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PubMed1993

Effect of glutamine on heat-shock-induced mRNA and stress proteins.

Our aim was to delineate the effect of glutamine on the level of heat shock-inducible mRNA and synthesis of stress protein(s) in cultured kidney cells. Experiments were carried out using opossum kidney (OK) cells. The induction of HSP70 mRNA as well as the synthesis of 72,73 kDa stress proteins was evaluated in cell monolayers exposed to 45 degrees C for 15 minutes followed by a recovery period at 37 degrees C for 3 hours. Incubations were performed in Krebs buffer supplemented with 0, 2, 5, or 10 mM glutamine. A separate series of experiments was performed in the presence of glutamine metabolites, such as NH4Cl, glutamate, or aspartate. Glutamine without preincubation at 37 degrees C remarkably increased the steady-state level of HSP70 mRNA as well as the production of 72,73 kDa stress proteins in a dose-dependent manner. The production of stress protein(s) in the presence of glutamine was associated with decreased percent LDH efflux, suggesting cytoprotective action of glutamine in cultured kidney cells. However, when OK cells were preincubated for 1 hour at 37 degrees C with 10 mM glutamine, there was an approximately fourfold decline in level of HSP70 mRNA compared with experiments in the presence of 10 mM glutamine without preincubation. In addition, metabolites of glutamine, i.e., ammonia and glutamate decreased the level of heat-inducible HSP70 mRNA. Furthermore, aspartate or NH4Cl had little effect on LDH release compared with heat shock experiments, without addition of amino acids. These observations suggest that metabolites of glutamine may blunt the steady-state level of glutamate or HSP70 mRNA. The decreased level of HSP70 mRNA in the presence of NH4Cl may explain the role of ammonia in renal injury and brain toxicity, as well as glutamate excitotoxicity.

Ammonium Chloride↗

PubMedDate not supplied

Activity of the lactate-alanine shuttle is independent of glutamate-glutamine cycle activity in cerebellar neuronal-astrocytic cultures.

The glutamate-glutamine cycle describes the neuronal release of glutamate into the synaptic cleft, astrocytic uptake, and conversion into glutamine, followed by release for use as a neuronal glutamate precursor. This only explains the fate of the carbon atoms, however, and not that of the ammonia. Recently, a role for alanine has been proposed in transfer of ammonia between glutamatergic neurons and astrocytes, denoted the lactate-alanine shuttle (Waagepetersen et al. [ 2000] J. Neurochem. 75:471-479). The role of alanine in this context has been studied further using cerebellar neuronal cultures and corresponding neuronal-astrocytic cocultures. A superfusion paradigm was used to induce repetitively vesicular glutamate release by N-methyl-D-aspartate (NMDA) in the neurons, allowing the relative activity dependency of the lactate-alanine shuttle to be assessed. [(15)N]Alanine (0.2 mM), [2-(15)N]/[5-(15)N]glutamine (0.25 mM), and [(15)N]ammonia (0.3 mM) were used as precursors and cell extracts were analyzed by mass spectrometry. Labeling from [(15)N]alanine in glutamine, aspartate, and glutamate in cerebellar cocultures was independent of depolarization of the neurons. Employing glutamine with the amino group labeled ([2-(15)N]glutamine) as the precursor, an activity-dependent increase in the labeling of both glutamate and aspartate (but not alanine) was observed in the cerebellar neurons. When the amide group of glutamine was labeled ([5-(15)N]glutamine), no labeling could be detected in the analyzed metabolites. Altogether, the results of this study support the existence of the lactate-alanine shuttle and the associated glutamate-glutamine cycle. No direct coupling of the two shuttles was observed, however, and only the glutamate-glutamine cycle seemed activity dependent.

Alanine↗

PubMed2006

Glutamine regulates the expression of proteins with a potential health-promoting effect in human intestinal Caco-2 cells.

