Effects of parenteral nutrition supplemented with glutamine or glutamine dipeptides on liver antioxidant and detoxication systems in rats

Histopathological and ultra-structural investigation of the damaging effects of hypoinsulinemia, hyper glycaemia and oxidative stress caused by parenteral nutrition combined with fasting on the small intestine of rabbits

BACKGROUND AND STUDY AIMS

Parenteral nutrition (PN) is a life-saving practice when the use of the gastrointestinal tract is not appropriate. Despite its great benefits, however, PN may cause several complications. In this study, we conducted histopathological and ultra-structural examinations of the effect of PN combined with starvation on the small intestines of rabbits.

MATERIALS AND METHODS

Rabbits were divided into four groups. A fasting + PN group was left completely unfed and received all its daily required energy by PN through an intravenous central catheter. An oral feeding + PN group received half the necessary daily calories by oral feeding and the other half through PN. A semi-starvation group received only half the necessary daily calories by oral feeding and no PN. The fourth group, serving as a control, was supplied with its entire daily energy requirements through oral feeding. After 10 days, the rabbits were euthanized. Blood and small intestine tissue samples were collected from all groups. Blood samples were biochemically analysed, and tissue samples were examined by light and transmission electron microscopy.

RESULTS

The fasting + PN group exhibited lower insulin levels, higher glucose levels, and increased systemic oxidative stress than the other groups. Ultra-structural and histopathological examinations revealed a significant increase in apoptotic activity in this group's small intestines and a significant decrease in villus length and crypt depth. Severe damage to the intracellular organelles and nuclei of enterocytes was also observed.

CONCLUSION

PN combined with starvation appears to cause apoptosis in the small intestine due to oxidative stress and hyperglycaemia with hypoinsulinemia, with destructive effects on small intestine tissue. Adding enteral nutrition to PN may reduce these destructive effects.

Histopathologic and electron microscopic investigation of the damage to liver tissue caused by parenteral nutrition combined with starvation in rabbits

AIM OF THE STUDY

To conduct a histopathological examination of the damaging effects of the combination of parenteral nutrition (PN) with starvation on liver tissue using transmission electron and light microscopy.

MATERIAL AND METHODS

Four groups (n = 14 each) consisting of equal numbers of female and male New Zealand rabbits were formed: a group left completely unfed and receiving full-dose PN (full-dose PN group), a group provided with feed covering half its nutritional needs and receiving half-dose PN (half-dose PN + oral nutrition group), a group provided with feed covering half its nutritional needs (semi-starvation group), and a group provided with feed covering all its nutritional needs (control group). After 10 days, all rabbits were weighed, anesthetized, and euthanized, and liver tissue samples were collected. Histopathologic examination was performed by a surgical pathologist blinded to the experimental groups. Portal inflammation, ballooning degeneration, apoptosis and fibrosis were evaluated and statistically analyzed.

RESULTS

Severe portal inflammation, moderate portal fibrosis, slight ballooning degeneration, and moderate apoptosis were found in the full-dose PN group. Mild portal inflammation, fibrosis and mild apoptosis were found in the half-dose PN + oral nutrition group. The results of the other two groups were found normal.

CONCLUSIONS

Liver damage caused by PN combined with starvation can be devastating. The damage can be minimized by combining PN with enteral nutrition.

The dipeptidyl peptidase IV inhibitory activity and multifunctional antidiabetic properties of SQSPA: Structure - Activity relationship evaluated with alanine scanning

Type 2 diabetes is a multifactorial disease and drugs with multifunctional properties are required. The peptide, SQSPA, was reported to be a potent and gastrointestinally stable α-glucosidase inhibitory peptide. In this study, the structure-activity relationship of this peptide was studied using alanine scanning. Four analogs; AQSPA, SASPA, SQAPA and SQSAA were designed and investigated for multifunctional antidiabetic effects. Molecular docking studies on human dipeptidyl peptidase-IV (DPP-IV) suggested that the binding affinities were in the order; AQSPA>SASPA>SQSPA>SQSAA>SQAPA while for in vitro DPP-IV inhibitory activity, it was SQSPA>SQSAA>AQSPA>SASPA>SQAPA. Enzyme kinetic studies revealed that the peptides are uncompetitive inhibitors with the exception of SQSAA and SQSPA. In 3T3-L1 differentiated adipocytes, SASPA was the only analog that significantly (p < 0.05) reduced and prevented lipid accumulation and did not induce cytotoxicity to differentiated 3T3-L1 cells. All peptides, especially SASPA scavenged methylglyoxal and peroxyl radicals thereby preventing advanced glycosylated end products formation and oxidative stress. The nitric oxide scavenging activity of all peptides was comparable to IPI and glutathione. Findings indicate that the amide side chain of Q2 is probably the most critical functional group for modulating the multifunctional antidiabetic effects of SQSPA while SASPA has been identified, as a novel peptide with enhanced multifunctional antidiabetic activity.

