Glycyl-glutamine-supplemented long-term total parenteral nutrition selectively improves structure and function in heterotopic small-bowel autotransplantation in the pig

Dietary glycyl-glutamine supplementation ameliorates intestinal integrity, inflammatory response, and oxidative status in association with the gut microbiota in LPS-challenged piglets

During weaning transition, mammalian newborns suffer severe enteric infections and thus induced gut microbiota dysbiosis, which in turn aggravates enteric disorder. The synthetic dipeptide glycyl-glutamine (GlyGln) has been used as a diet supplement to improve the weaning transition of newborns. However, the effect of dietary GlyGln supplementation on the gut microbiota of piglets with enteric infection remains unclear. Here, weaned piglets received a basal diet or a basal diet supplemented with 0.25% GlyGln for 3 weeks. Five piglets in each group received an intraperitoneal injection of lipopolysaccharide (LPS) (100 μg per kg BW) (LPS and GlyGln + LPS groups) and meanwhile five piglets in a control group received an intraperitoneal injection of saline (Ctrl group). The results showed that dietary GlyGln supplementation improved the LPS induced inflammation response and damage to the ileum morphology by increasing interleukin 10, tight junction proteins, villus height, and the ratio villus height/crypt depth, but decreasing the crypt depth. For the oxidative status, dietary GlyGln supplementation increased the ileal superoxide dismutase and meanwhile reduced the malondialdehyde and nitric oxide synthase activity (NOS) (total NOS and inducible NOS), compared with that in the LPS group. LPS challenge reduced the diversity of gut microbiota and enriched the facultative anaerobic Escherichia coli. The GlyGln restored alpha diversity and the structure of the gut microbiota by enriching obligate anaerobes and short-chain fatty acid (SCFA)-producing bacteria, including Clostridium, Lachnospira, Phascolarctobacterium, Roseburia, Lachnospiraceae, and Synergistetes. GlyGln enriched the gut microbiota function of carbohydrate metabolism and elevated the ileal SCFA concentrations of propionic acid and butyric acid that had been decreased by the LPS challenge. The beneficial effects of dietary GlyGln supplementation are closely associated with its enriched bacteria and SCFAs. Taken together, dietary GlyGln supplementation improved the gut microbiota dysbiosis induced by LPS challenge and enriched obligate anaerobes and SCFA-producing bacteria, which contributed to the amelioration of intestinal integrity, inflammatory responses, and oxidative status.

Nutritional Intervention for the Intestinal Development and Health of Weaned Pigs

Weaning imposes simultaneous stress, resulting in reduced feed intake, and growth rate, and increased morbidity and mortality of weaned pigs. Weaning impairs the intestinal integrity, disturbs digestive and absorptive capacity, and increases the intestinal oxidative stress, and susceptibility of diseases in piglets. The improvement of intestinal development and health is critically important for enhancing nutrient digestibility capacity and disease resistance of weaned pigs, therefore, increasing their survival rate at this most vulnerable stage, and overall productive performance during later stages. A healthy gut may include but not limited several important features: a healthy proliferation of intestinal epithelial cells, an integrated gut barrier function, a preferable or balanced gut microbiota, and a well-developed intestinal mucosa immunity. Burgeoning evidence suggested nutritional intervention are one of promising measures to enhance intestinal health of weaned pigs, although the exact protective mechanisms may vary and are still not completely understood. Previous research indicated that functional amino acids, such as arginine, cysteine, glutamine, or glutamate, may enhance intestinal mucosa immunity (i.e., increased sIgA secretion), reduce oxidative damage, stimulate proliferation of enterocytes, and enhance gut barrier function (i.e., enhanced expression of tight junction protein) of weaned pigs. A number of feed additives are marketed to assist in boosting intestinal immunity and regulating gut microbiota, therefore, reducing the negative impacts of weaning, and other environmental challenges on piglets. The promising results have been demonstrated in antimicrobial peptides, clays, direct-fed microbials, micro-minerals, milk components, oligosaccharides, organic acids, phytochemicals, and many other feed additives. This review summarizes our current understanding of nutritional intervention on intestinal health and development of weaned pigs and the importance of mechanistic studies focusing on this research area.