Glutamine is an essential amino acid for the enterocytes with respect to maintaining the gut mucosal integrity and function. This study was conducted to explore a molecular basis for the beneficial effects of glutamine on intestinal cells by searching for glutamine-dependent changes in the proteome. Caco-2 cells were exposed to different concentrations of L-glutamine with or without L-methionine sulfoximine, an inhibitor of the glutamine synthetase activity. 2-DE combined with MALDI-TOF-MS was used to identify proteins whose expression is changed by glutamine. To assess the relative protein synthesis rate, incorporation of L-[2H5]glutamine into individual proteins was monitored. The expression levels of 14 proteins changed significantly with the glutamine availability. Examples of differentially expressed proteins with potential health-promoting effects on the intestine are plasma retinol-binding protein, ornithine aminotransferase, apolipoprotein A-I, mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase, and acyl-CoA synthetase 5. Expression of these proteins was not changed by arginine deprivation. The differential change in the expression levels of the proteins was not correlated with their rate of synthesis, excluding an effect of glutamine depletion on general protein synthesis. Together, this study shows a gene-specific effect of glutamine on intestinal cells.

Arginine↗

PubMed1989

Transport of glutamine in Xenopus laevis oocytes: relationship with transport of other amino acids.

We have investigated transport of the amino acid glutamine across the surface membranes of prophase-arrested Xenopus laevis oocytes. Glutamine accumulation was linear with time for 30 min; it was stereospecific with a Km of 0.12 +/- 0.02 mM and Vmax of 0.92 +/- 0.17 pmol/oocyte.min for L-glutamine. Transport of L-glutamine was Na(+)-dependent, the cation not being replaceable with Li+, K+, choline, tris(hydroxymethyl)-aminomethane (Tris), tetramethylammonium (TMA) or N-methyl D-glucamine (NMDG); external Cl- appeared to be necessary for full activation of Na(+)-dependent glutamine transport. Two external Na+ may be required for the transport of one glutamine molecule. L-glutamine transport (at 50 microM glutamine) was inhibited by the presence of other amino acids: L-alanine, D-alanine, L-leucine, L-asparagine and L-arginine (about 60% inhibition at 1 mM); L-histidine, L-valine and glycine (25 to 40% inhibition at 1 mM); L-serine, L-lysine, L-phenylalanine and L-glutamate (45 to 55% inhibition at 10 mM). N-methylaminoisobutyric acid (MeAIB) had no effect at 10 mM, but 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid (BCH) inhibited Na+/glutamine transport by about 50% at 10 mM. L-glutamine was a competitive inhibitor of the Na(+)-dependent transport of L-alanine, D-alanine and L-arginine; this evidence is consistent with the existence of a single system transporting all four amino acids. Glutamine uptake in oocytes appears to be catalyzed by a transport system distinct from the cotransport Systems A, ASC, N and Gly, although it resembles System B0,+.

Amino Acids↗

PubMed1995

Effect of glutamine on tumor and host growth.

BACKGROUND: Oral glutamine supplementation has been found to support gastrointestinal mucosal growth and increase intestinal and systemic toxicity after chemotherapy and radiation therapy. Glutamine is also an important nutrient for rapidly proliferating tumor cells. However, it is not clear whether long-term glutamine supplementation in the tumor-bearing host has a selective benefit for host growth or tumor cell proliferation. METHODS: To study the effect of glutamine in tumor-bearing animals, 30 Lewis/Wistar rats with subcutaneous mammary tumor implants (MAC-33) were randomized to receive a 3% glutamine- or 3% glycerine-enriched (control) diet for 25 days. RESULTS: No significant difference was found in carcass weight, primary tumor weight, or spontaneous pulmonary metastasis with glutamine supplementation. Tumor cell cycle kinetics (aneuploidy, %S and %S [synthetic] + G2/M [growth fraction]) were similar between glutamine-supplemented and control animals. A trophic effect of glutamine on distal ileal mucosa was seen with increased DNA content (344 +/- 68 vs. 184 +/- 38 micrograms/100 mg tissue) (p < 0.05) and RNA content (435 +/- 44 vs. 335 +/- 30 micrograms/100 mg tissue) (p = 0.06) compared with control animals. No detectable differences were observed in liver or muscle, or in tumor DNA, RNA, or protein content. CONCLUSIONS: These findings confirm the trophic effect of glutamine on small intestinal mucosa and suggest that glutamine can be administered to the tumor-bearing host over a long period of time without significantly stimulating tumor growth kinetics or metastasis.

