Prevention of chronic radiation enteropathy by dietary glutamine

Background: Nearly 50% of all cancer patients receive therapeutic radiation during the course of their disease. The risk of late complications is the main dose-limiting factor in the delivery of radiation therapy. The small intestine, the major site of chronic radiation enteropathy, is also the principal organ of glutamine consumption. We therefore hypothesized that the provision of supplemental glutamine may have a protective effect on the development of chronic radiation enteropathy. Methods: This study evaluated the effects of supplemental oral glutamine on the development of chronic radiation (XRT) enteropathy. After scrotalization of a loop of small intestine, rats were randomized to receive 1 g/kg/day glutamine (GLN) or glycine (GLY) by gavage. After 2 days of prefeeding, rats were randomized to 1 of 4 groups: GLN + XRT (n=10), GLY + XRT (n=10), GLN only (n=10), GLY only (n=10). Twenty Gy was delivered to the scrotalized bowel in the GLN + XRT and GLY + XRT groups via a collimated beam. Gavage was continued for 10 days. Animals were then pair-fed chow. Rats were killed at 2 months postirradiation. Chronic radiation injury was assessed microscopically. Results: Injury scores in GLN + XRT were similar to those of unirradiated bowel and significantly different from GLY + XRT (1.89 ± 0.48 in XRT + GLN vs. 6.42 ± 1.55 in the XRT + GLY,p<0.01). Elevated Injury Scores in the XRT + GLY group correlated with gross thickening and fibrosis, a 10-fold decrease in gut GLN extraction (1.40 ± 4.3% in GLY + XRT vs. 16.0 ± 5.1% in GLN + XRT,p<0.05), and a 30% decrease in glutathione content (2.46 ± 0.19 and GLY + XRT vs. 3.17 ± 0.17 GLN + XRT,p<0.05). Conclusions: Provision of GLN during abdominal/pelvic XRT may prevent XRT injury and decrease the long-term complications of radiation enteropathy. Presented at the 46th Annual Cancer Symposium of the Society of Surgical Oncology, Los Angeles, March 18–21, 1993. Dr. Jensen is a recipient of the Armand Hammer Travel Award from the Society of Surgical Oncology.     

Effect of glutamine on methotrexate efficacy and toxicity.

OBJECTIVE: To examine the effect of oral glutamine (GLN) on the efficacy and toxicity of methotrexate (MTX). SUMMARY BACKGROUND DATA: The use of high-dose chemotherapy regimens is limited by the severity of their toxicities. Oral GLN has been shown to decrease the gut toxicity seen with MTX treatment while enhancing its tumoricidal effect. METHODS AND RESULTS: Studies were done in laboratory rats and in breast cancer outpatients. Fischer 344 rats were randomized to 48 hours of prefeeding with GLN (1 g/kg/day) or an isonitrogenous amount of glycine. Rats were killed 24 hours after receiving a 20-mg/kg intraperitoneal dose of MTX. In the GLN group, there was a threefold increase in total MTX in the tumor as compared with the control group, and this increase was in both the diglutamated and pentaglutamated MTX. Inversely, there was a significant decrease in the total polyglutamated MTX in the gut in the GLN group. Given the results of this preclinical study, the authors performed a phase I trial. Nine patients diagnosed with inflammatory breast cancer received GLN (0.5 g/kg/day) during MTX neoadjuvant therapy, escalating from doses of 40 mg/m2 to 100 mg/m2 weekly for 3 weeks, followed by a doxorubicin-based regimen. No toxicity of oral GLN was detected. No patient showed any sign of chemotherapy-related toxicity. One patient had a grade I mucositis. Except for one, all patients responded to the chemotherapy regimen. Median survival was 35 months. CONCLUSIONS: These studies suggest that GLN supplementation is safe in its administration to the tumor-bearing host receiving MTX. By preferentially increasing tumor retention of MTX over that of normal host tissue, GLN may serve to increase the therapeutic window of this chemotherapeutic age.     

The effects of glutamine-enriched total parenteral nutrition on tumor growth and host tissues.