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.

Oral Glutamine Ameliorates Chemotherapy-induced Changes of Intestinal Permeability and Does not Interfere with the Antitumor Effect of Chemotherapy in Patients with Breast Cancer: A Prospective Randomized Trial

Aims and Background

Sixty patients with breast cancer were randomly assigned to oral glutamine or placebo pre-neoadju-vant chemotherapy (CEF regimen).

Methods and Study Design

Oral glutamine supplementation was continued for at least 12 days. Patients kept a daily record of diarrhea and stomatitis. The plasma glutamine level, intestinal permeability (lactulose-mannitol test), and tumor size were analyzed. The expression of Ki-67 and PCNA antigens in breast carcinoma was assessed.

Results

The plasma glutamine level was significantly higher in the glutamine group than in the placebo group (420.39 ± 52.39 mmol/L vs 309.76 ± 42.34 mmoi/L, P <0.05). After one cycle of chemotherapy, the lactulose-mannitol ratio was higher in the placebo group than in the glutamine group (0.0630 ± 0.0091 vs 0.0471 ± 0.0094, P <0.05). No differences were observed in the grades of stomatitis and diarrhea, in the changes in tumor size, and in the expression of Ki-67 and PCNA antigens between the two groups.

Conclusions

Prophylactic oral glutamine could ameliorate the neoadjuvant chemotherapy-induced increase in intestinal permeability, but had no significant positive clinical effect on stomatitis and diarrhea and did not interfere with the antitumor effect of chemotherapy.

Alanyl-glutamine but not glycyl-glutamine improved the proliferation of enterocytes as glutamine substitution in vitro

The synthetic dipeptides alanyl-glutamine (Ala-Gln) and glycyl-glutamine (Gly-Gln) are used as Gln substitution to provide energy source in the gastrointestinal tract due to their high solubility and stability. This study aimed to investigate the effects of Gln, Ala-Gln and Gly-Gln on mitochondrial respiration and protein turnover of enterocytes. Intestinal porcine epithelial cells (IPEC-J2) were cultured for 2 days in Dulbecco's modified Eagle's-F12 Ham medium (DMEM-F12) containing 2.5 mM Gln, Ala-Gln or Gly-Gln. Results from 5-ethynyl-2'-deoxyuridine incorporation and flow cytometry analysis indicated that there were no differences in proliferation between free Gln and Ala-Gln-treated cells, whereas Gly-Gln treatment inhibited the cell growth compared with Gln treatment. Significantly lower mRNA expressions of Sp1 and PepT1 were also observed in Gly-Gln-treated cells than that of Ala-Gln treatment. Ala-Gln treatment increased the basal respiration and ATP production, compared with free Gln and Gly-Gln treatments. There were no differences in protein turnover between free Gln and Ala-Gln-treated cells, but Gly-Gln treatment reduced protein synthesis and increased protein degradation. Ala-Gln treatment stimulated mTOR activation whereas Gly-Gln decreased mTOR phosphorylation and increased the UB protein expression compared with free Gln treatment. These results indicate that Ala-Gln has the very similar functional profile to free Gln in porcine enterocytes in vitro and can be substituted Gln as energy and protein sources in the gastrointestinal tract.

Enteral supplementation with glycyl-glutamine improves intestinal barrier function after liver transplantation in rats

BACKGROUND

Most patients after liver transplantation (LT) suffer from intestinal barrier dysfunction. Glycyl-glutamine (Gly-Gln) by parenteral supplementation is hydrolyzed to release glutamine, which improves intestinal barrier function in intestinal injury. This study aimed to investigate the effect of Gly-Gln by enteral supplementation on intestinal barrier function in rats after allogenetic LT under immunosuppressive therapy.

