outcome in VLBW infants. However, infectious morbidity was significantly lowered in infants who received glutamine-enriched enteral nutrition.

Effect of glutamine and spray-dried plasma on growth performance, small intestinal morphology, and immune responses of Escherichia coli K88+-challenged weaned pigs1,2

Forty weaned barrows (5.32 +/- 0.3 kg BW) at 17 +/- 2 d of age were used to investigate the effects of feeding glutamine and spray-dried plasma on the growth performance, small intestinal morphology, and immune responses of Escherichia coli K88-challenged pigs. Pigs were allotted to four treatments including: 1) nonchallenged control (NONC); 2) challenged control (CHAC); 3) 7% (as-fed basis) spray-dried plasma (SDP); and 4) 2% (as-fed basis) glutamine (GLN). On d 11 after weaning, all pigs were fitted with an indwelling jugular catheter. On d 12 after weaning, pigs in the CHAC, SDP, and GLN groups were orally challenged with skim milk E. coli K88 culture, whereas pigs in the NONC group were orally inoculated with sterilized skim milk. Rectal temperatures and fecal diarrheic scores were recorded and blood samples collected at 0 (baseline), 6, 12, 24, 36, and 48 h after the challenge for serum hormone and cytokine measurements. At 48 h postchallenge, all pigs were killed for evaluation of small intestinal morphology. There was no effect of feeding SDP or GLN on growth performance during the 11-d prechallenge period (P = 0.13). At 48 h after the challenge, CHAC pigs had decreased ADG (P = 0.08) and G:F (P = 0.07) compared with the NONC pigs; however, SDP and NONC pigs did not differ in G:F, and GLN and NONC pigs did not differ for ADG and G:F. At 6, 36, and 48 h after the challenge, CHAC, SDP, and GLN pigs had increased rectal temperature relative to the baseline (P = 0.09). At 12 and 36 h after the challenge, CHAC pigs had the highest incidence of diarrhea among treatments (P = 0.08). Serum IL-6 and ACTH were not affected by treatment or time after E. coli challenge (P = 0.11). In proximal, midjejunum, and ileum, CHAC pigs had greater villous atrophy and intestinal morphology disruption than NONC pigs (P < 0.01), whereas SDP and GLN pigs had mitigated villous atrophy and intestinal morphology impairment after E. coli challenge. Pigs in the SDP had the lowest GH at 12 h and the greatest GH at 36 h after the challenge among treatments (P = 0.08). Pigs in the NONC had the highest IGF-1 at 12 and 36 h postchallenge (P < 0.04). These results indicate that feeding glutamine has beneficial effects in alleviating growth depression of E. coli K88-challenged pigs, mainly via maintaining intestinal morphology and function, and/or possibly via modulating the somatotrophic axis.

Growth responses to dietary energy and lysine at high and low ambient temperature in male turkeys

The effects of ambient temperature (T; 18 vs. 28 degrees C), dietary energy level [E; 90, 100, and 110% of NRC (1994) recommendations], and dietary lysine level [LYS; 105 vs. 120% of NRC (1994) recommendations], and their interactions on feed intake, BW gain, feed:gain ratio, and carcass yields of male turkeys were studied from 29 to 140 d of age. The experiment was designed as a split plot, including T as the main plot and E and LYS as the subplot, with 60 pens containing 10 male turkeys each. Overall, feed intake, BW gain, and feed:gain ratio were significantly lower at high compared with low T. Feed intake decreased linearly as E increased and was more pronounced at low compared with high T. Metabolizable energy intake increased more at high compared with low T as E increased. Turkeys that were fed the highest E gained less weight until 84 d of age than those fed the lowest E. Dietary lysine was not the limiting amino acid because birds showed no response to extra lysine. Feed:gain decreased linearly as E level increased. Until 84 d of age, feed:gain decreased more at low compared with high T as E level increased. Breast meat yields were lower, and thigh, drum, and wing yields were higher at high than at low T. The highest E resulted in lower cold carcass yields, and breast meat yields, and higher thigh and drum yields than the lowest E. Dietary lysine level did not affect carcass yield. The results imply that when dietary lysine levels are adequate, dietary energy may be increased above NRC (1994) to improve feed efficiency, but some of the limiting amino acids after lysine may be increased in high-density diets to optimize breast meat yield. Particularly at high temperature in the period after 16 wk of age, dietary energy contents may be increased to at least 110% of NRC (1994) because turkeys will need more energy to dissipate heat.

