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

Amino acid HPLC-FLD analysis of spirulina and its protective mechanism against the combination of obesity and colitis in wistar rats

Objective

The cafeteria diet (CD), designed as an experimental diet mimicking the obesogenic diet, may contribute to the pathogenesis of inflammatory bowel diseases (IBD). This study delves into the influence of spirulina (SP) on obesity associated with colitis in Wistar rats.

Methods

The amino acids composition of SP was analyzed using HPLC-FLD. Animals were equally separated into eight groups, each containing seven animals and treated daily for eight weeks as follows: Control diet (SD), cafeteria diet (CD) group, CD + SP (500 mg/kg) and SD + SP. Ulcerative colitis was provoked by rectal injection of acetic acid (AA) (3 % v/v, 5 ml/kg b.w.) on the last day of treatment in the following groups: SD + AA, SD + AA + SP, CD + AA, and CD + AA + SP.

Results

Findings revealed that UC and/or CD increased the abdominal fat, weights gain, and colons. Moreover, severe colonic alteration, perturbations in the serum metabolic parameters associated with an oxidative stress state in the colonic mucosa, defined by overproduction of reactive oxygen species (ROS) and increased levels of plasma scavenging activity (PSA). Additionally, obesity exacerbated the severity of AA-induced UC promoting inflammation marked by the overexpression of pro-inflammatory cytokines. Significantly, treatment with SP provided notable protection against inflammation severity, reduced histopathological alterations, attenuated lipid peroxidation (MDA), and enhanced antioxidant enzyme activities (CAT, SOD, and GPX) along with non-enzymatic antioxidants (GSH and SH-G).

Conclusions

Thus, the antioxidant effects and anti-inflammatory proprieties of SP could be attributed to its richness in amino acids, which could potentially mitigate inflammation severity in obese subjects suffering from ulcerative colitis. These results imply that SP hold promise as a therapeutic agent for managing of UC, particularly in individuals with concomitant obesity. Understanding SP's mechanisms of action may lead novel treatment strategies for inflammatory bowel diseases and hyperlipidemia in medical research.

Dexmedetomidine against intestinal ischemia/reperfusion injury: A systematic review and meta-analysis of preclinical studies

BACKGROUND

Intestinal ischemia/reperfusion injury (IRI) is a multifactorial, complex pathophysiological process in clinical settings. In recent years, intestinal IRI has received increasing attention due to increased morbidity and mortality. To date, there are no effective treatments. Dexmedetomidine (DEX), a highly selective α2-adrenergic receptor agonist, has been demonstrated to be effective against intestinal IRI. In this systematic review and meta-analysis, we evaluated the efficacy and potential mechanisms of DEX as a treatment for intestinal IRI in animal models.

METHODS

Five databases (PubMed, Embase, Web of Science, Cochrane Library, and Scopus) were searched until March 15, 2023. Using the SYRCLE risk bias tool, we assessed methodological quality. Statistical analysis was conducted using STATA 12 and R 4.2.2. We analyzed the related outcomes (mucosa damage-related indicators; inflammation-relevant markers, oxidative stress markers) relied on the fixed or random-effects models.

RESULTS

There were 15 articles including 18 studies included, and 309 animals were involved in the studies. Compared to the model groups, DEX improved intestinal IRI. DEX decreased Chiu's score and serum diamine oxidase (DAO) level. DEX reduced the level of inflammation-relevant markers (interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α). DEX also improved oxidative stress (decreased malondialdehyde (MDA), increased superoxide dismutase (SOD)).

CONCLUSIONS

DEX's effectiveness in ameliorating intestinal IRI has been demonstrated in animal models. Antioxidation, anti-inflammation, anti-apoptotic, anti-pyroptosis, anti-ferroptosis, enhancing mitophagy, reshaping the gut microbiota, and gut barrier protection are possible mechanisms. However, in light of the heterogeneity and methodological quality of these studies, further well-designed preclinical studies are warranted before clinical implication.

Glucose- and glutamine-dependent bioenergetics sensitize bone mechanoresponse after unloading by modulating osteocyte calcium dynamics

Disuse osteoporosis is a metabolic bone disease resulting from skeletal unloading (e.g., during extended bed rest, limb immobilization, and spaceflight), and the slow and insufficient bone recovery during reambulation remains an unresolved medical challenge. Here, we demonstrated that loading-induced increase in bone architecture/strength was suppressed in skeletons previously exposed to unloading. This reduction in bone mechanosensitivity was directly associated with attenuated osteocytic Ca2+ oscillatory dynamics. The unloading-induced compromised osteocytic Ca2+ response to reloading resulted from the HIF-1α/PDK1 axis-mediated increase in glycolysis, and a subsequent reduction in ATP synthesis. HIF-1α also transcriptionally induced substantial glutaminase 2 expression and thereby glutamine addiction in osteocytes. Inhibition of glycolysis by blockade of PDK1 or glutamine supplementation restored the mechanosensitivity in those skeletons with previous unloading by fueling the tricarboxylic acid cycle and rescuing subsequent Ca2+ oscillations in osteocytes. Thus, we provide mechanistic insight into disuse-induced deterioration of bone mechanosensitivity and a promising therapeutic approach to accelerate bone recovery after long-duration disuse.

Protective effects of glutamine on lipopolysaccharide/D-galactosamine-induced fulminant hepatitis in mice

Fulminant hepatitis remains a critical health problem owing to its high mortality rate and the lack of effective therapies. An increasing number of studies have shown that glutamine supplementation provides protective benefits in inflammation-related disorders, but the pharmacological significance of glutamine in lipopolysaccharide (LPS)/D-galactosamine (D-Gal)-induced fulminant hepatitis remains unclear. In the present study, the potential effects of glutamine on LPS/D-Gal-induced fulminant hepatitis were investigated. Pretreatment with glutamine decreased plasma activities of alanine and aspartate aminotransferases, and ameliorated hepatic morphological abnormalities in LPS/D-Gal-exposed mice. Glutamine pretreatment also inhibited LPS/D-Gal-induced tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) production. In addition, glutamine pretreatment decreased the level of cleaved cysteinyl aspartate-specific proteinase 3 (caspase-3), suppressed the activities of caspase-3, caspase-8, and caspase-9, and reduced the number of cells positive for TdT-mediated dUTP nick-end labeling in LPS/D-Gal-challenged mice. Interestingly, post-treatment with glutamine also provided protective benefits against LPS/D-Gal-induced acute liver injury, although these effects were less robust than those of glutamine pre-treatment. Thus, glutamine may have potential value as a pharmacological intervention in fulminant hepatitis.

