Glutamine metabolism by the intestinal tract

Treatment of acute diarrhea with oral rehydration solutions containing glutamine

OBJECTIVE

In a randomized, double-blind, controlled clinical trial we compared the efficacy of adding 90 mmol/L L-glutamine to the standard World Health Organization oral rehydration salts (WHO-ORS).

SUBJECTS

One hundred twenty male infants, > 1 month and < 1 year of age, with acute non-cholera diarrhea and dehydration were randomly assigned to one of the two treatment groups.

METHODS

Patients were kept in a metabolic unit where body weight, ORS, water and food intake, as well as stool, urine and vomitus output were recorded at 6-hour intervals. Laboratory evaluation, including blood gases and electrolytes, were monitored during hospitalization.

RESULTS

Diarrheal stool output, duration of diarrhea and volume of ORS required to achieve and maintain hydration was not significantly different between the treatment groups.

CONCLUSION

This study demonstrated that a glutamine-based ORS did not provide any additional therapeutic advantage over the standard WHO-ORS during treatment of dehydration in infants with acute non-cholera diarrhea.

Supplementation of an elemental enteral diet with alanyl-glutamine decreases bacterial translocation in burned mice

Although there are many reports of the importance of early enteral feeding in maintaining gastrointestinal integrity and preventing bacterial translocation (BT) following burn injury, no diet has been shown clinically to protect the GI tract postburn. Several studies suggest that glutamine (GLN) may benefit gut integrity following injury, shock and other stress. Unfortunately, the free amino acid GLN is unstable in solution. Alanyl-glutamine (ALA-GLN), a soluble form of GLN, maintains long-term stability in solution and could be supplemented to conventional liquid enteral diets. We studied the effects of ALA-GLN supplementation of the elemental diet Vivonex TEN on effecting BT in mice following 32 per cent TBSA full skin thickness burns. Groups A-D were burned. Group A (30 mice) was fed standard rodent chow, which contains extremely high (clinically non-useable) levels of protein. Group B (51 mice) was fasted 24 h, then fed chow 24 h. Group C (64 mice) was fed Vivonex TEN, and Group D (65 mice) received Vivonex TEN plus ALA-GLN (GLN equivalent, 14 g/l). A control group (Group E) consisted of 22 normal mice (no burn injury, chow diet). Mice were assessed for BT by sterile harvesting and plating of mesenteric lymph node tissue, 48 h postburn. Plates were considered positive if any bacterial growth was noted. Non-burned mice exhibited no BT, while burn-fasted mice showed a 64.3 per cent incidence of BT (P = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Glutamine supplementation does not prevent small bowel mucosal atrophy after total parenteral nutrition in the rat

Glutamine supplementation to non-lipid parenteral nutrition has been demonstrated to attenuate villus atrophy and increase mucosal DNA content in the rat. This study was performed in order to determine the effects of glutamine supplementation to a balanced TPN mixture (including lipids) on epithelial cell kinetics using autoradiography. Male Sprague-Dawley rats were used. Group 1 (control) received food and an intravenous saline infusion. Group 2 received an intravenous TPN mixture including lipids but without glutamine. The same TPN mixture, glutamine replacing an isonitrogenous amount of non-essential amino acids, was given to Group 3. Animals were fed for 7 days, whereafter blood and intestinal samples were taken 1 h after injection of tritiated thymidine. Microscopy of specimens from proximal jejunum revealed a significant reduction in the number of cells in crypts and villi in both TPN groups (2 and 3) compared to orally fed animals (p < 0.001). Epithelial cell numbers were not significantly different in Group 2 and 3. Similarly, the labelling index (number of labelled cells/number of crypt cells) was not affected by glutamine administration. In plasma, glucagon concentrations in Group 2 (TPN without glutamine) seemed to decrease compared to Group 1 and 3 (p = 0.06). In this study, glutamine supplementation did not affect apithelial atrophy or cell proliferation. It is concluded, that the effects of glutamine on mucosal atrophy and renewal in jejunum may depend on the composition of the TPN mixture supplied during parenteral feeding.

Rationale and efficacy of specialized enteral nutrition

Enteral nutrition, whenever feasible, is the preferred route of nutrition support. There has been a tremendous increase in the number of enteral products available on the market. Many of these are designed for use in specific disease states. This review will summarize the scientific rationale and supporting research for specialized enteral nutrition.

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.