Impact of glutamine and Oasis hatchling supplement on growth performance, small intestinal morphology, and immune response of broilers vaccinated and challenged with Eimeria maxima

Seven hundred and twenty hatchling broilers were allotted to 12 treatment groups. Groups 1 and 2 were fasted for 48 h posthatch; groups 3 and 4 were fasted for 48 h followed by ad libitum access to a 1% glutamine (Gln) diet; groups 5 and 6 had ad libitum access to a common diet; groups 7 and 8 had access to a 1% Gln diet posthatch; groups 9 and 10 were fed regular Oasis hatchling supplement; and groups 11 and 12 were fed Oasis sprayed with 1% Gln for the first 48 h posthatch. The birds in treatment groups 2, 4, 6, 8, 10, 11, and 12 were vaccinated with Eimeria maxima posthatch, and all birds were orally challenged with high dose E. maxima on d 22. During the first 2 wk, birds in group 7 had the highest gain and feed efficiency among treatments (P < 0.01). Compared with birds in the nonGln groups, birds in the Gln group had higher gain, feed efficiency, and livability (P < 0.05). Among the Fast (groups 1 to 4), Feed (groups 5 to 8), and Oasis (groups 9 to 12) groups, birds in the Feed groups had the highest gain during d 0 to 21 (P < 0.01). During d 22 to 28, birds in the Fast groups had the lowest BW and livability (P < 0.01), and the nonvaccinated birds had lower gain and feed efficiency relative to vaccinated birds (P < 0.01). Birds in the Feed and Oasis groups had higher villus height (VH) of mid small intestine than Fast groups at d 2 and 7 (P < 0.05), and nonvaccinated birds had higher VH than vaccinated birds (P < 0.01) at d 7 after hatch. On d 14, there were differences in serum interferon-gamma (P < 0.05) levels among treatments. During d 22 to 28, vaccinated birds had lower lesion scores in the mid small intestine than nonvaccinated birds (P < 0.01), and birds in the Feed or Oasis groups had lower lesion scores compared with the Fast groups (P < 0.02). These results indicated the importance of immediate access to feed posthatch, the beneficial effects of feeding Oasis hatching supplement and Gln after hatch, as well as the necessity of the vaccination program against coccidiosis challenge.

Glutamine-enriched enteral nutrition in very low birth weight infants. Design of a double-blind randomised controlled trial [ISRCTN73254583]

Background

Enteral feeding of very low birth weight (VLBW) infants is a challenge, since metabolic demands are high and administration of enteral nutrition is limited by immaturity of the gastrointestinal tract. The amino acid glutamine plays an important role in maintaining functional integrity of the gut. In addition, glutamine is utilised at a high rate by cells of the immune system. In critically ill patients, glutamine is considered a conditionally essential amino acid. VLBW infants may be especially susceptible to glutamine depletion as nutritional supply of glutamine is limited in the first weeks after birth. Glutamine depletion has negative effects on functional integrity of the gut and leads to immunosuppression. This double-blind randomised controlled trial is designed to investigate the effect of glutamine-enriched enteral nutrition on feeding tolerance, infectious morbidity and short-term outcome in VLBW infants. Furthermore, an attempt is made to elucidate the role of glutamine in postnatal adaptation of the gut and modulation of the immune response.

Methods

VLBW infants (gestational age <32 weeks and/or birth weight <1500 g) are randomly allocated to receive enteral glutamine supplementation (0.3 g/kg/day) or isonitrogenous placebo supplementation between day 3 and 30 of life. Primary outcome is time to full enteral feeding (defined as a feeding volume ≥ 120 mL/kg/day). Furthermore, incidence of serious infections and short-term outcome are evaluated. The effect of glutamine on postnatal adaptation of the gut is investigated by measuring intestinal permeability and determining faecal microflora. The role of glutamine in modulation of the immune response is investigated by determining plasma Th1/Th2 cytokine concentrations following in vitro whole blood stimulation.