METHODS

Twelve inbred Lewis rats were selected randomly as donors, and 24 inbred Brown Norway (BN) rats as recipients of allogenetic LT. The recipients were divided into a control group (Ala, n=12) and an experimental group (Gly-Gln, n=12). In each group, 6 normal BN rats were sampled for normal parameters on preoperative day 3. The 6 recipients in the control group received alanine (Ala) daily by gastric perfusion for 3 preoperative days and 7 postoperative days, and the 6 recipients in the experimental group were given Gly-Gln in the same manner. The 12 BN recipients underwent orthotopic LT under sterile conditions after a 3-day fast and were given immunosuppressive therapy for 7 days. They were harvested for sampling on postoperative day 8. The following parameters were assessed: intestinal mucosal protein content, mucosal ultrastructure, ileocecal sIgA content, portal plasma levels of endotoxin and TNF-alpha, and bacterial translocation.

RESULTS

All recipients were alive after LT. On preoperative day 3, all parameters were similar in the two groups. On postoperative day 8, all parameters in the two groups were remarkably changed from those on preoperative day 3. However, compared to the Ala group, supplementation with Gly-Gln increased the levels of intestinal mucosal protein and ileocecal sIgA, improved mucosal microvilli, and decreased portal plasma levels of endotoxin and TNF-alpha as well as bacterial translocation.

CONCLUSION

Enteral supplementation with Gly-Gln improved intestinal barrier function after allogenetic LT in rats.

Cervical heterotopic small intestinal transplantation in rats using artery sleeve anastomosis

Our goal was to establish a simple and stable cervical heterotopic small intestinal transplantation (SIT) rat model that minimizes mortality.

METHODS

The graft was removed en bloc consisting of small intestine, portal vein (PV), and donor superior mesenteric artery. The graft was perfused in situ and the gut lumen irrigated during the operation. The donor artery was end-to-end anastomosed to the recipient left common carotid artery using a sleeve technique, and the donor vein to the recipient right external jugular vein using a cuff technique. The proximal and distal ends of the graft were formed as cervical cutaneous stomas.

RESULTS

Among 106 intestinal transplantations, 40 were a formal experimental group, displaying a survival rate of 95%. Surgery lasted 70 +/- 10 minutes. The average time for the arterial anastomosis and the venous anastomosis was 5 +/- 2 minutes and 2 +/- 1 minutes, respectively. Two rats died due to late anastomotic hemorrhage or intestinal fistula; 38 survived more than 6 months.

CONCLUSION

The cervical heterotopic technique has the advantages of being easier and faster to perform with shorter cold ischemia time and higher graft survival rate as well as fewer complications.

Tracking of Green Fluorescent Protein Labeled Escherichia coli Confirms Bacterial Translocation in Blind Loop Rat

BACKGROUND

Previous investigators have documented small intestinal mucosal injury in blind loop rats. However, the definitive evidence of intestinal bacterial translocation in blind loop animals has been lacking. The purpose of this study was to confirm bacterial translocation in blind loop rats and to evaluate the preventive effect of glutamine on bacterial translocation caused by blind loops.

MATERIALS AND METHODS

Escherichia coli TG1 labeled with green fluorescent protein was used to track bacterial translocation by gavage to rats. Six groups (n = 10) of rats were studied: unoperated control rats; rats with self-emptying blind loop; rats with self-filling blind loop; unoperated control rats treated with glutamine, 400 mg/d; rats with self-emptying blind loop treated with glutamine, 400 mg/d; rats with self-filling blind loop treated with glutamine, 400 mg/d. Representative tissue specimens of the mesenteric lymph nodes, liver, spleen, and kidney were aseptically harvested for bacteria culture.