Blood Levels of Glutamine and Nitrotyrosine in Patients with Chronic Viral Hepatitis

Purpose

Oxidative stress is involved in pathogenesis of chronic viral hepatitis. Glutamine is an antioxidant, but there is a controversy about its risk-benefits. Nitrotyrosine is an oxidative stress marker. This observational cross-sectional study was designed to compare blood levels of glutamine and nitrotyrosine in treated versus untreated chronic viral hepatitis patients.

Patients and Methods

Five groups (n = 250) were included: hepatitis B untreated (HBV), hepatitis C untreated (HCV), HBV treated (HBVT), and HCV treated (HCVT) groups plus a normal control group. Liver function tests and blood levels of glutamine, nitrotyrosine, viral loads, and HBsAg were measured.

Results

Blood levels of glutamine and nitrotyrosine in all patient groups significantly increased compared with normal controls with non-significant differences in-between. Both tests showed significant large correlations with HBV-DNA or HCV-RNA test positivity, high accuracies, and cutoff scores with high sensitivities and specificities. The viral loads and HBsAg levels were significantly lower in treated versus untreated groups. However, they poorly correlated with levels of glutamine and nitrotyrosine in all patient groups.

Conclusion

Blood levels of glutamine and nitrotyrosine significantly increased in treated and untreated chronic viral hepatitis B and C patients compared with normal controls. Both tests showed high accuracies and cutoff scores with high sensitivities and specificities. However, they did not differ significantly in treated versus untreated patients. To our knowledge, this is the first data showing elevation of glutamine and nitrotyrosine in treated and untreated chronic viral hepatitis. A prospective longitudinal study with repeated measurements of glutamine and nitrotyrosine is recommended to verify if they can predict response to treatment. Study of other oxidative stress markers is also advised to clarify if the elevated nitrotyrosine could be an oxidative stress marker in these patients, and whether the increased glutamine could act as an antioxidant or as a predictive agent for deleterious consequences.

Effects of glutamine on the IKK/IκB/NF-кB system in the enterocytes of turbot Scophthalmus maximus L. stimulated with soya-saponins

Soya-saponins represent key anti-nutritional factors that contribute to soybean meal-induced enteritis, and glutamine is an effective fish intestine protectant that combats the negative effects of soya-saponins. Nuclear transcription factor-kappa B (NF-кB) systems are involved in the interactions between soya-saponins and glutamine, and the goal of the present work was to clarify the related molecular mechanisms used by the NF-кB kinase (IKK)/inhibitor of NF-κB (IκB)/NF-кB system. Primary cultured turbot (Scophthalmus maximus L.) intestinal epithelial cells were concurrently administrated with 1 mg/mL of soya-saponins and several levels of glutamine (0, 0.5, 1.0 and 2.0 mM) for 12 h and then subjected to real-time PCR and Western blot assays. Compared with cells treated with soya-saponins alone, glutamine significantly decreased the expression of interleukin-1 beta, interleukin 8 and tumor necrosis factor α genes, significantly reduced nuclear and cytosolic NF-κB p65 abundance levels in a dose-dependent manner, increased the IκBα protein level but decreased its phosphorylation, and down-regulated the IKKα/β and phosphorylated IKKα/β levels. In conclusion, this in vitro work confirmed that glutamine attenuated soya-saponin-induced inflammatory responses in turbot intestines. Moreover, it identified molecular pathways in which glutamine first decreased the p65 level and then prevented its nuclear translocation. In addition, glutamine reduced IκBα phosphorylation and maintained its level. Finally, glutamine decreased IKK expression and phosphorylation.

Nutritional considerations to counteract gastrointestinal permeability during exertional heat stress

Intestinal barrier integrity and function are compromised during exertional heat stress (EHS) potentially leading to consequences that range from minor gastrointestinal (GI) disturbances to fatal outcomes in exertional heat stroke or septic shock. This mini-review provides a concise discussion of nutritional interventions that may protect against intestinal permeability during EHS and suggests physiological mechanisms responsible for this protection. Although diverse nutritional interventions have been suggested to be protective against EHS-induced GI permeability, the ingestion of certain amino acids, carbohydrates, and fluid per se is potentially effective strategy, whereas evidence for various polyphenols and pre/probiotics is developing. Plausible physiological mechanisms of protection include increased blood flow, epithelial cell proliferation, upregulation of intracellular heat shock proteins, modulation of inflammatory signaling, alteration of the GI microbiota, and increased expression of tight junction (TJ) proteins. Further clinical research is needed to propose specific nutritional candidates and recommendations for their application to prevent intestinal barrier disruption and elucidate mechanisms during EHS.

MicroRNA-200a-3p accelerates the progression of osteoporosis by targeting glutaminase to inhibit osteogenic differentiation of bone marrow mesenchymal stem cells

To uncover the role of microRNA-200a-3p in regulating osteogenic differentiation of MSCs via targeting glutaminase, thus influencing the progression of OP. Serum level of microRNA-200a-3p in OP patients and healthy controls was determined by qRT-PCR. MicroRNA-200a-3p level in MSCs undergoing osteogenic differentiation for different days was examined as well. ALP activity, calcification nodules and relative levels of Bglap, Runx2 and OPN in MSCs overexpressing microRNA-200a-3p undergoing osteogenic differentiation were detected. Relative l-glutaminase uptake in MSCs undergoing osteogenic differentiation for different days was determined. After transfection of si-GLS in MSCs undergoing osteogenic differentiation, l-glutaminase uptake, ALP activity and relative levels of Bglap, Runx2 and OPN were detected. The potential binding relationship between microRNA-200a-3p and GLS was tested by dual-luciferase reporter gene assay. Finally, rescue experiments were conducted to elucidate the role of microRNA-200a-3p/GLS in osteogenic differentiation of MSCs. MicroRNA-200a-3p level was higher in serum of OP patients relative to controls. Its level in MSCs gradually decreased with the prolongation of osteogenic differentiation. Overexpression of microRNA-200a-3p reduced cell viability, ALP activity, number and volume of calcification nodule. The mRNA levels of Bglap, Runx2 and OPN were downregulated by overexpressed microRNA-200a-3p. The cell viability, ALP activity, number and volume of calcification nodule were reduced when microRNA-200a-3p was knocked down. The mRNA levels of Bglap, Runx2 and OPN were upregulated when transfected microRNA-200a-3p inhibitor. l-glutaminase uptake increased with the prolongation of osteogenic differentiation in MSCs. Knockdown of GLS attenuated l-glutaminase uptake and ALP activity, as well as downregulated Bglap, Runx2 and OPN. Besides, GLS was verified to directly bind to microRNA-200a-3p. GLS overexpression reversed the inhibitory effects of overexpressed microRNA-200a-3p on osteogenic differentiation of MSCs. MicroRNA-200a-3p suppresses osteogenic differentiation of MSCs via targeting glutaminase, thereafter accelerating the progression of OP.