The effects of glutamine-enriched total parenteral nutrition (TPN+GLN) were studied in tumor-bearing rats because glutamine can benefit host tissues but also may stimulate tumor growth. Rats were implanted with the methylcholanthrene-induced fibrosarcoma (MCA sarcoma) and were studied when the tumor constituted less than 5% of carcass weight (small tumor) and when the tumor constituted 10% of carcass weight (large tumor). Provision of 20% of TPN protein as glutamine produced a significant increase in the arterial glutamine level and maintained the skeletal muscle intracellular glutamine concentration (2.02 +/- 0.1 versus 1.39 +/- 0.07 mumol/g, p less than 0.01). Concurrently, hindquarter GLN fractional release increased nearly threefold (p less than 0.05) in the TPN+GLN group. Glutamine-enriched total parenteral nutrition did not affect carcass weight, tumor weight, tumor DNA content, or tumor glutaminase activity. Furthermore, DNA flow cytometric analysis did not demonstrate any difference in percentage of aneuploid tumor cells within the G1, S, or G2M cell cycles. However, the ratio of aneuploid to diploid cells within the tumor mass increased by 20% in animals receiving glutamine. Glutamine-enriched total parenteral nutrition had no effect on tumor glutathione (GSH) levels. No increase in hepatic GSH levels was observed, but gut mucosal GSH levels were 20% greater in the TPN+GLN group (p less than 0.05). The provision of glutamine-enriched TPN may be beneficial to the host by maintaining skeletal muscle glutamine stores and by supporting gut GSH biosynthesis. In this tumor model, TPN+GLN does not appear to increase tumor size, tumor DNA content, or tumor glutamine metabolism, but the ratio of tumor cells to host infiltrating cells within the tumor mass appears to be increased.     

Effect of supplemental dietary glutamine on methotrexate concentrations in tumors.

This study evaluated the effects of supplemental dietary glutamine (GLN) on methotrexate sodium concentrations in tumors and serum of sarcoma-bearing rats following the initiation of methotrexate. After randomization to a GLN diet (+GLN) or GLN-free diet (-GLN), tumor-bearing rats received 20 mg/kg of methotrexate sodium by intraperitoneal injection. The provision of supplemental GLN in the diet increased methotrexate concentrations in tumor tissues at 24 and 48 hours (38.0 +/- 0.20 nmol/g for the +GLN group vs 28.8 +/- 0.10 nmol/g for the -GLN group and 35.6 +/- 0.18 nmol/g for the +GLN group vs 32.5 +/- 0.16 nmol/g for the -GLN group, respectively). Arterial methotrexate levels were elevated only at 48 hours (0.147 +/- 0.007 microns/L for the +GLN group vs 0.120 +/- 0.006 microns/L for the -GLN group). Tumor morphometrics were not different between the groups but significantly greater tumor volume loss was seen even at 24 hours (-2.41 +/- 1.3 cm3 for the +GLN group vs -0.016 +/- 0.9 cm3 for the -GLN group). Tumor glutaminase activity was suppressed in both groups at 48 hours, but more so in the +GLN group (0.94 +/- 0.13 mumol/g per hour for the +GLN group vs 1.47 +/- 0.22 mumol/g per hour for the -GLN group). This study suggests that GLN may have therapeutic as well as nutritional benefit in oncology patients.     

Effects of glutamine supplements and radiochemotherapy on systemic immune and gut barrier function in patients with advanced esophageal cancer.