Proteome characteristics of liver tissue from patients with parenteral nutrition-associated liver disease

Background

Parenteral nutrition (PN)-associated liver disease (PNALD) is a common and life-threatening complication in patients receiving PN. However, its definitive etiology is not yet clear. Therefore, performed proteomic analyses of human liver tissue to explore the same.

Methods

Liver tissue was derived and compared across selected patients with (n = 3) /without (n = 4) PNALD via isobaric Tag for Relative and Absolute Quantitation (iTRAQ)-based quantitative proteomics. Bioinformatics analysis was performed using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases to explore the mechanisms of PNALD based on differentially expressed proteins (DEPs). The essential proteins that were differentially expressed between the two groups were explored and verified by western blotting.

Results

A total of 112 proteins were found to be differentially expressed, of which 73 were downregulated, and 39 were upregulated in the PNALD group. Bioinformatics analysis showed DEPs to be associated with mitochondrial oxidative phosphorylation (mainly involved in mitochondrial respiratory chain complex I assembly), hepatic glycolipid metabolism (involved primarily in glycogen formation and gluconeogenesis), and oxidative stress (mainly involved in antioxidant change).

Conclusion

Overall, our results indicated that mitochondrial energy metabolism impairment, hepatic glycolipid metabolism disorder, and excessive oxidative stress injury might explain the comprehensive mechanism underlying PNALD. Moreover, we have provided multiple potential targets for further exploring the PNALD mechanism.

Dietary supplemental Kluyveromyces marxianus alters the serum metabolite profile in broiler chickens

Metabolomics is used to evaluate the bioavailability of food components, as well as to validate the metabolic changes associated with food consumption. This study was conducted to investigate the effects of the dietary supplement Kluyveromyces marxianus on the serum metabolite profile in broiler chickens. A total of 240 1-d-old broilers were divided into 2 groups with 8 replicates. Birds were fed basal diets without or with K. marxianus supplementation (5 × 1010 CFU kg-1 of diet). Serum samples were collected on d 21 and were analyzed by high-performance liquid chromatography with quadrupole time-of flight/mass spectrometry. The results showed that supplemental K. marxianus altered the concentrations of a variety of metabolites in the serum. Thereinto, a total of 39 metabolites were identified at higher (P < 0.05) concentrations while 21 metabolites were identified at lower (P < 0.05) concentrations in the treatment group as compared with the control. These metabolites were primarily involved with the regulation of amino acids and carbohydrate metabolism. Further metabolic pathway analysis revealed that glutamine and glutamate metabolism was the most relevant and critical pathway identified from these two groups. The activated pathway may partially interpret the beneficial effects of K. marxianus. Overall, the present research could promote our understanding of the probiotic action of K. marxianus and provide new insight into the design and application of K. marxianus-containing functional foods.

Improvement of Pancreatic Islet Isolation Outcomes Using Glutamine Perfusion during Isolation Procedure

During procurement, isolation, and transplantation, islets are exposed to high levels of oxidative stress triggering a variety of signaling pathways that can ultimately lead to cell death. Glutamine is an important cellular fuel and an essential precursor for the antioxidant glutathione. The aim of this study was to examine the role of intraductal glutamine administration in facilitating recovery of isolated rat islets from pancreases subjected to a clinically relevant period of warm ischemia. Islets were isolated in Sprague-Dawley (SD) rats (n= 18 per group). Pancreata in groups 1 and 2 were procured immediately while groups 3 and 4 were subjected to 30-min warm ischemia. Groups 2 and 4 were treated intraductally with 5 mM glutamine prior to pancreatectomy. Exposure to 30-min warm ischemia significantly reduced islet yield [groups 1 & 2 (nonischemia): 503 ± 29 islets/rat vs. groups 3 & 4 (ischemia): 247 ± 26 islets/rat; p < 0.05]. Intraductal glutamine treatment significantly improved islet yield when pancreata were subjected to 30-min warm ischemia [144 ± 16 islets/rat without glutamine (group 3) vs. 343 ± 36 islets/rat with glutamine (group 4), p < 0.05]. Glutamine also significantly improved islet viability (values were 50 ± 4% in group 4 vs. 27 ± 3% in group 3, p < 0.05). Similarly, glutathione (reduced) levels were significantly elevated in both glutamine-treated groups; however, this increase was greatest in tissues exposed to ischemia (2.76 ± 0.04 nmol/mg protein in group 4 vs. 1.66 ± 0.04 nmol/mg protein in group 3, p < 0.05). Intraductal glutamine administration considerably improves the islet yield, viability, and augments endogenous glutathione levels in pancreata procured after a clinically relevant period of ischemia. Intraductal administration of glutamine at the time of digestive enzyme delivery into the harvested pancreas may represent a simple yet effective tool to improve islet yields in clinical isolations.