Effects of Metabolites Derived From Gut Microbiota and Hosts on Pathogens

Intestinal metabolites participate in various physiological processes, including energy metabolism, cell-to-cell communication, and host immunity. These metabolites mainly originate from gut microbiota and hosts. Although many host metabolites are dominant in intestines, such as free fatty acids, amino acids and vitamins, the metabolites derived from gut microbiota are also essential for intestinal homeostasis. In addition, some metabolites are only generated and released by gut microbiota, such as bacteriocins, short-chain fatty acids, and quorum-sensing autoinducers. In this review, we summarize recent studies regarding the crosstalk between pathogens and metabolites from different sources, including the influence on bacterial development and the activation/inhibition of immune responses of hosts. All of these functions would affect the colonization of and infection by pathogens. This review provides clear ideas and directions for further exploring the regulatory mechanisms and effects of metabolites on pathogens.

Mechanism underlying methyl eugenol attenuation of intestinal ischemia/reperfusion injury

Intestinal ischemia/reperfusion (I/R) injury is associated with a high risk of mortality in the clinical situation. Many factors are involved in I/R, including reactive oxygen species, cytokine release, and apoptosis. We aimed to determine whether a pure methyl eugenol (ME) given before intestinal ischemia, protects against intestinal I/R injury and the possible mechanism involved in this protection. Rat received ME (100 mg/kg) for 30 days then underwent intestinal I/R with 30 min ischemia and 60 min reperfusion. Serum lactate dehydrogenase (LDH) level, tissue malondialdehyde (MDA), as well as some antioxidant biomarkers were assessed, while the serum level of tumor necrosis factor alpha (TNF-α) was determined by ELISA. The change in TNF-α and interleukin 6 (IL-6) gene expressions were evaluated and confirmed by assessing protein level of TNF-α in the intestinal tissue by immunohistochemistry. Apoptosis was evaluated using DNA-laddering assay and by detecting caspase-3 immunohistochemically. Administration of ME prior to I/R injury resulted in a modulation of the production of MDA, LDH, and nitric oxide and restoration of the tested oxidative stress biomarkers. Pretreatment with ME downregulated messenger RNA of TNF-α and IL-6 inflammatory cytokines and their protein expressions in I/R rats. Marked inhibition of the apoptotic DNA and improvement of the architectures of small intestine were observed after pretreatment with ME. ME exhibits a protective effect against intestinal I/R via amelioration of the oxidative stress and inflammatory cytokines gene expression. Therefore, the supplementation of ME prior to intestinal I/R might be helpful in the attenuation of I/R complications.

Electroacupuncture improves acute bowel injury recovery in rat models

Electroacupuncture (EA) accelerates intestinal functional recovery in sepsis. The present study investigated ghrelin and ghrelin receptor (GSH-R) levels during EA in rats with acute bowel injury (ABI). Rats were grouped into four groups: Sham, ABI, ABI+EA and ABI+GHRA+EA (n=12 per group). ABI was induced by cecal ligation and puncture (CLP). EA on bilateral Zusanli acupoints was performed following CLP. GSH-R blocker (GHRA) was used following CLP but prior to EA for ABI+GHRA+EA rats. Rats were sacrificed 12 h following CLP. Serum ghrelin, tumor necrosis factor-α (TNF-α) and high mobility group box 1 (HMGB1) levels, as well as ghrelin and GSH-R protein expression, water content, pathological changes and myeloperoxidase (MPO) and diamine oxidase (DAO) activities in the bowel tissues, were measured. ABI rats, compared with the sham rats, had significantly lower levels of ghrelin and GSH-R in the serum and bowel tissue, and higher Chiu's score (all P<0.05). The ABI+EA rats, compared with the ABI rats, had significantly reduced serum TNF-α and HMGB1 levels, bowel water content, MPO activity and Chiu's score (all P<0.05), and significantly higher serum ghrelin (121.2±10.7 vs. 86.7±6.4 pg/ml), bowel ghrelin (0.12±0.02 vs. 0.08±0.01), GSH-R (0.05±0.04 vs. 0.03±0.01) and DAO activity (18.74±4.18 vs. 13.52±2.33 U/ml; all P<0.05), indicating an improvement of the intestinal mucosal barrier. GHRA reversed the protective effects of EA. Therefore, EA improved ABI recovery by promoting ghrelin secretion and upregulating GSH-R expression.

Glutamine and citrulline concentrations reflect nitric oxide synthesis in the human nervous system

INTRODUCTION

Although citrulline is produced by nitric oxide (NO) synthase upon activation of the NMDA glutamate receptor, nitrite and nitrate (NO_x) concentration is considered the best marker of NO synthesis, as citrulline is also metabolised by other enzymes. This study analyses the correlation between human cerebrospinal fluid NO_x and citrulline concentrations in order to determine the extent to which citrulline reflects NO synthesis and glutamatergic neurotransmission.

METHODS

Participants were patients with acute neurological diseases undergoing lumbar puncture (n=240). NO_x and amino acid concentrations were determined by HPLC.

RESULTS

NO_x concentrations did not vary significantly where infection (p=0,110) or inflammation (p=0,349) were present. Multiple regression analysis showed that NO_x concentration was correlated with glutamine (r=-0,319, p<0,001) and citrulline concentrations (r=0,293, p=0,005) but not with the citrulline/arginine ratio (r=-0,160, p=0,173). ANCOVA confirmed that NO_x concentration was correlated with citrulline concentration (F=7,6, p=0,007) but not with the citrulline/arginine ratio (F=2,2, p=0,136), or presence of infection (F=1,8, p=0,173) or inflammation (F=1,4, p=0,227). No association was found between NO_x and arginine or glutamate concentrations.

CONCLUSION

The results suggest that CSF citrulline concentration reflects NO_x synthesis to some extent, despite the contribution of other metabolic pathways. In addition, this study shows that glutamine is an important modulator of NO synthase activity, and that arginine and glutamate are not correlated with NO_x.

Reduced fasting periods increase intestinal permeability in chickens

Fasting of up to 24 hr has been shown to increase intestinal permeability (IP) in chickens. The aim of this study was to determine whether fasting duration of 4.5 and 9 hr increased IP and whether l-glutamine (a non-essential amino acid) supplementation before fasting provided some protection of barrier function as shown in other species. Ross 308 male broilers (n = 96) were fed either a control diet or the same diet supplemented with 1% glutamine from d0 to d38 post-hatch. On d37, the birds were assigned to single-bird metabolism cages and were fasted for either 0, 4.5, 9 or 19.5 hr. This study design was 2 × 4 factorial with two levels of glutamine and four levels of fasting. Birds in the 0-hr fasting group had free access to feed. All birds had ad libitum access to water. To measure IP on day 38, following their respective fasting periods, birds were administered two separate oral gavages of fluorescein isothiocyanate dextran (FITC-d) followed by lactulose, mannitol and rhamnose (LMR) sugars, 60 min apart. Whole blood was collected from the jugular vein 90 min post-LMR sugar gavage. FITC-d and L/M/R ratios were measured by spectrophotometry and high-performance ionic chromatography respectively. Lipopolysaccharide (LPS) endotoxins in plasma of the birds fed the control diet were also measured using chicken-specific LPS antibody ELISA. Serum FITC-d and plasma L/M and L/R ratios for 4.5, 9 and 19.5 hr were significantly (p < .05) higher compared to the non-fasting group. However, IP was not different in the glutamine-supplemented group (p > .05) compared to the control group. LPS concentrations measured by the ELISA were below the detectable range. We conclude that fasting periods of 4.5 and 9 hr increased IP compared to non-fasted birds and dietary glutamine supplementation did not ameliorate changes in IP.

