Exploring and Enhancing the Anti‐Inflammatory Properties of Polymeric Formula

Background: Exclusive enteral nutrition (EEN) therapy using a polymeric formula (PF) can substantially attenuate intestinal inflammation in Crohn's disease (CD) patients. However, the mechanism(s) by which EEN suppresses inflammation are not yet fully understood. The aims were to examine cellular mechanism(s) through which EEN may suppress inflammation and investigate potential pathways to enhance anti‐inflammatory properties of EEN. Methods: Glutamine, arginine, vitamin D₃, and α linolenic acid (ALA), present in PF, along with curcumin, were identified as immunoactive nutrient therapies. Tumor necrosis factor (TNF)–α–exposed HT‐29 colonic epithelial cells were used to investigate the immunosuppressive activity of the nutrients by assessing their effect on cell viability, cell activity, chemokine response (interleukin‐8 [IL‐8]), nuclear factor (NF)–κB, P38 mitogen‐activated protein kinase, IκB kinase (Iκκ), and nitric oxide (NO). Results: Cellular viability and activity were maintained with all nutrient treatments. Glutamine, arginine, and vitamin D₃, but not ALA, significantly attenuated IL‐8 production. Glutamine and arginine led to phosphorylation blockade of the signaling components in NF‐κB and P38 pathways, reduction in kinase activity, and enhancement in NO production. Combining glutamine, arginine, and curcumin at optimal concentrations completely abolished the IL‐8 response. Conclusions: These data indicate that glutamine, arginine, and vitamin D₃ can suppress inflammation at concentrations equivalent to those used in PF. The mechanisms of this action were mediated through influencing the NF‐κB and P38 cascades. Glutamine and arginine‐fortified PF with curcumin might be a promising option to enhance the effectiveness and expand the scope of EEN therapy in CD treatment.     

卡巴胆碱对缺血再灌流大鼠肠黏膜组织炎症反应和血流量的影响

目的 研究缺血再灌流时卡巴胆碱对缺血再灌流大鼠肠组织炎症反应和血流量的影响.方法 Wistar大鼠开腹制做空肠袋,夹闭肠系膜上动脉(SMA)阻断血流45 min后恢复血流,制成肠缺血-再灌流模型.动物随机分为假手术组、缺血-再灌流+生理盐水组(I/R+NS)和缺血-再灌流+卡巴胆碱组(I/R+Ca).I/R+Ca组在SMA阻断血流同时向肠袋内注射卡巴胆碱(0.1mg/kg),I/R+NS组给予相同剂量的生理盐水.观察肠黏膜损伤情况;检测肠组织中DAO含量;ELLSA法测定肠组织中TNF-α含量;应用多普勒血流仪测定肠黏膜血流量.结果 I/R+Ca组与I/R+NS组相比,肠黏膜病理变化较轻.I/R+Ca组肠袋黏膜组织DAO活性较L/R+NS组显著增加(P<0.01);同时L/R+Ca组与I/R+NS组相比,肠黏膜血流量明显增加(P<0.01),而肠I/R+Ca组黏膜组织中TNF-α含量较I/R+Ns明显减少(P<0.01).结论 卡巴胆碱能促进缺血再灌流时肠黏膜血流恢复,增加肠黏膜血流量;抑制肠组织中TNF-α的生成,减轻肠黏膜病理损害,时肠黏膜具有保护作用.     

Anti-inflammatory and antioxidant effects of infliximab in a rat model of intestinal ischemia/reperfusion injury

The aim of this study was to investigate the possible protective effects of infliximab on oxidative stress, cell proliferation and apoptosis in the rat intestinal mucosa after ischemia/reperfusion (I/R). A total of 30 male Wistar albino rats were divided into three groups: sham, I/R and I/R+ infliximab; each group comprised 10 animals. Sham group animals underwent laparotomy without I/R injury. I/R groups after undergoing laparotomy, 1 hour of superior mesenteric artery ligation occurred, which was followed by 1 hour of reperfusion. In the infliximab group, 3 days before I/R, infliximab (3?mg/kg) was administered intravenously. All animals were killed at the end of reperfusion and intestinal tissues samples were obtained for biochemical and histopathological investigation in all groups. To date, no biochemical and histopathological changes have been reported regarding intestinal I/R injury in rats due to infliximab treatment. Infliximab treatment significantly decreased the elevated tissue malondialdehyde levels and increased reduced superoxide dismutase and glutathione peroxidase enzyme activities in intestinal tissues samples. I/R caused severe histopathological injury including mucosal erosions, inflammatory cell infiltration, necrosis, hemorrhage, and villous congestion. Infliximab treatment significantly attenuated the severity of intestinal I/R injury, inhibiting I/R-induced apoptosis, and cell proliferation. Because of its anti-inflammatory and antioxidant effects, infliximab pretreatment may have protective effects on the experimental intestinal I/R model of rats.     

