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Plasma glutamine responses to high-intensity exercise before and after endurance training.

Glutamine responses to strenuous interval exercise were examined before and after 6 weeks of endurance training. Glutamine measures were obtained before and after the interval exercise sessions and training in untrained males assigned to training (T; n = 10) or control (C; n = 10) groups. Before training, C and T group glutamine progressively decreased (p < 0.05) by 18% and 16%, respectively, by 150-min postinterval exercise. Over the training period C group glutamine did not change, while T group values increased (p < 0.05) by 14%. After training, glutamine again decreased (p < 0.05) by similar percentages (C = 16% and T = 15%) by 150-min postinterval exercise, but the T group recorded higher (p < 0.05) resting and postexercise glutamine concentrations than the C group. Training induced increases in glutamine may prevent the decline in glutamine levels following strenuous exercise falling below a threshold where immune function might be acutely compromised.

Adult↗
PubMed2001

Glutamine: commercially essential or conditionally essential? A critical appraisal of the human data.

Glutamine is a nonessential amino acid that can be synthesized from glutamate and glutamic acid by glutamate-ammonia ligase. Glutamine is an important fuel source for the small intestine. It was proposed that glutamine is necessary for the maintenance of normal intestinal morphology and function in the absence of luminal nutrients. However, intestinal morphologic and functional changes related to enteral fasting and parenteral nutrition are less significant in humans than in animal models and may not be clinically significant. Therefore, it is unclear whether glutamine is necessary for the preservation of normal intestinal morphology and function in humans during parenteral nutrition. It was suggested that both glutamine-supplemented parenteral nutrition and enteral diets may pre-vent bacterial translocation via the preservation and augmentation of small bowel villus morphology, intestinal permeability, and intestinal immune function. However, it is unclear whether clinically relevant bacterial translocation even occurs in humans, much less whether there is any value in the prevention of such occurrences. Results of the therapeutic use of glutamine in humans at nonphysiologic doses indicate limited efficacy. Although glutamine is generally recognized to be safe on the basis of relatively small studies, side effects in patients receiving home parenteral nutrition and in those with liver-function abnormalities have been described. Therefore, on the basis of currently available clinical data, it is inappropriate to recommend glutamine for therapeutic use in any condition.

Animals↗
PubMed1975

Glutamine production by the isolated perfused rat heart during ammonium chloride perfusion.

Myocardial levels of ammonia, glutamate, and glutamine and the release of glutamate and glutamine were studied in the isolated perfused rat heart during perfusion with ammonium chloride, epinephrine, and conditions of anoxia or ischaemia. Perfusion for 15 min with effective ammonium chloride concentrations of 0.53, 0.71, and 2.06 mmol/l resulted in glutamine production of 1.34, 0.95, and 4.41 mmol with 15 min-1/200 dry weight compatible with the presence of glutamine synthetase in rat myocardium. Myocardial ammonium content was unchanged by perfusion with 0.53 and 0.71 mmol/l ammonium chloride, but was increased by 1.36 mumol with 15 min-1/200 mg dry weight by perfusion with 2.06 mmol/l ammonium chloride. Increased myocardial contents of ammonia and glutamine were not accompanied by depression of left ventricular pressure. Perfusion with epinephrine (0.20 mug/ml) resulted in an increased myocardial content of glutamine. Anoxia or ischaemia resulted in no changes in ammonia content, and no changes in glutamine or glutamate production. The net release of glutamine into the perfusate was about 10 times the net release of glutamate.

Ammonia↗
PubMed1982

Effects of azaserine treatment on plasma glutamine concentration and uric acid production in chickens fed low and high protein diets.

Azaserine injected intravenously decreased uric acid in the blood and urine 1.6 and 2 times, respectively. It also resulted in 3 times larger increase in plasma glutamine concentration in chickens fed a 20% protein diet than in those fed a 5% protein diet, but it had no effect on liver glutamine synthetase activity in either dietary group. Thus the resultant concentration of plasma glutamine in the chickens fed the high protein diet was higher than in those fed the low protein diet, the reverse of the relationship observed before the injection. The infusion of ammonium acetate caused less of a rise in plasma glutamine concentration, but increased uric acid in the urine and blood, more with the high protein feeding than the low protein feeding. Pretreatment with azaserine further augmented the increase in plasma glutamine concentration caused by the infusion of ammonium acetate in the chickens fed the high protein diet but not in those fed the low protein diet, and concurrently removed the stimulatory effect of ammonia on uric acid in the blood and urine of both dietary groups. These data indicate that both glutamine in intact chickens and the increased glutamine in the ammonia-infused chickens are converted to uric acid more by high protein feeding than by low protein feeding, and this is a major reason for the low concentration of plasma glutamine in the chickens fed a high protein diet.