Alterations in Intestinal Permeability: The Role of the "Leaky Gut" in Health and Disease

All species, including horses, suffer from alterations that increase intestinal permeability. These alterations, also known as "leaky gut," may lead to severe disease as the normal intestinal barrier becomes compromised and can no longer protect against harmful luminal contents including microbial toxins and pathogens. Leaky gut results from a variety of conditions including physical stressors, decreased blood flow to the intestine, inflammatory disease, and pathogenic infections, among others. Several testing methods exist to diagnose these alterations in both a clinical and research setting. To date, most research has focused on regulation of the host immune response due to the wide variety of factors that can potentially influence the intestinal barrier. This article serves to review the normal intestinal barrier, measurement of barrier permeability, pathogenesis and main causes of altered permeability, and highlight potential alternative therapies of leaky gut in horses while relating what has been studied in other species. Conditions resulting in barrier dysfunction and leaky gut can be a major cause of decreased performance and also death in horses. A better understanding of the intestinal barrier in disease and ways to optimize the function of this barrier is vital to the long-term health and maintenance of these animals.

Glutamine and the regulation of intestinal permeability: from bench to bedside

PURPOSE OF REVIEW

Glutamine is the most abundant amino acid in plasma and plays a key role in maintaining the integrity of intestinal barrier.

RECENT FINDINGS

Experimental studies showed that glutamine is able to modulate intestinal permeability and tight junction protein expression in several conditions. Recent articles underlined its putative beneficial role in gastrointestinal disorders such as irritable bowel syndrome.

SUMMARY

Glutamine is a major nutrient to maintain intestinal barrier function in animals and humans. Depletion of glutamine results in villus atrophy, decreased expression of tight junction proteins and increased intestinal permeability. Moreover, glutamine supplementation can improve gut barrier function in several experimental conditions of injury and in some clinical situations. Furthermore, preventive effects of glutamine in experimental models of intestinal injuries have been recently reported. Despite promising data in experimental models, further studies are needed to evaluate glutamine supplementation in clinical practice.

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.

L-Alanyl-Glutamine Attenuates Oxidative Stress in Liver Transplantation Patients

BACKGROUND

Ischemia/reperfusion injury during liver transplantation can cause severe damage to the graft. The objective of this randomized, double-blind study was to evaluate the possible protective effects of L-alanyl-glutamine on the liver graft.

METHODS

The sample included 33 patients from a liver transplantation service in Northeastern Brazil. Before cold ischemia, the patients received 50 g of L-alanyl-glutamine (treatment group) or saline (control group) through the portal vein. The graft was biopsied at the time of recovery, at the beginning of warm ischemia, and at the end of transplantation to determine malondialdehyde (MDA), heat-shock protein (Hsp)70, nuclear factor kappa-beta (NFkB), superoxide dismutase (SOD), and reduced glutathione (GSH) levels.

RESULTS

The blood parameters were similar in the two groups. In the treatment group, MDA did not increase at the beginning of cold ischemia and decreased at the end of transplantation. This phenomenon was not observed in the control group. GSH, SOD, Hsp70, and NFkB levels were similar in the two groups.

CONCLUSIONS

Our findings suggest that preconditioning with L-alanyl-glutamine attenuates the effects of ischemia/reperfusion-related oxidative stress and reduces lipid peroxidation in the grafts of liver transplantation patients.

Perioperative glutamine supplementation restores disturbed renal arginine synthesis after open aortic surgery: a randomized controlled clinical trial

Postoperative renal failure is a common complication after open repair of an abdominal aortic aneurysm. The amino acid arginine is formed in the kidneys from its precursor citrulline, and citrulline is formed from glutamine in the intestines. Arginine enhances the function of the immune and cardiovascular systems, which is important for recovery after surgery. We hypothesized that renal arginine production is diminished after ischemia-reperfusion injury caused by clamping of the aorta during open abdominal aortic surgery and that parenteral glutamine supplementation might compensate for this impaired arginine synthesis. This open-label clinical trial randomized patients who underwent clamping of the aorta during open abdominal aortic surgery to receive a perioperative supplement of intravenous alanyl-glutamine (0.5 g·kg(-1)·day(-1); group A, n = 5) or no supplement (group B, n = 5). One day after surgery, stable isotopes and tracer methods were used to analyze the metabolism and conversion of glutamine, citrulline, and arginine. Whole body plasma flux of glutamine, citrulline, and arginine was significantly higher in group A than in group B (glutamine: 391 ± 34 vs. 258 ± 19 μmol·kg(-1)·h(-1), citrulline: 5.7 ± 0.4 vs. 2.8 ± 0.4 μmol·kg(-1)·h(-1), and arginine: 50 ± 4 vs. 26 ± 2 μmol·kg(-1)·h(-1), P < 0.01), as was the synthesis of citrulline from glutamine (4.8 ± 0.7 vs. 1.6 ± 0.3 μmol·kg(-1)·h(-1)), citrulline from arginine (2.3 ± 0.3 vs. 0.96 ± 0.1 μmol·kg(-1)·h(-1)), and arginine from glutamine (7.7 ± 0.4 vs. 2.8 ± 0.2 μmol·kg(-1)·h(-1)), respectively (P < 0.001 for all). In conclusion, the production of citrulline and arginine is severely reduced after clamping during aortic surgery. This study shows that an intravenous supplement of glutamine increases the production of citrulline and arginine and compensates for the inhibitory effect of ischemia-reperfusion injury.