The modulatory role of gut hormones in elemental diet and intravenous total parenteral nutrition-induced bacterial translocation in rats

We have previously shown that parenteral and certain elemental diets promote bacterial translocation and that this diet-induced bacterial translocation can be prevented by the provision of bulk-forming dietary fiber. The goal of the current study was to test the hypothesis that fiber's protective effect on diet-induced bacterial translocation was mediated by trophic gut hormones. This hypothesis was tested by using bombesin (which stimulates gut hormone release) or the somatostatin analog Sandostatin (which inhibits gut hormone release) to modulate gut hormone release in rats receiving rat food, intravenous total parenteral nutrition, or an elemental diet. Both bombesin and fiber were effective in preventing elemental diet-induced bacterial translocation, whereas octreotide acetate abrogated the protective effect of fiber. Bombesin was also effective in limiting bacterial translocation in parenterally fed rats. Although both enteral (elemental diet) and parenteral diet-induced bacterial translocation were associated with cecal bacterial overgrowth, loss of small-bowel weight, and loss of mucosal protein content, none of these factors seemed to be primarily responsible for bacterial translocation. Because bombesin decreased the incidence of villous injury in the elemental diet-fed rats and decreased the incidence of villous injury and prevented loss of intestinal barrier function to horseradish peroxidase in the parenterally fed rats, it is possible that bombesin exerted its protective effect by limiting mucosal injury and preserving barrier function.

Nutrition care of patients with acute and chronic respiratory failure

Nutrition is intimately linked to pulmonary function and an understanding of these relationships have therapeutic utility. Malnutrition is known to be associated with impaired mechanical function of the lung in both chronic and acute respiratory insufficiency. Refeeding results in improvement in functional characteristics and may be critical in the weaning of patients from mechanical ventilation. In contrast, overfeeding may result in an increased ventilatory demand resulting in the inability to wean from respiratory support. This article considers the background as well as recommendations for the nutritional care of patients with acute and chronic respiratory failure.

Effect of L-glutamine on hepatic lipids at different energy levels in rats receiving total parenteral nutrition

The effect of glutamine on hepatic steatosis and serum amino acid pattern was studied in rats receiving total parenteral nutrition (TPN) with different levels of caloric intake. Rats were divided into four groups; a control group (n = 10) was fed a chow diet and infused with saline only. Three experimental groups (n = 8 to 10) received TPN solutions at energy levels of 25 kcal, 30 kcal, and 35 kcal/100 g body weight, respectively. The experimental groups were maintained with TPN for a period of 6 days. Each experimental group was divided into two subgroups, one of which was supplemented with glutamine, replacing 40% of the total amino acid nitrogen. All of the basal TPN solutions were isonitrogenous and identical in nutrient composition, except for the difference in energy level, which was adjusted with glucose. The results demonstrated that liver fat increased in accordance with the increase of glucose supply, and this increase was mainly due to triglyceride accumulation. Very-low-density lipoprotein-triglyceride and serum free fatty acid were significantly higher in the 30-kcal groups. There were no differences in hepatic lipid content, very-low-density lipoprotein-triglyceride secretion, or hepatic uptake of fatty acids between subgroups with and without glutamine supplementation. It was concluded that glutamine enrichment of a TPN solution did not have any effect on hepatic steatosis in normal rats.

Chronic pouchitis after ileal pouch-anal anastomosis: responses to butyrate and glutamine suppositories in a pilot study

Nonspecific, idiopathic inflammation of ileal pouch mucosa ("pouchitis") after ileal pouch-anal anastomosis is a common complication of this surgical approach. The epithelium of the pouch is ileal, but variable degrees of colonic metaplasia are natural sequelae of construction of such a pouch. One hypothesis is that pouchitis is caused by a deficiency of epithelial nutrition. Thus, a lack of butyric acid (the principal metabolic fuel of colonocytes) or of glutamine (the main fuel of enterocytes) may develop. In this study, our aims were to determine the concentration of total short-chain fatty acids in random stool samples obtained from patients with an ileal pouch-anal anastomosis with and without pouchitis and to test the therapeutic effects of butyrate and glutamine suppositories on pouchitis. During the study, all conventional therapy for pouchitis was discontinued. For 21 days, 9 patients participated in a butyrate trial, and 10 patients were treated with glutamine. Total concentrations of fecal short-chain fatty acids were significantly less in patients with pouchitis than in those without pouchitis. During treatment, 6 of the 10 patients who received glutamine had no recurrence of symptoms, but only 3 of the 9 patients who received butyrate responded similarly. Hence, further studies of glutamine in the treatment of pouchitis seem warranted.

