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Background: In severe acute pancreatitis (AP), intravenous glutamine has been shown to reduce the rate of complications, hospital stay, and mortality. In the present randomized trial, we aimed to evaluate the effect of enteral glutamine supplementation on clinical outcomes, gut permeability, systemic inflammation, oxidative stress, and plasma glutamine levels in patients with severe and predicted severe AP., Methods: Patients with AP admitted within 72 h of onset of symptoms were included. The primary outcome measure was development of infected pancreatic and peri-pancreatic necrosis and in-hospital mortality. High-sensitivity C-reactive protein (HS-CRP) and interleukin-6 (IL-6) were evaluated as markers of inflammation; plasma thiobarbituric acid reactive substances (TBARS) and activities of serum superoxide dismutase and glutathione peroxidase were determined to evaluate oxidative stress; serum polyethylene glycol (PEG) was tested for intestinal permeability; subjective global assessment (SGA) was used for nutritional assessment, and an improvement in organ function was measured by the Modified Marshall score. Intention-to-treat analysis was used. A p-value of < 0.05 was considered statistically significant., Results: After power calculation, we enrolled 18 patients in the glutamine and 22 in the control arm. There was no significant improvement in the development of infected necrosis and in-hospital mortality between the groups. Improvement in Modified Marshall score was observed in a higher proportion of patients receiving glutamine (15 [83.3%] vs. 12 [54.5%]; p = 0.05). Plasma glutamine levels improved more in glutamine-treated group (432.72 ± 307.83 vs. 618.06 ± 543.29 μM/L; p = 0.004), while it was lower in controls (576.90 ± 477.97 vs. 528.20 ± 410.45 μM/L; p = 0.003). PEG level was lower after glutamine supplementation (39.91 ± 11.97 vs. 32.30 ± 7.39 ng/mL; p = 0.02). Statistically significant reduction in IL-6 concentration was observed in the glutamine group at the end of treatment (87.44 ± 7.1 vs. 63.42 ± 33.7 μM/L; p = 0.02)., Conclusions: Despite absence of improvement in infected necrosis and in-hospital mortality, enteral glutamine supplementation showed improvement in gut permeability, oxidative stress, and a trend towards improvement in organ function as depicted by improvement in the Modified Marshall score., Trial Registration: NCT01503320.

Deoxynivalenol (DON) has critical health effects if the contaminated grains consumed by humans or animals. DON can have negative effects on the active transport of glucose and amino acids in the small intestine of chickens. As the underlying mechanisms are not fully elucidated, the present study was performed to delineate more precisely the effects of cycloheximide (protein synthesis inhibitor, CHX) and DON on the intestinal absorption of nutrients. This was to confirm whether DON effects on nutrient absorption are due to an inhibition of protein synthesis. Changes in ion transport and barrier function were assessed by short-circuit current (Isc) and transepithelial ion conductance (Gt) in Ussing chambers. Addition of D-glucose or L-glutamine to the luminal side of the isolated mucosa of the jejunum increased (P < 0.001) the Isc compared with basal conditions in the control tissues. However, the Isc was not increased by the glucose or glutamine addition after pre-incubation of tissues with DON or CHX. Furthermore, both DON and CHX reduced Gt, indicating that the intestinal barrier is compromised and consequently induced a greater impairment of the barrier function. The remarkable similarity between the activity of CHX and DON on nutrient uptake is consistent with their common ability to inhibit protein synthesis. It can be concluded that the decreases in transport activity by CHX was evident in this study using the chicken as experimental model. Similarly, DON has negative effects on the active transport of some nutrients, and these can be explained by its influence on protein synthesis.

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.