Effects of Parenteral Nutrition Supplemented with Alanyl-Glutamine on Nutrition Status in Rats

BACKGROUND

Glutamine, a nonessential amino acid, has received increasing attention because it becomes essential during stress and catabolic conditions. Many investigations have shown that during severe stress, the consumption of glutamine exceeds glutamine synthesis, resulting in depletion of glutamine stores. The aim of this study was to evaluate the effects of supplementing parenteral diets with a glutamine-containing dipeptide, L-alanyl-L-glutamine, on rat nutrition status.

METHODS

Male Wistar rats were used. Animals (n = 36) were centrally catheterized and randomly assigned to 1 of the following groups based on method of parenteral nutrition (PN): control group with oral nutrition and IV infusion of a saline solution; standard parenteral nutrition (SPN) group; or alanyl-glutamine-supplemented PN (ALA-GLN PN) group (20 g/L). Parenteral nutrition was isocaloric and isonitrogenous. Infusions were administered at a rate of 2.0 mL/h over 5 days. Nutrition status was assessed by body weight change, plasma proteins, accumulated urinary creatinine, and nitrogen balance.

RESULTS

Accumulated urinary creatinine increased significantly after day 4 in the ALA-GLN PN group, compared with the SPN group and the controls. Body weight change significantly differed on day 5 between the ALA-GLN PN and SPN groups. After 3 days, nitrogen balance was significantly lower and nitrogen retention higher in the ALA-GLN PN group when compared with the SPN group. Albumin and transferrin concentrations decreased significantly in the SPN group, but did not differ from the controls in the ALA-GLN PN group.

CONCLUSIONS

Weight, plasma proteins, urinary accumulated creatinine, and nitrogen retention showed a better evolution in the group supplemented with the glutamine dipeptide when compared with the SPN group. Our results suggest a more suitable nutrition support in animals receiving L-alanyl-L-glutamine.

Surface Electromyography Assessments of the Vastus medialis and Rectus femoris Muscles and Creatine Kinase after Eccentric Contraction Following Glutamine Supplementation

Purpose

L-glutamine is the most abundant amino acid found in human muscle and plays an important role in protein synthesis and can reduce the levels of inflammation biomarkers and creatine kinase (CK) after training sessions. Delayed onset muscle soreness (DOMS) develops after intense exercise and is associated with an inflammatory response. The purpose of this study was to investigate the effect of glutamine supplementation on surface electromyography activity of the vastus medialis muscle (VMM) and rectus femoris muscle (RFM) and levels of creatine kinase after an eccentric contraction.

Methods

Seventeen healthy men (age: 22.35±2.27yr; body mass: 69.91± 9.78kg; height: 177.08±4.32cm) were randomly assigned to experimental (n=9) and control groups (n=8) in a double-blind manner. In both groups, subjects were given L-glutamine supplementation (0.1g.kg^-1) or placebo three times a week for 4 weeks. Median frequency (MDF) and mean power frequency (MPF) for VMM and RFM muscles and also CK measurements were performed before, 24h and 48 h after a resistance training session. The resistance training included 6 sets of eccentric leg extensions to exhaustion with 75% of 1RM.

Results

There was no significant difference between groups for MDF or MPF in VMM and RFM. The difference of CK level between the groups was also not significant.

Conclusion

The results of this study indicate that glutamine supplementation has no positive effect on muscle injury markers after a resistance training session.