Acetates↗
PubMed1994

Glutamine supplementation to total parenteral nutrition promotes extracellular fluid expansion in piglets.

The effect of glutamine-supplemented total parenteral nutrition was studied in 18 neonatal piglets (1.97 kg, 3 d old) for 8 d. They were grouped as follows: total parenteral nutrition with 0 (controls), 5 or 10 g glutamine/100 g total amino acids. Live weight gain (g/d) tended (P < 0.07) to increase with supplementation (129, 143, and 166 [SD = 20] for control, 5% and 10% glutamine), but there was no effect on total gain (g) in body protein (180, 171, 197; SD = 25), fat (135, 126, 143; SD = 33) or ash (13, 13, 16; SD = 5) for control, 5% and 10% glutamine groups, respectively. Total body water gains were significantly higher in the 10% group than in controls, with the 5% group showing intermediate gains (control = 696 g; 5% glutamine = 822 g, 10% glutamine = 970 g, SD = 119). Increased glutamine supplementation was accompanied by a trend (P < 0.08) toward increasing total body chloride space, an indicator of extracellular volume, explaining, in part, the observed differences in water gains. These results indicate that glutamine may not be a conditionally indispensable amino acid for the neonate on total parenteral nutrition. Furthermore, glutamine supplementation to total parenteral nutrition leads to disturbances in water balance that could cause increased accumulation, particularly in the extracellular space.

Animals↗
PubMed2000

Glutamine appearance rate in plasma is not increased after gastrointestinal surgery in humans.

The metabolic response to surgical stress is characterized by muscle protein breakdown and mobilization of amino acids and has been postulated to furnish glutamine and other amino acids to the immune system, gut and liver. The present study was undertaken to investigate whether the whole body appearance rate (R(a))(3) of glutamine in plasma is increased after major elective surgery. Fourteen patients (8 males, 6 females) were measured prior to laparotomy and on the second postoperative day. Patients received a primed continuous 6-h infusion of L-[5-(15) N]glutamine and L-[1-(13)C]leucine, and arterial blood samples and muscle biopsies were taken for concentration and enrichment measurements. As expected, the metabolic response to surgery was characterized by a rise in whole body protein breakdown (n = 14, P < 0.001) and a decreased concentration of glutamine in plasma (n = 14, P < 0.001) and muscle (n = 8, P < 0.01). However, these catabolic changes were not reflected by an increase in the plasma R(a) of glutamine: 246 +/- 8 micromol. kg(-1). h(-1) before surgery vs. 241 +/- 10 micromol. kg(-1). h(-1) on the second postoperative day. We conclude that the whole body R(a) of glutamine in plasma is not increased 2 d after elective gastrointestinal surgery. Further studies are warranted to establish whether the lack of an increase in plasma glutamine R(a) provides a rationale for glutamine supplementation.

Aged↗
PubMed2001

Glutamine and cell signaling in liver.

In the liver, glutamine plays an important role in ammonia detoxication and the regulation of pH homeostasis ("intercellular glutamine cycle"). In addition, this amino acid regulates liver metabolism and transport by mechanisms that cannot be attributed to its metabolism. Examples include the stimulation of protein and glycogen synthesis and bile acid secretion and the inhibition of proteolysis in liver. The major trigger for such effects is an increased hepatocyte hydration due to the cumulative uptake of glutamine into the cells, which activates osmosignaling pathways involving mitogen-activated protein kinases (MAPK). Glutamine- and hypoosmolarity-induced cell swelling activates extracellular signal-regulated kinases (ERK) and p38(MAPK). Activation of these MAPK results in an increased capacity of bile acid excretion into bile due to a rapid translocation of canalicular transport ATPases from a subcanalicular storage compartment to the canalicular membrane. Similarly, glutamine augments biliary excretion of cysteinyl leukotrienes in endotoxin-treated rat livers. Also, the antiproteolytic effect of glutamine is largely due to glutamine-induced cell swelling, which activates osmosignaling pathways. Here, the glutamine-induced p38(MAPK) activation mediates the inhibition of autophagic proteolysis at the level of autophagosome formation.