Alanyl-glutamine-supplemented parenteral nutrition prevents intestinal ischemia-reperfusion injury in rats

BACKGROUND: Intestinal ischemia-reperfusion (I/R) injury plays an important role in the pathogenesis of systemic inflammation and multiple-organ failure. We studied whether glutamine, the primary fuel of the small intestine, prevents intestinal mucosal damage after intestinal I/R in rats. METHODS: Rats were randomly divided into 4 groups: a sham-standard amino acid (SAA) group (n = 8); a sham-glutamine (Gln) group (n = 8); an I/R-SAA group (n = 10); and an I/R-Gln group (n = 9). Alanyl-glutamine solution was produced by replacing 36% of the total amino acid nitrogen with Gln. The superior mesenteric artery was ligated. After 60 minutes of ischemia, reperfusion was initiated and infusion was started. After 24-hour reperfusion, the intestinal segment was removed for morphological and biochemical analysis, and blood samples were drawn from the portal vein. Fluorescein isothiocyanate-conjugated dextran 70,000 (FITC-dextran) was infused into the duodenum 2 hours before animal death. RESULTS: In the I/R-SAA group, extensive epithelial sloughing and mucosal ulceration of villous tips were observed, whereas these findings did not occur in the I/R-Gln group. Mucosal wet weight, DNA, and protein content decreased significantly in the I/R-SAA group compared with the sham-SAA group and increased significantly in the I/R-Gln group compared with the I/R-SAA group. Plasma FITC-dextran significantly increased in the I/R-SAA group compared with the sham-SAA group, but the plasma level in the I/R-Gln group was comparable with that of each sham group. Mucosal glutaminase activity significantly increased in both the I/R-SAA and I/R-Gln groups compared with the sham-SAA and sham-Gln groups, respectively. CONCLUSIONS: Alanyl-glutamine protects against morphologic and functional mucosal injury after intestinal I/R in rats.     

Adaptations of Arginine's Intestinal-Renal Axis in Cachectic Tumor-Bearing Rats

Malignancies induce disposal of arginine, an important substrate for the immune system. To sustain immune function, the tumor-bearing host accelerates arginine's intestinal-renal axis by glutamine mobilization from skeletal muscle and this may promote cachexia. Glutamine supplementation stimulates argi-nine production in healthy subjects. Arginine's intestinal-renal axis and the effect of glutamine supplementation in cancer cach-exia have not been investigated. This study evaluated the long-term adaptations of the interorgan pathway for arginine production following the onset of cachexia and the metabolic effect of glutamine supplementation in the cachectic state. Fischer-344 rats were randomly divided into a tumor-bearing group (n = 12), control group (n = 7) and tumor-bearing group receiving a glutamine-enriched diet (n = 9). Amino acid fluxes and net fractional extractions across intestine, kidneys, and liver were studied. Compared to controls, the portal-drained viscera of tumor-bearing rats took up significantly more glutamine and released significantly less citrulline. Renal metabolism was unchanged in the cachectic tumor-bearing rats compared with controls. Glutamine supplementation had no effects on intestinal and renal adaptations. In conclusion, in the cachectic state, an increase in intestinal glutamine uptake is not accompanied by an increase in renal arginine production. The adaptations found in the cachectic, tumor-bearing rat do not depend on glutamine availability.     

