The Role of L‐Arginine and Inducible Nitric Oxide Synthase in Intestinal Permeability and Bacterial Translocation

Background: Arginine has been shown to have several immunological and trophic properties in stressful diseases. Its metabolites, nitric oxide (NO) and polyamines, are related to arginine's effects. Thus, the aim of this study was to determine the effects of the NO donor L‐arginine and the role of inducible NO synthase (iNOS) on intestinal permeability and bacterial translocation in a model of intestinal obstruction (IO) induced by a simple knot in the terminal ileum. Material and Methods: Male C57BL6/J wild‐type (WT) and iNOS knockout (iNOS–/–) mice were randomized into 6 groups: Sham and Sham–/– (standard chow), IO and IO–/– (standard chow +IO), and Arg and Arg–/– (standard chow supplemented with arginine + IO). After 7 days of treatment with standard or supplemented chows, IO was induced and intestinal permeability and bacterial translocation were evaluated. The small intestine and its contents were harvested for histopathological and morphometric analysis and the determination of polyamine concentration. Results: Pretreatment with arginine maintained intestinal permeability (P > .05; Arg and Arg–/– groups vs Sham and Sham–/– groups), increased polyamine concentration in intestinal content (P < .05; Arg vs IO group), and decreased bacterial translocation in WT animals (Arg group vs IO and IO–/– groups). Absence of iNOS also presented a protective effect on permeability but not on bacterial translocation. Conclusion: Arginine supplementation and synthesis of NO by iNOS are important factors in decreasing bacterial translocation. However, when intestinal permeability was considered, NO had a detrimental role.     

Pretreatment with arginine preserves intestinal barrier integrity and reduces bacterial translocation in mice

ObjectiveTo evaluate the effects of arginine on intestinal barrier integrity and bacterial translocation (BT) in mice undergoing intestinal obstruction.MethodsMice were divided into 3 groups, treated for 7 d before surgical intervention with isocaloric and isoprotein diets. The ARG group received a diet containing 2% arginine, the IO (intestinal obstruction) and Sham groups, standard chow diet. On the eighth day of treatment, all animals received diethylenetriamine pentaacetic acid (DTPA) solution labeled with ^99mTechnetium (^99mTc-DTPA) by gavage for intestinal permeability analysis. After 90 min, the animals were anesthetized and the terminal ileum ligated. The Sham group only underwent laparotomy. After 4, 8, and 18 h, blood was collected for radioactivity determination. Samples of ileum were collected 18 h after surgery for histological analysis. In another set of animals, BT was evaluated. After 7 d of treatment, all animals received 10⁸ CFU/mL of ^99mTc-E.coli by gavage; 90 min later they were submitted to the surgical procedure described above. BT was determined by the uptake of ^99mTc-E.coli in blood, mesenteric lymph nodes, liver, spleen, and lungs, assessed 18 h after the surgery.ResultsThe intestinal permeability and BT were higher in the IO group when compared with the Sham group (P < 0.05). Arginine supplementation reduced intestinal permeability and BT to physiologic levels. Histological analysis showed mucosal ileum preservation in animals treated with arginine.ConclusionArginine was able to preserve barrier integrity, thus reducing BT.     

Arginine Supplementation Induces Arginase Activity and Inhibits TNF‐α Synthesis in Mice Spleen Macrophages After Intestinal Obstruction

Background: The purpose of this study was to assess the effect of arginine supplementation on arginase activity, tumor necrosis factor–α (TNF‐α) and interleukin‐10 (IL‐10) synthesis in cultured splenic macrophages from a murine model of intestinal obstruction (IO). The effects of nitric oxide synthase (iNOS) inhibition were also studied using iNOS knockout animals. Material and Methods: Male C57BL6/J wild‐type (WT) and iNOS knockout (iNOS–/–) mice were randomized into 6 groups: Sham and Sham–/– (standard chow), IO and IO–/– (standard chow + IO), and Arg and Arg–/– (standard chow supplemented with arginine + IO). After 7 days of treatment with standard or supplemented chow, IO was induced. Arginase activity as well as TNF‐α and IL‐10 levels were analyzed in splenic macrophage cultures. Results: Arginine supplementation and the absence of iNOS increased arginase activity in splenic macrophages (Arg, IO–/–, and Arg–/– groups vs the Sham group; P < .05). Arginine was also related to a decrease in TNF‐α levels (Arg vs IO group, P < .05) and maintenance of IL‐10 levels (Arg vs other groups, P > .05). The inhibition of iNOS did not result in effects on the concentration of cytokines (Sham–/–, IO–/–, and Arg–/– vs other, P < .05). Conclusions: Arginine supplementation and iNOS inhibition led to increased arginase activity. Arginine availability decreased plasma TNF‐α levels, which may be directly related to nitric oxide derived from arginine.     