Adenocarcinoma↗

PubMed2006

Intravenous glutamine supplementation to head trauma patients leaves cerebral glutamate concentration unaffected.

OBJECTIVE: There is reluctance to use glutamine-containing i.v. nutrition for neurosurgical patients, as this may result in elevated intracerebral glutamate levels, which are thought to be associated with neuronal injury and cell swelling, causing an increase in ICP and an unfavourable outcome. As general ICU patients benefit from i.v. glutamine supplementation in terms of reduced mortality and morbidity, neurosurgical patients might also be candidates for such treatment, if the possible relation between i.v. glutamine supplementation and a possible increase in cerebral glutamate could be sorted out. DESIGN AND SETTING: The study protocol had a crossover design with a 24h treatment period and a 24h placebo period in random order. Treatment was a glutamine containing dipeptide, L-alanyl-L-glutamine 200mg/ml, for 20h; placebo was saline. The rate of infusion was 0.125ml/kg/h, which is equal to 0.34g/kg of glutamine over the 20h period. Microdialysate was collected for analysis in 120min portions. The flow through the microdialysis catheter was 0.3microl/min. SUBJECTS: Patients with severe head trauma (GCS<or=8; n=15) on routine monitoring, including intracerebral microdialysis, were randomly assigned to treatment followed by placebo or placebo followed by treatment. MEASUREMENTS AND RESULTS: Glutamine infusion increased plasma glutamine concentration by 30%, but not plasma glutamate concentration. Intracerebral glutamate was unaffected in median values and in all individual patients. CONCLUSION: Intravenous glutamine in clinically relevant doses leaves cerebral glutamate unaffected. This opens the possibility of evaluating the effects of i.[Symbol: see text]v. glutamine supplementation upon outcome for neurosurgical ICU patients.

Adolescent↗

PubMed1992

Cytokine regulation of intestinal glutamine utilization.

The effects of cytokines on intestinal glutamine metabolism were studied to gain further insight into the regulation of altered glutamine metabolism that occurs during severe infection. One hundred thirteen adult rats were given a single dose of interleukin-1 (IL-1, 50 micrograms/kg), tumor necrosis factor (TNF, 50 micrograms/kg or 150 micrograms/kg), or saline (controls), and flux studies were performed 4 or 12 hours later. Intestinal blood flow was not different between control and cytokine-treated animals at either time point. At the 4-hour time point, arterial glutamine fell by 16% to 21% in the cytokine-treated animals (p less than 0.05); at the 12-hour time point, the arterial glutamine concentration had returned to normal. Intestinal glutamine extraction decreased in the animals treated with IL-1 at both time points (4 hours: 13% +/- 1.3% in IL-1 versus 20% +/- 1.6% in controls, p less than 0.05; and 12 hours: 9% +/- 2% in IL-1 versus 17% +/- 2% in controls, p less than 0.05). Consequently, net intestinal glutamine uptake fell in the animals treated with IL-1 at both time points (p less than 0.05). Similarly, the activity of mucosal glutaminase, the principal enzyme of glutamine hydrolysis in the gut, fell by 50% in the 4-hour study (6.1 +/- 0.6 mumol/h/mg protein in IL-1 versus 9.6 +/- 0.8 mumol/h/mg protein in controls, p less than 0.01) and by 40% in the 12-hour study (5.4 +/- 0.5 mumol/h/mg protein in IL-1 versus 8.8 +/- 0.4 mumol/h/mg protein in controls, p less than 0.05). Concomitant with the aforementioned decrease in gut glutamine metabolism was a 25% incidence of positive blood cultures for gram-negative organisms in IL-1 treated rats studied at the 12-hour time point (p = 0.05 versus controls). In the doses administered and at the time points studied, TNF had no effects on the parameters of gut glutamine metabolism examined. The results indicate that IL-1 is a potential mediator of the alterations in gut glutamine metabolism observed in sepsis and endotoxemia.