OBJECTIVE: The objective of this study was to determine whether oral glutamine supplements can protect lymphocyte and gut barrier function in patients with advanced esophageal cancer undergoing radiochemotherapy. SUMMARY BACKGROUND DATA: Glutamine supplements improved protein metabolism in tumor bearing rats who underwent chemotherapy and reduced the toxicity of chemotherapy through an enhancement of glutathione production in rats. METHODS: Thirteen patients with esophageal cancer were randomly placed in either a control or a glutamine group. Glutamine was administered orally (30 g/day) at the start of radiochemotherapy and for the subsequent 28 days. All patients underwent mediastinal irradiation and chemotherapy consisting of 5-fluorouracil and cisplatin. The lymphocyte count was determined, and blast formation was assessed after stimulation with phytohemagglutinin and concanavalin A. Gut barrier function was assessed by measuring the total amount of phenolsulfonphthalein excreted in the urine after the oral administration of phenolsulfonphthalein. RESULTS: Glutamine supplements prevented a reduction in the lymphocyte count (control: 567 +/- 96/mm3 vs. glutamine: 1007 +/- 151, p < 0.05), and blast formation of lymphocyte (phytohemagglutinin, control: 19478 +/- 2121 dpm vs. glutamine: 33860 +/- 1433, p < 0.01, concanavalin A, control: 19177 +/- 1897 dpm vs. glutamine: 29473 +/- 2302, p < 0.01), and amount of phenolsulfonphthalein excretion in the urine was greater with control than with glutamine group (control: 15.4 +/- 2.4% vs. glutamine: 7.4 +/- 1.2, p < 0.05) 7 days after the initiation of radiochemotherapy. CONCLUSIONS: Oral glutamine supplementation protects lymphocytes and attenuates gut permeability in patients with esophageal cancer during radiochemotherapy.     

Timing of oral glutamine on DMBA-induced tumorigenesis

INTRODUCTION: A single dose of oral 7,12-dimethylbenz(a)anthracene (DMBA) in pubertal rats causes breast tumors by 11 weeks and is associated with ablation of the normal gut glutathione (GSH) production for up to 4 weeks. We hypothesized that glutamine (GLN), known to restore the gut GSH production inhibited by DMBA, given only during this 4-week period, would prevent breast cancer initiation. METHODS: 160 Female Sprague-Dawley rats were divided to 10 groups (n = 16/group): Long Term (LT): DMBA + GLN, DMBA + FA, DMBA + H2O, OIL + GLN, OIL + FA, OIL + H2O; Short Term (ST): DMBA + GLN, DMBA + FA, OIL + GLN, OIL + FA At age 50 days old, rats received a one-time dose of 100 mg/kg DMBA or sesame oil. LT rats were gavaged daily with isonitrogenous GLN, (FA), or water (H2O) the entire study. ST rats were gavaged with GLN, freamine, or H2O the first 4 weeks and then H2O the remaining 7 weeks. All rats were pair-fed defined chow. Rats were sacrificed at 11 weeks, observed for tumors, blood assayed for GLN, GSH, gut GLN and GSH and uptake or production calculated using labeled C-14-PAH. RESULTS: ST and LT GLN were equally effective in preventing tumor formation. GLN doubled gut GSH production in LT animals as compared to all other groups (P < 0.05). Control rats developed no tumors and had superior gut GSH production as compared with tumor-bearing rats. CONCLUSIONS: Oral GLN when given only during the 4 weeks of known gut GSH ablation had the same tumor prevention efficacy as prolonged GLN administration. Not previously reported, GLN appears to affect the initiation of tumor formation in this model.     

Gut glutathione metabolism and changes with 7,12-DMBA and glutamine

INTRODUCTION: The mechanism by which oral glutamine (GLN) prevents 7,12-dimethylbenz(a)anthracene (DMBA)-induced breast cancer is unknown. While GLN triples the negative extraction of gut glutathione (GSH) in rats, DMBA significantly disrupts it. Actual gut GSH flux has not been reported. We hypothesized that the gut is a producer of GSH; DMBA blocks gut GSH production and supplemental oral GLN antagonizes this effect. MATERIALS AND METHODS: Eighty Sprague-Dawley rats were randomized to four groups (n = 20/group): DMBA + GLN, DMBA + FA, OIL + GLN, OIL + FA. Rats (age 50 days) were gavaged with a one-time dose of 100 mg/kg DMBA or oil. Rats were gavaged with AES-14 as GLN (1 gm/kg/day) or an isonitrogenous amount of Freamine (FA) from 1 week before till sacrifice at 1 week after DMBA (greatest effect on gut GSH extraction). Arterial and portal blood was taken for GLN and GSH levels, and blood flow was measured using (14)C-PAH. Gut GLN and GSH fluxes (uptake or production) were calculated. RESULTS: DMBA abrogated the normal GSH production (negative flux) in OIL + FA while not affecting GLN metabolism. GLN maintained GSH production in DMBA + GLN. CONCLUSIONS: Oral GLN restores to normal GSH production in DMBA-treated animals suggesting one of the mechanism(s) by which GLN prevents breast cancer in this model. Unchanged uptake of GLN in the DMBA-treated animals may indicate a block in GSH transport rather than actual intracellular production.     