Pilot Experimental Study on the Effect of Arginine,Glutamine, and β‐Hydroxy β‐Methylbutyrate on Secondary Wound Healing

Background: Wound healing is a complex process, dependent on available nutrition substrates. When used together with β‐hydroxy β‐methylbutyrate, arginine and glutamine have been shown to increase collagen deposition in human subjects. However, there are no experimental investigations on the influence of this amino acid mixture with regard to secondary wound healing. The aim of this study is to investigate the effects of the supplementation of these 3 amino acids on the healing of open wounds in otherwise healthy animals. Materials and Methods: Twelve rats were divided into control and treatment groups. Two 2‐cm × 1‐cm full‐thickness skin defects were prepared on each subject. The rats in both groups received a diet containing 1.2 g of protein per 100 g of body weight per day. The treatment group, in addition, received 200 mg/kg L‐arginine, 200 mg/kg L‐glutamine, and 40 mg/kg β‐hydroxy β‐methylbutyrate every day. Wound sizes were measured every 2 days. On the 10th day, tissue samples were taken for histopathologic evaluation and also for the measurement of hydroxyproline concentrations. Results: There was no statistically significant difference between mean wound sizes for the 2 groups (P > .05). There was also no statistically significant difference between the groups with regard to histological healing parameters (reepithelialization [P = 1.00], granulation tissue [P = 1.00], collagen accumulation [P = .455], inflammatory cell accumulation [P = .455], angiogenesis [P = .242]) or tissue hydroxyproline concentrations (P = .240). Conclusion: Diet supplemented with arginine, glutamine, and β‐hydroxy β‐methylbutyrate is not beneficial in enhancing secondary healing of open wounds in rats. Further research regarding this topic is warranted.     

Lymph duct ligation during ischemia/reperfusion prevents pulmonary dysfunction in a rat model with ω-3 polyunsaturated fatty acid and glutamine

Objective

The release of injurious factors into the mesenteric lymph from the ischemic intestine has been shown to contribute to lung injury and systemic inflammation after severe injury. We studied the effects of lung injury and systemic inflammatory reaction after intestinal ischemia/reperfusion and mesenteric lymph duct ligation with different nutritional statuses.

Methods

Rats (n = 72) were fed with a normal diet or received one of three diets (enteral nutrition, glutamine, or ω-3 polyunsaturated fatty acid) that were isocaloric and isonitrogenous. After 7 d, rats were subjected to 60 min of intestinal ischemia, ischemia plus mesenteric lymph duct ligation, or sham procedures. After 3 d of ischemia, the lymph nodes, lung, intestinal, liver, and blood were harvested and analyzed.

Results

In the different groups, lung injury, including levels of myeloperoxidase, nitric oxide, nitric oxide synthase, and the index of alveolar apoptosis, were partly prevented by mesenteric lymph duct ligation (P < 0.05). Likewise, the rats with ischemia/reperfusion, but not those with duct ligation plus ischemia/reperfusion, had a significant increase in intestinal permeability and decreased mucosal thickness. The serum cytokine and endotoxin concentrations were also lower in the lymph duct ligation groups, although there was no significant difference between lymph duct ligation and sham procedure. The lung and intestinal injuries were attenuated in the groups fed with glutamine and ω-3 polyunsaturated fatty acid.

Conclusion

These results indicate that lymph duct ligation prevents lung injury, a systemic inflammation reaction, and gut-barrier dysfunction. Enteral glutamine and ω-3 polyunsaturated fatty acid modified the gut inflammation, prevented lung injury, and attenuated the systemic inflammation reaction.     

The route of administration (enteral or parenteral) affects the conversion of isotopically labeled L-[2-15N]glutamine into citrulline and arginine in humans

