Arginine-supplemented diets improve survival in gut-derived sepsis and peritonitis by modulating bacterial clearance. The role of nitric oxide

Association of perioperative immunonutrition with anastomotic leak among patients undergoing elective colorectal surgery within a robust enhanced recovery after surgery program

BACKGROUND

Immunonutrition supplementation has been shown to reduce the risk of surgical infectious complications; however, its effect on decreasing anastomotic leak rates, in the context of an otherwise robust Enhanced Recovery After Surgery (ERAS) program, remains unclear. This study aims to assess the association between perioperative immunonutrition supplementation and anastomotic leak in an elective Enhanced Recovery After Surgery colorectal surgical population.

METHODS

We performed a retrospective single-institution cohort study consisting of adult patients enrolled in an Enhanced Recovery After Surgery pathway and undergoing elective colorectal surgery from 2018 to 2023. Immunonutrition supplementation was defined as a 10-day perioperative supply of commercially available nutritional shakes. Relevant demographic covariates, preoperative characteristics, and operative methods were identified and analyzed. Multivariable logistic regression was performed to determine the association of immunonutrition with anastomotic leak.

RESULTS

A total of 708 patients were included in the study, of which n = 400 (56.5%) received perioperative immunonutrition. Patients who received immunonutrition were more likely to be older (median age 57.9 vs 55.7), male (52.7% vs 44.8%), have a higher body mass index (27.7 vs 26.3), and less likely to be current smokers (9.8% vs 16.2%). On adjusted analysis, there was no association between immunonutrition use and anastomotic leak (odds ratio = 0.96, 95% confidence interval = 0.45, 2.08), 30-day readmission (odds ratio = 0.97, 95% confidence interval = 0.60, 1.57), or length of stay (β = .40, 95% confidence interval = -0.06, 0.86) CONCLUSION: We did not observe an association between perioperative immunonutrition supplementation and postoperative anastomotic leak, suggesting that the role of immunonutrition within a comprehensive Enhanced Recovery After Surgery program for elective colorectal surgery may warrant further evaluation.

Pharmaconutrition: Which substrates?

With the term "pharmaconutrition" or "immunonutrition" is intended the use of specific nutritional substrates having the ability of modulating specific mechanisms involved in several immune and inflammatory pathways. To achieve these goals, these substrates have to be administered with over physiologic dose. Glutamine and omega-3 polyunsaturated fatty acids, used as single substrate, did not show clear clinical advantages on solid endpoints such as postoperative complications. Despite several multiple substrate enteral feeds are available on the market, very few of them have been tested in randomized clinical trial to prove efficacy. The most extensive investigated formulation is a combination of arginine, omega-3 fatty acids, ribonucleic acid with or without glutamine. Several meta-analyses of randomized clinical trials have been conducted to compare the effects of enteral immunonutrition with control diets on post-surgical morbidity. The results consistently showed that the use of enteral multiple substrate formulas significantly reduced infectious complications and duration of hospitalization. In a more contemporary view, pharmaconutrition should be tested more accurately in the contest of enhanced recovery programs, during neoadjuvant chemotherapy, and in the prehabilitation setting.

Improving geriatric outcomes through nutritional and immunonutritional strategies: Focus on surgical setting by a comprehensive evidence review

The aging population worldwide has led to an increased request for surgical interventions in older, geriatric, and frail patients. However, all the physiological changes related to aging are associated with many challenges in the perioperative period, strongly impacting surgical outcomes. Nutritional status plays a pivotal role in determining the resilience of older adults to surgical stress and their ability to recover postoperatively. It is well known that malnutrition, a prevalent concern in geriatrics, is linked to increased adverse outcomes, including morbidity and mortality. Recognizing the significance of preoperative nutritional screening, assessment, diagnosis, intervention, and monitoring is essential for optimizing surgical outcomes. In this context, immunonutrition, which involves the supplementation of specific nutrients to modulate immune responses, emerges as a promising strategy to mitigate the increased inflammatory response observed in geriatric surgical patients. This study reviews current literature on the impact of nutrition and immunonutrition on surgical outcomes in geriatrics, highlighting the potential benefits in terms of reduced complications, enhanced wound healing, and shortened hospital stays. Recognizing and addressing the specific nutritional needs of older persons undergoing surgery is essential for promoting successful surgical outcomes and improving overall quality of life in this vulnerable population.