Glutamine peptide does not improve gut barrier function and mucosal immunity in total parenteral nutrition

In two separate experiments, three groups of 10 (first experiment) and 12 (second experiment) rats each were catheterized for the long term via the right jugular vein and fed one of the following dietary regimens for 7 days while in individual metabolism cages. The rat food control groups were fed powdered rat food. The total parenteral nutrition (TPN) formula for one group was enriched with the stable dipeptide L-alanyl-L-glutamine (ALA-GLN) equivalent to a 1% or 2% glutamine concentration. For the control TPN groups, the dipeptide was replaced by isonitrogenous amounts of alanine (ALA). In both experiments, bacterial translocation was promoted to a similar extent by the ALA-GLN and ALA TPN formulas compared with the rat food groups. Bacterial overgrowth in the cecum and intestinal atrophy, quantitated by the mucosal protein content, did not differ between ALA-GLN and ALA groups. The nitrogen balances of the three groups showed similar values in the second experiment. The secretory immunoglobulin A was measured in washings of the jejunum and ileum (soluble fraction) and in the homogenates of the gut mucosa (insoluble fraction). The secretory immunoglobulin A values of both fractions showed no difference between the ALA and ALA-GLN groups, irrespective of whether they were normalized for gut segment length or corrected for mucosal protein content. In conclusion from these results, the supplementation of TPN with glutamine does not seem to improve gut barrier function or mucosal immunity in unstressed rats.

Elemental diet-induced immune suppression is caused by both bacterial and dietary factors

Because it is unclear whether elemental diet-induced immune suppression is an indirect effect caused by the translocating bacteria or is directly caused by the elemental diet, we tested whether prevention of diet-induced bacterial translocation or disruption of the gut microflora ecology would prevent diet-induced impaired lymphocyte function in a rat elemental diet model. Prevention of diet-induced bacterial translocation was accomplished by the addition of cellulose fiber or oral antibiotics (penicillin and streptomycin) to the elemental diet feeding regimen. Control groups consisted of rat food-fed and elemental diet-fed (4.25% amino acids; 28% glucose) rats. Immune function was quantitated by measuring the mitogen-induced blastogenic response of peripheral blood or splenic mononuclear cells to the mitogens concanavalin A and phytohemagglutinin. Bacterial translocation from the gut to the mesenteric lymph node and cecal bacterial population levels were measured in all groups. Although the incidence of elemental diet-induced bacterial translocation was reduced from 100% to 25% (p < .01) by the addition of dietary fiber, fiber did not prevent diet-induced impaired lymphocyte function. Because fiber supplementation of the elemental diet did not completely prevent diet-induced intestinal bacterial overgrowth or bacterial translocation, the experiment was repeated in antibiotic-decontaminated rats. Antibiotic decontamination completely prevented diet-induced intestinal bacterial overgrowth and bacterial translocation. Although antibiotic decontamination reduced the magnitude of lymphocyte mitogen suppression (p < .05), it was not fully effective in reversing the diet-induced lymphocyte suppression. These results indicate that elemental diet-induced lymphocyte blastogenic suppression is related to both bacterial and dietary factors.

Parenteral nutrition: hospital to home

Parenteral nutrition support is the provision of essential nutrients intravenously, bypassing the intestinal tract. It is used in a variety of clinical settings and medical conditions. Parenteral nutrition is a complex technology that requires the input of many professionals, including dietitians. The role of the dietitian in parenteral nutrition support involves direct patient care, consultative services, education, program development, and research. Even though this field of practice is still developing, some common practices can be described. Nutrition assessment determination of macronutrient and micronutrient requirements, and monitoring are vital aspects of the provision of parenteral nutrition support that benefit from the knowledge and experience of a dietitian. The future of parenteral nutrition includes identification of preferred fuels for specific disease states, development of new lipid emulsions, and identification of conditionally essential nutrients.

Alanyl glutamine-enriched total parenteral nutrition restores intestinal adaptation after either proximal or distal massive resection in rats

This study was designed to determine whether alanyl glutamine-containing total parental nutrition (TPN) can restore the impaired adaptive process of the remaining intestine, observed with administration of conventional TPN, after massive small-bowel resection. Seventy-four male Sprague-Dawley rats weighing 250 g were randomly divided into seven groups. Group I rats (n = 10) were killed after overnight fasting. Group II animals (n = 32) underwent massive small bowel resection (85%) with preservation of the first 15 cm of jejunum. Group III animals (n = 32) were also submitted to massive small-bowel resection with preservation of 15 cm of terminal ileum. Three different TPN solutions were prepared. Solution A was a conventional formulation that did not contain glutamine. Solution B contained 1.88 times the amino acid concentration of solution A. Solution C was prepared by adding alanyl glutamine (2 g/100 mL) to solution A. Solutions B and C were isonitrogenous and isocaloric. Each solution was infused to groups II and III, which were subdivided into groups IIA (n = 10), IIB (n = 11), IIC (n = 11), IIIA (n = 10), IIIB (n = 11), and IIIC (n = 11). After 1 week of TPN (270 kcal/kg per day), the experimental animals were killed and the intestine was taken for examination. Final body weight did not differ significantly among the groups, and there was no difference in nitrogen balance among the animals that received solution B or C.(ABSTRACT TRUNCATED AT 250 WORDS)