Animals↗

PubMed1990

Metabolism of glutamine and glutamate in human lenses.

Glutamate is important to lenses as a central intermediate in amino acid metabolism, as well as for synthesis of proteins and glutathione. In rat and calf lenses, the principal source of lenticular glutamate is glutamine, which enters the lens and is deamidated to form glutamate. In contrast, monkey lenses use external glutamate more readily than glutamine. Amino acid metabolism was studied in human lenses by incubating them with amino-labeled [15N]glutamine or [15N]glutamate. The lenticular free amino acids were then isolated and analysed by gas chromatography-mass spectrometry to determine 15N-labeled products. The results were compared with those of similar experiments with lenses from other species. Label was measured in aspartate, alanine, serine and proline, as well as lenticular glutamine and glutamate. Glutamine enters lenses more readily than glutamate in all the species examined. Nevertheless, aspartate, alanine and serine were more rapidly labeled by incubating human lenses in [15N]glutamate than in [15N]glutamine. This observation is similar to reports of experiments with monkey lenses, which unlike rat lenses, preferentially utilize glutamate rather than glutamine. In contrast, human lens proline was more rapidly labeled by incubating lenses with [15N]glutamine than with [15N]glutamate. In human lenses, the relatively slow utilization of glutamine for the transamination reactions which form aspartate, alanine and serine appears to result from slow deamidation. The relative preference for glutamine over glutamate as a precursor for proline synthesis in human lenses may be related to the mitochondrial location of the enzymes involved.

Adolescent↗

PubMed1994

Glutamine stimulates prostaglandin-sensitive Na(+)-H+ exchange in experimental porcine cryptosporidiosis.

BACKGROUND/AIMS: Recent studies of piglet cryptosporidiosis showed an injury-induced impairment of sodium-glucose cotransport and a prostaglandin-mediated inhibition of neutral NaCl absorption. Because glutamine has been shown to stimulate both neutral and electrogenic Na+ absorption, this study examined the mechanism of prostaglandin-mediated inhibition of NaCl absorption and the effect of glutamine on these processes. METHODS: Ileal mucosa from control and infected pigs was mounted in Ussing chambers for flux studies or incubated with [14C]glutamine or [14C]-glucose for metabolism studies. RESULTS: Glucose and glutamine induced equivalent increases, 2-2.5 microEq.cm-2.h-1, in Na+ absorption and short-circuit current in control ileum. Despite a reduction in villous surface area to one third of the control, glutamine enhanced both neutral and electrogenic Na+ absorption in the infected ileum by 3.5 +/- 0.5 microEq.cm-2.h-1, whereas glucose was only half as effective (P < 0.05). In addition, glutamine was oxidized to CO2 at rates three times those of glucose. Indomethacin enhanced, whereas amiloride, prostaglandin E2, and Cl-free solutions inhibited the glutamine-induced neutral Na+ transport. CONCLUSIONS: Glutamine-stimulated neutral Na+ absorption is mediated by a prostaglandin-sensitive apical Na(+)-H+ exchange mechanism. The heightened Na(+)-H+ exchange and tissue oxidation of glutamine suggest that glutamine is superior to glucose for use in oral rehydration solutions.

Animals↗

PubMed1988

Use of L-glutamine in total parenteral nutrition.

Gut atrophy develops during prolonged total parenteral nutrition (TPN). TPN solutions do not contain glutamine, an energy substrate of the intestinal tract. This study evaluated the effect of addition of L-glutamine to TPN on gut nitrogen content, histology, and disaccharidase enzyme activity. Five groups of six Fisher 344 rats received rat chow, D5W, TPN (23% calories as lipid), or TPN with 1 or 2% L-glutamine. Animals given TPN received 30 kcal and 0.22 g nitrogen/100 g/day. Metabolic cages allowed nitrogen balance for each group. After 6 days infusion, stomach, small bowel, and colon were assayed for total nitrogen and sucrase, lactase, and maltase activity. Mucosal height and fatty infiltration of the liver were determined from histologic sections. Adding either 1 or 2% L-glutamine resulted in no toxic clinical effects. Glutamine preserved intestinal nitrogen content of the stomach and colon compared to standard TPN and increased nitrogen content of small bowel to greater than that in chow-fed animals. Glutamine maintained mucosal height of the stomach and colon, but was no better than TPN alone in maintenance of small bowel mucosal height. One percent glutamine increased and standard TPN depressed maltase activity compared to chow. Standard TPN and 1% glutamine both stimulated sucrase and lactase activity compared to chow. Addition of 1 or 2% glutamine protected the liver from fatty infiltration seen with standard TPN. These studies would suggest the addition of glutamine might be beneficial during provision of standard total parenteral nutrition.