RESULTS

Bacteria were detected in extraintestinal organs of rats with self-emptying blind loop, self-filling blind loop, and self-filling blind loop treated with glutamine. By fluorescence microscope and XbaI restriction digestion analysis, we elucidated that the bacteria isolated from extraintestinal organs were the same bacteria we gavaged to the rats.

CONCLUSION

We confirmed bacterial translocation in self-filling blind loop and self-emptying blind loop rats. In addition, we also showed that glutamine prevents bacterial translocation in self-emptying blind loop rats.

Two-step procedure of whole orthotopic intestinal transplantation in rats: considerations of techniques and graft functional adaptation

Intestinal transplantation may eventually become the definitive therapeutic modality for irreversible intestinal failure. To date, immunological, functional, and technical problems still hamper clinical success. In this paper, the technical aspects of a two-stage procedure for a whole orthotopic intestinal transplantation model of rats with systemic drainage are illustrated. Graft mucosal Na(+)/K(+)-ATPase and disaccharidase revealed recovery of graft function. From this study, we conclude that the present model may provide an excellent tool to further investigate the physiology and immunology of intestinal transplantation.

Absorption of orthotopically transplanted intestine in rats: evaluation of amino acid absorption

During the early phase of our intestinal transplant program, a low-lipid, amino acid-based feeding was employed for most recipients. However, relatively little is known regarding the amino acid absorption by a graft following intestinal transplantation. Sixty Wistar rats were randomly divided into two groups (n = 30). The animals received two-step orthotopic intestine transplantation (OIT), or the control; enterectomy with anastomoses. We measured mucosal Na(+)/K(+)-ATPase and intestinal absorption using stable isotope techniques in vivo. Compared with controls, mucosal Na(+)/K(+)-ATPase activity in OIT decreased by 38.3% and 38.4% at 2 and 4 weeks, and returned to baseline and control group values at 8 weeks. Glycine absorption decreased at 2 weeks and returned to baseline at 4 weeks in OIT compared with that in controls. These results suggested that absorption as assessed by mucosal Na(+)/K(+)-ATPase and glycine, returned to baseline at least 4 weeks after transplantation.

The effect of glutamine-supplemented total parenteral nutrition on nutrition and intestinal absorptive function in a rat model

The aim of the present study was to evaluate the effect of short-term (7 days) glycyl-glutamine-supplemented total parenteral nutrition (TPN) on nutrition and intestinal absorptive function in a rat model. Thirty Wistar rats, weighting 140-180 g, were divided into three groups (n=10) randomly. The animals received isonitrogenous and isocaloric TPN solutions for 7 days. The nitrogen was supplied by glycyl-glutamine dipeptide-supplemented amino acid solution (group G), and two standard amino acid solutions (group V, group N), respectively. Body weight, plasma glutamine level, nitrogen balance, total tissue water and intestinal absorptive function, assessed by (15-N)-glycine absorption, were investigated. Body weight decreased in three groups at the end of TPN; there was no significant difference in relative body-weight changes. There was a significant improvement of cumulative nitrogen balance and nitrogen retention in group G compared to other groups (P<0.05). There was no significant difference in intestinal glycine absorption (P>0.05) among the three groups. Total tissue water of left thigh muscle was significantly higher in group V and group N than that in group G (P<0.05). The results indicated that short-term (7 days) TPN supplemented with glycyl-glutamine improved plasma glutamine level and nitrogen balance, decreased water content of muscle, but had no beneficial effect on absorptive function in a rat model.

Effects of L-arginine on serum nitric oxide, nitric oxide synthase and mucosal Na+-K+-ATPase and nitric oxide synthase activity in segmental small-bowel autotransplantation model

AIM: To explore a simple method to create intestinal autotransplantation in rats and growing pigs and to investigate the effect of L-arginine supplementation on serum nitric oxide (NO), nitric oxide synthase (NOS) and intestinal mucosal NOS and Na⁺-K⁺-ATPase activity during cold ischemia-reperfusion (IR) in growing pigs.