Intravenous administration of nucleosides and a nucleotide mixture diminishes intestinal mucosal atrophy induced by total parenteral nutrition

Total parenteral nutrition (TPN) is associated with atrophic changes in the structure and function of the intestinal mucosa. Because rapidly renewing intestinal mucosal cells may require an external source of purines and pyrimidines for their optimal growth, it can be assumed that supplementation of nucleosides and a nucleotide mixture (OG-VI) during TPN may prevent the progression of mucosal atrophy by compensating for a relatively insufficient delivery from liver. To test that hypothesis, male Wistar rats receiving TPN for 7 days were divided into four groups according to different TPN solutions. Group C (n = 10) received a standard solution, group O (n = 10) received OG-VI in addition to the standard solution, and group G (n = 10) received a glutamine-rich TPN solution containing almost the same amount of calories and nitrogen as the standard solution. Group O+G (n = 10) received OG-VI in addition to the glutamine-rich solution. Various parameters were examined on the eighth day in the jejunal and ileal segments. The following significant changes in comparison with group C were observed: total wet weight of the jejunal segment in group O was significantly greater, as was mucosal wet weight of the jejunal and ileal segments in groups O and O+G; protein contents of the ileal segment in group O as well as the DNA content of the jejunal segment in group O increased significantly; and maltase activity of the jejunal segment in group O+G increased, as did the villus height of the jejunal segment in groups O and O+G and the villus height of the ileal segment in group G.(ABSTRACT TRUNCATED AT 250 WORDS)

Glutamine enhancement of structure and function in transplanted small intestine in the rat

Total parenteral nutrition is required by all patients in need of small bowel transplantation. Untoward side effects of total parenteral nutrition include atrophy and hypofunction of the small intestine. Glutamine, the preferred fuel for the enterocyte, is presumably present in insufficient amounts in diets given to patients with intestinal dysfunction. In a rat model of total parenteral nutrition and small bowel transplantation, this study investigated the following: (1) whether glutamine improves graft structure and function, (2) the optimal route of glutamine delivery (intravenous vs direct infusion into the graft), and (3) the effect of glutamine on ultrastructure of the graft enterocyte. Lewis rats underwent small bowel transplantation as a Thiry-Vella graft and received total parenteral nutrition for 14 days while assigned to one of four infusion groups: 2% intravenous glutamine; 2% intravenous isonitrogenous mixture, nonessential amino acids (control); 2% glutamine into the graft; or 2% nonessential amino acids into the graft (control). Graft mucosal villous height, villous surface area, crypt depth, weight, protein, deoxyribonucleic acid content, glucose absorption, and enterocyte ultrastructure were then evaluated. Infusion of glutamine directly into the graft significantly increased mucosal villous height (p = .045), surface area (p = .029), and glucose absorption (p = .004) when compared with controls. Intravenous glutamine infusion significantly increased mucosal villous height (p = .002), surface area (p = .001), weight (p = .005), and glucose absorption (p = .04) when compared with controls. Most enterotrophic and functional benefits of glutamine were not significantly different between intravenous infusions and direct administration into the graft.(ABSTRACT TRUNCATED AT 250 WORDS)

Partial enterectomy in the rat does not diminish muscle glutamine production

The hypothesis was posed that consumption of the amino acid glutamine by the splanchnic tissues is an important regulating mechanism for its production in muscle. Therefore, glutamine consumption or production in portal-drained viscera (PDV), liver, and hindquarter was measured by determining fluxes and intracellular concentrations after 80% enterectomy or SHAM operation in rats. Moreover, fluxes and intracellular concentrations of several other amino acids, ammonia, and liver urea production were determined concomitantly. After enterectomy, arterial glutamine concentration was increased, PDV glutamine consumption was decreased by 77%, and liver glutamine consumption was unchanged compared with values in SHAM-operated rats. Although hindquarter glutamine production remained unchanged after enterectomy, intracellular glutamate concentration (glutamine precursor) was lower, suggesting that enterectomy induces changes in muscle metabolism without changing the flux of glutamine. For the remaining gut, it was calculated that after enterectomy glutamine consumption per gram remaining gut tissue increased. These results cast doubt on the hypothesis that diminished splanchnic glutamine uptake can reduce muscle glutamine production.