Animals↗

PubMed1993

Glutamine is a potentially limiting amino acid for milk production in dairy cows: a hypothesis.

Recently, extensive research has been focused on glutamine because of its key position between energy and protein metabolism. Evidence is growing that glutamine is essential in situations of metabolic stress; practical application of this knowledge can already be found in parenteral nutrition of severely ill patients. Furthermore, glutamine is claimed to increase muscle protein synthesis. Glutamine and its counterpart, glutamic acid, are the most abundant amino acids in milk protein. Nevertheless, the role of nonessential amino acids (NEAA) in milk protein synthesis in high-yielding dairy cows has been practically neglected during the past 20 years. Evaluating current literature on glutamine metabolism in ruminants with emphasis on data related to milk protein production, we conclude the following: (1) Ruminants have a relatively low glutamine synthetase capacity compared with monogastric species, reflected in relatively low plasma glutamine levels; (2) The uptake of glutamine by the mammary gland is effectively 100% of the arterial supply; (3) Milk production in high-yielding dairy cows represents a metabolic stress comparable to fasting or acidosis; and (4) Responses of plasma and tissue glutamine pools in conditions of "metabolic stress," including high milk production, resemble those of most essential amino acids (EAA). Therefore we hypothesize that glutamine, although regarded as a NEAA, limits milk protein synthesis in high-yielding dairy cows.

Amino Acids↗

PubMed1995

Genetic engineering of hybridoma glutamine metabolism.

The murine hybridoma PQXB1/2 cannot be adapted to grow in culture media containing < 0.5 mM glutamine. Transformants selected following electroporation of PQXB1/2 cells with vectors containing a Chinese hamster glutamine synthetase (GS) cDNA under the control of the SV40 early promoter also failed to grow in the absence of glutamine in the culture medium. PQXB1/2 cells have, however, been transformed to glutamine independence following electroporation with a vector containing this glutamine synthetase cDNA under the control of the human cytomegalovirus immediate early promoter. In these cells, sufficient active glutamine synthetase was expressed from one vector per cell to enable growth in glutamine-free media. The specific activity of glutamine synthetase in two transformed cell lines producing parental levels of antibody was increased by 128 and 152%, respectively (0.57 and 0.63 mumol min-1 per 10(6) cells in transformants compared with parental levels of 0.25 mumol min-1 per 10(6) cells). This reprogramming of glutamine synthetase expression and glutamine metabolism is important for developing strategies to deal with ammonia toxicity and the production of cell lines with improved metabolic processes.

Animals↗

PubMed1995

The effects of cell number, concentrations of mitogen and glutamine and time of culture on [3H]thymidine incorporation into cervical lymph node lymphocytes stimulated by concanavalin-A.

The amount of [3H]thymidine incorporated into DNA in lymphocytes stimulated with Concanavalin-A increases exponentially with time at different concentrations of glutamine, reaches a peak value, then gradually decreases. When the value (log10 thymidine incorporation glutamine present -log10 thymidine incorporation glutamine absent) obtained from the exponential phase is plotted against time, a linear plot is obtained for each glutamine concentration. When these linear rates of incorporation are plotted against glutamine concentration, hyperbolic curves are obtained for different times of culture. The peak value of incorporation (which reflects the final number of cells which entered the cell cycle) is determined by the concentration of mitogen and occurs at an earlier time as the number of cells in culture is increased and as the concentration of glutamine is increased. These findings suggest that increasing the plasma glutamine concentration above the normal physiological level may be of value in increasing the proliferation of lymphocytes in conditions of lymphopenia. Adenosine, a fuel of purine nucleotide synthesis, which may affect the lymphoproliferative response also via specific adenosine receptors, increases the rate of incorporation of [3H]thymidine but this effect depends upon the concentration of glutamine; at low concentrations of glutamine, the stimulation by adenosine is apparent whereas at high concentrations of glutamine adenosine appeared to inhibit proliferation.