Pretreatment with citrulline improves gut barrier after intestinal obstruction in mice

Background: Citrulline has been shown to be an important marker of gut function, regulator of protein metabolism, and precursor of arginine. The authors assessed the effects of citrulline on gut barrier integrity and bacterial translocation (BT) in mice undergoing intestinal obstruction. Methods: Mice were divided into 3 groups: sham, intestinal obstruction (IO), and citrulline (CIT). The CIT group received a diet containing 0.6% citrulline; the IO and sham groups were fed a standard chow diet. On the eighth day of treatment, all animals received a diethylenetriamine pentaacetic acid (DTPA) solution labeled with ^99mTechnetium (^99mTc‐DTPA) by gavage for the intestinal permeability study. Terminal ileum was ligated except the sham group, which only underwent laparotomy. After 4, 8, and 18 hours, blood was collected to determine radioactivity. Samples of ileum were removed 18 hours after intestinal obstruction for histological analysis. In another set of animals, BT was evaluated. Animals received 10⁸ CFU/mL of ^99mTc–Escherichia coli by gavage; 90 minutes later, they underwent ileum ligation. Intestinal fluid and serum were collected to measure sIgA and cytokines. Results: The CIT group presented decreased intestinal permeability and BT when compared with the IO group (P < .05). Histopathology showed that citrulline preserved the ileum mucosa. The sIgA concentration was higher in the CIT group (P < .05). The IO group presented the highest levels of interferon‐γ (P < .05). Conclusions: Pretreatment with citrulline was able to preserve barrier integrity and also modulated the immune response that might have affected BT decrease.     

Glutamine Restores Tight Junction Protein Claudin‐1 Expression in Colonic Mucosa of Patients With Diarrhea‐Predominant Irritable Bowel Syndrome

Background:Recent studies showed that patients with diarrhea‐predominant irritable bowel syndrome (IBS‐D) had an increased intestinal permeability as well as a decreased expression of tight junctions. Glutamine, the major substrate of rapidly dividing cells, is able to modulate intestinal permeability and tight junction expression in other diseases. We aimed to evaluate, ex vivo, glutamine effects on tight junction proteins, claudin‐1 and occludin, in the colonic mucosa of patients with IBS‐D. Materials and Methods: Twelve patients with IBS‐D, diagnosed with the Rome III criteria, were included (8 women/4 men, aged 40.7 ± 6.9 years). Colonic biopsy specimens were collected and immediately incubated for 18 hours in culture media with increasing concentrations of glutamine from 0.6–10 mmol/L. Claudin‐1 and occludin expression was then measured by immunoblot, and concentrations of cytokines were assessed by multiplex technology. Claudin‐1 expression was affected by glutamine (P < .05, analysis of variance). In particularly, 10 mmol/L glutamine increased claudin‐1 expression compared with 0.6 mmol/L glutamine (0.47 ± 0.04 vs 0.33 ± 0.03, P < .05). In contrast, occludin expression was not significantly modified by glutamine. Interestingly, glutamine effect was negatively correlated to claudin‐1 (Pearson r = ‐0.83, P < .001) or occludin basal expression (Pearson r = ‐0.84, P < .001), suggesting that glutamine had more marked effects when tight junction protein expression was altered. Cytokine concentrations in culture media were not modified by glutamine treatment. Conclusion: Glutamine increased claudin‐1 expression in the colonic mucosa of patients with IBS‐D. In addition, glutamine effect seems to be dependent on basal expression of tight junction proteins.     