Gastrin attenuates ischemia-reperfusion-induced intestinal injury in rats

Intestinal ischemia-reperfusion (I/R) injury is a devastating complication when the blood supply is reflowed in ischemic organs. Gastrin has critical function in regulating acid secretion, proliferation, and differentiation in the gastric mucosa. We aimed to determine whether gastrin has an effect on intestinal I/R damage. Intestinal I/R injury was induced by 60-min occlusion of the superior mesenteric artery followed by 60-min reperfusion, and the rats were induced to be hypergastrinemic by pretreated with omeprazole or directly injected with gastrin. Some hypergastrinemic rats were injected with cholecystokinin-2 (CCK-2) receptor antagonist prior to I/R operation. After the animal surgery, the intestine was collected for histological analysis. Isolated intestinal epithelial cells or crypts were harvested for RNA and protein analysis. CCK-2 receptor expression, intestinal mucosal damage, cell apoptosis, and apoptotic protein caspase-3 activity were measured. We found that high gastrin in serum significantly reduced intestinal hemorrhage, alleviated extensive epithelial disruption, decreased disintegration of lamina propria, downregulated myeloperoxidase activity, tumor necrosis factor-α, and caspase-3 activity, and lead to low mortality in response to I/R injury. On the contrary, CCK-2 receptor antagonist L365260 could markedly impair intestinal protection by gastrin on intestinal I/R. Severe edema of mucosal villi with severe intestinal crypt injury and numerous intestinal villi disintegrated were observed again in the hypergastrinemic rats with L365260. The survival in the hypergastrinemic rats after intestinal I/R injury was shortened by L365260. Finally, gastrin could remarkably upregulated intestinal CCK-2 receptor expression. Our data suggest that gastrin by omeprazole remarkably attenuated I/R induced intestinal injury by enhancing CCK-2 receptor expression and gastrin could be a potential mitigator for intestinal I/R damage in the clinical setting.

Inhibition of P38 MAPK Downregulates the Expression of IL-1β to Protect Lung from Acute Injury in Intestinal Ischemia Reperfusion Rats

Acute lung injury (ALI) induced by intestinal ischemia/reperfusion (II/R) has high incidence and mortality, in which IL-1β was essential for the full development of ALI. However, the detailed regulating mechanism for this phenomenon remains to be unclear. The purpose of this study was to investigate whether inhibition of P38 MAPK could downregulate the expression of IL-1β to protect lung from acute injury in II/R rats. Here, we found that the level of pulmonary edema at 16 hours after operation (hpo) was obviously enhanced compared to that in 8hpo and sham groups. Immunofluorescent staining demonstrated that IL-1β and P38 MAPK were detected in lung tissues. And rats with II/R have the highest translation level for IL-1β and phosphorylation of P38 MAPK in lung tissues at 16hpo compared with 8hpo and sham groups. Moreover, administration of SB239063, an inhibitor of P38 α and β, could effectively downregulate the expressions of IL-1β and protects lung tissues from injury in II/R rats. Our findings indicate that the inhibition of P38 α and β may downregulate the expression of IL-1β to protect lung from acute injury in II/R, which could be used as a potential target for reducing ALI induced by II/R in the future clinical trial.

Pentoxifylline associated to hypertonic saline solution attenuates inflammatory process and apoptosis after intestinal ischemia/reperfusion in rats

PURPOSE

To evaluate intestinal inflammatory and apoptotic processes after intestinal ischemia/reperfusion injury, modulated by pentoxifylline and hypertonic saline.

METHODS

It was allocated into four groups (n=6), 24 male Wistar rats (200 to 250 g) and submitted to intestinal ischemia for 40 min and reperfusion for 80 min: IR (did not receive any treatment); HS group (Hypertonic Saline, 4 ml/kg-IV); PTX group (Pentoxifylline, 30 mg/kg-IV); HS+PTX group (Hypertonic Saline and Pentoxifylline). All animals were heparinized (100 U/kg). At the end of reperfusion, ileal fragments were removed and stained on hematoxylin-eosin and histochemical studies for COX-2, Bcl-2 and cleaved caspase-3.

RESULTS

The values of sO2 were higher on treated groups at 40 minutes of reperfusion (p=0.0081) and 80 minutes of reperfusion (p=0.0072). Serum lactate values were lower on treated groups after 40 minutes of reperfusion (p=0.0003) and 80 minutes of reperfusion (p=0.0098). Morphologic tissue injuries showed higher grades on IR group versus other groups: HS (p=0.0006), PTX (p=0.0433) and HS+PTX (p=0.0040). The histochemical study showed lesser expression of COX-2 (p=0.0015) and Bcl-2 (p=0.0012) on HS+PTX group. A lower expression of cleaved caspase-3 was demonstrated in PTX (p=0.0090; PTXvsIR).

CONCLUSION

The combined use of pentoxifylline and hypertonic saline offers best results on inflammatory and apoptotic inhibitory aspects after intestinal ischemia/reperfusion.

Impact of alanyl-glutamine dipeptide on proliferative and inflammatory changes in jejunal mucosa after acute mesenteric ischemia

PURPOSE

The aim of our study was to determinate the impact of dipeptide (alanyl-glutamine) administration on inflammatory and proliferative changes in jejunal mucosa after acute mesenteric ischemia.

METHODS

Male Wistar rats (n=30) were divided into three groups: ischemia/reperfusion (IR) group which undergoes 60min of mesenteric ischemia and 1 or 24h of reperfusion (IR1, IR24, n=12). Groups with dipeptide administration (D+IR1, D+IR24, Dipeptiven con inf., i.v., 0.75 g/kg) prior to IR injury were followed by 1 and 24h of reperfusion. At the end of reperfusion period jejunal bioptic samples were obtained for histological (H&E), histochemical (Alcian blue) and immunohistochemical (anti-PCNA, anti-MPO) evaluations.

RESULTS

Our results pointed out a significant (p<0.001) increase of histopathological injury score in IR1 group compared to D+IR1 group. Immunohistochemical evaluation showed that MPO-positivity was significantly increased in IR groups after 1 (p<0.001) as well as 24h of reperfusion (p<0.01) compared to dipeptide pretreated groups. Proliferative/reparatory rate was assessed using anti-PCNA antibody and showed a significant increase (p<0.01) in PCNA cell positivity in lamina propria in dipeptide treated group compared to IR group.

CONCLUSION

In conclusion we may suggest that administration of alanyl-glutamine dipeptide prior to IR injury may help to protect small intestine and its mucous membrane integrity against insult such as intestinal ischemic/reperfusion injury presents.

Glutamine prevents oxidative stress in a model of mesenteric ischemia and reperfusion

AIM: To evaluate preventative effects of glutamine in an animal model of gut ischemia/reperfusion (I/R).

METHODS: Male Wistar rats were housed in a controlled environment and allowed access to food and water ad libitum. Twenty male Wistar rats were divided into four experimental groups: (1) control group (control) - rats underwent exploratory laparotomy; (2) control + glutamine group (control-GLU) - rats were subjected to laparotomy and treated intraperitoneally with glutamine 24 and 48 h prior to surgery; (3) I/R group - rats were subjected to occlusion of the superior mesenteric artery for 30 min followed by 15 min of reperfusion; and (4) ischemia/reperfusion + glutamine group (G + I/R) - rats were treated intraperitoneally with glutamine 24 and 48 h before I/R. Local and systemic injuries were determined by evaluating intestinal and lung segments for oxidative stress using lipid peroxidation and the activity of superoxide dismutase (SOD), interleukin-6 (IL-6) and nuclear factor kappa beta (NF-κB) after mesenteric I/R.