Antioxidants in patients receiving total parenteral nutrition after gastrointestinal cancer surgery

Total parenteral nutrition (TPN) is essential for patients with postoperative impairing gastrointestinal function who are unable to receive and absorb oral/enteral feeding for at least 7 days. Oxidative stress plays a major role in the ethiopathogenesis of cancers. In this study, total antioxidant status (TAS), glutathione peroxidase (GPx), superoxide dismutase, malondialdehyde and ascorbic acid were studied in patients operated because of small intestine, colorectal or pancreatic cancer and subsequently receiving TPN in comparison with patients receiving standard nutrition after the operation. TAS level and GPx activity were decreased in patients with small intestine cancer but did not differ in patients with colorectal and pancreatic cancer before and after surgery. In all patient groups receiving TPN, superoxide dismutase activity after the surgery was kept at the same level as before. On the fifth day after the surgery, malondialdehyde concentration in each group was restored to the value observed before surgery. On the fifth day of TPN treatment, ascorbic acid concentration was increased in every group of patients. TPN applied during the postoperative period alleviates oxidative stress resulting from surgery. In the case of small intestine cancer, the addition of vitamins and antioxidants to the nutrition mixture seems to result in depletion of antioxidant enzymes' activities.

Biochemical studies on the cardioprotective effect of glutamine on tissue antioxidant defense system in isoprenaline-induced myocardial infarction in rats

Oxidative stress is one of the mechanisms with a central role involved in the pathogenesis of myocardial infarction. The protective effect of glutamine on myocardial antioxidant defense system was investigated during isoprenaline-induced myocardial infarction, an animal model of myocardial infarction of human beings. Levels of diagnostic marker enzymes in plasma, reduced glutathione (GSH) and lipid peroxides and the activities of glutathione peroxidase, glutathione-S-transferase, catalase and superoxide dismutase in heart tissue were determined. Injection of isoprenaline caused significant increases in the levels of diagnostic marker enzymes in plasma and lipid peroxidation in heart tissue. A parallel decline in the levels of ATP (Adenosine triphosphate) and GSH and the activities of glutathione-dependent antioxidant enzymes and antiperoxidative enzymes in heart tissue was also observed. Prior oral administration of glutamine significantly prevented isoprenaline-induced adverse effects and maintained myocardial antioxidant status at near normal status. The cardioprotective effect of glutamine is probably related to a strengthening of the myocardial membrane by its membrane stabilizing action, or to a counteraction of free radicals by its antioxidant property, or to its ability to maintain near to normal status the activities of free radical scavenging enzymes and the level of GSH, which protect myocardial membrane against oxidative damage by decreasing lipid peroxidation.

Glutamine treatment attenuates the development of ischaemia/reperfusion injury of the gut

Intestinal ischemia/reperfusion causes tissue hypoxia and damage, leading to the pathophysiology of inflammation. The aim of this study was to investigate the effects of glutamine on the tissue injury caused by ischemia/reperfusion of the gut. Ischemia/reperfusion injury of the intestine was caused by clamping both the superior mesenteric artery and the celiac trunk for 30 min followed by the release of the clamp allowing reperfusion for 1h. This procedure results in splanchnic artery occlusion-injury. Based on our findings we propose that the amino acid glutamine, administered 15 min before reperfusion at the dose of 1.5mg/kg, i.v. may be useful in the treatment of various ischemia and reperfusion diseases. The present study was performed in order to determine the pharmacological effects of glutamine ischemia/reperfusion-induced intestinal injury in rats. In particular, to gain a better insight into the mechanism(s) of action of glutamine, we evaluated the following endpoints of the inflammatory response: (1) histological damage; (2) neutrophil infiltration of the reperfused intestine (MPO activity); (3) NF-kappaB activation and cytokines production; (4) expression of ICAM-1 and P-selectin during reperfusion; (5) nitrotyrosine and poly-ADP-ribose formation; (6) pro-inflammatory cytokine production; (7) inducible nitric oxide synthase expression; (8) apoptosis as shown by TUNEL staining and (9) Bax/Bcl-2 expression.

Mitochondria-initiated apoptosis triggered by oxidative injury play a role in total parenteral nutrition-associated liver dysfunction in infant rabbit model

PURPOSE

The aim of the study was to investigate oxidative injury and apoptosis as the mechanisms underlying total parenteral nutrition (TPN)-associated liver dysfunction.

METHODS

Twenty New Zealand rabbits (2 weeks old) were divided into 2 groups as follows: 10 in the control group (maternal feed) and 10 in the TPN group. The rabbits in the TPN group received continuous PN infusion through a silastic catheter inserted in the right jugular vein.