Animals↗

PubMed1978

The effect of ammonium chloride and glucagon on the metabolism of glutamine in isolated liver cells from starved rats.

1. Glucagon stimulated gluconeogenesis from glutamine in isolated liver cells to a far greater extent than that from any other amino-acid precursor. 2. Low concentrations of ammonium chloride (less than 1 mM) stimulated glucose production from glutamine. Glucagon further stimulated this glucose production, even in the presence of saturating concentrations of ammonium chloride. 3. In agreement with previous reports, glutamine hydrolysis by isolated mitochondria was found to be stimulated by ammonium chloride. It was found that ammonium chloride activated mitochondrial glutamine hydrolysis at the same concentrations at whict it stimulated glucose production from glutamine in liver cells. The effective activation of glutamine hydrolysis by ammonimum chloride in intact mitochondria was partially inhibited by rotenone and was abolished by uncoupling agents. 4. The addition of glucagon to hepatocytes metabolising glutamine led to a decrease in the intracellular concentration of glutamine and an increase in the intracellular concentration of glutamate. 5. It is likely that glucagon stimulates gluconeogenesis from glutamine by mechanisms which are additional to those that may operate in the stimulation of gluconeogenesis from other amino-acid precursors. It is suggested that both ammonium chloride and glucagon exert their effects on glutamine metabolism by increasing the effective activity of mitochondrial glutaminase (EC 3.5.1.2.).

Amino Acids↗

PubMed1981

The stimulus-secretion coupling of amino acid-induced insulin release. Metabolic interaction of L-glutamine and 2-ketoisocaproate in pancreatic islets.

1. The metabolic situation found in pancreatic islets exposed to both L-glutamine and 2-ketoisocaproate was investigated in order to assess its relevance to the synergistic effects of these nutrients upon insulin release. 2. In islet homogenates, serveral 2-keto acids could be used as partners for the transamination of L-glutamate to 2-ketoglutarate. The rate of transamination did not correlate positively with the capacity of each 2-keto acid to stimulate insulin release in the presence of L-glutamine. 3. L-Glutamine enhanced the production of L-leucine from 2-ketoisocaproate and inhibited the conversion of the 2-keto acid to acetoacetate and CO2. L-Glutamine also inhibited the oxidation of pyruvate. 4. In the presence of 2-ketoisocaproate, the rate of generation of 2-ketoglutarate from exogenous L-glutamine was increased, but the oxidative deamination of glutamate was suppressed. 5. L-Valine antagonized the effect of 2-ketoisocaproate to augment 14CO2 output from islets prelabelled with L-[U-14C]glutamine. 6. L-Glutamine did not increase the islet content of reduced pyridine nucleotides beyond the high level reached in the sole presence of 2-ketoisocaproate. 7. If allowance was made for the influence of exogenous nutrients upon the oxidation of endogenous nutrients, the insulin output evoked by L-glutamine and/or 2-keto acids tightly depended on the increment in oxidation rate attributable to these nutrients. 8. The metabolic and secretory responses to L-glutamine and 2-ketoisocaproate were best explained by a stimulation of transamination reactions between 2-ketoisocaproate and glutamate derived from exogenous glutamine.

Animals↗

PubMed1994

Glutamine metabolism in rat small intestine: synthesis of three-carbon products in isolated enterocytes.