RESULTS: Lipid peroxidation of the membrane was increased in the animals subjected to I/R (P < 0.05). However, the group that received glutamine 24 and 48 h before the I/R procedure showed levels of lipid peroxidation similar to the control groups (P < 0.05). The activity of the antioxidant enzyme SOD was decreased in the gut of animals subjected to I/R when compared with the control group of animals not subjected to I/R (P < 0.05). However, the group that received glutamine 24 and 48 h before I/R showed similar SOD activity to both control groups not subjected to I/R (P < 0.05). The mean area of NF-κB staining for each of the control groups was similar. The I/R group showed the largest area of staining for NF-κB. The G + I/R group had the second highest amount of staining, but the mean value was much lower than that of the I/R group (P < 0.05). For IL-6, control and control-GLU groups showed similar areas of staining. The I/R group contained the largest area of IL-6 staining, followed by the G + I/R animals; however, this area was significantly lower than that of the group that underwent I/R without glutamine (P < 0.05).

CONCLUSION: These results demonstrate that pretreatment with glutamine prevents mucosal injury and improves gut and lung recovery after I/R injury in rats.

Serum diamine oxidase as a hemorrhagic shock biomarker in a rabbit model

Background

In prolonged hemorrhagic shock, reductions in intestinal mucosal blood perfusion lead to mucosal barrier damage and systemic inflammation. Gastrointestinal failure in critically ill patients has a poor prognosis, so early assessment of mucosal barrier injury in shock patients is clinically relevant. Unfortunately, there is no serum marker that can accurately assess intestinal ischemia-reperfusion injury.

Objective

The aim of this study was to assess if serum diamine oxidase levels can reflect intestinal mucosal injury subsequent to prolonged hemorrhagic shock.

Methods

Thirty New Zealand white rabbits were divided into three groups: a control group, a medium blood pressure (BP) group (exsanguinated to a shock BP of 50 to 41 mm Hg), and a low BP group (exsanguinated to a shock blood pressure of 40 to 31 mm Hg), in which the shock BP was sustained for 180 min prior to fluid resuscitation.

Results

The severity of hemorrhagic shock in the low BP group was significantly greater than that of the medium BP group according to the post-resuscitation BP, serum tumor necrosis factor (TNF)-α, and arterial lactate. Intestinal damage was significantly more severe in the low BP group according to Chiu’s scoring, claudin-1, intercellular adhesion molecule (ICAM)-1, and myeloperoxidase expression. Serum diamine oxidase was significantly increased in the low BP group compared to the medium BP and control groups and was negatively correlated with shock BP.

Conclusion

Serum diamine oxidase can be used as a serological marker in evaluating intestinal injury and shows promise as an indicator of hemorrhagic shock severity.

Glutamine and intestinal barrier function

The intestinal barrier integrity is essential for the absorption of nutrients and health in humans and animals. Dysfunction of the mucosal barrier is associated with increased gut permeability and development of multiple gastrointestinal diseases. Recent studies highlighted a critical role for glutamine, which had been traditionally considered as a nutritionally non-essential amino acid, in activating the mammalian target of rapamycin cell signaling in enterocytes. In addition, glutamine has been reported to enhance intestinal and whole-body growth, to promote enterocyte proliferation and survival, and to regulate intestinal barrier function in injury, infection, weaning stress, and other catabolic conditions. Mechanistically, these effects were mediated by maintaining the intracellular redox status and regulating expression of genes associated with various signaling pathways. Furthermore, glutamine stimulates growth of the small intestinal mucosa in young animals and also enhances ion transport by the gut in neonates and adults. Growing evidence supports the notion that glutamine is a nutritionally essential amino acid for neonates and a conditionally essential amino acid for adults. Thus, as a functional amino acid with multiple key physiological roles, glutamine holds great promise in protecting the gut from atrophy and injury under various stress conditions in mammals and other animals.

How wasting is saving: weight loss at altitude might result from an evolutionary adaptation

At extreme altitude (>5,000 – 5,500 m), sustained hypoxia threatens human function and survival, and is associated with marked involuntary weight loss (cachexia). This seems to be a coordinated response: appetite and protein synthesis are suppressed, and muscle catabolism promoted. We hypothesise that, rather than simply being pathophysiological dysregulation, this cachexia is protective. Ketone bodies, synthesised during relative starvation, protect tissues such as the brain from reduced oxygen availability by mechanisms including the reduced generation of reactive oxygen species, improved mitochondrial efficiency and activation of the ATP-sensitive potassium (K_ATP) channel. Amino acids released from skeletal muscle also protect cells from hypoxia, and may interact synergistically with ketones to offer added protection. We thus propose that weight loss in hypoxia is an adaptive response: the amino acids and ketone bodies made available act not only as metabolic substrates, but as metabolic modulators, protecting cells from the hypoxic challenge.

Preconditioning with glutamine protects against ischemia/reperfusion-induced hepatic injury in rats with obstructive jaundice

OBJECTIVE

To ascertain whether glutamine (Gln) pretreatment protects rats with obstructive jaundice from hepatic ischemia/reperfusion (I/R) injury and to determine the underlying molecular mechanisms.

METHODS

An obstructive jaundice rat model was developed by bile duct ligation. On the first day after the operation, all rats were randomized into two groups and received oral Gln or normal saline (NS) daily for 7 days. Then both groups underwent a 15-min liver ischemia via the Pringle maneuver. Blood samples as well as liver and intestinal tissues were harvested and measured after 1, 6 and 24 h of reperfusion.

RESULTS

The results showed that the histological morphology of the liver and intestinal tissues significantly improved in the Gln group after I/R injury compared with the NS group. Serum proteins and enzymes associated with hepatic function also significantly improved in the Gln group. The level of glutathione increased and the levels of malondialdehyde and myeloperoxidase decreased in the Gln group. The levels of interleukin-1β and tumor necrosis factor-α decreased in the Gln group. Moreover, bcl-2 protein expression was upregulated and intercellular adhesion molecule 1 and bax protein expression downregulated in the Gln group; the caspase 3 mRNA level significantly increased in the Gln group.

CONCLUSIONS

The study demonstrates that preconditioning with Gln significantly improves hepatic structure and function after I/R injury in rats with obstructive jaundice. The protective effect of Gln was mediated by the inhibition of reactive oxygen species and inflammation as well as a reduction in hepatocyte apoptosis.