Effect of immunonutrition on infectious complications in low skeletal muscle mass patients after pancreaticoduodenectomy

BACKGROUND & AIMS

Sarcopenia is considered a risk factor of postoperative complications among patients undergoing abdominal surgery. However, few studies have demonstrated an effective strategy for reducing complications in sarcopenic patients. This study aimed to examine retrospectively the effect of preoperative immunonutrition on postoperative complications, especially infectious complications, in low skeletal muscle mass patients undergoing pancreaticoduodenectomy (PD).

METHODS

This was a retrospective, consecutive cohort study conducted in our institution. Skeletal muscle mass was assessed using preoperative computed tomography images in 298 consecutive patients who underwent PD between May 2009 and May 2016. Cross-sectional areas at the third lumbar vertebrae normalized for stature (cm²/m²) were defined as the skeletal muscle mass index (SMI). Low SMI was defined as the lowest sex-specific quartile of SMI. Risk factors for postoperative infectious complications and the effect of preoperative immunonutrition on low SMI patients who underwent PD were evaluated.

RESULTS

Results of multivariate analysis showed that the presence of low SMI and absence of preoperative immunonutrition were independent risk factors for postoperative infectious complications after PD (odds ratio [OR], 3.17 and 3.10, respectively; P < 0.001). In high SMI patients, the rate of postoperative infectious complications was significantly lower in those who received immunonutrition than in those who did not receive immunonutrition (31.9 vs. 46.1%, respectively; OR, 1.82; P = 0.045). Further, similar findings were exhibited in low SMI patients (26.3 vs. 83.6%, respectively; OR, 14.31; P < 0.001), even though OR was markedly higher in low vs. high SMI patients.

CONCLUSION

There is a stronger association with reduced infectious complications in patients who have low SMI and receive immunonutrition (UMIN-CTR Identifier: UMIN000035775.).

Combined Effectiveness of Honey and Immunonutrition on Bacterial Translocation Secondary to Obstructive Jaundice in Rats: Experimental Study

BACKGROUND Obstructive jaundice is a serious, life-threatening condition that can lead to death as a result of sepsis and multiorgan failure due to bacterial translocation. Treatment should be started as soon as possible after diagnosis. MATERIAL AND METHODS Forty 24-week-old male Sprague Dawley rats, with an average weight of 250 g to 300 g, were included in this study. The rats were randomly placed into five groups, each group consisted of eight rats. The sham group underwent only common bile duct (CBD) dissection and no ligation was performed. CBD ligation was applied to the other groups. After the operation, one CBD group was fed with rat chow only, the others were fed with rat chow supplemented with honey, or immunonutrients, or honey plus immunonutrients. After 10 to 12 days, all rats were sacrificed; blood and tissue samples were collected for biochemical, microbiological, and histopathological evaluation. RESULTS In the groups that were fed with honey and immunonutrients, alanine aminotransferase (ALT) levels were decreased significantly compared to the other groups. Statistically significant differences were detected in terms of bacterial translocation (BT) rates among liver and spleen samples, and laboratory values of serum, except for MLNs of the BDL+HI group, when compared to other groups. We found mean mucosal thickness of ileum samples have been improved notably in the BDL+HI group compared to the other groups, especially compared to the C/BDL group. CONCLUSIONS Immunonutrition applied with honey had immunostimulant effects, decreased BT due to an additive effect, and had positive effects on intestinal mucosa.

Arginine depletion increases susceptibility to serious infections in preterm newborns

Preterm newborns are highly susceptible to bacterial infections. This susceptibility is regarded as being due to immaturity of multiple pathways of the immune system. However, it is unclear whether a mechanism that unifies these different, suppressed pathways exists. Here, we argue that the immune vulnerability of the preterm neonate is critically related to arginine depletion. Arginine, a "conditionally essential" amino acid, is depleted in acute catabolic states, including sepsis. Its metabolism is highly compartmentalized and regulated, including by arginase-mediated hydrolysis. Recent data suggest that arginase II-mediated arginine depletion is essential for the innate immune suppression that occurs in newborn models of bacterial challenge, impairing pathways critical for the immune response. Evidence that arginine depletion mediates protection from immune activation during first gut colonization suggests a regulatory role in controlling gut-derived pathogens. Clinical studies show that plasma arginine is depleted during sepsis. In keeping with animal studies, small clinical trials of L-arginine supplementation have shown benefit in reducing necrotizing enterocolitis in premature neonates. We propose a novel, broader hypothesis that arginine depletion during bacterial challenge is a key factor limiting the neonate's ability to mount an adequate immune response, contributing to the increased susceptibility to infections, particularly with respect to gut-derived sepsis.