Oral Citrulline Mitigates Inflammation and Jejunal Damage via the Inactivation of Neuronal Nitric Oxide Synthase and Nuclear Factor–κB in Intestinal Ischemia and Reperfusion

Background: Intestinal ischemia and reperfusion (I/R) is a life‐threatening emergency accompanied by inflammation and organ damage. We compared the mechanisms and the effects of arginine, citrulline, and glutamine on inflammation and intestinal damage. Materials and Methods: Male Wistar rats underwent 60 minutes of superior mesenteric artery occlusion and either 3 (I/R3) or 24 (I/R24) hours of reperfusion and were orally administered vehicle, arginine, citrulline, or glutamine 15 minutes before reperfusion and at 3, 9, and 21 hours of reperfusion. Results: I/R3 rats experienced jejunal damage and apoptosis, and I/R24 rats had liver dysfunction compared with normal rats (one‐way ANOVA, P < .05). Arginine and citrulline administrations improved jejunal morphology, and citrulline and glutamine administrations alleviated the loss of jejunal mass in I/R3 rats. I/R3‐increased circulating nitrate/nitrite (NOx), tumor necrosis factor–α, and interleukin‐6 were significantly decreased by citrulline, glutamine and citrulline, and arginine, glutamine, and citrulline, respectively. These amino acids decreased plasma NOx and interferon‐γ in I/R24, decreased jejunal neuronal nitric oxide synthase (NOS) protein in I/R3 rats, and alleviated jejunal apoptosis in I/R3 and I/R24 rats. In addition, the jejunal phosphorylated to total nuclear factor–κB (NF‐κB) ratio was decreased by arginine and citrulline in I/R24 rats. Conclusion: Oral administration of arginine, citrulline, and glutamine may alleviate systemic inflammation, jejunal apoptosis, and neuronal NOS in intestinal I/R. Citrulline may further attenuate jejunal damage by preserving jejunal mass, partially via the inactivation of NOS and the NF‐κB pathway. In conclusion, oral citrulline may have more benefits than arginine and glutamine in mitigating intestinal ischemia and reperfusion‐induced adverse effects.     

Glutamine Supplementation Decreases Intestinal Permeability and Preserves Gut Mucosa Integrity in an Experimental Mouse Model

Background: Glutamine (GLN) is the preferred fuel for enterocytes, and GLN supplementation is critical during stressful conditions. The aim of this study was to evaluate the effect of GLN on intestinal barrier permeability and bacterial translocation in a murine experimental model. Methods: Swiss male mice (25–30 g) were randomized into 3 groups: (1) sham group; (2) intestinal obstruction (IO) group; (3) IO and GLN (500 mg/kg/d) group. Two different experiments were carried out to assess intestinal permeability and bacterial translocation. In the first experiment, the animals were divided into the 3 groups described above and received diethylenetriamine pentaacetate radiolabeled with technetium (^99mTc) on the eighth day. At different time points after intestinal obstruction, blood was collected to determine radioactivity. The animals were killed, and the small intestine was removed for histological analyses. In the bacterial translocation study, on the eighth day all groups received Escherichia coli labeled with ^99mTc. After 90 minutes, the animals underwent intestinal obstruction and were killed 18 hours later. Blood, mesenteric lymph nodes, liver, spleen, and lungs were removed to determine radioactivity. Statistical significance was considered when P ≤ .05. Results: The levels of intestinal permeability and bacterial translocation were higher in the IO group than in the sham and GLN groups (P < .05). GLN decreased intestinal permeability and bacterial translocation to physiologic levels in the treated animals and preserved intestinal barrier integrity. Conclusions: GLN had a positive impact on the intestinal barrier by reducing permeability and bacterial translocation to physiologic levels and preserving mucosal integrity.     