Glutamine plays an important role in nitrogen homeostasis and intestinal substrate supply. It has been suggested that glutamine is a precursor for arginine through an intestinal-renal pathway involving inter-organ transport of citrulline. The importance of intestinal glutamine metabolism for endogenous arginine synthesis in humans, however, has remained unaddressed. The aim of this study was to investigate the intestinal conversion of glutamine to citrulline and the effect of the liver on splanchnic citrulline metabolism in humans. Eight patients undergoing upper gastrointestinal surgery received a primed continuous intravenous infusion of [2-(15)N]glutamine and [ureido-(13)C-(2)H(2)]citrulline. Arterial, portal venous and hepatic venous blood were sampled and portal and hepatic blood flows were measured. Organ specific amino acid uptake (disposal), production and net balance, as well as whole body rates of plasma appearance were calculated according to established methods. The intestines consumed glutamine at a rate that was dependent on glutamine supply. Approximately 13% of glutamine taken up by the intestines was converted to citrulline. Quantitatively glutamine was the only important precursor for intestinal citrulline release. Both glutamine and citrulline were consumed and produced by the liver, but net hepatic flux of both amino acids was not significantly different from zero. Plasma glutamine was the precursor of 80% of plasma citrulline and plasma citrulline in turn was the precursor of 10% of plasma arginine. In conclusion, glutamine is an important precursor for the synthesis of arginine after intestinal conversion to citrulline in humans.

Intestinal glucose and amino acid transport is stimulated by the serum- and glucocorticoid-inducible kinase isoforms SGK1, SGK2, and SGK3 and protein kinase B which are, in turn, stimulated following activation of the phosphoinositol-3 kinase (PI3 kinase). The present study has been performed to explore whether pharmacological inhibition of the PI3 kinase affects electrogenic jejunal transport of glucose and amino acids. In Ussing chamber experiments, glucose (20 mM), phenylalanine (20 mM), glutamine (20 mM), cysteine (20 mM), and proline (20 mM) generated lumen negative currents (I (glc), I (phe), I (gln), I (cys), and I (pro)), respectively, which gradually declined following application of the PI3 kinase inhibitor Wortmannin (1 muM). Within 40 min, Wortmannin treatment significantly decreased I (glc) by 39 +/- 10% (n = 5), I (phe) by 70 +/- 7% (n = 4), I (gln) by 69 +/- 8% (n = 4), I (cys) by 67 +/- 8% (n = 6), and I (prol) by 79 +/- 12% (n = 3). A similar decline of I (glc) was observed following application of the PI3 kinase inhibitor LY294002 (50 microM). Exposure to the inhibitors did not significantly alter transepithelial potential difference and resistance in the absence of substrates for electrogenic transport. The observations suggest that the electrogenic transport of glucose and several amino acids requires the continued activity of PI3 kinase.

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.

The current experiments were designed to study the effect of beta-estradiol on type IIb sodium-coupled phosphate (NaPi-IIb) cotransporter gene expression. Uptake studies with intestinal brush-border membrane vesicles (BBMV) showed that estrogen treatment increased sodium-dependent phosphate absorption by approximately 45% in rat intestine. Northern blot analysis indicated that NaPi-IIb mRNA expression was increased by approximately 50% after estrogen treatment. Western blot analysis also detected an increase in BBMV NaPi-IIb protein expression in estrogen-treated rats. In human intestinal Caco-2 cells, NaPi-IIb mRNA abundance was increased approximately 60% after estrogen treatment, and this increase could be abolished by inhibition of gene transcription. Transfection studies with human NaPi-IIb promoter reporter constructs showed that the promoter was responsive to estrogen treatment. These studies demonstrate for the first time that estrogen stimulates intestinal sodium-dependent phosphate absorption in female rats. This stimulation is associated with increased NaPi-IIb mRNA and protein expression. Thus the effect of estrogen on intestinal Pi absorption may be partially due to activation of NaPi-IIb gene transcription.