Role of Arginine and Omega-3 Fatty Acids in Wound Healing and Infection

Significance: Only a few decades ago, the primary focus of nutritional supplementation was to prevent deficiencies of essential nutrients. It is now recognized that, at higher than essential levels, selected nutrients can have a pharmacologic effect to prevent or treat disease. Recent Advances: Two of the most important pharmaconutrients, arginine, and the omega-3 polyunsaturated fatty acids in fish oil, have been shown to have profound effects on wound healing and infections. Critical Issues: Both arginine and fish oils have independent benefits, but the combination appears to be much more effective. This combination has been shown to affect outcomes involving wound healing and infections, as reviewed here, and can also affect incidence and outcomes in cardiovascular disease, diabetes, organ transplant rejection, and other inflammatory conditions. These possibilities have not yet progressed to widespread clinical application. Future Directions: The optimal combinations of immunonutrients, timing of administration, and the doses needed for best results need to be determined in preclinical and clinical studies. Also, the mechanisms involved in the administration of pharmaconutrients need to be established.

Influence of uracil on bacterial translocation in an intestinal obstruction model in rats

INTRODUCTION

Bacterial translocation occurs when intestinal mucosa and the intestinal wall lose their barrier properties against bacteria such as in the case of intestinal obstruction. Enteral nutrition with immunonutrients strengthens the immune system and thickens the intestinal barrier thus preventing bacterial translocation.

AIM

The purpose of this study is to investigate the effect of uracil which is an immunonutrient on bacterial translocation using rats with intestinal obstruction as a model.

METHODS

Wistar albino rats were divided into three groups. The control group was fed with standard chow diet, while the other two groups were fed with uracil-supplemented chow diet. The rats were fed with these diets for seven days. And the end of the feeding period all groups were submitted intestinal obstruction and injected with (99m)Tc labeled Escherichia coli into the rats' terminal ileum under anesthetic. The rats were sacrificed 24 h later. Their blood, mesenteric lymph nodes (MLN), liver, spleen, lung and ileum were removed to determine level of radioactivity.

RESULTS

When compared with the control group it was determined that uracil supplementation reduced the level of bacterial translocation.

CONCLUSION

Uracil may be used in the prevention of bacterial translocation in cases of intestinal obstruction because it strengthens the intestinal barrier and the immune system. However, more studies are needed to clearly explain the mechanism behind uracil's beneficial role here.

Effects of dietary arginine on inflammatory mediator and receptor of advanced glycation endproducts (RAGE) expression in rats with streptozotocin-induced type 2 diabetes

Arginine (Arg) is known to possess numerous useful physiological properties and have immunomodulatory effects.In vitrostudies reported that Arg inhibits advanced glycation endproduct (AGE) formation; however, the effects of Arg on the receptor of AGE (RAGE) expression in inflammatory conditions are not clear. The present study investigated the effects of dietary Arg supplementation on inflammatory mediator production and RAGE expression in type 2 diabetic rats. There were one normal control (NC) group and two diabetic groups in the present study. Rats in the NC group were fed with a regular chow diet. One diabetic group (DM) was fed a common semi-purified diet while the other diabetic group received a diet in which part of the casein was replaced by Arg (DM-Arg) for 8 weeks. Diabetes was induced by an intraperitoneal injection of nicotinamide followed by streptozotocin. Rats with blood glucose levels exceeding 1800 mg/l were considered diabetic. Blood samples and the liver and lungs of the animals were collected at the end of the study for further analysis. Results showed that plasma glucose and fructosamine contents were significantly higher in the diabetic groups than those in the NC group. The DM group had higher fructosamine and C-reactive protein than the DM-Arg group. Immunohistochemical staining showed that the expressions of RAGE in liver and lung tissues were significantly lower in the DM-Arg group than in the DM group. These results suggest that supplemental dietary Arg can decrease AGE–RAGE interactions and consequently reduce tissue damage in rats with type 2 diabetes.

Interactions between ω3 polyunsaturated fatty acids and arginine on nutritional and immunological aspects in severe inflammation

BACKGROUND & AIMS

Immune-enhancing diets (IEDs) contain a mixture of nutrients claimed to have immunological properties. Therefore, it seemed relevant to determine the effect of each of their components. The aim of this study was to examine the role of arginine (Arg) and ω3 polyunsaturated fatty acids (ω3 PUFAs) in the effect of an IED (Crucial(®)) in a validated rat model of inflammation induced by turpentine (TI).