Animals↗
PubMed2001

Why is L-glutamine metabolism important to cells of the immune system in health, postinjury, surgery or infection?

Glutamine is normally considered to be a nonessential amino acid. However, recent studies have provided evidence that glutamine may become "conditionally essential" during inflammatory conditions such as infection and injury. It is now well documented that under appropriate conditions, glutamine is essential for cell proliferation, that it can act as a respiratory fuel and that it can enhance the function of stimulated immune cells. Studies thus far have determined the effect of extracellular glutamine concentration on lymphocyte proliferation and cytokine production, macrophage phagocytic plus secretory activities and neutrophil bacterial killing. Other cells of the immune system remain to be studied. The high rate of glutamine utilization and its importance to the function of lymphocytes, macrophages and neutrophils have raised the question "why glutamine?" because these cells have access to a variety of metabolic fuels both in vivo and in vitro. I have attempted to answer this question in this article. Additionally, knowledge of the rate of utilization and the pathway of metabolism of glutamine by cells of the immune system raises some intriguing questions concerning therapeutic manipulation of utilization of this amino acid such that the proliferative, phagocytic and secretory capacities of cells of the defense system may be beneficially altered. Evidence to support the hypothesis that glutamine is beneficially immunomodulatory in animal models of infection and trauma, as well as trauma in humans, is provided.

Adjuvants, Immunologic↗
PubMed2004

Inhibition of nitrate influx by glutamine in Lolium perenne depends upon the contribution of the HATS to the total influx.

Plants of Lolium perenne L. were grown in sterile solution culture supplied with 2 mol m(-3) nitrogen as either nitrate or ammonium. Glutamine at 5 mol m(-3) was added to the nutrient solution of half the plants for 24 h. Root nitrate influx (at external nitrate concentrations 0-2000 mmol m(-3)) and amino acid concentrations were determined. In a second experiment the concentration of the added glutamine was varied from 0-5 mol m(-3) and nitrate influx determined at 250 and 2000 mmol m(-3). The maximum rate of influx attributed to the high affinity transport system (HATS) was reduced by 66% by the presence of glutamine achieved through an 84% reduction in its constitutive component and a 59% reduction in its inducible component. Influx attributed to LATS was unaffected by the addition of glutamine. The inhibition of total nitrate influx by glutamine was positively related to the contribution of HATS to the total influx. In both nitrate- and ammonium-grown plants, the concentration of glutamine required to inhibit nitrate influx significantly was lower when influx was determined at 250 mmol m(-3) compared with 2000 mmol m(-3) nitrate. The addition of glutamine increased its concentrations in root tissue. However, the results cannot be attributed to changes in glutamine alone as its addition also resulted in increased concentrations of other amino acids. Implications for plants growing under field conditions are discussed.

Amino Acids↗
PubMed1992

Cytokine modulation of Na(+)-dependent glutamine transport across the brush border membrane of monolayers of human intestinal Caco-2 cells.

Previous studies have demonstrated that Na(+)-dependent brush border glutamine transport is diminished in septic patients. To examine the potential regulation of this decreased transport by endotoxin, cytokines, or glucocorticoids, the human intestinal Caco-2 cell line was studied in vitro. Na(+)-dependent glutamine transport across the apical brush border membrane was assayed in confluent monolayers of differentiated cells that were 10 days old. Uptake of 50 microM glutamine was determined after a 12-hour incubation with varying doses (10 to 1000 U/mL) of tumor necrosis factor-alpha, interleukin-1, interleukin-6, interferon-gamma, and various combinations of these cytokines. Studies were also done in cells incubated with E. coli endotoxin (1 micrograms/mL) or dexamethasone (1 and 10 microM). Endotoxin, tumor necrosis factor, interleukin-1, and interleukin-6 alone and in combination did not significantly reduce Na(+)-dependent glutamine transport across the brush border of Caco-2 cells. Dexamethasone decreased glutamine transport by 20%, but this decrease was not apparent for 48 hours. Interferon consistently decreased glutamine transport by 30%; this was due to a reduction in carrier maximal transport velocity (3427 +/- 783 pmol/mg protein/minute in controls versus 2279 +/- 411 in interferon, p less than 0.05) rather than a change in Km (276 +/- 29 microM in controls versus 333 +/- 74 in interferon, p = not interferon + dexamethasone + tumor necrosis factor + interleukin-1 resulted in a 38% decrease in transport activity. Cytokines and glucocorticoids may work independently and synergistically in regulating Na(+)-dependent brush border glutamine transport in human intestinal cells. Whether these signal molecules play a central role in the cause of the diminished brush border glutamine transport that occurs in septic patients requires further study.