Glutamine regulates Caco-2 cell tight junction proteins

Intestinal epithelial tight junction (TJ) barrier dysfunction may lead to inflammation and mucosal injury. Glutamine (GLN) plays a role in maintenance of intestinal barrier function in various animal models and critically ill humans. Recent evidence from intestinal cell monolayers indicates that GLN maintains transepithelial resistance and decreases permeability. The mechanisms of these effects remain undefined. We hypothesized that GLN affects proteins involved in the intercellular junctional complex. GLN availability was controlled in Caco-2 monolayers by addition to the medium and treatment with methionine sulfoximine (MSO) to inhibit glutamine synthetase (GS). Expression of TJ proteins, claudin-1, occludin, and zonula occluden (ZO)-1 was measured by immunoblotting. Localization of TJ proteins was evaluated by immunofluorescence light microscopy. Structure of TJ was determined by transmission electron microscopy (TEM). Deprivation of GLN decreased claudin-1, occludin, and ZO-1 protein expression and caused a disappearance of perijunctional claudin-1 and a reduction of occludin but had no effect on ZO-1. TEM revealed that MSO-treated cells in the absence of GLN formed irregular junctional complexes between the apical lateral margins of adjoining cells. These findings indicate that TJ protein expression and cellular localization in Caco-2 cell monolayers rely on GLN. This mechanism may similarly relate to GLN-mediated modulation of intestinal barrier function in stressed animals and humans.

Effects of protein deprivation on growth and small intestine morphology are not improved by glutamine or glutamate in gastrostomy-fed rat pups

OBJECTIVES

Critically ill neonates often have their enteral intake severely limited shortly after birth. Whether glutamine (Gln) or glutamate (Glu) can preserve intestinal structure and function in the neonate undergoing limited enteral feeding is not clear. We hypothesize that Gln and Glu can similarly preserve intestinal structure in the developing small intestine of infant rats fed a low protein diet.

METHODS

Using a gastrostomy-fed "pup-in-a-cup" rat model, the effects of Gln and Glu on the developing rat small intestine were examined. Four groups of 6- to 7-day-old pups were fed rat milk substitute (RMS) via gastrostomy tube. One group was provided 100% and three were provided 25% of the protein normally received from their mothers. Two of the groups fed 25% protein received additional Gln or Glu for 6 days.

RESULTS

Pups receiving the 100% protein RMS were larger than pups receiving the 25% protein RMS with or without Gln/Glu supplementation (P < 0.001). Average villus height (P < 0.01) and area (P < 0.01) were greater in pups receiving 100% protein RMS than in pups given 25% protein RMS formula. There was no significant difference among the groups in mucosal maltase or alkaline phosphatase activities. Tight junction protein claudin-1 was significantly higher in the group fed 100% protein RMS diet, while occludin did not differ among the 4 groups. Neither Gln nor Glu increased claudin-1 or occludin in rats fed 25% protein.

CONCLUSIONS

These results suggest that neither Gln nor Glu supplementation can substitute effectively for whole protein in the developing rat small intestine for the outcomes that were evaluated.

Glutamine decreases lipopolysaccharide-induced intestinal inflammation in infant rats

Using a gastrostomy-fed (GF) rat infant "pup-in-a-cup" model, the effects of protein deprivation and supplemental glutamine (Gln) and glutamate (Glu) were examined to test the hypothesis that Gln decreases the proinflammatory response induced by LPS in the developing infant rat small intestine. Four groups of 6- to 7-day-old pups were fed a rat milk substitute (RMS), one providing 100% and three providing 25% of normal protein intake for another 6 days. Two of the 25% protein-fed groups received supplemental Gln or Glu. GF and LPS treatment blunted body growth and intestinal villus height and increased intestinal cytokine-induced neutrophil chemoattractant (CINC) mRNA in the protein-deprived, non-Gln-treated group compared with mother-fed pups (P < 0.05). Gln blunted intestinal CINC mRNA (P < 0.05), but Glu did not. Intestinal CINC peptide in the LPS-treated pups provided 100 and 25% protein was elevated approximately 13-fold compared with the mother-reared pups (P < 0.001). Gln and Glu decreased intestinal CINC peptide by 73 and 80%, respectively. GF, LPS-treated pups also had a higher level of plasma CINC peptide (P < 0.05). Gln but not Glu decreased plasma CINC peptide (P < 0.05). An approximate sixfold elevation of intestinal MPO activity in the GF, LPS-treated rats was decreased by Gln and Glu by 92% (P < 0.001) and 54% (P < 0.05), respectively. Intestinal and plasma TNF-alpha were increased in GF, LPS-treated pups (P < 0.01), and Gln and Glu both blunted this increase (P < 0.05) in the intestine but not in the plasma. The results indicate that Gln decreases the LPS-induced inflammatory response in infant rat intestine under different conditions of protein intake.