Metabolism and nutritional frontiers in pediatric surgical patients

The successful treatment of pediatric surgical disease requires an understanding of the acute metabolic stress response. Poor clinical outcome can result when the metabolic demands of acute injury exceed the ability of endogenous host mechanisms to compensate. Appropriate exogenous supplementation may provide the metabolic and nutritional support crucial to recovery. As knowledge in this area grows, more effective treatment strategies are evolving. The potential for further advances, especially in the infant critical care population, offers the hope for substantial progress in the near future.

Ornithine alpha-ketoglutarate and glutamine supplementation during refeeding of food-deprived rats

The aim of this study was to compare the efficiency of ornithine alpha-ketoglutarate (OKG) and glutamine supplementation in an experimental model of denutrition that provides well-characterized disturbances of amino acid patterns. Male Wistar rats (187 +/- 11 g; five in each group) were starved for 3 days and then refed for 7 days with an oral diet (192 kcal kg-1.day-1 and 2.25 g of nitrogen kg-1.day-1), supplemented with 0.19 g of nitrogen kg-1.day-1 in the form of OKG, glutamine, or casein (control group). Food deprivation induced a fall in most tissue amino acids, with the notable exception of muscle leucine and liver glutamate, which increased by 43% (p < .01), and 11% (p < .05), respectively. The main effect of OKG was seen in the viscera, with a normalization of most amino acid pools (including proline and branched-chain amino acids) in the small bowel and liver. The main effect of glutamine was observed in the muscle, with a normalization of the glutamine and leucine pools. We conclude that, in this model and with the doses used, OKG and glutamine act in different target tissues, ie, splanchnic areas and muscle, respectively.

Intravenous glutamine fails to improve gut morphology after radiation injury

Male Sprague-Dawley rats housed in individual metabolic cages received total parenteral nutrients via chronic indwelling internal jugular catheters to determine whether supplementing parenteral nutrition with glutamine would accelerate recovery of small-bowel morphology after abdominal radiation. After recovering from catheter insertion for 3 days they received either 1000 cGy gamma radiation to the abdomen only or no radiation and immediately thereafter received isonitrogenous and isocaloric intravenous solutions containing either 0% or 2% glutamine at 1.58 mL/h for the next 5 days. Intestinal segments were then assayed for whole-bowel deoxyribose nucleic acid content and villus height. Irradiation caused a 40% decrement in these parameters, which were not restored by glutamine supplementation. Therefore, intravenous glutamine supplementation failed to accelerate recovery of small-bowel morphology in this model of combined surgical and radiation injury.

Multiple organ failure. Pathophysiology and potential future therapy

Multiple organ failure (MOF) has reached epidemic proportions in most intensive care units and is fast becoming the most common cause of death in the surgical intensive care unit. Furthermore, in spite of the development of successive generations of new and more powerful antibiotics and increasing sophisticated techniques of organ support, our ability to salvage patients once MOF has become established has not appreciably improved over the last two decades. Clearly, new therapeutic strategies aimed at preventing or limiting the development of the physiologic abnormalities that induce organ failure are needed to improve survival in these critically ill patients. Based on our rapidly increasing knowledge of the mechanisms of MOF and the fruits of molecular biology, a number of new therapeutic approaches are in various stages of development. To effectively use these new therapeutic options as they become available, it is necessary to have a clear understanding of the pathophysiology of MOF. Thus, the goals of this review are to integrate the vast amount of new information on the basic biology of MOF and to focus special attention on the potential therapeutic consequences of these recent advances in our understanding of this complex and perplexing syndrome.

Early enteral feeding, compared with parenteral, reduces postoperative septic complications. The results of a meta-analysis

This two-part meta-analysis combined data from eight prospective randomized trials designed to compare the nutritional efficacy of early enteral (TEN) and parenteral (TPN) nutrition in high-risk surgical patients. The combined data gave sufficient patient numbers (TEN, n = 118; TPN, n = 112) to adequately address whether route of substrate delivery affected septic complication incidence. Phase I (dropouts excluded) meta-analysis confirmed data homogeneity across study sites, that TEN and TPN groups were comparable, and that significantly fewer TEN patients experienced septic complications (TEN, 18%; TPN, 35%; p = 0.01). Phase II meta-analysis, an intent-to-treat analysis (dropouts included), confirmed that fewer TEN patients developed septic complications. Further breakdown by patient type showed that all trauma and blunt trauma subgroups had the most significant reduction in septic complications when fed enterally. In conclusion, this meta-analysis attests to the feasibility of early postoperative TEN in high-risk surgical patients and that these patients have reduced septic morbidity rates compared with those administered TPN.