Adenocarcinoma↗
PubMed2001

Oral feeding with glutamine prevents lymphocyte and glutathione depletion of Peyer's patches in endotoxemic mice.

OBJECTIVE: To determine the effect of oral glutamine feeding on lymphocyte subpopulations and glutathione metabolism in Peyer's patches (PPs) of healthy and endotoxemic mice. SUMMARY BACKGROUND DATA: Recent data indicate that nutrients both maintain nitrogen and energy balances and modulate cell and organ function. In particular, glutamine has an impact on gut and immune function. This is of special importance in the perioperative phase. METHODS: Female Balb/c mice were fed a glutamine-enriched diet or a control diet for 10 days. On day 7 25 microg lipopolysaccharide (LPS) or saline was injected. On day 3 after the challenge, mice were killed, total cell yield was determined, and lymphocyte subpopulations (total T cells, CD4+, CD8+ cells, and B cells) were analyzed by flow cytometry. One experimental group was treated with buthionine sulfoximine, a specific inhibitor of glutathione synthesis. The glutathione content in PPs was measured by high-performance liquid chromatography. RESULTS: Glutamine administration led to a significant increase in total cell yield, including T and B cells, in PPs. The LPS-induced reduction of T cells (-45%) and of B cells (-30%) was significantly lower in glutamine-treated mice. Endotoxemia caused a 42% decrease of glutathione in control animals, but not in glutamine-treated animals. As with LPS, buthionine sulfoximine also lowered lymphocyte numbers and glutathione content of the PPs. CONCLUSIONS: Administration of glutamine prevents LPS-stimulated lymphocyte atrophy in PPs, possibly by increasing the glutathione content in the PPs. Therefore, oral glutamine supply seems to be a suitable approach for improving intestinal immunity in immunocompromised patients.

Animals↗
PubMed1996

Starvation and endotoxin act independently and synergistically to coordinate hepatic glutamine transport.

OBJECTIVE: Because hepatic glutamine transport is markedly enhanced during critical illness, we tested the hypothesis that nutrient starvation and endotoxemia act coordinately to augment transport activity. DESIGN: Fed or starved (48 hours) rats received Escherichia coli endotoxin (LPS, 10 mg/kg of body weight, intraperitoneally) or saline before hepatocyte isolation for measurement of glutamine transport. MATERIALS AND METHODS: Hepatocytes were isolated from fed or fasted rats 4 hours after LPS treatment. [3H]glutamine uptake was measured and normalized to cellular protein. Data (mean +/- standard deviation, three separate determinations) were analyzed by Student's t test and analysis of variance. MAIN RESULTS: Starvation induced a 1.6-fold increase in glutamine transport, while LPS treatment of fed rats increased transport activity 2.6-fold. Treatment of fasted animals with LPS induced a sixfold increase in glutamine transport. Kinetically, this effect in endotoxemic starved rats was mediated by both an increase in System N Vmax and the induction of a high affinity System A amino acid carrier which transports glutamine. CONCLUSIONS: Starvation and endotoxemia regulate hepatocyte glutamine transport independently and synergistically. This hepatic response provides glutamine and other amino acids to support key metabolic pathways in the liver during critical illness.

Amino Acids↗
PubMed1996

Arterial-jugular vein free amino acid levels in patients with head injuries: important role of glutamine in cerebral nitrogen metabolism.