METHODS

Forty-two rats were randomized into five groups: AL (ad libitum), TI-EN (TI+standard enteral nutrition (EN): Sondalis(®)HP), TI-EN-Arg (TI+standard EN+Arg in equimolar concentration to Arg in the IED), TI-M-IED (TI+modified IED containing the same ω6/ω3 ratio as in standard EN) and TI-IED (TI+Crucial(®)). Blood was sampled to determine CD25 receptor density on lymphocytes. TNF-α, IL-6 and NO (production and expression) were evaluated on isolated macrophages. Mesenteric lymph nodes, spleen and liver were cultured for analysis of enterobacterial translocation and dissemination.

RESULTS

CD25 density was decreased after TI and was corrected in the TI-EN-Arg, TI-M-IED and TI-IED groups (p<0.05). TI induced an alteration of macrophage mRNA expression of IL-6, TNF-α and iNOS, corrected in the TI-EN-Arg and TI-M-IED groups (p<0.05), but not by the IED. Enterobacterial translocation was observed in all treated groups, nevertheless the amount tended (p=0.054) to be lower in the TI-EN-Arg group.

CONCLUSIONS

Arg and ω3 PUFAs make a major contribution to IED effects, but our study shows interaction between them on macrophage reactivity. This indicates that the individual properties of each pharmaconutrient are not additive in IEDs.

Attenuation of the systemic inflammatory response and infectious complications after gastrectomy with preoperative oral arginine and omega-3 fatty acids supplemented immunonutrition

BACKGROUND

Past trials have shown perioperative immunonutrition to improve the outcome for patients with gastric cancer. The present study was designed to evaluate the effect of preoperative oral immunonutrition on cellular immunity, the duration of the systemic inflammatory response syndrome (SIRS), and detailed postoperative complications in patients with gastric cancer.

METHODS

Sixty patients with gastric cancer were randomly assigned to two groups: one group received immune-enhanced formulas supplemented with arginine and omega-3 fatty acids (immune-enhancing diet (ID) group, n = 30); the other received standard formulas (conventional diet (CD) group, n = 30) for 7 days before the operation. These groups were well matched in terms of age, sex, operations, cancer stages, and intraoperative variables. The postoperative outcome was evaluated based on clinical variables, including postoperative infectious complications, noninfectious complications, and SIRS duration. In addition, the perioperative state of cellular immunity was evaluated and compared between the two groups.

RESULTS

The incidence of postoperative infectious complications in the ID group (6%) was significantly (p < 0.05) lower than that of the CD group (28%). The duration of SIRS in the ID group (0.77 +/- 0.9 days) was significantly (p < 0.05) shorter than that in the CD group (1.34 +/- 1.45 days). The postoperative lymphocyte and CD4(+)T-cell counts significantly decreased (p < 0.05) in both groups. However, the number of CD4(+)T-cells on preoperative day 1 and postoperative day 7 was significantly (p < 0.05) higher in the ID group than in the CD group.

CONCLUSIONS

Preoperative oral immune-enhanced formulas supplemented with arginine and omega-3 fatty acids enhanced the immune status of the patients, reduced the duration of SIRS, and decreased the incidence of postoperative infectious complications. CD4(+)T-cell immunity likely played an important role in the modulation of the postoperative immune and inflammatory response after gastrectomy.

Ileal mucosal and fecal pancreatitis associated protein levels reflect severity of salmonella infection in rats

BACKGROUND

Microbial infections induce ileal pancreatitis-associated protein/regenerating gene III (PAP/RegIII) mRNA expression. Despite increasing interest, little is known about the PAP/RegIII protein. Therefore, ileal mucosal PAP/RegIII protein expression, localization, and fecal excretion were studied in rats upon Salmonella infection.

RESULTS

Salmonella infection increased ileal mucosal PAP/RegIII protein levels in enterocytes located at the crypt-villus junction. Increased colonization and translocation of Salmonella was associated with higher ileal mucosal PAP/RegIII levels and secretion of this protein in feces.

CONCLUSIONS

PAP/RegIII protein is increased in enterocytes of the ileal mucosa during Salmonella infection and is associated with infection severity. PAP/RegIII is excreted in feces and might be used as a new and non-invasive infection marker.