Starvation‐Induced Proximal Gut Mucosal Atrophy Diminished With Aging

Background: Starvation induces small bowel atrophy with increased intestinal epithelial apoptosis and decreased proliferation. The authors examined these parameters after starvation in aged animals. Methods: Sixty‐four 6‐week‐old and 26‐month‐old C57BL/6 mice were randomly assigned to either an ad libitum fed or fasted group. The small bowel was harvested at 12, 48, and 72 hours following starvation. Proximal gut mucosal height was measured and epithelial cells counted. Apoptosis was identified by terminal deoxynucleotidyl transferase‐mediated dUTP nick end labeling (TUNEL) staining. Proliferation was determined by immunohistochemical staining for proliferating cell nuclear antigen. Comparison of fed vs fasted and adult vs old groups was done by one‐way ANOVA with Tukey's test and unpaired Student's t test. Significance was accepted at P < .05. Results: Aged mice had higher proximal gut weights, mucosal heights, and cell numbers at baseline compared with the adult group (P < .05). The rate of apoptosis was lower in the aged (P < .05), but proliferation was not different between groups before starvation. After starvation, proximal gut wet weight decreased only in adult mice (P < .05). Gut mucosal height and mucosal cell number decreased more in adult than in aged mice (P < .05). This was related to decreased proliferation only in the adult group (P < .05). The fold of epithelial apoptosis that increased was higher in the aged group than in the adult group after starvation (P < .05). Conclusions: Gut mucosal kinetics change with age and have lower rates of apoptosis and greater mucosal mass; the character of starvation‐induced atrophy is diminished with aging.     

Effect of arginine on gastrointestinal immunity during total parenteral nutrition

It has been well recognized that the prolonged use of total parenteral nutrition (TPN) leads to intestinal immunodeficiency and bacterial translocation (BT). Arginine (ARG) is known to have immunostimulatory effects. But its effects on gut immunity are unknown. This experiment was designed to evaluate the effects of arginine on gut immunity during TPN. Male Sprague Dowley rats were randomized to three groups: group I (chow) was fed rat chow and water ad libitum, group II (TPN) received a standard formula of TPN and group III (TPN-ARG) received the same formula of TPN as group II with the amino acid composition containing 0.5% arginine. With the duration of TPN, the rates of BT increased and interleukin 2 (IL-2) production decreased in TPN group. The results in TPN-ARG group were partly reversed. When TPN was administered for 2 weeks, the rate of BT decreased significantly (P < 0.05) and IL-2 production increased markedly (P < 0.01) in the TPN-ARG group compared with those in the TPN group. Our results suggest that arginine can decrease BT and increase IL-2 production in rats during prolonged TPN.     

Dietary L-arginine supplementation enhances intestinal development and expression of vascular endothelial growth factor in weanling piglets

Oral administration of L-arginine has been reported to prevent gut disease in human infants. However, little is known about the effects of dietary arginine supplementation on intestinal development of weaned piglets. In the present study, twenty 21-d-old castrated piglets with 5·3 (SEM 0·13) kg body weight (BW) were weaned from sows, individually housed and randomly assigned to one of the two maize- and soyabean meal-based diets supplemented with 0 or 1% L-arginine. After consuming the diets for 7 d, six pigs were randomly selected from each group to obtain various tissues. Compared with control pigs, dietary supplementation with 1% L-arginine did not affect feed intake but enhanced (P<0·05) the relative weight of the small intestine (+33 %), daily BW gain (+38 %) and feed efficiency (+28 %). The villus height of the duodenum, jejunum and ileum in arginine-supplemented piglets was 21, 28 and 25% greater (P<0·05) than in the nonsupplemented control group. Arginine supplementation increased (P<0·05) protein levels for vascular endothelial growth factor(VEGF) in duodenal, jejunal and ileal mucosae by 14, 39 and 35 %, respectively. Compared with the control group, dietary supplementation with 1% L-arginine increased (P<0·05) plasma concentrations of arginine and insulin (+36 %), and decreased (P<0·05) plasma concentrations of cortisol (233 %), NH3 (221 %) and urea (219 %). These results indicate that arginine supplementation enhances intestinal growth, development and expression of VEGF in early-weaned pigs fed a maize- and soyabean meal-based diet. The findings may have important implications for neonatal pigs under stressful or diseased conditions.     

Enteral Arginine Partially Ameliorates Parenteral Nutrition–Induced Small Intestinal Atrophy and Stimulates Hepatic Protein Synthesis in Neonatal Piglets