L-glutamine transport was evaluated in isolated cells from the guinea-pig small intestine by measuring [(3)H]- L-glutamine uptake. Villous and crypt cells expressed Na(+)-dependent and Na(+)-independent transport mechanisms. Glutamine transport systems were identified using various amino acids and analogues as inhibitors. In both villous and crypt cells, 2-(methylamino)-isobutyrate (MeAIB), a system A inhibitor, did not inhibit Na(+)-dependent glutamine influx. 2-Aminobicyclo(2,2,1)heptane-2-carboxylate (BCH), a system B(0) and B(0,+) substrate, had no effect on Na(+)-dependent influx. Serine, cysteine and threonine, system ASC inhibitors, reduced Na(+)-dependent influx by 50%. Asparagine, but not histidine, system N inhibitors, reduced Na(+)-dependent glutamine influx by 50%, however the effect of asparagine was not additive to that of threonine. The remaining Na(+)-dependent glutamine influx (50%) was only inhibited by glutamine itself, by Na(+) substitution ( N-methyl-glucamine, K(+), Li(+)) or by external pH reduction. Phenyl-acetyl-glutamine (PAG), a synthetic amino acid analogue, also inhibited this Na(+)-dependent, threonine-insensitive glutamine influx (IC(50) 2.45 mM). The Na(+)-independent uptake was partially inhibited by BCH, a system L inhibitor, and other neutral amino acids, but was not affect by PAG. Our results suggest that glutamine is transported in both villous and crypt cells by the Na(+)-independent system L, by the Na(+)-dependent system ASC and by an as yet undescribed Na(+)-dependent transport mechanism, highly specific for glutamine.

Background: The amino acid glutamine, while essential for gut epithelial growth, has also been shown to stimulate colon carcinoma proliferation and diminish differentiation. Human colon carcinomas are known to extract and metabolize glutamine at rates severalfold greater than those of normal tissues, but the regulation of this response is unclear. Previously we reported that phorbol esters regulate hepatoma System ASC/B(0)-mediated glutamine uptake and cell growth. As human colon carcinoma cells use this same transporter for glutamine uptake, the present studies were undertaken to determine whether similar regulation functions in colon carcinoma., Materials and Methods: Human colon carcinoma cell lines (WiDr and HT29) were treated with the protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA) and initial-rate transport of glutamine and other nutrients was measured at specific times thereafter. Growth rates were monitored during culture +/- PMA or an excess of System ASC/B(0) substrates relative to glutamine., Results: PMA treatment induced a rapid inhibition of glutamine uptake rates in WiDr and HT29 cells by 30 and 57%, respectively, after 1 h. Cycloheximide failed to block this response, indicating that the mechanism by which PMA exerts its effects is posttranslational. The inhibition of glutamine uptake by PMA was abrogated by the PKC inhibitor staurosporine, suggesting that this rapid System ASC/B(0) regulation may be mediated by a PKC-dependent pathway. PMA also significantly decreased transport via System y(+) (arginine) and System A (small zwitterionic amino acids). Chronic phorbol ester treatment inhibited WiDr cell growth, as did attenuation of System B(0)-mediated glutamine uptake with other transporter substrates., Conclusions: System ASC/B(0) uptake governs glutamine-dependent growth in colon carcinoma cell lines, and is regulated by a phorbol ester-sensitive pathway that may involve PKC. The results further establish the link between glutamine uptake and colon carcinoma cell growth, a relationship worthy of further investigation with the goal of discovering novel cancer therapeutic targets., (Copyright 2000 Academic Press.)

The demand for glutamine increased only in the preserved intestine in the early postoperative period (3 days after transplantation). Glutamine demand of the preserved grafts returned to control and immediate levels 7 and 14 days after transplantation. Three days after intestinal transplantation, when the intestinal mucosa was actively regenerating, the demand for glutamine was markedly enhanced. The enhanced demand for glutamine was met by increased output of glutamine by the liver and skeletal muscle. Glutamine uptake by the intestinal graft was enhanced by a brief infusion of glutamine. Thus, we believe exogenous glutamine supplementation may be beneficial for the recovery of intestinal grafts with severe mucosal injury.