Gut endotoxin restriction prevents catabolic changes in glutamine metabolism after surgery in the bile duct-ligated rat.

OBJECTIVE: The objective of this study was to investigate the role of gut-derived endotoxemia in postoperative glutamine (GLN) metabolism of bile duct-ligated rats. SUMMARY BACKGROUND DATA: Postoperative complications in patients with obstructive jaundice are associated with gut-derived endotoxemia. In experimental endotoxemia, catabolic changes in GLN metabolism have been reported. Glutamine balance is considered important in preventing postsurgical complications. METHODS: Male Wistar rats were treated orally with the endotoxin binder cholestyramine (n = 24, 150 mg/day) or saline (n = 24). On day 7, groups received a SHAM operation or a bile duct ligation (BDL). On day 21, all rats were subjected to a laparotomy followed 24 hours later by blood flow measurements and blood sampling. Glutamine organ handling was determined for the gut, liver, and one hindlimb. Intracellular GLN muscle concentrations were determined. RESULTS: Compared to the SHAM groups, BDL rats showed lower gut uptake of GLN (28%, p < 0.05); a reversal of liver GLN release to an uptake (p < 0.05); higher GLN release from the hindlimb (p < 0.05); and lower intracellular muscle GLN concentration (32%, p < 0.05). Cholestyramine treatment in BDL rats maintained GLN organ handling and muscle GLN concentrations at SHAM levels. CONCLUSIONS: Disturbances in postoperative GLN metabolism in BDL rats can be prevented by gut endotoxin restriction. Gut-derived endotoxemia after surgery in obstructive jaundice dictates GLN metabolism.     

Effect of glutamine on glutathione,IGF-I,and TGF-beta 1

BACKGROUND: Our previous results have showed that oral glutamine (GLN) supplementation decreased carcinogenesis in 7,12-dimethylbenz[a]antracene (DMBA) breast cancer model. We also have found that GLN raises blood glutathione (GSH) levels in an implantable breast cancer model. The process of tumor growth was accompanied by depressed GSH production and increased levels of insulin-like growth factor-I (IGF-I) and transforming growth factor beta1 (TGF-beta 1). GSH is counter-regulatory to IGF-I. We therefore hypothesized that in DMBA model of breast cancer, the increased GSH levels seen with oral GLN would be associated with lowered levels of IGF-I &TGF-beta(1). METHODS: Time-dated pubertal Sprague-Dawley rats were gavaged at time 0 with 1 g/kg/day glutamine (GLN) (n = 18), isonitrogenous Freamine (FA) (n = 18), or water (H(2)O) (n = 18). Rats were further randomized on day 7 to 100 mg/kg DMBA or oil. After 14 days, the animals were sacrificed and blood GSH, IGF-1, TGF-beta 1, breast tissue, and gut mucosa GSH levels were measured. RESULTS: Oral GLN increased significantly blood, breast tissue, and gut mucosa levels of GSH in both DMBA and control groups in comparison with the control groups not treated with GLN. At the same time, the levels of blood IGF-I and TGF-beta 1 decreased significantly in both DMBA-treated and control groups. DMBA did not significantly affect any of these levels. CONCLUSIONS ;Oral GLN increased GSH levels and lowered IGF-I and TGF-beta 1 in a range that is considered clinically significant. However, the effect of GLN in maintaining normal gut GSH production in the presence of DMBA was much more significant. Inconsistent with our hypothesis, reduction in IGF and TGF-beta 1 levels did not correlate with DMBA's effect on gut GSH production.     