Background: Arginine is an indispensable amino acid in neonates; de novo synthesis of arginine occurs in the small intestine (SI) but is reduced during parenteral nutrition (PN), limiting the arginine available to the mucosa. We assessed the effects of route of intake and dietary concentration of arginine on protein synthesis, superior mesenteric artery (SMA) blood flow, and SI morphology. Methods: Piglets (n = 18, 14–17 days old) were given complete PN for 3 days to induce SI atrophy, then switched to 1 of 3 treatments: arginine‐free PN plus an intragastric (IG) infusion of high arginine (1.6 g·kg^?1·d^?1, IG‐H Arg) or low arginine (0.6 g·kg^?1·d^?1, IG‐L Arg) or complete high‐arginine PN (1.6 g·kg^?1·d^?1, IV‐H Arg). Results: Enteral arginine, irrespective of amount provided, stimulated hepatic protein synthesis compared with intravenous delivery of arginine (P = .01). SMA blood flow declined for all groups following the initiation of PN. After 48 hours on the test diets, all groups reached low constant levels, but the IV‐H group was significantly higher than both IG groups (P < .05). Despite greater blood flow, the SI morphological characteristics in IV‐H Arg pigs were not significantly improved over the other groups. IV‐H Arg pigs had higher plasma concentrations of indispensable amino acids (tyrosine, isoleucine, and valine) compared with IG‐H Arg, despite identical amino acid intakes. Conclusions: Intravenous delivery of arginine sustained the best SMA blood flow, whereas even a moderate amount of enteral arginine stimulated liver protein synthesis and maintained SI growth, independent of blood flow.     

Pyruvate Is Superior to Citrate in Oral Rehydration Solution in the Protection of Intestine via Hypoxia‐Inducible Factor‐1 Activation in Rats With Burn Injury

Background: Recent studies have suggested that pyruvate‐enriched oral rehydration solution (Pyr‐ORS) may be superior to the standard bicarbonate‐based ORS in the protection of intestine from ischemic injury. The aim of this study was to compare the effects of Pyr‐ORS with citrate‐enriched ORS (Cit‐ORS) on the intestinal hypoxia‐inducible factor‐1 (HIF‐1)–erythropoietin (EPO) signaling pathway for enteral rehydration in a rat model of burn injury. Methods: Rats were randomly assigned to 4 groups (N = 20, 2 subgroups each: n = 10): scald sham (group SS), scald with no fluid resuscitation (group SN), scald and resuscitation with enteral Cit‐ORS (group SC), and scald and resuscitation with enteral Pyr‐ORS (group SP). At 2.5 and 4.5 hours after a 35% total body surface area (TBSA) scald, intestinal mucosal blood flow (IMBF), contents of HIF‐1, EPO, endothelial nitric oxide synthase (eNOS), nitric oxide (NO), barrier protein (ZO‐1), levels of serum diamine oxidase (DAO), and intestinal mucosal histology injury score were determined. Results: Serum DAO activities in the scalded groups were significantly elevated, but less raised in group SP than in group SC, at 2.5 hours and at 4.5 hours after the scald. Further, group SP more profoundly preserved intestinal HIF‐1 expression compared with group SC at the 2 time points. Compared with group SC, group SP had markedly elevated intestinal EPO, eNOS, and NO levels at the same time points, respectively (P < .05). Similarly, IMBF and ZO‐1 levels were significantly higher in group SP than in group SC. Intestinal mucosal histopathological scores were statistically higher at 2.5 hours and 4.5 hours after scalding but were more attenuated in group SP than in group SC (P < .05). Immunofluorescence expression of intestinal mucosal ZO‐1 was consistent with the above changes. The above parameters were also significantly different between groups SC and SN (all P < .05). Conclusion: Pyr‐ORS provides a superior option to Cit‐ORS for the preservation of intestinal blood flow and barrier function and the attenuation of histopathological alterations in enteral resuscitation of rats with burn injury. Its underlying mechanism may be closely related to the pyruvate in activation of intestinal HIF‐1‐EPO signaling cascades.     

Soybean and Fish Oil Mixture With Different ω‐6/ω‐3 Polyunsaturated Fatty Acid Ratios Modulates Dextran Sulfate Sodium–Induced Changes in Small Intestinal Intraepithelial γδT‐Lymphocyte Expression in Mice