Glutamine is a major respiratory fuel for enterocytes but the extent of glutamine decarboxylation in these cells is not certain. The metabolism of differentially labeled L-[14C]glutamine was studied in enterocytes isolated from fed rats. The results indicate that glutamine undergoes two decarboxylations and yields a three carbon end product. The first decarboxylation is presumably at alpha-ketoglutarate dehydrogenase but the identity of the second reaction is not clear. The addition of 3-mercaptopicolinate, an inhibitor of phosphoenolpyruvate carboxykinase, was without effect on either the rate of glutamine metabolism or the extent of decarboxylation. Labeled glutamine carbon was recovered in three carbon products primarily as alanine with lesser amounts as lactate. The addition of glucose to the incubation medium did not change the rate of glutamine metabolism, or decarboxylation, but lactate became the major labeled three carbon end product. The results show that the fate, alanine or lactate, of glutamine derived pyruvate in enterocytes depends on the relative rate of flux through pyruvate and indicates that one cytosolic pool of pyruvate exists in these cells. The limited oxidation of glutamine in enterocytes ensures that the gluconeogenic potential of glutamine is conserved within the body.

Animals↗

PubMed1992

Mechanisms of accelerated hepatic glutamine efflux in the tumour-bearing rat.

The mechanisms potentially controlling the net release of glutamine by the liver that occurs in tumour-bearing rats were investigated. Studies were undertaken when the tumour comprised approximately 7% (15 +/- 2 g) of total body weight. Hepatic glutamine gradient ratios were calculated by dividing hepatic glutamine content by arterial blood glutamine concentration. Both sodium-dependent and sodium-independent hepatocyte carrier-mediated glutamine transport were evaluated employing hepatic plasma membrane vesicles (HPMVs). In TBR the hepatic glutamine gradient ratio doubled (P < 0.001) secondary to a 52% increase in hepatic content (P < 0.005) and a 16% decrease in circulating glutamine (P < 0.001). Sodium-dependent glutamine transport was increased in HPMVs from TBR secondary to a 24 +/- 4% increase in the maximal velocity of transport (Vmax; P < 0.01) without alteration in apparent transporter affinity (Km). Saturable sodium-independent carrier-mediated glutamine transport was increased in HPMVs from TBR over CONT to a much greater relative degree owing to a 2.7-fold increase in transport Vmax (P < 0.05) without a change in transport Km. The accelerated hepatic efflux of glutamine which characterizes malignant growth appears to be the result of both mass-action gradient phenomena and alterations at the level of hepatocyte membrane transport activity.

Animals↗

PubMed2004

Effects of enteral supplementation with glutamine granules on intestinal mucosal barrier function in severe burned patients.

Glutamine is an important energy source in intestinal mucosa, the small intestine is the major organ of glutamine uptake and metabolism and plays an important role in the maintenance of whole body glutamine homeostasis. The purpose of this clinical study is to observe the protection effects of enteral supplement with glutamine granules on intestinal mucosal barrier function in severe burned patients. Forty-eight severe burn patients (total burn surface area 30-75%, full thickness burn area 20-85%) were randomly divided into two groups: burn control group (B group, 23 patients) and glutamine treated group (Gln group, 25 patients). Glutamine granules 0.5 g/kg were supplied orally for 14 days in Gln group, and the same dosage of placebo were given for 14 days in B group. The plasma level of glutamine, endotoxin and the activity of diamine oxidase (DAO), as well as intestinal mucosal permeability were determined. The results showed that the levels of plasma endotoxin, activity and urinary lactulose and mannitol (L/M) ratio in all patients were significant higher than that of normal control. After taking glutamine granules for 14 days, plasma glutamine concentration was significantly higher in Gln group than that in B group (607.86+/-147.25 microM/l versus 447.63 +/- 132.28 microM/l, P < 0.01). On the other hand, the levels of plasma DAO activity and urinary L/M ratio in Gln group were lower than those in B group. In addition, the wound healing was better and hospital stay days were reduced in the Gln group (46.59 +/- 12.98 days versus 55.68 +/- 17.36 days, P < 0.05). These results indicated that glutamine granules taken orally could abate the degree of intestine injury, lessen intestinal mucosal permeability, ameliorate wound healing and reduce hospital stay.

Administration, Oral↗