RESULTS

After 10 days of treatment, the serum levels of total bilirubin and bile acid were significantly higher in the TPN group than in the control group (P < .01, respectively). The light microscopic findings in the TPN rabbits included inflammatory cell infiltration and hepatic steatosis. Electron microscopy showed change in the cytosolic vacuoles and rare microvilli in the microbile duct. Moreover, 10 days of treatment resulted in an inhibition of the superoxide dismutase (SOD) activity in hepatocytes, an increase of the malondialdehyde level, a significant increase in cytochrome c release from the mitochondria, a significant increase in caspase 3 activity, and increased apoptosis (P < .01, individually).

CONCLUSIONS

Oxidative damage may be one of the essential mechanisms of TPN-associated liver dysfunction. Moreover, mitochondria-initiated apoptosis triggered by oxidative damage may play an important role in this process.

Parenteral nutrition related hepato-biliary disease in adults

Parenteral nutrition is a life-saving therapy in patients with intestinal failure. One of the major causes of morbidity and mortality in patients receiving long-term total parenteral nutrition (TPN) is liver disease. Early on, there is steatosis, which can evolve to steatohepatitis and eventually to cholestasis of varying severity. The etiology of parenteral nutrition related liver disease is multifactorial. Provision of excess calories in the TPN solution, along with lipids administered >1 g/kg are thought to increase the risk of parenteral nutrition related liver disease. Other factors such as nutrient deficiencies and nutrient toxicities may also play a role in the pathogenesis of liver disease, along with sepsis and the lack of enteral stimulation. Non-pharmacological management strategies for TPN-related liver disease include enteral stimulation, optimal TPN composition, and avoidance of excess carbohydrate and lipid calories. Pharmacological therapy with ursodeoxycholic acid and antibiotic therapy to reduce the risk of bacterial translocation and sepsis should be considered. Early referral for transplantation should be considered in patients with evidence of portal hypertension. This review focuses on the clinical aspects, pathogenesis, and management strategies of parenteral nutrition-related liver disease in adult patients.

Glutamine attenuates TPN-associated liver injury in infant rabbits

The aim of this study was to assess the effects of parenteral alanyl-glutamine dipeptide (Ala-Gln) on TPN-associated liver injury. Forty-three New Zealand rabbits (6-8 days old) were divided into three groups: 12 in the control group (maternal fed); 18 in the TPN group (TPN for 10 days); 13 in the Gln-PN group (TPN+Ala-Gln 400 mg kg(-1) day(-1) for 10 days). At the end of the experiment, liver function and histology were evaluated; MDA content of liver tissues and hepatocyte apoptosis by TUNEL assay were also determined. The serum concentration of direct bilirubin and bile acid in the Gln-PN group was significantly lower than TPN group (P < 0.05), but showed no difference compared with the control group. AST level of the Gln-PN group was lower than the other two groups. The light microscopy (LM) features in the TPN group included cholestasis or diffuse steatosis, while in the Gln-PN group, inflammatory infiltration and mild hydropic degenerative changes were mainly found without obvious cholestasis or proliferation of bile ducts. The electron microscopy appearances corresponded with LM findings. The liver MDA content in the Gln-PN group was clearly lower than the TPN group (P < 0.05), and was lower without statistical significance compared with control group. TUNEL assays showed the ratio of apoptotic hepatocytes in the TPN group was the highest among all the groups (44.59 +/- 6.68 vs. 0.92 +/- 0.85 in the control group, P < 0.01; 44.59 +/- 6.68 vs. 4.14 +/- 2.76 in the Gln-PN group, P < 0.01). There were significantly fewer apoptotic hepatocytes in the Gln-PN group. From this study, we found that glutamine dipeptide supplementation could attenuate TPN-associated liver injury in infant rabbits, and could also decrease liver MDA production and hepatocyte apoptosis during total parenteral nutrition.

Oxidative injury and hepatocyte apoptosis in total parenteral nutrition-associated liver dysfunction

PURPOSE

The aim of this study was to investigate the impact of oxidative injury and apoptosis on total parenteral nutrition (TPN)-associated hepatic dysfunction.

METHODS

Fifty-nine New Zealand rabbits (6-8 days old) were divided into 4 groups: 12 in the control group (maternal fed), 15 in the PN-3 group (TPN for 3 days), 14 in the PN-7 group (TPN for 7 days), and 18 in the PN-10 group (TPN for 10 days). At the end of the experiment, blood biochemistry analysis and histologic examination of the liver were performed; the malondialdehyde content of liver tissues was determined and hepatocyte apoptosis was evaluated by terminal deoxynucleotidyl transferase-mediated nick-end labeling assay.