The effects of sepsis and endotoxemia on gut glutamine metabolism.

The effects of sepsis on gut glutamine (GLN) metabolism were studied to gain further insight into the regulation of the altered glutamine metabolism that characterizes critical illnesses. Studies were done in laboratory rats and in hospitalized patients. The human studies were done in seven healthy surgical patients (controls) and six septic patients who underwent laparotomy. Radial artery and portal vein samples were obtained during operation and were analyzed for GLN and oxygen content. Despite no reduction in arterial glutamine concentration in the septic patients, gut glutamine extraction was diminished by 75% (12.0% +/- 1.6% in controls vs. 2.8% +/- 0.8% in septic patients, p less than 0.01). Similarly gut oxygen extraction was diminished by nearly 50% in the septic patients (p less than 0.05). To further investigate these abnormalities, endotoxin (10 mg/kg intraperitoneally) or saline (controls) was administered to adult rats 12 hours before cannulation of the carotid artery and portal vein. The arterial GLN concentration was increased by 13% in the endotoxin-treated animals (p less than 0.05) but gut glutamine uptake was diminished by 46% (526 +/- 82 nmol/100 g BW/minute in controls vs. 282 +/- 45 in endotoxin, p less than 0.01). Simultaneously gut glutaminase activity was diminished by 30% (p less than 0.01) and intestinal glutamate release fell by two thirds. Blood cultures were negative in control animals (0 of 20), but were positive in 25% of endotoxemic animals (6 of 24) for gram-negative rods (p = 0.019). Sepsis and endotoxemia impair gut glutamine metabolism. This impairment may be etiologic in the breakdown of the gut mucosal barrier and in the development of bacterial translocation.     

Oral glutamine reduces bacterial translocation following abdominal radiation

The effect of dietary glutamine on bacterial translocation was studied in rats following administration of a single dose of abdominal radiation (1000 rad) that causes a reproducible mucosal injury and results in a high incidence of culture-positive mesenteric lymph nodes after radiation (XRT). Following XRT, rats received only the amino acid glutamine (3%, +GLN) in their drinking water or a control nonessential amino acid (glycine, -GLN). Diets were isonitrogenous and isovolumetric. Four days after XRT, rats were anesthetized and a laparotomy was performed. Mesenteric lymph nodes were sterilely excised and cultured. Arterial blood was also obtained for whole blood glutamine determination. Control rats received no XRT but received identical diets. In XRT rats who received the GLN-free diet, the incidence of culture-positive mesenteric lymph nodes was 89% (eight of nine rats) while in the radiated rats receiving the GLN-enriched diet, the incidence fell to 20% (P less than 0.05). In non-radiated control rats receiving GLN-enriched and GLN-depleted diets for 4 days, bacterial translocation occurred in zero of eight and one of eight rats, respectively (NS). Provision of glutamine to XRT rats resulted in higher blood levels of glutamine (408 +/- 25 microM in XRT +GLN vs 311 +/- 19 microM in XRT -GLN, P less than 0.05). In addition, provision of GLN maintained mucosal mass and reduced weight loss (P less than 0.05). The data lend further support to the hypothesis that glutamine helps maintain the gut mucosal barrier and thereby decreases the incidence of bacterial translocation following bowel injury.(ABSTRACT TRUNCATED AT 250 WORDS)     