Background: This study investigated the effect of different ω‐6/ω‐3 polyunsaturated fatty acid (PUFA) ratios on dextran sulfate sodium (DSS)–induced changes to small intestinal intraepithelial lymphocyte (IEL) γδT‐cell expression. Methods: Mice were assigned to 3 control and 3 DSS‐treated groups and were maintained on a low‐fat semipurified diet. One of the control (S) groups and a DSS (DS) group were provided with soybean oil; the other 2 control (Hω‐3 and Lω‐3) groups and 2 other DSS (DHω‐3 and DLω‐3) groups were fed either a soybean and fish oil mixture with a ω‐6/ω‐3 ratio of 2:1 or 4:1. After feeding the respective diets for 2 weeks, the DSS groups were given distilled water containing 2% DSS, and the control groups were given distilled water for 5 days. All groups were further provided distilled water 5 days for recovery, and the small intestinal IEL γδT‐cell subset was isolated for analysis. Results: DSS treatment resulted in a lower small intestinal IEL γδT‐cell percentage and higher messenger RNA (mRNA) expressions of Reg IIIγ, keratinocyte growth factor (KGF), and complement 5a receptor (C5aR) by IEL γδT cells. Fish oil administration enhanced the proportion of small intestinal IEL γδT cells. Compared with the DLω‐3 group, the DHω‐3 group had lower Reg IIIγ, KGF, and C5aR mRNA expressions and higher expression of peroxisome proliferator‐activated receptor (PPAR)–γ gene by small intestinal IEL γδT cells. Conclusions: Fish oil diets with a ω‐6/ω‐3 PUFA ratio of 2:1 were more effective than those with a ratio of 4:1 in improving DSS‐induced small intestinal injury, and activation of PPAR‐γ in IEL γδT cells may be associated with resolution of small intestinal inflammation.     

Comparative Analysis of the Efficacy and Complications of Nasojejunal and Jejunostomy on Patients Undergoing Pancreaticoduodenectomy

Background: The efficacy and feeding‐related complications of a nasojejunal feeding tube and jejunostomy after pancreaticoduodenectomy (PD) was investigated with a randomized, controlled clinical trial at the Affiliated Drum Tower Hospital. Methods: Sixty‐eight patients who underwent PD in the Department of Hepatobiliary Surgery were randomly divided into 2 groups: 34 patients received enteral feeding via a nasojejunal tube (NJT group) and 34 patients received enteral feeding via a jejunostomy tube (JT group). The assessment of clinical outcome was based on postoperative investigation of complications. The second part of the assessment included tube related complications and an index on catheter efficiency. Results: There were 15 cases with infectious complications in the JT group and 13 cases in the NJT group, and there was no significant difference in the rate of infectious complications between the 2 groups. The rate of intestinal obstruction and delayed gastric emptying was significantly decreased in the NJT group (P < .05). Catheter‐related complications were more common in the JT group as compared with the NJT group (35.3% vs 20.6%, P < .05). The time for removal of the feeding tube and nasogastric tube was significantly decreased in the NJT group. The postoperative hospital stay in the NJT group was significantly decreased (P < .05), and there was no hospital mortality in this study. Conclusion: Nasojejunal feeding is safer than jejunostomy, and it is associated with only minor complications. Nasojejunal feeding can significantly decrease the incidence of delayed gastric emptying and shorten the postoperative hospital stay.     

Ganglioside Intake Increases Plasma Ganglioside Content in Human Participants

Background: Preclinical studies reveal associations between intestinal ganglioside content and inflammatory bowel disease (IBD). Since a low level of ganglioside is associated with higher production of proinflammatory signals in the intestine, it is important to determine safety and bioavailability of dietary ganglioside for application as a potential therapeutic agent. Materials and Methods: Healthy volunteers (HVs; n = 18) completed an 8‐week supplementation study to demonstrate safety and bioavailabity of ganglioside consumption. HVs were randomized to consume a milk fat fraction containing 43 mg/d ganglioside or placebo, and patients with IBD (n = 5) consumed ganglioside supplement in a small pilot study. Plasma gangliosides were characterized using reverse‐phase liquid chromatography–QQQ mass spectrometry. Intestinal permeability was assessed by oral lactulose/mannitol, and quality of life was assessed by quality of life in the IBD questionnaire. Results: There were no adverse events associated with dietary ganglioside intake. Ganglioside consumption increased (P < .05) plasma content of total GD3 by 35% over 8 weeks. HVs consuming ganglioside exhibited a 19% decrease in intestinal permeability (P = .04). Consumption of ganglioside was associated with a 39% increase (P < .01) in emotional health and a 36% improvement (P < .02) in systemic symptoms in patients with IBD. Conclusion: Impaired intestinal integrity characteristic of IBD results in increased permeability to bacterial antigens and decreased nutrient absorption. Intestinal integrity may be improved by dietary treatment with specific species of ganglioside. Ganglioside is a safe, bioavailable dietary compound that can be consumed to potentially improve quality of life in patients with IBD and treat other disorders involving altered ganglioside metabolism. This study was registered at clinicaltrials.gov as NCT02139709.     