Arginine and vitamin E improve the antibody responses to infectious bursal disease virus (IBDV) and sheep red blood cells in broiler chickens

1. Dietary arginine (ARG) and vitamin E (VE) have been shown to improve immune responses in broiler chickens, but their combined effects have not been well documented. The objective of this study was to evaluate the combined effects of dietary ARG and VE on antibody responses to sheep red blood cell (SRBC, agglutination assay) inoculation in 13-d-old chicks, and antibody titres (ELISA) to infectious bursal disease virus (IBDV) before and after vaccination of 20-d-old chicks. 2. One-day-old broiler chicks were fed diets with normal (NARG, 12 g/kg of feed) or high (HARG, 22 g/kg of feed) inclusion rates of ARG, and three rates of VE (40, 80, or 200 mg/kg of feed; 40 mg being the supplement used in commercial diets) in a factorial arrangement. 3. Antibody titres to SRBC at 5, 8, and 12 d after inoculation were higher in chicks fed on the HARG diet than in those on NARG, and in chickens on VE80 compared with those on VE200 at 5, 8, and 12 d after inoculation. Antibody titres to the IBDV 2 days before and 19 d after vaccination were higher in chickens on HARG compared with those on NARG, and in chicks on VE80 compared to those on VE40 but similar to those on VE200. Conversely, 5 d after vaccination titres against IBDV were higher in chicks on NARG than in those on HARG, and in chickens on VE40 compared with those on VE80, yet similar to those on VE200. 4. These results show that diets with high ARG and high VE (80 mg/kg) improved the humoral-mediated immune response of broilers to IBDV and SRBC, suggesting it could be a strategy to improve vaccination protection and resistance to diseases.

Effects of early enteral nutrition supplemented with arginine on intestinal mucosal immunity in severely burned mice

BACKGROUND

To investigate the effects of early enteral nutrition (EN) supplemented with Arginine (Arg) on intestinal mucosal immunity in severely burned mice.

METHODS

Forty-four mice were randomly assigned into four groups: a sham injury+EN group (n=10), a sham injury+EN+Arg group (n=10), a burn+EN group (n=12), and a burn+EN+Arg group (n=12) and the mice in two experimental groups received a 20% total body surface area (TBSA), full-thickness scald burn on the back. Then, the burned mice were given a 175 kcal/kg body wt/day of conventional enteral nutrition or an isonitrogenous and isocaloric enteral nutrition supplemented with Arg by gastric gavage for 7 days. There was isonitrogenous and isocaloric intake in two experimental groups. The mice in two control groups received the same procedures as above, except for burn injury. On day 7 after injury, all mice among four groups were euthanized and the entire intestine was harvested. Intestinal immunoglobulin A (IgA) levels, total lymphocyte yield, and lymphocyte subpopulations in Peyer's patches were analyzed. Levels of IFN-gamma, IL-2, IL-4 and IL-10 in gut homogenates were also measured by ELISA.

RESULTS

Total lymphocyte yield, numbers of lymphocyte subpopulations, and intestinal IgA levels in the EN+ARG group were higher than those in the EN group (p<0.05). Levels of gut tissue cytokines were significantly altered with enteral Arg supplementation: levels of IL-4 and IL-10 were increased, and levels of IFN-gamma and IL-2 declined, when compared with the EN-fed mice (p<0.05).

CONCLUSIONS

The results of this study suggested that enteral nutrition supplemented with Arg has changed the cytokine concentrations in intestinal homogenates from a pro- to an anti-inflammatory profile, increased sIgA levels and changed lymphocytes in severely burned mice.

Effect of arginine on angiogenesis induced by human colon cancer: in vitro and in vivo studies

This study investigated the effect of arginine (Arg) supplementation on angiogenesis in human colon cancer. The in vitro study investigated the effects of different Arg levels and inducible nitric oxide (iNO) synthase inhibitor on angiogenic protein expressions stimulated by SW480 cells. The results showed that the production of vascular endothelial growth factor (VEGF), basic fibroblast growth factor with 100 and 1000 micromol/L Arg and matrix metalloproteinase (MMP)-2 with 1000 micromol/L Arg was lower than that with 0 and 50 micromol/L Arg. Inhibition of iNO resulted in higher angiogenic protein expressions comparable with groups with low Arg administration, indicating that Arg administration at levels similar to or higher than physiological concentrations reduced the progression of colon cancer, and iNO may partly play a role in reducing angiogenesis. The in vivo study used a human colon cancer xenograft model in nude mice. Mice were inoculated with 1x10(7) SW480 cells and assigned to two groups. The control group was fed a semipurified diet, while the experimental group was supplied an Arg-supplemented diet. After 5 weeks, tumors were harvested and spleens were excised for further analysis. Results showed that the MMP-2, MMP-9 and VEGF receptor levels in tumors were significantly lower, whereas tumor NO levels and spleen natural killer (NK) cell activities were higher in the Arg group than in the control group. These results were consistent with the in vitro study that dietary Arg supplementation inhibits the progression of colon cancer possibly by increasing NO secretion and consequently enhancing NK cell activity.