Prevention of chemotherapy and radiation toxicity with glutamine

GOALS OF THE WORK

Malignancy produces a state of physiologic stress that is characterized by a relative deficiency of glutamine, a condition that is further exacerbated by the effects of cancer treatment. Glutamine deficiency may impact on normal tissue tolerance to antitumor treatment, and may lead to dose reductions and compromised treatment outcome. Providing supplemental glutamine during cancer treatment has the potential to abrogate treatment-related toxicity. We reviewed the available data on the use of glutamine to decrease the incidence and severity of adverse effects due to chemotherapy and/or radiation in cancer patients.

METHODS

We performed a search of the MEDLINE database during the time period 1980-2003, and reviewed the English language literature of both human and animal studies pertaining to the use of glutamine in subjects with cancer. We also manually searched the bibliographies of published articles for relevant references.

MAIN RESULTS

The available evidence suggests that glutamine supplementation may decrease the incidence and/or severity of chemotherapy-associated mucositis, irinotecan-associated diarrhea, paclitaxel-induced neuropathy, hepatic veno-occlusive disease in the setting of high dose chemotherapy and stem cell transplantation, and the cardiotoxicity that accompanies anthracycline use. Oral glutamine supplementation may enhance the therapeutic index by protecting normal tissues from, and sensitizing tumor cells to chemotherapy and radiation-related injury.

CONCLUSIONS

The role of glutamine in the prevention of chemotherapy and radiation-induced toxicity is evolving. Glutamine supplementation is inexpensive and it may reduce the incidence of gastrointestinal, neurologic, and possibly cardiac complications of cancer therapy. Further studies, particularly placebo-controlled phase III trials, are needed to define its role in chemotherapy-induced toxicity.

Gut mucosal and plasma concentrations of glutamine: a comparison between two enriched enteral feeding solutions in critically ill patients

Background

Addition of glutamine to enteral nutrition formulas is consistently associated with a significant decrease in septic morbidity in critically ill patients, possibly related to the attenuation of gut dysfunction. This pilot study was undertaken to compare the effects of enteral administration of two glutamine-enriched formulas containing either additional free glutamine or glutamine-rich proteins, with a standard solution on plasma and mucosal concentrations of glutamine in patients admitted in the Department of Intensive Care.

Methods

Following randomization, glutamine concentration was determined in endoscopically sampled duodenal biopsies and plasma, before and after a 7-day period of continuous administration of the designated solution.

Results

The mucosal concentration of glutamine increased in the duodenal biopsies sampled from patients randomized to the solution containing the glutamine-rich proteins (from 3.6 ± 2.2 to 6.7 ± 5.2 micro-mol/g protein), but not from the others. There were no differences between the 3 groups in the plasma concentrations of glutamine, which remained stable over time.

Conclusion

The source of supplemental glutamine can influence gut mucosal glutamine concentrations, suggesting differences in its availability or utilization.

Glutamine and barrier function in cultured Caco-2 epithelial cell monolayers

Dietary glutamine (Gln) has been shown to be important for maintenance of the intestinal barrier. To investigate the role of the epithelium in this Gln dependence, Caco-2 cells were raised on semipermeable membranes under conditions that model different regions of the crypt and villus. Gln availability was controlled by addition to the medium and treatment with methionine sulfoximine to inhibit Gln synthetase (GS). Barrier function was assayed by measuring transepithelial electrical resistance and fluxes of [(14)C]mannitol and fluorescein isothiocyanate-dextran. The barrier function of these monolayers was found to require the Gln provided either in the medium at the apical or basal surface or via GS. However, the barrier was no more sensitive to Gln deprivation than it was to accumulation or maintenance of total protein. These results suggest that the in vivo dependence of the gut mucosal barrier on Gln likely involves roles separate from maintenance of the epithelial barrier per se.