Burn injury alters intestinal glutamine transport

Several studies have established that intestinal glutamine (GLN) metabolism is altered during catabolic states. It remains unclear whether these alterations are due to a defect in metabolism or in transport of the amino acid. The present study examines the kinetics of GLN transport across basolateral membrane vesicles (BLMV) of enterocytes obtained from control rats and rats subjected to 20% full-thickness scald burn, 48 hr previously. BLMV were prepared from freshly isolated enterocytes using differential centrifugation with separation on a Percoll density gradient. BLMV were enriched (10- to 12-fold) with Na+-K+-ATPase while markers for brush border membranes were impoverished. Previous studies from our laboratory indicated that, in this preparation, GLN transport is into an osmotically sensitive space, dependent on GLN concentration, linear up to 30 sec, and both temperature and Na+ dependent. Our results indicate that in thermal injury, initial rates of GLN uptake were depressed (y = 3.67 + 0.435X for burned rats vs y = 18.7 + 0.907X for controls, P less than 0.01). Kinetic analysis of GLN uptake showed a marked decrease in transport Vmax (81.8 +/- 15 nmole/mg protein/15 sec for burned rats vs 185 +/- 17 nmole/mg protein/15 sec for controls, P less than 0.001). Transport Km also decreased from 0.25 +/- 0.004 mM for controls to 0.08 +/- 0.03 mM glutamine for burned rats (P less than 0.001). Kinetic studies performed at GLN levels greater than 0.6 mM showed that GLN uptake proceeded by a nonsaturable process in both the control and burned rats. No significant alteration in this nonsaturable component was observed.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Protective Effects of Alpha-Lipoic Acid on Methotrexate-Induced Oxidative Lung Injury in Rats

Objective: Oxidative stress is one of the major causes of methotrexate induced lung injury (MILI). Alpha-lipoic acid (ALA), which occurs naturally in human food, has antioxidative and anti-inflammatory activities. The aim of this study was to research the potential protective role of ALA on MILI in rats. Methods: Twenty one rats were randomly subdivided into three groups: control (group I), methotrexate (MTX) treated (group II), and MTX+ALA treated (group III). Lung injury was performed with a single dose of MTX (20 mg/kg) to groups 2 and 3. On the sixth day, animals in all groups were sacrificed by decapitation and lung tissue and blood samples were removed for histological examination and also measurement the levels of interleukin-1-beta (IL-1β), malondialdehyde (MDA), glutathione (GSH), tumour necrosis factor-alpha (TNF-α), myeloperoxidase (MPO), and sodium potassium-adenosine triphosphatase (Na+/K+ATPase). Results: In MTX group tissue GSH, Na+/K+ATPase activities were lower, tissue MDA, MPO and plasma IL-1?, TNF-? were significantly higher than the other groups. Histopathological examination showed that lung injury was less severe in group 2 according to group 3. Conclusions: Oxidative damage of MTX in rat lung is partially reduced when combined with ALA.     

Low plasma glutamine after multiple trauma: relationship with intracellular glutamine in polymorphonuclear neutrophils during prolonged ICU stay

BACKGROUND: Aim of the study was to evaluate whether low plasma glutamine (GLN) is related to low intracellular GLN in stress-affected cells such as polymorphonuclear neutrophil (PMN). We hypothesized, that because low plasma GLN is assumed to have an impact on clinical outcome, stress-affected cells may also show low GLN contents. METHODS: Thirty-nine consecutive severely injured trauma patients staying at least 10 days at a surgical intensive care unit (ICU) of a university hospital were separated into two groups: group one (n = 16) with low plasma GLN (< 420 micromol/l in average during ICU stay), and group two (n = 23) with normal plasma GLN. Initial blood samples for GLN analyses were collected within 24 h of admission at ICU. Further blood samples were taken on days 5 and 10 at 08:00 hours. RESULTS: Patients in both groups showed no differences regarding demographic data, surgical interventions or infections. Acute physiology and chronic health evaluation (APACHE) II and the sequential organ failure assessment (SOFA) score and mortality rate were also comparable. During the study period, intracellular PMN GLN contents and concentrations did not differ between both groups. On the first day, intracellular PMN GLN content in the low plasma GLN group peaked at 5.01 +/- 3.06 x 10(-16) mol and in normal plasma GLN group at 4.73 +/- 2.57 x 10(-16) mol above the level of healthy individuals. In both groups, content decreased significantly towards the end of the observation period (group one: 2.79 +/- 1.59 x 10(-16) mol and group two: 2.63 +/- 1.71 x 10(-16) mol). A correspondent course could be observed for cell volumes. In contrast, variation of intracellular GLN concentrations remained within the reference range throughout the observation period: group one 836 +/- 510 micromol/l on day 1 and 582 +/- 331 micromol/l on day 10, and group two 788 +/- 428 micromol/l on day 1 and 548 +/- 356 micromol/l on day 10. No correlation between plasma GLN and intracellular GLN was found in either group. CONCLUSION: No association between low plasma GLN and low intracellular GLN in PMN was found in a cohort of severely injured trauma patients with a minimum stay of 10 days at ICU.     