Transduced PEP-1-heme oxygenase-1 fusion protein protects against intestinal ischemia/reperfusion injury

BACKGROUND

Heme oxygenase-1 (HO-1) has been shown to have antioxidant and anti-apoptotic properties. The present study transduced HO-1 protein into intestinal tissues using PEP-1, a cell-penetrating peptide, and investigated its potentiality in prevention against intestinal ischemia/reperfusion (I/R) injury.

MATERIALS AND METHODS

PEP-1-HO-1 fusion protein was administered intravenously to explore the time and dose characteristics through measuring serum HO-1 levels. Twenty-four male Sprague-Dawley rats were randomly divided into three groups: sham, intestinal I/R (II/R), II/R + PEP-1-HO-1 fusion protein (HO). The model was established by occluding the superior mesenteric artery for 45 min followed by 120 min reperfusion. In HO group, PEP-1-HO-1 was administered intravenously 30 min before ischemia, whereas animals in sham and II/R groups received the equal volume of physiological saline. After the experiment, the intestines were harvested for determination of histologic injury, wet/dry ratio, enzyme activity, apoptosis, and His-probe protein (one part of PEP-1-HO-1).

RESULTS

Levels of serum HO-1 were dose- and time-dependent manner after intravenous injection of PEP-1-HO-1. I/R caused deterioration of histologic characteristics and increases in histologic injury scoring, wet/dry ratio, myeloperoxidase activity, malondialdehyde, and intestinal apoptosis. These changes were also accompanied by a decrease in superoxide dismutase activity (P < 0.05). PEP-1-HO-1 treatment significantly reversed these changes (P < 0.05). Furthermore, His-probe protein expression was only detected in PEP-1-HO-1-treated animals.

CONCLUSION

Treatment of PEP-1-HO-1 attenuates intestinal I/R injury, which might be attributable to its antioxidant and anti-apoptotic roles of HO-1.

Glutamine on Intestinal Inflammation: A Mechanistic Perspective

Intestinal inflammation is associated with various pathological diseases, such as gastritis from Helicobacter pylori infection, Crohn's and colitis in inflammatory bowel disease, and colorectal cancer. Thus, treatment with anti-inflammatory substances in these inflammation-associated diseases is critical. Increasingly compelling evidence indicates that glutamine is an anti-inflammatory compound candidate because it can influence the long-term outcome of the inflammatory diseases with in a low-risk way. However, before recommending its use in clinical practice, it is important to elucidate the molecular mechanism by which glutamine exerts its roles in modulating intestinal inflammation. In this study, we review the current knowledge on the detailed regulation pathway used by glutamine in its proinflammatory regulation, with a special emphasis on intestinal inflammation. These regulation pathways include nuclear factor kappa B (NF-κB), signal transducer and activator of transcription (STAT), mitogen-activated protein kinases (MAPK), phosphoinositide-3-kinases (PI3K)/PI3K-protein kinase B (Akt), activating protein-1 (AP-1), nitric oxide synthases (NOS)-nitric oxide (NO), peroxisome proliferator-activated receptor-Γ (PPARγ), heat shock factor-1 (HSF-1)- heat shock proteins (HSP) and glutathione (GSH) - reactive oxygen species (ROS). Although some regulatory pathways, such as PI3K/PI3K-Akt, GSH-ROS and AP-1, need to be further investigated, this review provides useful information to utilize glutamine as an immunonutritional or pharmaconutritional drug, not only for inflammation-associated diseases in the intestine, but also possibly for other inflammatory-associated diseases, i.e. arthritis, asthma, type 2 diabetes, etc.

Palmitoylethanolamide reduces early renal dysfunction and injury caused by experimental ischemia and reperfusion in mice

This study was designed to assess a protective effect of palmitoylethanolamide (PEA) in the development of inflammation after ischemia-reperfusion injury of the kidney. Moreover, to suggest a possible mechanism, renal ischemia-reperfusion was performed in mice with targeted disruption of peroxisome proliferator-activated receptor α (PPAR-α) gene (PPAR-αKO) to explain whether the observed PEA effect was dependent on PPAR-α pathway. Peroxisome proliferator-activated receptor-αKO and littermate wild-type controls (PPAR-αWT) were subjected to bilateral renal artery occlusion (30 min) and reperfusion (6 h) and received PEA (10 mg/kg i.p.) 15 min before release of clamps. Serum and urinary indicators of renal dysfunction and tubular and reperfusion injury were measured, specifically serum urea, creatinine, aspartate aminotransferase and γ-glutamyl transferase, and creatinine clearance. In addition, renal sections were used for histological scoring of renal injury and for immunologic evidence of nitrotyrosine formation, poly[adenosine diphosphate-ribose] (PAR), and adhesion molecules expression. The oxidative stress-sensitive nuclear factor κB signaling pathway was also investigated by Western blot analysis. Kidney myeloperoxidase activity and malondialdehyde levels were measured for assessment of polymorphonuclear leukocyte cell infiltration and lipid peroxidation, respectively. Apoptotic mechanisms were also investigated. Moreover, the infiltration and activation of mast cells were explored. In vivo, PEA administration during ischemia significantly reduced the increase in (i) creatinine, γ-glutamyl transferase, aspartate aminotransferase; (ii) nuclear translocation of nuclear factor κB p65; (iii) kidney myeloperoxidase activity and malondialdehyde levels; (iv) nitrotyrosine, PAR, and adhesion molecules expression; (v) the infiltration and activation of mast cells; and (vi) apoptosis. Our results clearly demonstrate that PEA significantly attenuated the degree of renal dysfunction, injury, and inflammation caused by ischemia-reperfusion injury. Moreover, the positive effects of PEA were at least in part dependent on PPAR-α pathway.

Glutamine treatment attenuates endoplasmic reticulum stress and apoptosis in TNBS-induced colitis

Endoplasmic reticulum (ER) stress and apoptotic cell death play an important role in the pathogenesis and perpetuation of inflammatory bowel disease (IBD). We aimed to explore the potential of glutamine to reduce ER stress and apoptosis in a rat model of experimental IBD. Colitis was induced in male Wistar rats by intracolonic administration of 30 mg of 2,4,6-trinitrobenzene sulfonic acid (TNBS). Glutamine (25 mg/dL) was given by rectal route daily for 2 d or 7 d. Both oxidative stress (TBARS concentration and oxidised/reduced glutathione ratio) and ER stress markers (CHOP, BiP, calpain-1 and caspase-12 expression) increased significantly within 48 h of TNBS instillation, and glutamine attenuated the extent of the changes. Glutamine also inhibited the significant increases of ATF6, ATF4 and spliced XBP-1 mRNA levels induced by TNBS instillation. TNBS-colitis resulted in a significant increase in p53 and cytochrome c expression, and a reduced Bcl-xL expression and Bax/Bcl-2 ratio. These effects were significantly inhibited by glutamine. Treatment with the amino acid also resulted in significant decreases of caspase-9, caspase-8 and caspase-3 activities. Double immunofluorescence staining showed co-localization of CHOP and cleaved caspase-3 in colon sections. Phospho-JNK and PARP-1 expression was also significantly higher in TNBS-treated rats, and treatment with glutamine significantly decreased JNK phosphorylation and PARP-1 proteolysis. To directly address the effect of glutamine on ER stress and apoptosis in epithelial cells, the ER stress inducers brefeldin A and tunicamycin were added to Caco-2 cells that were treated with glutamine (5 mM and 10 mM). The significant enhancement in PERK, ATF6 phosphorylated IRE1, BiP and cleaved caspase-3 expression induced by brefeldin A and tunicamycin was partly prevented by glutamine. Data obtained indicated that modulation of ER stress signalling and anti-apoptotic effects contribute to protection by glutamine against damage in TNBS-induced colitis.