Effect of glutamine-supplemented total parenteral nutrition on the small bowel of septic rats

In order to study the effect of total parenteral nutrition (TPN) with or without glutamine supplementation in septic rats, septic Wistar albino rats were randomly assigned to receive 0.23 g of nitrogen and 113 kJ (100 g BW)(-1) per day in the form of amino acids with (group 2) or without (group 1) glutamine supplementation or 10% (w/v) glucose only (group 3). After 4 days of TPN treatments, rats receiving glutamine-supplemented TPN had a cumulative nitrogen balance of -24.4 +/- 3.3 mg N, which was significantly (P < 0.001) better compared to other TPN-treated groups. Septic rats of group 2 survived sepsis significantly (P < 0.001) better than those in groups 1 and 3. Glutamine-supplemented TPN treatment resulted in significant increases in jejunal weight (P < 0.001), DNA and protein contents (P < 0.001), villous height (P < 0.001) and crypt depth (P < 0.001) when compared with septic rats of group 1. Septic rats of group 2 extracted and metabolised glutamine by the small bowel at higher rates (P < 0.001) than that observed in septic rats of group 1. Increases in jejunal glutaminase (38.2%, P < 0.001) and decreases in glutamine synthetase (41.7%, P < 0.001) activities were observed in response to glutamine-supplemented TPN treatment. It is concluded that the administration of glutamine-supplemented TPN is beneficial to the small bowel of septic rats.

Biosynthetic human growth hormone preserves both muscle protein synthesis and the decrease in muscle-free glutamine, and improves whole-body nitrogen economy after operation

As a reproducible human trauma model, patients (n = 17) undergoing elective cholecystectomy were studied for 3 postoperative days. They were randomly allocated to receive either recombinant human growth hormone (hGH; 0.3 U/kg/24 hours) or placebo together with total parenteral nutrition, including 0.2 gN/kg/24 hours and 135 kJ/kg/24 hours. Before operation and on the third postoperative day, percutaneous muscle biopsies were performed to determine the concentration and size distribution of ribosomes and the free amino acid concentrations. The significant postoperative decrease in the total ribosome concentration (15.3 +/- 6.4%) and the polyribosome concentration (20.9 +/- 6.5%) in the control group was impeded in the group receiving synthetic hGH. Muscle free glutamine decreased by 35.6 +/- 4.2% in the control group and to a lesser extent in the group that was given hGH after operation (p less than 0.05). The protein content of skeletal muscle was unchanged. The cumulated nitrogen balance for the study period was negative in the control group (-7.09 +/- 0.71 gN), but was not different from zero in the hGH group (-2.32 +/- 1.66 gN). It is concluded that synthetic hGH administered after operation has beneficial effects on the whole-body nitrogen economy, as indicated by the unchanged capacity for protein synthesis in skeletal muscle, the preserved levels of muscle free glutamine, and improvement in the whole-body nitrogen balance. The effects of hGH on skeletal muscle protein and amino acid metabolism can explain the postoperative nitrogen-sparing effect attributed to hGH.

Enteral feeding in the critically injured patient

Metabolic support is an integral component in the care of the critically injured patient. When hypermetabolism occurs, there are increases in energy demands along with changes in substrate utilization. This article reviews the prospective randomized clinical trials that were undertaken at Denver General Hospital over the past decade that address both the timing of nutritional support and the route of administration in this critically injured population. Also discussed is a review of a meta-analysis that attests to the feasibility of early postoperative enteral feeding with the possibility of decreased septic morbidity in high-risk surgical patients. With the clinical knowledge gained from these trials, an algorithm for nutritional intervention was developed that represents our current standard of practice.

Crohn's disease and nutrition

Malnutrition was included by Crohn as one of the features of the new disease he described. Most patients with Crohn's disease are malnourished even if their disease is not active. Nutritional factors may be implicated in the aetiology of the disease, but this remains unproven. The role of nutritional support and therapy is discussed and it is suggested that improving the patient's nutritional status may have a primary therapeutic as well as a supportive role in the treatment of the disease.