RESULTS

We found that the serum level of direct bilirubin became higher as PN duration was extended. The light microscopy features in the PN-3 and PN-7 groups included inflammatory cells infiltrated in portal areas and some degeneration changes, whereas in the PN-10 group, cholestasis (proliferation of bile ducts and bile pigments in hepatocytes) or diffuse steatosis was shown. Electron microscopic manifestation in PN groups included reduced numbers of microvilli and some preapoptosis changes. Both the malondialdehyde content and apoptosis index were the highest in the PN-10 group; there were more apoptotic hepatocytes in the groups with longer PN duration.

CONCLUSIONS

The longer the TPN duration, the more severe the liver injury. Both oxidative injury and apoptosis may play important roles in the mechanism of TPN-associated hepatic dysfunction.

No evidence for oxidative stress in patients on home parenteral nutrition

BACKGROUND & AIMS

Patients on total parenteral nutrition depend on the composition of the nutritional formulation for maintenance of their oxidant-antioxidant balance. The present observational study was conducted to evaluate a substantial part of our patient population for evidence of oxidative stress.

METHODS

Venous blood samples were obtained from 41 patients on home parenteral nutrition (HPN) and 41 healthy controls. Glutathione in plasma and whole blood, glutathione peroxidase and superoxide dismutase in erythrocytes and total plasma antioxidant capacity were measured to assess the antioxidant status. Oxidant status was evaluated by measuring the production of reactive oxygen species by leukocytes. Oxidative damage was assessed by measuring lipid peroxidation and protein oxidation products.

RESULTS

Patients on HPN showed some signs of increased oxidative stress, however, there were no signs for oxidative damage, compared with healthy controls. In addition, activity of any underlying disease was not associated with increased oxidative stress.

CONCLUSIONS

The current treatment regime for patients on HPN at our center apparently prevents the development of significant oxidative damage, despite signs of some oxidative stress. Based on these data, adaptations in the composition of parenteral nutritional formulations do not seem mandatory.

Hyperglycemia induced by glucose infusion causes hepatic oxidative stress and systemic inflammation, but not STAT3 or MAP kinase activation in liver in rats

The purpose of this study was to determine the effects of acute hyperglycemia induced by glucose infusion on oxidative stress, systemic inflammation, and several key signal intermediates in liver for the systemic inflammatory response in nonstressed rats. Rats received saline or glucose infusion (hyperglycemic clamp) for 3 hours. Rats without catheter insertion were included as an additional control for observing the effects of surgical stress. Levels of malondialdehyde (MDA) and total glutathione to assess oxidative stress were determined in liver and muscle. Proinflammatory cytokines including tumor necrosis factor (TNF), interleukin (IL)-1 and IL-6, and alpha 1 acid glycoprotein (alpha1-AG) were determined in serum. The protein content and phosphorylation of extracellular signal-regulated kinase (ERK)1/2, p38 stress-activated protein kinase (p38), and signal transducer and activator of transcription-3 (STAT-3) were examined in the liver tissue with or without IL-6 stimulation. The results showed that acute hyperglycemia significantly increased MDA release and depleted total glutathione in liver but not in muscle. Hyperglycemia also significantly elevated the production of TNF, IL-1, and alpha1-AG, but not IL-6 in serum. However, hyperglycemia for 3 hours in vivo did not activate ERK1/2, p38 and STAT3 in liver, and also did not alter the response of these signal proteins to IL-6 stimulation. These data suggest that acute (3 hours) hyperglycemia causes hepatic oxidative stress and activates a low-grade systemic inflammation but does not affect key components of the IL-6 signaling pathway in liver.

Glutamine and the gastrointestinal tract

The amino acid glutamine has become one of the most intensively studied nutrients in the field of nutrition and metabolic support. A variety of studies in cell culture systems, animal models of gut mucosal atrophy, injury/repair and adaptation and a limited number of clinical trials demonstrate trophic and cytoprotective effects of glutamine in small bowel and colonic mucosal cells. Although the routine clinical use of glutamine-enriched parenteral and enteral nutrient solutions remains controversial, available data demonstrate both the safety and metabolic and clinical efficacy of glutamine treatment in selected patient groups. Basic investigations are elucidating underlying mechanisms of glutamine action in intestinal cells. These will inform preclinical and clinical investigations designed to determine glutamine efficacy in selected gastrointestinal disorders. Emerging clinical trials will further define the utility of adjunctive glutamine supplementation as a component of specialized nutrition support in gastrointestinal disease.