Enteral glutamine supplementation and morbidity in low birth weight infants

Glutamine supplementation to prevent morbidity and mortality in preterm infants

BACKGROUND

Glutamine endogenous biosynthesis may be insufficient for tissue needs in states of metabolic stress. Trials in adults have suggested that glutamine supplementation improves clinical outcomes in critically ill adults. It has been suggested that glutamine supplementation may benefit preterm infants, particularly very low birth weight infants.

OBJECTIVES

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

SEARCH STRATEGY

We used the standard search strategy of the Cochrane Neonatal Review Group. This included searches of the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 3, 2004), MEDLINE (1966 - August 2004), EMBASE (1980 - August 2004), conference proceedings, and previous reviews.

SELECTION CRITERIA

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

DATA COLLECTION AND ANALYSIS

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

MAIN RESULTS

More than 2300 infants have participated in six randomised controlled trials. All of the participating infants were of very low birth weight. Three trials assessed enteral glutamine supplementation, and three trials assessed parenteral glutamine supplementation. These trials were generally of good methodological quality with adequate allocation concealment, blinding of care-givers and assessors to the intervention, and complete or near-complete follow-up of recruited infants. We found that glutamine supplementation does not have a statistically significant effect on mortality: typical relative risk 0.98 (95% confidence interval 0.80 to 1.21); typical risk difference 0.00 (95% confidence interval -0.03 to 0.03). One of the trials assessed longer term neurodevelopmental outcomes (Poindexter 2004). The investigators reported that they did not find any statistically significant differences in various assessments of neurodevelopment (including Bayley scales) on follow up at 18 months corrected age. We found that glutamine supplementation does not have a statistically significant effect on the incidence of systemic infection (typical relative risk 1.02 (95% confidence interval 0.92 to 1.13); typical risk difference 0.01 (95% confidence interval -0.03 to 0.05)), necrotising enterocolitis (typical relative risk 1.02 (95% confidence interval 0.79 to 1.33); typical risk difference 0.00 (95% confidence interval -0.02 to 0.03)), days to full enteral nutrition (weighted mean difference -1.1 days (95% confidence interval -3.4 to 1.2)), or duration of hospital stay (weighted mean difference 0.65 days (95% confidence interval -2.9 to 4.2)).

AUTHORS' CONCLUSIONS

The available data from good quality randomised controlled trials suggest that glutamine supplementation does not confer clinically significant benefits for preterm infants. The narrow confidence intervals for the effect size estimates suggest that a further trial of this intervention is not a research priority.

Glutamine supplementation in infants with gastrointestinal disease: A randomized, placebo-controlled pilot trial

OBJECTIVE

Glutamine (Gln) is a non-essential amino acid that plays an important role in energy metabolism for gastrointestinal epithelia and other cells with rapid turnover. We evaluated the effects of enteral supplementation with Gln in infants undergoing surgery for congenital or acquired gastrointestinal disease.

METHODS

This was a randomized, double-masked, controlled clinical trial.

RESULTS

Twenty infants were randomly assigned to receive Gln (n = 9) or placebo amino acid (n = 11), with a goal of supplemental amino acid intake of 0.4 g.kg(-1).d(-1). Infants were weaned from parenteral nutrition, and enteral feeds were started according to a standardized feeding protocol. Median (interquartile range) durations of parenteral nutrition were 39 d (12 to 99) in the Gln group and 21 d (6 to 59) in the control group (P = 0.201). Median (interquartile range) durations needed to reach 80% of the US recommended dietary allowance for energy with enteral nutrition were 24 d (8 to 55) in the Gln group and 12.5 d (5 to 32) in the control group (P = 0.313). There were no differences in the occurrence of infections between groups. Among all infants enrolled, significant correlations were found between duration of parenteral nutrition and residual small bowel length, peak concentrations of direct bilirubin, and alanine aminotransferase. Peak direct bilirubin was associated with longer duration of parenteral nutrition, shorter gestation, older age before feeds were started, shorter bowel length, and larger amounts of parenteral energy and protein intake.

CONCLUSIONS

In this pilot trial, enteral Gln supplementation was well tolerated among infants with surgical gastrointestinal disease. There was no effect observed on the duration of parenteral nutrition, tolerance of enteral feeds, or intestinal absorptive or barrier function. Larger, multicenter trials in infants with surgical gastrointestinal disease are needed due to the variability in important outcome measurements.

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.

Parenteral glutamine supplementation does not reduce the risk of mortality or late-onset sepsis in extremely low birth weight infants

BACKGROUND

Glutamine is one of the most abundant amino acids in both plasma and human milk, yet it is not included in standard intravenous amino acid solutions. Previous studies have suggested that parenteral nutrition (PN) supplemented with glutamine may reduce sepsis and mortality in critically ill adults. Whether glutamine supplementation would provide a similar benefit to extremely low birth weight (ELBW) infants is not known.

METHODS

We performed a multicenter, randomized, double-masked, clinical trial to assess the safety and efficacy of early PN supplemented with glutamine in decreasing the risk of death or late-onset sepsis in ELBW infants. Infants 401 to 1000 g were randomized within 72 hours of birth to receive either TrophAmine (control) or an isonitrogenous study amino acid solution with 20% glutamine whenever they received PN up to 120 days of age, death, or discharge from the hospital. The primary outcome was death or late-onset sepsis.

RESULTS

Of the 721 infants who were assigned to glutamine supplementation, 370 (51%) died or developed late-onset sepsis, as compared with 343 of the 712 infants (48%) assigned to control (relative risk: 1.07; 95% confidence interval: 0.97-1.17). Glutamine had no effect on tolerance of enteral feeds, necrotizing enterocolitis, or growth. No significant adverse events were observed with glutamine supplementation.

CONCLUSIONS

Parenteral glutamine supplementation as studied did not decrease mortality or the incidence of late-onset sepsis in ELBW infants. Consequently, although no harm was demonstrated, routine use of parenteral glutamine supplementation cannot be recommended in this population.

Glutamine: recent developments in research on the clinical significance of glutamine

PURPOSE OF REVIEW

The aim of this review is to describe the clinical relevance of supplementation of glutamine from the recent literature. First, new basic research is examined and subsequently recent clinical trials and a metaanalysis are illustrated.

RECENT FINDINGS

Glutamine has a major impact on the functionality of the immune system. It has recently been established that glutamine not only has a protective effect on cells of the immune system, but also on other cells of the body, for instance cardiomyocytes. Evidence is accumulating for an effect of glutamine via glutathione, heat shock proteins as well as taurine. Another area of interest is the way glutamine enhances gut barrier function. More and more research is concentrating on the positive effect of glutamine on the gut-associated lymphoid tissue.

SUMMARY

Based on a recent meta-analysis and up-to-date clinical trials, we may conclude that glutamine has a beneficial effect on infectious complications and reduces hospital stay. In critically ill patients glutamine supplementation may reduce morbidity and mortality. The greatest effect was observed in patients receiving high dose parenteral glutamine. A recent study with high dose enteral glutamine demonstrated a reduced mortality in the glutamine supplemented group. In the future more trials with larger numbers of participants are needed, especially with high dose enteral glutamine in the perioperatively and the intensive care unit setting.

New perspectives on nutrition enhance outcomes for premature infants

Significant advances have occurred during the past 20 years in the understanding of the complex relationships of the environment, the developing gut-associated immune system, the bacterial flora, the barrier functions of the gut, and the effects of nutrient intake. These advances have produced a profoundly different way of interpreting the nutritional requirements for normal growth and development of premature infants throughout their entire life.