Defining the nonreturn time for intestinal ischemia reperfusion injury in mice

Among the abdominal organs, the intestine is probably the most sensitive to ischemia reperfusion injury (IRI), a phenomenon that occurs in many intestinal disorders. Few studies have reported in detail the impact of intestinal ischemia time in mice. We evaluated the effect of various warm intestinal ischemia times in an intestinal IRI model in mice. Adult male Balb/c mice were divided into 4 groups that differed in intestinal ischemia time: G1, 30; minutes; G2, 35 minutes; G3, 40 minutes; and G4, 45 minutes. Histological evaluation showed average Park scores as follows: G1 0.6 ± 0.55; G2 1.8 ± 0.45; G3 4.8 ± 2.25; and G4 5 ± 1.79. All animals from G1 survived 30 hours. G2 animals showed intermediate behavior with all succumbing between 18 and 30 hours postprocedure. G3 and G4 displayed similar survival results with animals succumbing before 6 hours after intestinal reperfusion. These data showed that Park index scores of 3 or higher were related to early death. We concluded that the 5 minutes between 35 and 40 minutes is the critical limit, after which all mice die after reperfusion. This result may represent a valuable tool for future research in mice.

Physiology and pathophysiology of splanchnic hypoperfusion and intestinal injury during exercise: strategies for evaluation and prevention

Physical exercise places high demands on the adaptive capacity of the human body. Strenuous physical performance increases the blood supply to active muscles, cardiopulmonary system, and skin to meet the altered demands for oxygen and nutrients. The redistribution of blood flow, necessary for such an increased blood supply to the periphery, significantly reduces blood flow to the gut, leading to hypoperfusion and gastrointestinal (GI) compromise. A compromised GI system can have a negative impact on exercise performance and subsequent postexercise recovery due to abdominal distress and impairments in the uptake of fluid, electrolytes, and nutrients. In addition, strenuous physical exercise leads to loss of epithelial integrity, which may give rise to increased intestinal permeability with bacterial translocation and inflammation. Ultimately, these effects can deteriorate postexercise recovery and disrupt exercise training routine. This review provides an overview on the recent advances in our understanding of GI physiology and pathophysiology in relation to strenuous exercise. Various approaches to determine the impact of exercise on the individual athlete's GI tract are discussed. In addition, we elaborate on several promising components that could be exploited for preventive interventions.

Glutamine contributes to ameliorate inflammation after renal ischemia/reperfusion injury in rats

The aim of this study was to investigate the effects of glutamine in an in vivo rat model of renal ischemia/reperfusion (I/R) injury. Male Wistar rats underwent bilateral renal pedicle clamping for 45 min followed by reperfusion for 6 h. Glutamine (1.5 mg/kg) was administered intraperitoneally (i.p.) 15 min prior to reperfusion. Plasma concentrations of urea, creatinine, γ-glutamyl transferase (γ-GT), and aspartate aminotransferase (AST) were measured for the assessment of renal function and reperfusion injury. Markers of oxidative stress, expression of the pro-inflammatory mediators inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), AT-1 expression, and changes in the oxidative stress-sensitive nuclear factor kappa B (NF-κB) signaling pathway were measured to investigate whether glutamine can reduce the renal dysfunction. Kidney myeloperoxidase (MPO) activity and malondialdehyde (MDA) levels were measured for assessment of polymorphonuclear (PMN) cell infiltration and lipid peroxidation, respectively. Renal sections were used for histologic grading of renal injury and for immunohistochemical localization of nitrotyrosine and poly(ADP-ribose) synthetase (PARS). In vivo, glutamine significantly reduced the increase in urea, creatinine, γ-GT, AST, produced by renal ischemia/reperfusion (I/R), suggesting an improvement in both renal function and injury. Glutamine significantly reduced iNOS and NF-κB, kidney MPO activity and MDA levels, indicating a reduction in PMN infiltration and lipid peroxidation, respectively. Glutamine reduced the histological evidence of renal damage associated with I/R and caused a substantial reduction in the staining for nitrotyrosine and PARS, suggesting reduced nitrosative and oxidative stress. Moreover, glutamine attenuated the reduction of COX-2 expression and prevented the increased AT-1 expression after I/R. Our results suggest that glutamine reduces the renal dysfunction and injury associated with I/R of the kidney.

Glutamine treatment attenuates the development of organ injury induced by zymosan administration in mice

Glutamine is the most abundant amino acid in the bloodstream. It is important in nucleotide synthesis, is anti-catabolic, has anti-oxidant properties via metabolism to glutathione, may enhance immune responsiveness and possesses immunoregulatory functions. Moreover, it reduces atrophy of intestinal mucosa in animals on total parenteral nutrition and prevents intestinal mucosal injury accompanying small bowel transplantation, chemotherapy and radiation. In the present study, we investigated the effects of glutamine on development of non-septic shock caused by zymosan. Mice received either zymosan (500 mg/kg, administered i.p., as a suspension in saline) or vehicle (saline). Glutamine (1.5 mg/kg i.p.) was administered 1 and 6h after zymosan administration. Organ failure and systemic inflammation in mice were assessed 18 h after administration of zymosan and/or glutamine. Glutamine-treatment reduced the peritoneal exudation and the migration of polymorphonuclear cells caused by zymosan-injection and also attenuated the pancreatic and gut injury. Inflammatory and apoptotic parameters were evaluated to better investigate the effects of the glutamine-administration. So, by immunohistochemical analysis and in vitro assays, we have clearly showed that glutamine reduces: 1) the histological damage in pancreas and gut; 2) the inducible nitric oxide synthase expression; 3) nitrotyrosine and poly (ADP-ribose) formation; 4) TNF-α and IL-1β tissue and plasma levels; 5) FasL localization; and 6) alteration of the balance between Bax and Bcl-2. In addition, at the end of the observation period (7 days), zymosan causes severe illness in the mice characterized by a systemic toxicity, significant loss of body weight and mortality. Glutamine-treatment significantly reduced all these parameters.