Glutamine content of protein and peptide-based enteral products

Exudative glutamine losses contribute to high needs after burn injury

Background

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

Methods

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

Results

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

Conclusions

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

Inhibitory action of soybean beta-conglycinin hydrolysates on Salmonella typhimurium translocation in Caco-2 epithelial cell monolayers

Soybean protein hydrolysates are widely used as functional foods as they have antioxidative properties able to enhance immune responses in humans. The alcalase enzymatic hydrolysates of beta-conglycinin were fractionated by ultrafiltration, and two main fractions, SP1 (<10 kDa) and SP2 (10-20 kDa), were obtained. The effects of these two fractions on the growth, development of epithelial cells, and formation of intercellular tight junctions were tested on an in vitro Caco-2 cell culture system. The inhibitory effects of SP1 and SP2 on the penetration of Salmonella typhimurium into Caco-2 epithelial cells were also examined. The results showed that the addition of >0.05 g/L of SP2 improved epithelial cell growth and that a concentration of 0.5 g/L of SP2 increased intercellular tight junction formation, which resulted in increased of transepithelial monolayer resistance (TER) values. Moreover, a lower S. typhimurium count compared to control was obtained when Caco-2 cells were grown in 0.05 and 0.5 g/L of SP2. These results show that beta-conglycinin hydrolysates play an important role in resisting S. typhimurium penetration into intestinal epithelial cells and that high molecular mass peptides (10-20 kDa) were more effective overall than low molecular mass peptides.

Risk assessment for the amino acids taurine, L-glutamine and L-arginine

Taurine, glutamine and arginine are examples of amino acids which have become increasingly popular as ingredients in dietary supplements and functional foods and beverages. Animal and human clinical research suggests that oral supplementation of these amino acids provides additional health and/or performance benefits beyond those observed from normal intake of dietary protein. The increased consumer awareness and use of these amino acids as ingredients in dietary supplements and functional foods warrant a comprehensive review of their safety through quantitative risk assessment, and identification of a potential safe upper level of intake. The absence of a systematic pattern of adverse effects in humans in response to orally administered taurine (Tau), l-glutamine (Gln) and l-arginine (Arg) precluded the selection of a no observed adverse effect level (NOAEL) or lowest observed adverse effect level (LOAEL). Therefore, by definition, the usual approach to risk assessment for identification of a tolerable upper level of intake (UL) could not be used. Instead, the newer method described as the Observed Safe Level (OSL) or Highest Observed Intake (HOI) was utilized. The OSL risk assessments indicate that based on the available published human clinical trial data, the evidence for the absence of adverse effects is strong for Tau at supplemental intakes up to 3 g/d, Gln at intakes up to 14 g/d and Arg at intakes up to 20 g/d, and these levels are identified as the respective OSLs for normal healthy adults. Although much higher levels of each of these amino acids have been tested without adverse effects and may be safe, the data for intakes above these levels are not sufficient for a confident conclusion of long-term safety, and therefore these values are not selected as the OSLs.

Consensus meeting: monosodium glutamate - an update

OBJECTIVE

Update of the Hohenheim consensus on monosodium glutamate from 1997: Summary and evaluation of recent knowledge with respect to physiology and safety of monosodium glutamate.

DESIGN

Experts from a range of relevant disciplines received and considered a series of questions related to aspects of the topic.

SETTING

University of Hohenheim, Stuttgart, Germany.

METHOD

The experts met and discussed the questions and arrived at a consensus.

CONCLUSION

Total intake of glutamate from food in European countries is generally stable and ranged from 5 to 12 g/day (free: ca. 1 g, protein-bound: ca. 10 g, added as flavor: ca. 0.4 g). L-Glutamate (GLU) from all sources is mainly used as energy fuel in enterocytes. A maximum intake of 6.000 [corrected] mg/kg body weight is regarded as safe. The general use of glutamate salts (monosodium-L-glutamate and others) as food additive can, thus, be regarded as harmless for the whole population. Even in unphysiologically high doses GLU will not trespass into fetal circulation. Further research work should, however, be done concerning the effects of high doses of a bolus supply at presence of an impaired blood brain barrier function. In situations with decreased appetite (e.g., elderly persons) palatability can be improved by low dose use of monosodium-L-glutamate.

Total glutamine content in human milk is not influenced by gestational age

BACKGROUND

Glutamine may be a conditionally indispensable amino acid in neonates and should be given in adequate amounts. Reliable information concerning the glutamine content of human milk is lacking.

AIM

To assess total glutamine content in human milk using a novel analytical procedure, and to evaluate the potential influence of time of delivery and lactational stage.

METHODS

The content of free and protein-bound glutamine was assessed in transitional (days 4-7 of lactation) and mature (days 29-34) human milk, after preterm (<35 wk of gestation, n=20) or term (>37 wk, n=20) delivery. Milk samples were obtained by manual expression and stored at <or=70 degrees C. Measurement of protein-bound glutamine was performed after stabilization by bis(1,1-trifluoroacetoxy)iodobenzene (BTI). Free glutamine was detected by HPLC.

RESULTS

There was no difference concerning glutamine content in human milk after term or preterm delivery (median of 5000 vs 4960 micromol/l milk). The protein-bound glutamine content decreased with the duration of lactation (6230 vs 4540 micromol/l milk). Free glutamine accounted for only 3-10% of the protein-bound glutamine content. The free glutamine content showed a high variability after preterm and term delivery.

CONCLUSION

This study presents for the first time data on glutamine intake in preterm and term neonates fed human milk. With these data, it is possible to formulate adequately composed nutritional therapy for infants at risk of glutamine imbalance.