The small intestine has been identified as an important site of metabolism of glutamine. The impairment of gut mucosa integrity during total parenteral nutrition (TPN) has been ascribed to a diminished supply of glutamine, due to the lack of glutamine in standard TPN. In addition, nutritional depletion diminishes glutamine availability in the intestine. The uptake of glutamine in the gut is dependent on the plasma glutamine concentration. This study was performed to observe changes in plasma and mucosa amino acid content during infusion of standard TPN and during infusion of TPN supplemented with glutamine. Twenty patients were randomly allocated to an experimental group (GTPN, TPN containing 0.23 g glutamine/kg.day) and a control group (CTPN, standard TPN). Patients received the iso-nitrogenous and isocaloric TPN during 10-14 days. After an overnight fast, before TPN was started, biopsies were taken from the duodenum. Amino acid concentrations were determined in the biopsies. Blood was taken for routine laboratory measurements and amino acid determination. This procedure was repeated on the last day of TPN infusion. Plasma glutamine in the GTPN group rose about 25% whereas plasma glutamine concentrations in the CTPN group remained unchanged. Mucosa glutamine rose with about 75% in the GTPN group whereas in the CTPN group no increase was observed. The rise of total plasma and mucosa amino acids was equal in both groups. The rise in plasma and mucosa glutamine was limited to nutritionally depleted patients. In conclusion, parenteral glutamine administration increases plasma and subsequently mucosa glutamine, specifically in depleted patients.

This study examined whether growth hormone treatment deprived the intestinal tract of glutamine after trauma. Piglets were treated with growth hormone 24 units daily 3 days before and at the start of the trauma (GH-3, n = 8) or at the start of the trauma only (GH-1, n = 8). Eight piglets acted as non-treated controls. The trauma consisted of a standardized abdominal surgical procedure. Primed constant infusions of U-14C-glutamine were given. Intestinal, hepatic, renal and hindleg glutamine fluxes were measured. Growth hormone treatment increased mean(s.e.m.) net intestinal glutamine uptake: GH-3, 39.7(9.4) and 48.7(12.7) mumol/min; GH-1, 33.2(5.5) and 25.7(12.3) mumol/min; controls, 19.5(10.3) and 2.0(15.3) mumol/min at 1 h and 5 h after trauma, respectively, (P = 0.02). The treatment increased glutamine oxidation (P = 0.025), and decreased hindleg glutamine net (P = 0.0052) and absolute release (P = 0.0063), glutamine rate of appearance (P = 0.01), and percentage of glucose coming from glutamine (P = 0.05). Growth hormone treatment before trauma increased intestinal glutamine uptake.