Glutamine supports recovery from loss of transepithelial resistance and increase of permeability induced by media change in Caco-2 cells

Recent evidence suggests that the conditionally essential amino acid glutamine is important for intestinal barrier function. However, the mechanism remains undefined. To determine the effects of glutamine on permeability of intestinal epithelial cell monolayers, Caco-2 cells were grown on membrane filters and exposed to 4 mmol/L sodium butyrate in order to rapidly achieve high levels of alkaline phosphatase and high transepithelial resistance as seen in functionally mature enterocytes. A standard method of medium exchange consisting of removal and replacement resulted in a catastrophic loss of transepithelial resistance and increase of mannitol and dextran fluxes that required 2-4 hrs and protein synthesis to recover. The effect was attributed to exposure of the upper monolayer surface to atmosphere and could be avoided by refeeding by incremental perfusion. Spontaneously-differentiated Caco-2 monolayers were resistant to this stress. This novel stress test was employed as a sensitive assay for the requirement of glutamine for monolayer transepithelial resistance and mannitol permeability. Pre-stress glutamine availability was more important than Gln-availability during the recovery phase. Thus the transepithelial resistance and permeability of butyrate-induced monolayers is dynamically-regulated in response to atmospheric exposure, by a mechanism that depends on threshold levels of glutamine availability.

Glutamine supplementation in serious illness: a systematic review of the evidence

OBJECTIVE

To examine the relationship between glutamine supplementation and hospital length of stay, complication rates, and mortality in patients undergoing surgery and experiencing critical illness.

DATA SOURCES

Computerized search of electronic databases and search of personal files, abstract proceedings, relevant journals, and review of reference lists.

STUDY SELECTION

We reviewed 550 titles, abstracts, and articles. Primary studies were included if they were randomized trials of critically ill or surgical patients that evaluated the effect of glutamine vs. standard care on clinical outcomes. DATA EXTRACTION We abstracted relevant data on the methodology and outcomes of primary studies in duplicate, independently. DATA SYNTHESIS There were 14 randomized trials comparing the use of glutamine supplementation in surgical and critically ill patients. When the results of these trials were aggregated, with respect to mortality, glutamine supplementation was associated with a risk ratio (RR) of 0.78 (95% confidence interval [CI], 0.58-1.04). Glutamine supplementation was also associated with a lower rate of infectious complications (RR, 0.81; 95% CI, 0.64-1.00) and a shorter hospital stay (-2.6 days; 95% CI, -4.5 to -0.7). We examined several -specified subgroups. Although there were no statistically significant subgroup differences detected, there were some important trends. With respect to mortality, the treatment benefit was observed in studies of parenteral glutamine (RR, 0.71; 95% CI, 0.51-0.99) and high-dose glutamine (RR, 0.73; 95% CI, 0.53-1.00) compared with studies of enteral glutamine (RR, 1.08; 95% CI, 0.57-2.01) and low-dose glutamine (RR, 1.02; 95% CI, 0.52-2.00). With respect to hospital length of stay, all of the treatment benefit was observed in surgical patients (-3.5 days; 95% CI, -5.3 to -1.7) compared with critically ill patients (0.9 days; 95% CI, -4.9 to 6.8).

CONCLUSION

In surgical patients, glutamine supplementation may be associated with a reduction in infectious complication rates and shorter hospital stay without any adverse effect on mortality. In critically ill patients, glutamine supplementation may be associated with a reduction in complication and mortality rates. The greatest benefit was observed in patients receiving high-dose, parenteral glutamine.

Glutamine supplementation and deprivation: effect on artificially reared rat small intestinal morphology

The mechanisms of how glutamine benefits critically ill patients have not been established. The purpose of this study was to determine the effects of dietary and endogenously produced glutamine on small intestinal morphology using light and transmission electron microscopy in artificially reared rat pups. It was hypothesized that deprivation of dietary glutamine leads to intestinal disease that is exacerbated by inhibition of glutamine synthetase by methionine sulfoximine (MS). Rat pups were placed into five different test groups: The first was a reference group that was reared by their mother. The other four groups were reared artificially and received a 10% Travasol amino acid solution at 5 g/kg per day, which does not contain glutamine, added to a mixture containing carbohydrates, lipids, and vitamins. This dose was chosen because it represents an approximation of the amount of glutamine these rats would be receiving in a normal rat diet (approximately 40 g/kg per day total protein, 10 to 15% of which is glutamine + glutamate). The glutamine was manipulated by adding glutamine (Q) or MS or both. The four groups were as follows: MS-Q-, MS-Q+, MS+Q-, and MS+Q+. Light microscopy revealed the greatest blunting of villus height in the ileum of rats from the MS+Q- group when compared with the MS-Q+ group (123 +/- 48.9 micro m versus 207 +/- 36 microm, p < 0.05). The other two groups exhibited intermediate villus heights, but all were shorter than the villi from the mother-reared animals. The number of villi per unit length of bowel was also lowest in the animals that were treated with MS and not provided with dietary glutamine. Transmission electron microscopy demonstrated breakdown of the epithelial junctions in the glutamine-deprived and glutamine synthetase-inhibited intestines. Glutamine-deprived animals also displayed sloughing of microvilli, decreased actin cores, and degeneration of the terminal web. In summary, these studies support the hypothesis that glutamine is involved with maintenance of intestinal epithelial integrity.