Postabsorptive plasma citrulline concentration is a marker of absorptive enterocyte mass and intestinal failure in humans

BACKGROUND & AIMS

No blood marker assessing the functional absorptive bowel length has been identified. Plasma citrulline, a nonprotein amino acid produced by intestinal mucosa, is one candidate. We tested this hypothesis in adult patients with the short-bowel syndrome, whose condition can lead to intestinal failure.

METHODS

In 57 patients, after a minimal follow-up of 2 years subsequent to final digestive circuit modification, postabsorptive citrulline concentration was measured and parenteral nutrition dependence was used to define permanent (n = 37) and transient (n = 20) intestinal failure. Absorptive function, studied over a 3-day period, was evaluated by net digestive absorption for protein and fat (n = 51). Relations between quantitative values were assessed by linear regression analysis and cutoff citrulline threshold, for a diagnosis of intestinal failure by linear discriminant analysis. Cox model was used to compare citrulline threshold and anatomic variables of the short bowel as indicators of transient as opposed to permanent intestinal failure.

RESULTS

In patients with short-bowel syndrome, citrulline levels were lower than in controls (n = 51): 20 +/- 13 vs. 40 +/- 10 micromol/L (mean +/- SD), respectively (P < 0.001). After multivariate analysis, citrullinemia was correlated to small bowel length (P < 0.0001, r = 0.86) and to net digestive absorption of fat, but to neither body mass index nor creatinine clearance. A 20-micromol/L threshold citrullinemia, (1) classified short bowel patients with permanent intestinal failure with high sensitivity (92%), specificity (90%), positive predictive value (95%), and negative value (86%); and (2) was a more reliable indicator (odds ratio, 20.0; 95% confidence interval, 1.9-206.1) than anatomic variables (odds ratio, 2.9; 95% confidence interval, 0. 5-15.8) to separate transient as opposed to permanent intestinal failure.

CONCLUSIONS

In patients with short-bowel syndrome, postabsorptive plasma citrulline concentration is a marker of functional absorptive bowel length and, past the 2-year adaptive period, a powerful independent indicator allowing distinction of transient from permanent intestinal failure.

Determination of glutamine in muscle protein facilitates accurate assessment of proteolysis and de novo synthesis-derived endogenous glutamine production

BACKGROUND

Results of tracer studies indicate that skeletal muscle contributes to approximately 70% of overall glutamine production in healthy adults; the contribution of de novo synthesis being estimated at approximately 60%. However, measurement of the de novo synthesis rate in muscle tissue requires knowledge of the appearance rate of glutamine in plasma and the quantity of glutamine derived from intracellular proteolysis. Thus, the content of glutamine in muscle protein is a prerequisite for an accurate calculation.

OBJECTIVE

The objective of the study was to measure glutamine in muscle protein.

DESIGN

Muscle specimens (open biopsies) were obtained from humans (10 men and 4 women), rats (n = 4), cows (n = 4), and pigs (n = 4). Glutamine was assessed via prehydrolysis derivatization, rapid microwave-enhanced acid hydrolysis, and 5-dimethylaminonaphthalene-1-sulfonyl chloride (dansyl chloride) reversed-phase HPLC, and expressed per mg alkali-soluble protein (ASP) and DNA.

RESULTS

Glutamine concentrations in muscle cell protein of various species ranged from 41 to 49 microg/mg ASP; the differences were not species related. The combined means (+/-SDs) for the 4 species were 43.6 +/- 4.9 microg/mg ASP and 11.9 +/- 2.0 mg/mg DNA, respectively. In humans, there was no apparent influence of age, sex, or BMI.

CONCLUSIONS

Direct and specific measurements of glutamine in intact muscle protein were 50% lower than assumed previously. We used data compiled from earlier studies to recalculate the contributions of proteolysis and de novo synthesis to the endogenous production of glutamine in selected age groups of healthy humans; these contributions remained remarkably constant at approximately 13% and approximately 87%, respectively.

Formulation of enteral diets

The number of enteral diets has increased from a handful in the 1970s to over 100 at present. These can be classified as polymeric, chemically defined, disease-specific, and specialized diets, as well as oral dietary supplements. The properties, indications, pros and cons for the use of these diets are outlined in an effort to assist clinicians in their selection.

Whole-body protein metabolism assessed by leucine and glutamine kinetics in adult patients with active celiac disease

To assess the effect of increased renewal of intestinal epithelial cells on leucine and glutamine (Gln) turnover, 4-hour intravenous infusions of L-[1-(13)C]leucine and L-[2-(15)N]Gln were administered to five adult patients with active celiac disease in the postabsorptive state. There was a 35% increase in leucine flux (micromoles per kilogram per hour) in patients (117 +/- 17) compared with healthy controls (96 +/- 11, P < .03). Gln flux was increased by 13% in patients (377 +/- 35) versus controls (335 +/- 16, P < .04). These results suggest that active celiac disease, characterized by villous atrophy and crypt cell hyperplasia, is associated with a dramatic increase in whole-body protein breakdown as assessed by 13C-leucine, which may contribute per se to the protein malnutrition status of the patients. The increase in Gln utilization as assessed by L-[2-(15)N]Gln was moderate, but may have been offset due to the villose atrophy and ensuing reduced intestinal epithelial cell mass. The results are consistent with the concept that increased renewal of intestinal epithelial cells represents a sizable fraction of whole-body protein turnover and that Gln is an important fuel for epithelial intestinal cells in vivo.