METHODS: In adult Wistar rat models of small bowel autotransplantation, a fine tube was inserted into mesenteric artery via the abdominal aorta. The superior mesenteric artery and vein were occluded. Isolated terminal ileum segment was irrigated with Ringer’s solution at 4 °C and preserved in the same solution at 0-4 °C for 60 min. Then, the tube was removed and reperfusion was established. In growing pig models, a terminal ileum segment, 50 cm in length, was isolated and its mesenteric artery was irrigated via a needle with lactated Ringer’s solution at 4 °C. The method and period of cold preservation and reperfusion were described above. Ten white outbred pigs were randomly divided into control group and experimental group. L-arginine (150 mg/kg) was continuously infused for 15 min before reperfusion and for 30 min after reperfusion in the experimental group. One, 24, 48, and 72 h after reperfusion, peripheral vein blood was respectively collected for NO and NOS determination. At the same time point, intestinal mucosae were also obtained for NOS and Na⁺-K⁺-ATPase activity measurement.

RESULTS: In adult rat models, 16 of 20 rats sustained the procedure, three died of hemorrhage shock and one of deep anesthesia. In growing pig models, the viability of small bowel graft remained for 72 h after cold IR in eight of 10 pigs. In experimental group, serum NO level at 1 and 24 h after reperfusion increased significantly when compared with control group at the same time point (152.2±61.4 μmol/L vs 60.8±31.6 μmol/L, t = 2.802, P = 0.02<0.05; 82.2±24.0 μmol/L vs 54.0±24.3 μmol/L, t = 2.490, P = 0.04<0.05). Serum NO level increased significantly at 1 h post-reperfusion when compared with the same group before cold IR, 24 and 48 h post-reperfusion (152.2±61.4 μmol/L vs 75.6±16.2 μmol/L, t = 2.820, P = 0.02<0.05, 82.2 ±24.0 μmol/L, t = 2.760, P = 0.03<0.05, 74.2±21.9 μmol/L, t = 2.822, P = 0.02<0.05). Serum NOS activity at each time point had no significant difference between two groups. In experimental group, intestinal mucosal NOS activity at 1 h post-reperfusion reduced significantly when compared with pre-cold IR (0.79±0.04 U/mg vs 0.46±0.12 U/mg, t = 3.460, P = 0.009<0.01). Mucosal NOS activity at 24, 48, and 72 h post-reperfusion also reduced significantly when compared with pre-cold IR (0.79±0.04 U/mg vs 0.57±0.14 U/mg, t = 2.380, P = 0.04<0.05, 0.61±0.11 U/mg, t = 2.309, P = 0.04<0.05, 0.63±0.12U/mg, t = 2.307, P = 0.04<0.05). In control group, mucosal NOS activity at 1 and 24 h post-reperfusion was significantly lower than that in pre-cold IR (0.72±0.12 U/mg vs 0.60±0.07 U/mg, t = 2.320, P = 0.04<0.05, 0.58±0.18 U/mg, t = 2.310, P = 0.04<0.05). When compared to the normal value, Na⁺-K⁺-ATPase activity increased significantly at 48 and 72 h post-reperfusion in experimental group (2.48±0.59 μmol/mg vs 3.89±1.43 μmol/mg, t = 3.202, P = 0.04<0.05, 3.96±0.86 μmol/mg, t = 3.401, P = 0.009<0.01) and control group (2.48±0.59 μmol/mg vs 3.58±0.76 μmol/mg, t = 2.489, P = 0.04<0.05, 3.67±0.81 μmol/mg, t = 2.542, P = 0.03<0.05).

CONCLUSION: This novel technique for intestinal autotransplantation provides a potentially consistent and practical model for experimental studies of graft cold preservation. L-arginine supplementation during cold IR may act as a useful adjunct to preserve the grafted intestine.