Traumatic brain injury is the single largest contributor of trauma center deaths. Injury to the brain cannot be considered as an isolated event, affecting only this organ. Profound hypoglutaminemia commonly seen in patients with head injuries may be caused by the diminished release of glutamine from the brain to the systemic circulation. To assess this hypothesis, we have simultaneously measured the free amino acid (AA) levels in systemic arterial (A, radial artery), cerebral venous (JV, jugular bulb), and systemic venous (PA, pulmonary artery) plasma in 11 adult patients with severe head injuries once within 48 hours of the initial injury before starting nutritional support and again after 3 to 4 days of enteral feeding. Cerebral organ (A-JV) changes of AA levels were compared with whole body systemic (A-PA) changes. Arterial total AA levels when compared with reported normal values are diminished by 46% in patients with isolated severe injuries. Cerebral outflow of glutamine is 6% of the total AA output compared with 73% in normals. The systemic outflow of glutamine in patients with brain injuries is 28% of total AA flow. Despite this high systemic output, significant hypoglutaminemia persists. Feeding for 3 days did not appreciably change the arterial plasma AA levels except that of glutamate and citrulline. A significant (p = 0.01) linear relationship between glutamine (product) and glutamate (precursor) was seen in JV samples but not in A or PA samples. The ratio of plasma glutamine to glutamate was decreased significantly only in JV during nutritional support, and this was caused mainly by an increase in glutamate levels. This may be owing to defective amidation to glutamine, inasmuch as gamma aminobutyric acid (GABA) levels were only minimally affected. Nutritional support improves the net release of glutamine from the brain. This suggests that supplementing the diet with glutamine may be beneficial to support systemic requirements in patients with severe head injuries.

Adolescent↗
PubMed1996

Plasma glutamine and upper respiratory tract infection during intensified training in swimmers.

The purposes of this study were to determine the effects of 4 wk of intensified training on resting plasma glutamine concentration, and to determine whether changes in plasma glutamine concentration relate to the appearance of upper respiratory tract infection (URTI) in swimmers during intensified training. Resting plasma glutamine concentration was measured by high performance liquid chromatography in 24 elite swimmers (8 male, 16 female, ages 15-26 yr) during 4 wk of intensified training (increased volume). Symptoms of overtraining syndrome (OT) were identified in eight swimmers (2 male, 6 female) based on decrements in swim performance and persistent high fatigue ratings; non-overtrained subjects were considered well-trained (WT). Ten of 24 swimmers (42%, 1 OT and 9 WT) exhibited URTI during the study. Plasma glutamine concentration increased significantly (P = 0.04, ANOVA) over the 4 wk, but the increase was significant only in WT swimmers (P < 0.05, post-hoc analysis). Compared with WT, plasma glutamine was significantly lower in OT at the mid-way timepoint only (P < 0.025, t-test with Bonferroni correction). There was no significant difference in glutamine levels between athletes who developed URTI and those who did not. These data suggest that plasma glutamine levels may not necessarily decrease during periods of intensified training, and that the appearance of URTI is not related to changes in plasma glutamine concentration in overtrained swimmers.

Adolescent↗
PubMed1997

Dietary L-glutamine does not improve lymphocyte metabolism or function in exercise-trained rats.

Decreased glutamine availability is proposed as a mechanism for changes in immune function with intense exhaustive exercise. Less is known about the immunomodulatory effects of regular nonexhaustive exercise. To determine the effects of low intensity regular exercise and dietary glutamine supplementation on plasma glutamine concentrations, lymphocyte metabolism, and immune function, male (278 +/- 5 g) and female (182 +/- 1 g) Sprague-Dawley Buffalo rats were fed nutritionally complete casein-based semi-purified diets +/- 2% w/w glutamine. Rats were trained (21 d), as confirmed by higher (P < 0.05) succinate dehydrogenase activity in soleus muscle, to swim 2 or 4 h.d-1 or remained sedentary. Exercise lowered plasma concentrations of tryptophan, glutamate, methionine, alanine, threonine, aspartate, asparagine, and ornithine and increased the lysine concentration (P < 0.05). Neither diet nor exercise altered plasma glutamine concentrations, lymphocyte phenotypes in spleen, or the in vitro rates of splenocyte energy metabolism (production of glucose and glutamine metabolites or ATP concentrations in the incubation media). Compared with nonsupplemented rats, splenic cytolytic activity (lysis of 51Cr labeled YAC-1 cells) was reduced (P < 0.05) in the glutamine-supplemented exercising group. Under these conditions, glutamine supplementation does not appear to provide any added benefit to the exercise-trained animal.

Amino Acids↗
PubMed1998

Effect of glutamine supplementation on changes in the immune system induced by repeated exercise.