BACKGROUND: Glutamine exhibits numerous beneficial effects in experimental and clinical studies. It has been suggested that these effects may be partly mediated by the conversion of glutamine into citrulline and arginine. The intestinal metabolism of glutamine appears to be crucial in this pathway. The present study was designed to establish the effect of the feeding route, enteral or parenteral, on the conversion of exogenously administered glutamine into citrulline and arginine at an organ level in humans, with a focus on gut metabolism. METHODS: Sixteen patients undergoing upper gastrointestinal surgery received an IV or enteral (EN) infusion of L-[2-(15)N]glutamine. Blood was sampled from a radial artery and from the portal and right renal vein. Amino acid concentrations and enrichments were measured, and net fluxes of [(15)N]-labeled substrates across the portal drained viscera (PDV) and kidneys were calculated from arteriovenous differences and plasma flow. RESULTS: Arterial [(15)N]glutamine enrichments were significantly lower during enteral tracer infusion (tracer-to-tracee ratio [labeled vs unlabeled substrate, TTR%] IV: 6.66 +/- 0.35 vs EN: 3.04 +/- 0.45; p < .01), reflecting first-pass intestinal metabolism of glutamine during absorption. Compared with IV administration, enteral administration of the glutamine tracer resulted in a significantly higher intestinal fractional extraction of [(15)N]glutamine (IV: 0.15 +/- 0.03 vs EN: 0.44 +/- 0.08 micromol/kg/h; p < .01). Furthermore, enteral administration of the glutamine tracer resulted in higher arterial enrichments of [(15)N]citrulline (TTR% IV: 5.52 +/- 0.44 vs EN: 8.81 +/- 1.1; p = .02), and both routes of administration generated a significant enrichment of [(15)N]arginine (TTR% IV: 1.43 +/- 0.12 vs EN: 1.68 +/- 0.18). This was accompanied by intestinal release of [(15)N]citrulline across the PDV, which was higher with enteral glutamine (IV: 0.38 +/- 0.07 vs EN: 0.72 +/- 0.11 micromol/kg/h; p = .02), and subsequent [(15)N]arginine release in both groups. CONCLUSIONS: In humans, the gut preferably takes up enterally administered glutamine compared with intravenously provided glutamine. The route of administration, enteral or IV, affects the quantitative conversion of glutamine into citrulline and subsequent renal arginine synthesis in humans.     

Pretreatment and Treatment With L‐Arginine Attenuate Weight Loss and Bacterial Translocation in Dextran Sulfate Sodium Colitis

Background: Imbalances in a variety of factors, including genetics, intestinal flora, and mucosal immunity, can contribute to the development of ulcerative colitis and its side effects. This study evaluated the effects of pretreatment or treatment with arginine by oral administration on intestinal permeability, bacterial translocation (BT), and mucosal intestinal damage due to colitis. Methods: C57BL/6 mice were distributed into 4 groups: standard diet and water (C: control group), standard diet and dextran sodium sulfate (DSS) solution (Col: colitis group), 2% L ‐arginine supplementation for 7 days prior to DSS administration and during disease induction (PT: pretreated group), and 2% L ‐arginine supplementation during disease induction (T: treated group). Colitis was induced by administration of 1.5% DSS for 7 days. After 14 days, intestinal permeability and BT were evaluated; colons were collected for histologic analysis and determination of cytokines; feces were collected for measurement of immunoglobulin A (IgA). Results: The Col group showed increased intestinal permeability (C vs Col: P < .05) and BT (C vs Col: P < .05). In the arginine‐supplemented groups (PT and T), this amino acid tended to decrease intestinal permeability. Arginine decreased BT to liver during PT (P < .05) and to blood, liver, spleen, and lung during T (P < .05). Histologic analysis showed that arginine preserved the intestinal mucosa and tended to decreased inflammation. Conclusions: Arginine attenuates weight loss and BT in mice with colitis.     

大鼠肠道缺血/再灌注损伤后肠淋巴阻断对肺损伤的保护作用

目的比较大鼠肠道缺血再灌注时肠淋巴干结扎与不结扎对急性肺损伤的影响,探讨肠道淋巴在急性肺损伤发生中的作用。方法将40只健康雄性SPF级SD大鼠随机分为空白组、假手术组、肠道缺血再灌注组和肠道缺血再灌注 淋巴干结扎组,每组10只。在缺血再灌注后通过TUNEL法及HE染色分别检测肺组织Ⅱ型肺泡上皮细胞的凋亡和形态学变化,髓过氧化物酶(MPO)的活性和肺组织NO及一氧化氮合酶(NOS)水平。结果与肠道缺血再灌注组相比,肠道缺血再灌注 淋巴干结扎组的肺组织损伤程度明显减轻,平均Ⅱ型肺泡上皮细胞凋亡数显著降低(P<0.05);与其他3组比较,缺血再灌注组大鼠的肺组织MPO活性、NO及NOS浓度均显著增高(P<0.05)。结论肠淋巴干结扎可明显减轻肠道缺血再灌注引起的肺组织损伤,减少急性肺损伤的发生,这可能与肠淋巴阻断减少了经淋巴途径到达肺部的炎症介质相关。     