Glutamine content of whole proteins: implications for enteral formulas

In two recent clinical trials in surgical patients, supplementation of total parenteral nutrition with daily doses of 12 or 20 g of glutamine resulted in a diminished loss of free glutamine in skeletal muscle tissue. Studies in animals exploring the use of both enteral and parenteral glutamine supplementation suggest that glutamine may be an essential nutrient in the maintenance of gut structure and function during critical illness. These findings have led to heightened interest in the glutamine content of enteral formulas. This article describes a method for estimating the glutamine content of whole-protein enteral formulas. The average amount of glutamine in selected, whole-protein formulas ranges from a minimum of 3.55 g/4200 kJ to a maximum of 5.15 g/4200 kJ. Although it is still too early to define the safest and most effective dose of glutamine, there are two points regarding glutamine supplementation that clearly merit further investigation: no clinical trials have been conducted to assess the potential benefits of glutamine supplementation of an enteral diet or to assess the effects of using diets containing protein-bound glutamine rather than free glutamine.

Nutrition support in inflammatory bowel disease

Many patients with the inflammatory bowel diseases, Crohn's disease, or ulcerative colitis have significant protein-calorie malnutrition and micronutrient deficiencies. Factors that contribute to these nutritional deficits include inadequate nutrient intake, malabsorption, excessive nutrient secretion across the diseased gastrointestinal tract, drug-nutrient interactions, and increased nutrient requirements. In this review, the use of enteral and parenteral nutrition support as primary therapy for active Crohn's disease and ulcerative colitis is discussed. Other roles for nutrition support in patients with inflammatory bowel disease, including preoperative nutrition support, nutritional treatment of intestinal fistulas and growth retardation, and home parenteral nutrition for gut failure, are also reviewed.

Septic Shock

The incidence of sepsis and septic shock has been increasing dramatically over the past 10 years. Despite advances in antimicrobial therapy, the mortality of septic shock remains very high. We review the clinical manifestations of sepsis and septic shock and describe the cardiovascular manifestations. Pathophysiology of the cardiovascular changes is discussed, and mediators believed to be involved in the pathogenesis are reviewed. Management of septic shock is also discussed, including antimicrobial therapy, supportive care, and adjunctive treatment aimed at affecting the mediators involved in producing the sepsis syndrome.

Altered glutamine metabolism in rat portal drained viscera and hindquarter during hyperammonemia

In normal rats, muscle is the major glutamine releasing organ and gut is the major glutamine consuming organ. It has been suggested that enhanced muscle ammonia detoxification and gut ammonia production occurs during liver insufficiency-induced hyperammonemia. Therefore, ammonia and amino acid fluxes across portal-drained viscera and hindquarter, and muscle concentrations were measured in portacaval shunted and acute liver ischemia rats. Arterial ammonia and most amino acids were increased after portacaval shunting and increased progressively during liver ischemia, but net hindquarter ammonia uptake was not observed. Net hindquarter glutamine efflux was increased during portacaval shunting, but it decreased during liver ischemia, while muscle glutamine concentrations increased. The comparable net portal drained viscera glutamine uptake in normal and portacaval shunted rats changed during liver ischemia from net uptake to release, coinciding with release of most other amino acids. These results cast doubt on the ammonia detoxifying role of muscle during acute liver ischemia-induced hyperammonemia in the rat. The portal drained viscera glutamine release during severe hyperammonemia could be due to intestinal damage.

Influence of N-acetylglutamine or glutamine infusion on plasma amino acid concentrations during the early phase of small-bowel adaptation in the dog

Glutamine is a nonessential neutral amino acid that is widely consumed by the intestinal tract in catabolic states. We have followed up the plasma amino acid profile after extensive small-bowel resection in dogs receiving total parenteral nutrition (TPN) with or without glutamine (GLN) or N-acetylglutamine (aGLN) supplementation. Animals were divided into four groups according to the type of surgery (enterectomy or transection) and nutrition (TPN, TPN with aGLN, or TPN with GLN). Plasma GLN levels decreased in group I (enterectomy and TPN) on day 2 (p = .03) and significantly increased on postoperative days in groups III (enterectomy and TPN with aGLN) and IV (enterectomy and TPN with GLN). A significant increase of plasma GLN was observed in groups III and IV compared with group I on days 6 and 8 (p = .03 and p = .01). Plasma alanine decreased in groups with bowel resection, whereas no change was observed in the control group (transection) and the decrease of plasma alanine was significantly less pronounced in groups III and IV compared with group I. The increase of crypt depth and villous height was more pronounced in groups III and IV. These results suggest that GLN is a required substrate for mucosal growth and function, which could improve the intestinal adaptation encountered after enterectomy.