UNLABELLED: The ability of lymphocytes to proliferate and generate lymphokine activated killer (LAK) cell activity in vitro is dependent on glutamine. In relation to intense exercise the lymphocyte concentration, the proliferative response, the natural killer and LAK cell activity, and the plasma glutamine concentration decline. It has been hypothesized that in relation to physical activity a lack of glutamine may temporarily affect the function of the immune system. PURPOSE: The purpose of this study was to examine the influence of glutamine supplementation on exercise-induced immune changes. METHODS: In a randomized cross-over placebo-controlled study, eight healthy male subjects performed three bouts of ergometer bicycle exercise lasting 60, 45, and 30 min at 75% of their VO2max separated by 2 h of rest. RESULTS: The arterial plasma glutamine concentration declined from 508 +/- 35 (pre-exercise) to 402 +/- 38 microM (2 h after the last exercise bout) in the placebo trial and was maintained above pre-exercise levels in the glutamine supplementation trial. The numbers of circulating lymphocytes and the phytohemagglutinin-stimulated lymphocyte proliferative response declined 2 h after, respectively, during each bout of exercise, whereas the LAK cell activity declined 2 h after the third bout. Glutamine supplementation in vivo, given in the described doses at the specific times, did not influence these changes. CONCLUSION: The present study does not appear to support the hypothesis that those aspects of postexercise immune changes studied are caused by decreased plasma glutamine concentrations.

Adult↗
PubMed2001

The influence of diet and exercise on muscle and plasma glutamine concentrations.

PURPOSE: This study examined the relationship between muscle glutamine, muscle glycogen, and plasma glutamine concentrations over 3 d of high-intensity exercise during which dietary carbohydrate (CHO) intake varied. METHODS: Five endurance-trained men completed two exercise trials in randomized order, over a 14-d period. Each trial required subjects to perform 50 min of high-intensity continuous and interval exercise on three consecutive days while consuming a diet that provided 45% of the energy as CHO or a diet in which CHO provided 70% of the total energy. Four days of inactivity and consumption of a 55% CHO diet separated the two randomized trials. Menus and food were provided for the subjects and all food and drink consumed were weighed and recorded for later analysis. Before exercise on the first day of each trial, at the start of exercise on day 3 and on completion of exercise on day 3, muscle was biopsied from the vastus lateralis for the analysis of glutamine and glycogen concentrations. Venous blood was sampled before and twice after exercise on each day for the analysis of plasma glutamine and cortisol concentrations. RESULTS: Mean plasma glutamine concentration was significantly higher during the 70% CHO exercise trial when compared with the 45% CHO trial (P < 0.05). Glycogen decreased by the same magnitude during both trials and there was no relationship between changes in plasma glutamine and changes in muscle glycogen concentration. Muscle glutamine concentration did not change in either trial. CONCLUSIONS: These data suggest that the influence of carbohydrate intake upon the concentration of plasma glutamine is not mediated through the concentration of intramuscular glycogen.

Adult↗
PubMed2004

Enteral glutamine but not alanine maintains small bowel barrier function after ischemia/reperfusion injury in rats.

We previously demonstrated that glucose and glutamine, solutes metabolized by the gut, replenish ATP and enhance gut function compared with alanine, a solute not metabolized by the gut, following mesenteric ischemia/reperfusion (I/R). The purpose of the present study was to determine if the nonmetabolizable solute alanine differentially modulates cytoskeletal organization and paracellular small intestinal permeability compared with the metabolizable solutes glucose and glutamine following mesenteric I/R. At laparotomy, rats had jejunal sacs filled with 10 mM glucose, glutamine, alanine, or magnesium sulfate (5 mm, osmotic control) followed by superior mesenteric artery clamping for 60 min and 30 min of reperfusion or sham laparotomy. Jejunum was harvested for evaluation by deconvolution microscopy, fluorescent measurement of F:G actin ratio, or mounted in an Ussing chamber for determination of intestinal permeability. Deconvolution microscopy revealed that the actin cytoskeleton was preserved by enteral glutamine, comparable to shams, but disrupted by enteral alanine. Glucose and controls resulted in comparable disruption, which was less than that with alanine. The F:G actin ratio was highest for glutamine and lowest for alanine; glucose was comparable to controls. Intestinal permeability was highest for alanine and lowest for glutamine, which was comparable to shams. Permeability following glucose and controls was higher than that following glutamine but lower than that following alanine. The nonmetabolizable solute alanine resulted in disruption of the actin cytoskeleton and enhanced intestinal permeability under conditions of mesenteric I/R. The metabolizable solute glutamine was protective under these conditions, whereas glucose exerted minimal effect on the integrity of the cytoskeleton and intestinal permeability. The individual components of enteral diets may differentially modulate intestinal barrier function, which could have important implications when administered to critically injured patients.

Alanine↗