Mixture of Arginine,Glutamine, and β‐hydroxy‐β‐methyl Butyrate Enhances the Healing of Ischemic Wounds in Rats

Background: This study investigated the effects of an amino acid mixture containing arginine, glutamine, and β‐hydroxy‐β‐methyl butyrate on secondary healing of ischemic wounds in a rat model (N = 18). Methods: After the formation of a bipediculated flap on each rat, 2 full‐thickness excisional skin wounds (2 × 2 cm) were created on every flap. The rats were then randomized into the control and treatment groups. Every rat received standardized rat food throughout the study. The rats in the treatment group were administered an extra 200 mg/kg of L‐arginine, 200 mg/kg of L‐glutamine, and 40 mg/kg of β‐hydroxy‐β‐methyl butyrate per day. Wound sizes were measured on days 0, 4, 10, and 14. The rats were sacrificed, and the wounds were excised for biochemical and histologic examination on the 14th day. Results: As compared with the control group, the treatment group's wound sizes were significantly smaller on days 10 and 14 (P < .001), as was its inflammatory cell accumulation score (P = .008). There was no significant difference between the 2 groups in collagen accumulation (P = .340), granulation tissue maturation (P = .161), angiogenesis (P = .387), or reepithelialization (P = .190) and no significant difference between hydroxyproline concentrations in wounds (P = .287). Discussion: This amino acid combination seems to have a positive impact on the secondary healing of experimental ischemic wounds when introduced as a supplement to the standard diet, and the reduction in the inflammatory process appears to play a role in this effect.     

Interorgan amino acid exchange in humans: consequences for arginine and citrulline metabolism

BACKGROUND: The liver plays a central role in amino acid metabolism. However, because of limited accessibility of the portal vein, human data on this subject are scarce. OBJECTIVE: We studied hepatic amino acid metabolism in noncirrhotic fasting patients undergoing liver surgery. DESIGN: Twenty patients undergoing hepatectomy for colorectal metastases in a normal liver were studied. Before resection, blood was sampled from a radial artery, portal vein, hepatic vein, and renal vein. Organ blood flow was measured by duplex ultrasound scan. RESULTS: The intestine consumed glutamine and released citrulline. Citrulline was taken up by the kidney. This was accompanied by renal arginine release, which supports the view that glutamine is a precursor for arginine synthesis through an intestinal-renal pathway. The liver was found to extract citrulline from this pathway at a rate that was dependent on intestinal citrulline release (P < 0.0001) and hepatic citrulline influx (P = 0.03). Fractional hepatic extractions of citrulline (8.4%) and arginine (11.5%) were not significantly different. Eighty-eight percent of arginine reaching the liver passed it unchanged. Splanchnic citrulline release could account for one-third of renal citrulline uptake. CONCLUSIONS: This is the first study of hepatic and interorgan amino acid metabolism in humans with a normal liver. The data indicate that glutamine is a precursor of ornithine, which can be converted to citrulline by the intestine; citrulline is transformed in the kidneys to arginine. Hepatic citrulline uptake limits the amount of gut-derived citrulline reaching the kidney. These findings may have implications for interventions aimed at increasing systemic arginine concentrations.     