The effects of glutamine-supplemented parenteral nutrition on protein metabolism, small intestinal mucosal metabolism, morphology, and barrier function were studied in endotoxin-treated rats. Forty-six male Wistar rats were randomized to two groups of 23 animals each and received total parenteral nutrition solutions supplemented with either glutamine (GLN group) or glycine (GLY group) at 2% wt/vol. Endotoxemia was induced by continuous intravenous infusion of endotoxin at a dose of 2 mg/kg per day throughout the 4-day study period. The GLN group had a less-negative cumulative nitrogen balance (-14.0 +/- 132.8 mg of nitrogen in the GLN group and -86.8 +/- 161.7 mg of nitrogen in the GLY group, p < .05) and less cumulative excretion of urinary 3-methylhistidine (2910 +/- 593 nmol) than the GLY group (4447 +/- 933 nmol, p < .01). Jejunal mucosal glutaminase activity and the arterio-portal venous blood glutamine concentration differences were significantly higher in the GLN group compared with the GLY group (15.6 +/- 2.3 vs 11.1 +/- 1.9 mumol/g per minute, p < .05, and 181 +/- 52 vs 147 +/- 36 nmol/mL, p < .05, respectively). The morphology of the jejunal mucosa in the GLN group was significant for having greater mucosal weight (23.4 +/- 3.1 vs 17.6 +/- 2.5 mg/cm), villus height (445 +/- 75 vs 357 +/- 57 microns), crypt depth (197 +/- 34 vs 161 +/- 28 microns), and wall thickness (751 +/- 77 vs 648 +/- 102 microns) than the GLY group (p < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Using in vivo and in vitro techniques, the mechanism by which intestinal mucosa obtains glutamine from luminal oligopeptides was investigated in humans. The rate of hydrolysis by mucosal brush border membrane was more than threefold greater for alanylglutamine than for glycylglutamine. Despite this difference, rates of dipeptide and amino acid disappearance during intestinal perfusion were greater from test solutions containing glycylglutamine than alanylglutamine. Furthermore, rates of intraluminal appearance of products of hydrolysis during the infusion of two dipeptides were similar and less than 5% of the disappearance rate of the parent dipeptide. In contrast to free glutamine, uptake of peptide-bound glutamine by brush border membrane vesicles was not inhibited by deletion of sodium or addition of free amino acids to the incubation medium but was inhibited by other oligopeptides and stimulated by a proton gradient. Inhibition constants for the saturable uptake of glycylglutamine and alanylglutamine by vesicles were not significantly different, suggesting similar affinities for the peptide transporter. It is concluded that in human intestine the predominant mechanism for assimilation of glutamine-dipeptides is absorption as intact dipeptide rather than hydrolysis.

Malnutrition and dehydration are the immediate consequences of diarrheal diseases. To investigate the biological significance of glutamine, alanine and glucose in the intestinal mucosa, we have used Ussing chambers to determine electrolyte transport by measuring short-circuit current (Isc), potential difference (PD) and tissue resistance (TR) in rabbit intestinal mucosa. Increasing doses (10(-5) M to 10(-1) M) of glutamine, alanine and glucose cause a significant increase in intestinal cation cotransport. Although glucose had a slightly earlier effect, 30 mM glutamine and 0.1 M alanine had a maximal effect which was more than two times that caused by 30 mM glucose. The pD2 values for glucose, glutamine and alanine were 3.0, 2.5, and 2.0, respectively. The dose-response curves of these substrates suggest that the intestinal cotransport kinetics for glutamine is different from that of glucose and alanine. Our results demonstrate that all three substrates cause a significant increase in Isc or PD, suggesting an increase in the intestinal mucosa cation cotransport. Glutamine has a larger effect on cation cotransport than alanine and glucose. These combinations should be studied further for the development of an oral rehydrating solution for diarrhea treatment which could prevent the resulting malnutrition, especially in those cases of prolonged diarrheal diseases.

This study characterizes for the first time, by use of a well-validated technique, glutamine transport across human basolateral membrane vesicles. Glutamine transport represented uptake into an osmotically active intravesicular space without significant metabolism. Glutamine uptake was temperature- and pH-dependent with maximal uptake at pH 7.5, and it was mediated by sodium-dependent and -independent processes. The initial rate of uptake was linear up to 20 s, as depicted by the formula gamma (nmol/mg protein) = 0.0009 X (s) - 0.0011 (r = 0.99). Kinetic analysis of glutamine uptake at concentrations between 0.01 and 0.3 mmol/L at 5 s under sodium and potassium gradients showed a maximal transport capacity (Vmax) of 0.39 +/- 0.04 and 0.21 +/- 0.02 nmol.mg protein-1.5 s-1 for sodium-dependent and -independent processes, respectively (p less than 0.01). Km values were 0.17 +/- 0.04 and 0.06 +/- 0.2 mmol/L, respectively (p less than 0.05). Glutamine uptake under the sodium-gradient condition was electrogenic whereas under the potassium-gradient it was electroneutral. Neutral amino acids inhibited both sodium-dependent and -independent processes. This study confirms and characterizes the presence of carrier-mediated glutamine uptake at the basolateral membranes of human enterocytes.