Glutamine therapy improves outcome of in vitro and in vivo experimental colitis models

Background: Pharmacologic doses of glutamine (GLN) can improve clinical outcome following acute illness and injury. Recent studies indicate enhanced heat shock protein (HSP) expression is a key mechanism underlying GLN's protection. However, such a link has not yet been tested in chronic inflammatory states, such as experimental inflammatory bowel disease (IBD). Methods: Experimental colitis was induced in Sprague‐Dawley rats via oral 5% dextran sulfate sodium (DSS) for 7 days. GLN (0.75 g/kg/d) or sham was administered to rats by oral gavage during 7‐day DSS treatment. In vitro inflammatory injury was studied using YAMC colonic epithelial cells treated with varying concentrations of GLN and cytokines (tumor necrosis factor–α/interferon‐γ). Results: Pharmacologic dose, bolus GLN attenuated DSS‐induced colitis in vivo with decreased area under curve for bleeding (8.06 ± 0.87 vs 10.38 ± 0.79, P < .05) and diarrhea (6.97 ± 0.46 vs 8.53 ± 0.39, P < .05). This was associated with enhanced HSP25 and HSP70 in colonic mucosa. In vitro, GLN enhanced cell survival and reduced proapoptotic caspase3 and poly(ADP‐ribose) polymerase cleavage postcytokine injury. Cytokine‐induced inducible nitric oxide synthase expression and nuclear translocation of nuclear factor‐κB p65 subunit were markedly attenuated at GLN concentrations above 0.5 mmol/L. GLN increased cellular HSP25 and HSP70 in a dose‐dependent manner. Conclusions: These data demonstrate the therapeutic potential of GLN as a “pharmacologically acting nutrient” in the setting of experimental IBD. GLN sufficiency is crucial for the colonic epithelium to mount a cell‐protective, antiapoptotic, and anti‐inflammatory response against inflammatory injury. The enhanced HSP expression observed following GLN treatment may be responsible for this protective effect.     

Plasma Arginine Levels and Blood Glucose Control in Very Preterm Infants Receiving 2 Different Parenteral Nutrition Regimens

Background: Improving parenteral nutrition (PN) amino acid (AA) intake in very preterm infants is associated with less hyperglycemia. AAs stimulate newborn insulin secretion with arginine, demonstrating a specific effect. We hypothesized that low arginine levels would be associated with increased insulin‐treated hyperglycemia and higher mean daily blood glucose levels in very preterm infants. Methods: We performed a secondary analysis on previous study data comparing high‐protein/calorie PN (HPC‐PN) and control groups in infants <29 weeks’ gestation. Infants were substratified (within original groups) according to high (highARG) and low (lowARG) plasma arginine levels on days 8–10 using a reference population‐derived threshold for high/low arginine (57 µmol/L). Daily protein, arginine, carbohydrate intake, mean daily blood glucose, and insulin treatment data from the first 15 days of life were collected. Results: Control group infants (n = 60) were stratified into lowARG (n = 41) and highARG (n = 19) groups. There were no differences in basic demographic data or carbohydrate intake. LowARG infants had higher mean daily blood glucose levels (P < .05) and a trend to more insulin treatment on days 6–10. HPC‐PN group infants (n = 55) were stratified into lowARG (n = 33) and highARG (n = 22) groups. LowARG infants had lower gestation and birth weight and were sicker than highARG infants. There were no differences in carbohydrate intake. LowARG infants had higher mean daily blood glucose levels (P < .01) and more insulin treatment (P < .01) on days 1–5 and 6–10. Insulin‐treated hyperglycemia was also associated with low plasma glutamine levels. Conclusion: Low plasma arginine levels (≤57 µmol/L) in very preterm infants are associated with poorer blood glucose control.     