大鼠肠道缺血/再灌注时肠淋巴干结扎对肠道屏障的影响

目的比较大鼠肠道缺血/再灌注时肠淋巴干结扎与不结扎对肠道屏障的影响,探讨肠道淋巴及肠道屏障功能在危重病发生中的作用。方法健康雄性SPF级SD大鼠随机分为4组:空白组、假手术组、肠道缺血/再灌注组、肠道缺血/再灌注 淋巴干结扎组。分别检测肠道损伤程度,细菌、内毒素的移位情况及循环中D-乳酸、二胺氧化酶(DAO)的水平。结果假手术组、肠道缺血/再灌注组、肠道缺血/再灌注 淋巴干结扎组的黏膜厚度及绒毛高度均较空白组显著降低(P<0.05),肠道缺血/再灌注组、肠道缺血/再灌注 淋巴干结扎组间差异无显著性;空白组、假手术组未检测到细菌移位,肠道缺血/再灌注组细菌移位率为40%,肠道缺血/再灌注 淋巴干结扎组细菌移位率为20%;内毒素水平肠道缺血/再灌注组最高,肠道缺血/再灌注 淋巴干结扎组较肠道缺血/再灌注组显著降低(P<0.05),但肠道缺血/再灌注组、肠道缺血/再灌注 淋巴干结扎组均较空白组、假手术组增高(P<0.05);肠道缺血/再灌注组、肠道缺血/再灌注 淋巴干结扎组D-乳酸与DAO水平较空白组、假手术组显著增加(P<0.05),且肠道缺血/再灌注组高于肠道缺血/再灌注 淋巴干结扎组(P<0.05)。结论肠道缺血/再灌注损伤可导致肠黏膜厚度和绒毛高度显著降低,肠淋巴干结扎对肠道形态虽无明显保护作用,但减少细菌在肠系膜淋巴结的定植并降低血循环中内毒素、D-乳酸与DAO的水平。     

Dietary arginine deficiency alters flux of glutamine and urea cycle intermediates across the portal-drained viscera and liver of rats.

The effect of an arginine-deficient diet on net flux of amino acids across the portal-drained viscera and across the liver was studied in rats. Blood was obtained after food deprivation and 1 and 2 h after a meal of a 1.0% arginine control diet or an arginine-deficient diet containing 3.4% glutamate. The arginine-deficient diet decreased net portal-drained viscera flux of arginine and increased net portal-drained viscera flux of ornithine and proline. However, net portal-drained viscera flux of citrulline (0.35 +/- 0.05 mumol/min) was not influenced by diet; of this rate, 46% (0.16 mumol/min) bypassed the liver and was available for extrahepatic arginine synthesis. However, rats continued to exhibit signs of arginine deficiency such as decreased blood arginine concentrations (by 28%) and increased orotic acid excretion (90-fold). Arterial blood glutamine concentration was 25% higher in rats fed the arginine-deficient diet. In the fed state, net hepatic flux of glutamine was elevated from 0.15 (control) to 1.39 mumol/min, indicating that the liver was a major source of the increased blood glutamine concentrations. Increased production of hepatic glutamine and orotic acid may help rats compensate for dietary arginine deficiency, whereas splanchnic output of citrulline was not increased with dietary arginine deficiency even with a substantial dietary supply of glutamate.     

Endotoxin level in ischemia–reperfusion injury in rats: Effect of glutamine pretreatment on endotoxin levels and gut morphology

ObjectiveWe aimed to investigate the effect of enteral glutamine (Gln) pretreatment on plasma endotoxin level and intestinal histopathologic changes during intestinal ischemia–reperfusion (I/R) injury in rats.MethodsIntestinal I/R was induced by 60-min occlusion of the superior mesenteric artery followed by 60 min of reperfusion. Animals were pretreated with Gln by orogastric route for different periods and doses. To investigate the effects of gut decontamination on intestinal I/R injury, animals were pretreated with neomycin sulfate and erythromycin phosphate by orogastric route. In another series, dl-α-tocopherol hydrogen succinate was used to investigate the effects of vitamin E on intestinal I/R injury. Plasma endotoxin level was measured by the colorimetric “limulus amebocyte lysate” test. Intestinal mucosal injury was scored on a scale described by Chiu et al. (Archive in Surgery 1970;101:478–483).ResultsIntestinal I/R increased the plasma endotoxin level and worsened the histopathologic score significantly. Gln pretreatment (1 g/kg) for 4 d reduced the I/R-induced elevation of plasma endotoxin level. However, a significant improvement in histopathologic score could only be achieved when the pretreatment was given for 7 d. Antibiotic pretreatment lowered plasma endotoxin level without affecting the I/R-induced histopathologic changes, whereas vitamin E pretreatment affected plasma endotoxin level and histopathologic changes.ConclusionThese results suggest a lack of association between plasma endotoxin level and intestinal histopathologic alterations in intestinal I/R.     