Glutamine metabolism by the endotoxin-injured lung.

The alterations in lung glutamine (GLN) metabolism that occurs in the endotoxin-injured lung were studied in rats and subsequently correlated with flux changes that occur in patients with the adult respiratory distress syndrome (ARDS). Measurements in animals were made at various time-points following the administration of endotoxin, while studies in surgical patients were done in a group of healthy controls, in patients with "early" sepsis who had normal chest x-ray films, and in patients with radiographic and physiologic evidence of ARDS. In healthy control rats, net amounts of GLN are released by the lungs into the systemic circulation. This release rate doubled 30 minutes after intravenous endotoxin (1,580 +/- 320 nmol GLN/100 g BW/min vs. 736 +/- 179 in controls, p less than 0.01) but glutamine synthetase activity was unchanged, suggesting an outpouring of cellular glutamine stores. Two hours after endotoxin treatment, this accelerated fractional release of glutamine by the lungs was no longer detected. By the 12-hour time-point, the lungs reversed to an organ of net glutamine balance (234 +/- 248 nmol/100 g BW/min, p less than 0.05 vs. controls and ENDO30 min) despite a more than two-fold increase in glutamine synthetase activity (p less than 0.01). Simultaneously, lung weights were increased by 21% (p less than 0.01) and histologic examination showed an interstitial infiltrate and pulmonary edema. Similar observations were made in humans; patients with "early" sepsis exhibited a marked increase in lung glutamine release, while patients with ARDS demonstrated glutamine balance across the lungs (4,030 +/- 910 nmol GLN/kg BW/min vs. 637 +/- 496 in ARDS, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Glutamine protects against doxorubicin-induced cardiotoxicity.

Doxorubicin (DOX) dose-intensive therapy for breast cancer is limited by a cardiomyopathy that often results in overt congestive heart failure. We hypothesized that dietary glutamine (GLN) can diminish DOX-induced cardiotoxicity by maintaining tissue glutathione (GSH) levels and thus preventing the proposed mechanism of cardiac injury: oxidation. METHODS: Forty-two female Fisher 344 rats were randomized into one of six groups: GLN + saline (SAL), GLN + DOX, freamine (FA) + SAL, FA + DOX, H2O + SAL, and H2O + DOX. Rats were pair-fed chow and gavaged with 1 g/kg/day GLN or an isonitrogenous amount of FA or H2O for 28 days. Rats were injected intravenously with a single dose of SAL or 9 mg/kg DOX on day 7 of gavage. At 28 days (21 days post-DOX), rats were sacrificed and blood and cardiac tissue were assayed for GLN and GSH content and lipid peroxidation (LP). RESULTS: There were no differences in cardiac GSH levels and cardiac lipid peroxidation in GLN + SAL versus GLN + DOX groups. However, blood and cardiac GSH levels were significantly decreased in H2O + DOX and FA + DOX groups compared to controls (H2O + SAL and FA + SAL). CONCLUSION: These data suggest that dietary GLN supplementation may diminish DOX-induced oxidative damage and thus cardiotoxicity through upregulation of cardiac GSH metabolism.     

The early response of the jejunal brush border glutamine transporter to endotoxemia.