Glutamine Improves Innate Immunity and Prevents Bacterial Enteroinvasion During Parenteral Nutrition

Background: Patients receiving parenteral nutrition (PN) are at increased risk of infectious complications compared with enteral feeding, which is in part explained by impaired mucosal immune function during PN. Adding glutamine (GLN) to PN has improved outcome in some clinical patient groups. Although GLN improves acquired mucosal immunity, its effect on innate mucosal immunity (defensins, mucus, lysozymes) has not been investigated. Methods: Forty‐eight hours following venous cannulation, male Institute of Cancer Research mice were randomized to chow (n = 10), PN (n = 12), or PN + GLN (n = 13) for 5 days. Small intestine tissue and luminal fluid were collected for mucin 2 (MUC2), lysozyme, cryptdin 4 analysis, and luminal interleukin (IL)–4, IL‐10, and IL‐13 level measurement. Tissue was also harvested for ex vivo intestinal segment culture to assess tissue susceptibility to enteroinvasive Escherichia coli. Results: In both luminal and tissue samples, PN reduced MUC2 and lysozyme (P < .0001, respectively) compared with chow, whereas GLN addition increased MUC2 and lysozyme (luminal, P < .05; tissue, P < .0001, respectively) compared with PN alone. PN significantly suppressed cryptdin 4 expression, while GLN supplementation significantly enhanced expression. IL‐4, IL‐10, and IL‐13 decreased significantly with PN compared with chow, whereas GLN significantly increased these cytokines compared with PN. Functionally, bacterial invasion increased with PN compared with chow (P < .05), while GLN significantly decreased enteroinvasion to chow levels (P < .05). Conclusions: GLN‐supplemented PN improves innate immunity and resistance to bacterial mucosal invasion lost with PN alone. This work confirms a clinical rationale for providing glutamine for the protection of the intestinal mucosa.     

Effect of high stearic acid containing fat on markers for in vivo lipid peroxidation

The objective of this study was to determine the effect of high stearic acid (SA) diets versus high polyunsaturated fatty acid (PUFA) diets on several measures of lipid peroxidation in vivo. Sprague–Dawley rats were fed diets that differed only in the fat source (8% by weight) for 19 weeks. High SA fats were beef tallow (BT) and cocoa butter (CB), high PUFA fats were soybean oil (SO) and menhaden oil (MO). Urine was analyzed for lipophilic aldehydes, the secondary products of lipid peroxidation, by HPLC. Decreases (P<0.05) were found for 4 nonpolar lipophilic aldehydes and related carbonyl compounds (NPC) and 4 polar lipophilic aldehydes and related carbonyl compounds (PC) when the BT-fed group was compared to the SO-fed group. Decreases were also found to be significant for total NPC (P<0.01) and total PC (P<0.05) between BT and SO-fed groups. Serum increase in resistance to oxidation (P<0.01) was found in the BT group when compared to the SO group. The differences in urine and serum measurements in the present experiment indicate lower level of lipid peroxidation in vivo due to the consumption of high SA containing BT diet compared to high PUFA containing SO diet without raising serum triglycerides and cholesterol levels significantly for the BT-fed groups.     

Effect of Conjugated Linoleic Acid-enriched Butter After 24 hours of Intestinal Mucositis Induction

Mucositis is the most common side effect due to chemotherapy or radiotherapy. It refers to the inflammation of intestinal mucous membranes, and it is associated with complications such as diarrhea, weight loss, and increased intestinal permeability (IP). This study was designed to evaluate the effect of diet containing conjugated linoleic acid (CLA)-enriched butter on intestinal damage and inflammatory response after 24 h of 5-fluorouracil (5-FU)-induced mucositis. Mice were divided into four groups: CTL; CLA; 5-FU, and CLA 5-FU, and they were fed for 31 days. On the 30th experimental day, mucositis was induced by unique injection of 300 mg/kg of 5-FU. After 24 h (31st experimental day), IP was evaluated; ileum and fecal material were collected to determine cytokine level and myeloperoxidase (MPO) activity and secretory immunoglobulin A (sIgA). The 5-FU group showed an increase in IP and MPO activity (CTL vs. 5-FU: P < 0.05). Additionally, increased levels of IP and MPO were observed in CLA 5-FU group compared to those in the test groups (P < 0.05). Animals in the CLA 5-FU group showed reduced concentrations of sIgA (CTL vs. CLA 5-FU: P < 0.05). CLA-enriched butter exacerbating the 5-FU-induced intestinal damage. Safety concerns regarding the use of CLA require further investigation.