The feeding route (enteral or parenteral) affects the plasma response of the dipetide Ala-Gln and the amino acids glutamine, citrulline and arginine, with the administration of Ala-Gln in preoperative patients

Enhancement of depressed plasma concentrations of glutamine and arginine is associated with better clinical outcome. Supplementation of glutamine might be a way to provide the patient with glutamine, and also arginine, because glutamine provides the kidney with citrulline, from which the kidney produces arginine when plasma levels of arginine are low. The aim of the present study was to investigate the parenteral and enteral response of the administered dipeptide Ala-Gln, glutamine, citrulline and arginine. Therefore, seven patients received 20 g Ala-Gln, administered over 4 h, parenterally or enterally, on two separate occasions. Arterial blood samples were taken before and during the administration of Ala-Gln. ANOVA and a paired t test were used to test differences (P<0.05). Ala-Gln was undetectable with enteral administration, whereas Ala-Gln remained stable at a plasma concentration of 268 micromol/l throughout parenteral infusion and rapidly decreased towards zero after infusion was stopped. The highest level of glutamine was observed with parenteral infusion of the dipeptide, although enteral infusion also significantly increased plasma levels of glutamine. The highest plasma response of citrulline was observed with the enteral administration of the dipeptide, although parenteral administration also increased plasma levels of citrulline. Plasma arginine increased significantly with parenteral infusion, but not with enteral administration of Ala-Gln. In conclusion, administrations of Ala-Gln, parenteral or enteral, resulted in an increased plasma glutamine response, as compared with baseline. Interestingly, in spite of the high availability of citrulline with enteral administration of the dipeptide, only parenteral infusion of Ala-Gln increased plasma arginine concentration.     

The 2007 ESPEN Sir David Cuthbertson Lecture: amino acids between and within organs. The glutamate-glutamine-citrulline-arginine pathway

In daily practice, the plasma concentration of amino acids is usually viewed as a parameter of production. However, both a high production and/or a reduced disposal capacity can result in an increased plasma concentration. In this presentation, I will discuss my research on interorgan relationships of the amino acids glutamate, glutamine, citrulline and arginine to explain the regulation of the plasma arginine level. The reduced glutamine disposal during liver failure is related to enhanced plasma glutamine level without any change in muscle and gut production or consumption rate. In contrast during sepsis, a small reduction in plasma glutamine is related to a substantially enhanced organ glutamate and glutamine production or consumption rate. These observations are a good example that plasma levels are directly related to production or consumption rates. Because glutamine breakdown in the gut produces citrulline, there is a good relation between the amount of metabolically active gut tissue and gut and whole body citrulline production. Arginine is produces from citrulline in the kidney and a reduced gut glutamine to citrulline conversion during sepsis explains the reduced de novo arginine production that is related to the reduced plasma arginine level. The interorgan route between muscle, gut, liver and kidney of the amino acids glutamate, glutamine, citrulline and arginine is a very good example of how complicated the regulation of plasma amino acid levels can be. However, in-depth research is necessary and will give us important clues to new nutritional strategies.     

Maintenance of Small Bowel Mucosa with Glutamine-Enriched Parenteral Nutrition

Glutamine is an important fuel utilized by the intestinal mucosa that is not present in standard amino acid nutrition solutions. In order to determine the effects of glutamine on the intestine, glutamine enriched nutrition was administered intravenously to male Wistar rats. A standard amino acid solution was enriched with 1 and 2 g/100 ml of glutamine or glycine and used as part of a parenteral nutrition regime for 7 days. Intestinal samples were taken for measurements of jejunal weight, DNA, protein, mucosal thickness and villus height. Animals receiving 2 g glutamine/100 ml in the nutrition solution had increased intestinal weight, DNA, and villus height when compared to animals receiving 2 g/100 ml of glycine. No increase in the intestinal parameters was noted when 1 g/100 ml of glutamine was used. To investigate the dose-response effects of glutamine, further studies were performed using iso-nitrogenous and isocaloric solutions containing 0, 2, and 3 g of glutamine/100 ml. Animals receiving glutamine had a significant increase in mucosal weight, DNA, protein and villus height when compared to animals receiving no glutamine in the parenteral solutions. There was a dose-response relationship between the increase in jejunal DNA and the increased intake of glutamine (r = 0.93, p < 0.01) but no correlation with the nitrogen content of the solutions (r = 0.18, p = 0.8). Total body nitrogen retention was greater in animals receiving 2 g/100 ml of glutamine (166 ± 12 mg, days 6/7) when compared to those receiving 0 and 3 g of glutamine/100 ml (126 ± 14 mg and 138 ± 16 mg, respectively, p < 0.05). These studies demonstrate that glutamine enriched nutrition protects against atrophy of the intestinal mucosa and when given at 2 g/100 ml improves nitrogen retention during intravenous feeding. (Journal of Parenteral and Enteral Nutrition 13: 579–585, 1989)     