Medical management of severe inflammatory disease of the rectum: nutritional aspects

It is clear that the nutritional state of patients with inflammatory bowel disease is often impaired and can be improved by the provision of nutritional support. Improvement in nutritional status can be achieved as effectively with enteral as with parenteral nutrition. Nutritional support appears to have no primary therapeutic effect in patients with ulcerative colitis. With regard to nutritional support in Crohn's disease, parenteral nutrition should be restricted to use as supportive rather than primary therapy. Available information now seems to suggest that most of the benefits of parenteral nutrition in Crohn's disease are related to an improvement in nutritional state rather than as primary therapy, and its use should be restricted to the treatment of specific complications of Crohn's disease, such as intestinal obstruction related to stricture formation or short bowel syndrome following repeated resection. Although some doubt exists over the efficacy of oligopeptide-containing elemental and polymeric enteral diets, the present evidence indicates that chemically defined free amino acid-containing elemental diets have primary therapeutic efficacy in the management of acute exacerbations of Crohn's disease. As such, these diets are worthy of therapeutic trial in patients with severe Crohn's disease involving the distal colon and rectum, particularly in those patients who are malnourished and who prove to be resistant to treatment with a combination of topical corticosteroids and 5-aminosalicylic acid-containing compounds. Clinicians should be aware, though, that the beneficial effects are likely to be restricted to the short term, with high relapse rates by 1 year, this being particularly so in patients with distal Crohn's proctocolitis (Teahon et al, 1988). Volatile fatty acid enemas clearly have potential in the management of patients with severe steroid-resistant proctitis. Finally, one of the most important observations made in recent years is the one concerning the large losses of nitrogen that will occur in patients with inflammatory bowel disease treated with corticosteroids in the absence of adequate protein intake (O'Keefe et al, 1989). Hopefully the days of treating patients with severe inflammatory bowel disease with high dose corticosteroids and a peripheral dextrose or dextrose-saline drip have passed into history.

Plasma and jejunal glutamine levels after extensive small bowel resection in dogs

Recent studies have demonstrated that glutamine may be required for mucosal growth and that it is widely utilised by the intestinal tract after surgery. This study has evaluated the effect of massive small bowel resection on plasma and jejunal glutamine and related amino-acids level evolution after surgery. Transection was performed in 6 dogs (control group) and enterectomy in 10 dogs leaving 25cm of jejunum, associated with colectomy (group 1). Plasma glutamine levels decreased on D2 (p = 0.03) in the resected group while a significant decrease of plasma alanine levels was observed on D2 (p = 0.002), D4, D6 and D8 (p < 0.001). Intestinal mucosa glutamic acid content was increased on D8 in this group (p < 0.001). No changes were observed in the control group. These results suggest that glutamine is a required substrate after massive small bowel resection which could improve the intestinal adaptation encountered after enterectomy.

Protein malnutrition alone and in combination with endotoxin impairs systemic and gut-associated immunity

Because protein-malnourished or endotoxemic patients are at an increased risk of developing nosocomial infections, this study was performed to investigate the effects of protein malnutrition and endotoxemia, alone and in combination, on systemic and intestinal immunity. Protein malnutrition was created by feeding the animals a solid diet containing 0.03% protein. Subgroups of these protein-malnourished mice were killed after being challenged with saline or endotoxin on days 0, 7, 14, or 21. At death, the animals were weighed, tissues were harvested for histologic analysis (ileum, mesenteric lymph node [MLN], liver, and spleen), mitogen responsiveness (MLN, Peyer's patches, and spleen), and xanthine oxidase measurements (ileum and cecum). Separate groups were evaluated for survival. Both the saline and endotoxin-challenged mice had lost about 30% of their body weight after 21 days on the low-protein diet. The protein-malnourished mice were more susceptible to endotoxin-induced mortality (70% at 21 days) than the normally nourished mice (0%) (p less than .001). The mitogen responsiveness of the protein-malnourished mice to the T-cell mitogens (PHA and Con-A) progressively decreased the longer the mice were protein malnourished, and this decreased in blastogenic responsiveness was associated with histologic evidence of lymphoid atrophy. In contrast, the blastogenic response to the primarily B-cell mitogen, PWM, was largely preserved. The endotoxin challenge further depressed the immune state of mice tested after 0, 7, or 14 (but not 21) days of protein malnutrition. Thus, both protein malnutrition and endotoxin impaired systemic and gut-associated immune responsiveness to mitogens. However, in the protein-malnourished mice, the degree of immune suppression did not correlate with endotoxin-induced mortality.