The early effects of endotoxin (4 hr after a single dose of Escherichia coli LPS, 7.5 mg/kg) on L-glutamine (GLN) transport across the jejunal brush border of rats were studied. Jejunal brush border membrane vesicles (BBMVs) were prepared by a Mg2+ aggregation/differential centrifugation technique. Vesicle purity and integrity were confirmed by a 15-fold enrichment of brush border marker enzymes, osmotic activity, transport overshoots in the presence of sodium, and similar 1- and 2-hr equilibrium values. L-[3H]GLN transport in jejunal BBMVs was measured by a millipore filtration technique. Na(+)-dependent glutamine transport, which accounted for greater than 80% of total transport, was increased twofold in BBMVs from endotoxin-treated rats (67 +/- 5 pmole/mg protein/15 sec vs 38 +/- 3, P less than 0.01). Endotoxin treatment did not alter the activity of the Na(+)-independent carrier. Simultaneously, intestinal extraction of glutamine from the bloodstream fell by 56% (15.1 +/- 2.3% in controls vs 6.6 +/- 1.3% in endotoxin-treated rats, P less than 0.01). This reduction in the uptake of circulating glutamine could not be accounted for by a fall in the arterial concentration. Thus, soon after endotoxemia brush border glutamine uptake is increased while consumption of glutamine across the basolateral membrane is decreased. This increased uptake may support protein synthesis and may provide a biochemical rationale for the use of early enteral nutrition after the onset of critical illness.     

Glutamine preserves liver glutathione after lethal hepatic injury.

Glutathione (GSH) is a major antioxidant that protects tissues from free radical injury. Glutamine augments host defenses and may be important in GSH synthesis. Acetaminophen toxicity causes hepatic GSH depletion and hepatic necrosis. The authors hypothesized that glutamine-supplemented nutrition would enhance liver GSH stores and diminish hepatic injury and death after acetaminophen overdose. Wistar rats received either a standard total parenteral nutrition (TPN) solution (STD) or an isocaloric, isonitrogenous glutamine-supplemented solution (GLN). On the 5th day of feeding, animals were given acetaminophen (400 mg/kg intraperitoneally) and then killed at various time points. Standard TPN solution animals had a rapid depletion of hepatic glutathione, whereas GLN animals were resistant to this drop and rapidly repleted hepatic GSH stores. Glutamine-supplemented animals maintained higher plasma glutamine concentrations, had lesser elevations in hepatic enzymes, and sustained significantly fewer complications compared with STD animals. The authors conclude that glutamine-supplemented nutrition preserves hepatic glutathione, protects the liver, and improves survival during acetaminophen toxicity. Glutamine may augment host defenses by enhancing antioxidant protection.     

Effects of tumor necrosis factor on system ASC-mediated glutamine transport by human fibroblasts.

The effects of tumor necrosis factor-alpha (TNF) on glutamine GLN transport by cultured human fibroblasts were studied. Uptake of 3H-GLN was assayed in both the presence and absence of sodium in order to differentiate Na(+)-dependent and Na(+)-independent transport systems. GLN transport was linear (r = 0.99) for at least 15 min and occurred predominantly via a single Na(+)-dependent pathway, consistent with System ASC. Incubation of fibroblasts with TNF (1000 units/ml) for 12 hr resulted in a significant decrease in system ASC-mediated glutamine transport activity. TNF did not alter cell morphology or protein content. Kinetic studies indicated that the decrease in carrier-mediated Na(+)-dependent GLN transport was not due to a change in transporter affinity (Km = 117 +/- 23 microM in controls vs 86 +/- 23 microM in TNF, P = NS), but instead to a 45% decrease in maximal transport rate (Vmax = 4088 +/- 354 pmole/mg protein/30 sec in controls vs 2230 +/- 510 in TNF, P less than 0.05). TNF also decreased Na(+)-independent transport by 50% (mean uptake of 50 microM GLN = 94 +/- 13 pmole/mg protein/30 sec in controls vs 46 +/- 6 in TNF, P less than 0.02). In human fibroblasts, the activity of System ASC, which has generally been viewed as a hormonally unresponsive carrier, is decreased by TNF. This impairment in glutamine transport may result in inadequate amounts of intracellular glutamine to support fibroblast metabolism and possibly function.