Glutamine Administration in Early or Late Septic Phase Downregulates Lymphocyte PD‐1/PD‐L1 Expression and the Inflammatory Response in Mice With Polymicrobial Sepsis

Background: Sepsis is a severe inflammatory response to infection. Excessive compensation to inflammation leads to dysregulated immune response that ultimately results in organ damage and lethality of sepsis. This study administered glutamine (GLN) in the early or late phase of sepsis to investigate its effects on regulating leukocyte programmed cell death 1 (PD‐1) and its ligand (programmed cell death ligand 1 [PD‐L1]) expression, macrophage function, inflammation, and acute kidney injury in sepsis. Methods: Mice were randomly assigned to cecal ligation and puncture (CLP) or sham‐operated groups. Septic mice were respectively injected once with saline or 0.75 g GLN/kg body weight at 3 or 10 hours post‐CLP via tail vein. All mice were sacrificed 24 hours after CLP. Results: Sepsis enhanced the percentage of interferon‐γ–expressing and interleukin (IL)‐17A–expressing CD4⁺ T cells, expression of PD‐1 on T cells, and PD‐L1 on B cells and monocytes. Inflammatory mediator messenger RNA (mRNA) expression in kidney tissues and proapoptotic caspase‐3 mRNA expression in mesenteric lymph nodes were also upregulated. GLN administration decreased plasma IL‐6 level, downregulated the percentage of IL‐17A–expressing CD4⁺ T cells, attenuated macrophage dysfunction, decreased caspase‐3 mRNA expression, and reduced PD‐1/PD‐L1 expression by T and B cells. Histological findings also showed that kidney damage was attenuated. GLN administered at 3 and 10 hours after CLP offered nearly equal effects on PD‐1/PD‐L1 and inflammatory mediator expression after CLP. Conclusions: These findings suggest that a single dose of GLN administration in either the early or late phase during sepsis promotes a more balanced immune regulation and reduced systemic and kidney inflammatory responses in mice.     

Parenteral but Not Enteral Omega‐3 Fatty Acids (Omegaven) Modulate Intestinal Regrowth After Massive Small Bowel Resection in Rats

Background: The purpose of the present study was to evaluate the effects of ω‐3 fatty acids (Omegaven) on early intestinal adaptation in rats with short bowel syndrome (SBS). Methods: Male Sprague‐Dawley rats were randomly assigned to 1 of 4 groups: sham rats underwent bowel transection; SBS rats underwent 75% bowel resection; SBS‐O ω‐3 rats underwent bowel resection and were treated with oral Omegaven given by gavage; and SBS‐I ω‐3 rats underwent bowel resection and were treated with Omegaven given intraperitoneally. Rats were killed on day 14. Parameters of intestinal adaptation (bowel and mucosal weight, mucosal DNA and protein, villus height and crypt depths, cell proliferation and apoptosis) were determined at time of death. Real‐time polymerase chain reaction was used to determine the level of Bax and Bcl‐2 messenger RNA (mRNA). Statistical analysis was performed using Kruskal‐Wallis test followed by post hoc test, with P < .05 considered statistically significant. Results: Oral ω‐3 supplementation did not significantly change intestinal regrowth. In contrast, parenteral ω‐3 in rats that underwent resection resulted in higher bowel and mucosal weights, mucosal DNA and protein in ileum, villus height in ileum, crypt depth in jejunum and ileum, and greater rates of cell proliferation in jejunum and ileum compared with SBS animals. The initial decreased levels of apoptosis corresponded with the early decrease in Bax and increase in Bcl‐2 mRNA levels. Conclusions: Parenteral but not enteral Omegaven augments and accelerates structural bowel adaptation in a rat model of SBS. Increased cell proliferation and decreased apoptosis reflect increased cell turnover in Omegaven‐treated animals.