Update on host defense and immunonutrients

Neonatal intensive care in the past three decades has provided exciting modalities for improving the survival of critically ill neonates. There remains a great need for improving the quality of life for these survivors. In this article, the role the developing GI tract and its microenvironment play in the well-being of the neonate has been emphasized. Future therapies based on manipulation of the GI tract and its microenvironment by functional foods, immunonutrients, or pharmacologic agents may have effects not only during the neonatal period, but also throughout the individual's entire life.

Key nutrients and growth factors for the neonatal gastrointestinal tract

The nutritional support of gastrointestinal growth and function is an important consideration in the clinical care of neonatal infants. In most health infants, the provision of either breast milk or formula seems to support normal intestinal mucosal growth, but the most significant advantages of breast milk may be for host defense or gut barrier-related functions that are involved in reducing infection. The specific effects of various milk-borne growth factors on key mucosal immune and barrier functions are likely to provide valuable new clues to the advantages of human milk. A substantial number of preterm, low-birth weight babies or those suffering from compromised intestinal function, however, often cannot tolerate oral feedings and instead receive TPN. The consequences of TPN on gastrointestinal function and how this contributes to morbidity of these infants warrants further study, with respect to both clinical and basic research questions. Although enteral nutrition seems to be a critical stimulus for intestinal function, the minimal amounts and composition of nutrients necessary to maintain specific intestinal functions remain to be established. The experimental tools exist to start defining the specific nutrient requirements for the infant gut and some of these nutrients are known (e.g., glutamate, glutamine, and threonine). Peptide growth factors and gut hormones clearly play a role in gut growth and in several ways mediate the trophic actions of enteral nutrition. Although a number of these growth factors are good candidates for therapeutic use, their clinical application in the management of gastrointestinal insufficiency and disease has been slow. The emergence of GLP-2 as a trophic peptide that seems to target the gut is a promising candidate on the horizon.

Glutamine supplementation. Heal the gut, help the patient

Glutamine is the most abundant amino acid in the body. It is also one of the most widely researched amino acids, with multiple clinical trials on various aspects of medical nutritional care including gastrointestinal disease, oncology, burn-trauma, HIV/AIDS, and chronic wound management. Glutamine often is used as a singular nutrient supplement in both hospital and home settings. The goal of this article is to review patient applications and supportive literature, and to provide the reader with guidelines for daily use of glutamine as an oral or enteral supplement.

Glutamine and the bowel

Since the pioneering work of Windmueller and Spaeth, the importance of glutamine to the support of intestinal mucosal metabolic function has become generally accepted. Nevertheless, the mechanisms underlying this role still remain obscure. This paper explores a number of questions: 1) Is glutamine essential for intestinal function? 2) To what extent does this relate to its intermediary metabolism? 3) What is the importance of glutamine as a biosynthetic precursor? 4) Is glutamine supplementation of the nutrient mixture presented to patients of any metabolic or clinical benefit? As a result of this exploratory exercise, the following general conclusions were reached: 1) Much suggestive biochemical and physiologic evidence exists that implies that glutamine, especially systemic glutamine, supports the function of the intestinal mucosal system. 2) Despite the extensive metabolism of this amino acid by the intestinal tissues, most evidence suggests that if glutamine does play a physiologic role in the bowel, it is not compellingly related to its intermediary metabolism. 3) There is, on the other hand, evidence that the mucosal cells not only utilize extracellular glutamine but synthesize the amino acid. Given that inhibition of glutamine synthesis inhibits both proliferation and differentiation of mucosal cell cultures, this suggests some more subtle regulatory role. This notion is supported by the demonstration that glutamine will activate a number of genes associated with cell cycle progression in the mucosa. 4) Despite the accumulated evidence, the mechanisms underlying glutamine's function and the question whether glutamine supplementation uniformly benefits mucosal health remain equivocal at best.