Pros and cons of L-arginine supplementation in disease

The amino acid arginine and one of its metabolites NO have gathered broad attention in the last decade. Although arginine is regarded as a conditionally essential amino acid in disease, L-arginine supplementation in severe illness has not found its way into clinical practice. This might be due to the invalid interpretation of results from studies with immune-enhancing diets containing L-arginine amongst other pharmaconutrients. However, not much attention is given to research using L-arginine as a monotherapy and the possibility of the alternative hypothesis: that L-arginine supplementation is beneficial in disease. The present review will discuss data from studies in healthy and diseased animals and patients with monotherapy of L-arginine to come to an objective overview of positive and negative aspects of L-arginine supplementation in disease with special emphasis on sepsis, cancer, liver failure and wound healing.

Immune-modulating enteral formulations: optimum components, appropriate patients, and controversial use of arginine in sepsis

Nutrients have traditionally been viewed as a means to provide basic calories to sustain homeostasis. However, critically ill, surgical, and trauma patients are in a constant dynamic state between systemic inflammatory response (SIRS) and compensatory anti-inflammatory response (CARS). Results from ongoing research strongly support the use of specific nutrients to modulate the immune and/or metabolic response. These agents can now be considered therapeutic tools in the management of complex hypermetabolic diseases. The principle of using nutrients as a therapeutic strategy rather than just as "nutritional support" requires a shift in the current dogma. The most common nutrients found in currently available enteral immune-modulating formulas are omega-3 fatty acids (eicosapentaenoic acid and docosahexaenoic acid), antioxidants, nucleotides, glutamine, and arginine. Multiple individual reports and at least five meta-analyses using combinations of immune-modulating nutrients have reported almost uniform beneficial results. However, certain conflicting hypotheses continue to revolve around the use of arginine in septic patients.

Exogenous arginine in sepsis

Sepsis is a severe condition in critically ill patients and is considered an arginine deficiency state. The rationale for arginine deficiency in sepsis is mainly based on the reduced arginine levels in sepsis that are associated with the specific changes in arginine metabolism related to endothelial dysfunction, severe catabolism, and worse outcome. Exogenous arginine supplementation in sepsis shows controversial results with only limited data in humans and variable results in animal models of sepsis. Since in these studies the severity of sepsis varies but also the route, timing, and dose of arginine, it is difficult to draw a definitive conclusion for sepsis in general without considering the influence of these factors. Enhanced nitric oxide production in sepsis is related to suggested detrimental effects on hemodynamic instability and enhanced oxidative stress. Potential mechanisms for beneficial effects of exogenous arginine in sepsis include enhanced (protein) metabolism, improved microcirculation and organ function, effects on immune function and antibacterial effects, improved gut function, and an antioxidant role of arginine. We recently performed a study indicating that arginine can be given to septic patients without major effects on hemodynamics, suggesting that more studies can be conducted on the effects of arginine supplementation in septic patients.

Arginine in the critical care setting

Arginine is a nonessential amino acid in the normal physiological state that becomes conditionally essential during periods of hypermetabolic stress. Recent literature supports the hypothesis that arginine plays an important role in the intermediary metabolism of the critically ill patient. Current critical care literature is conflicting on arginine use in the clinical setting, with some proposing it as a panacea, whereas others report it as poison. Multiple individual reports and at least 5 major meta-analyses using combinations of immune-modulating nutrients have reported mostly beneficial results, but few have evaluated the effects of arginine when given as a single supplemental nutrient. This review attempts to objectively analyze the literature and evaluate the potential role of arginine in the critical care setting.

Prospective randomized study on perioperative enteral immunonutrition in laparoscopic colorectal surgery

BACKGROUND

Perioperative nutrition for patients undergoing colon surgery seems to be effective in reducing catabolism and improving immunologic parameters. A relatively low-fiber and highly absorbable diet may facilitate the intestinal cleansing and loop relaxation fundamental for laparoscopic surgery with a lower dose of iso-osmotic laxative.

METHODS

From 1 February 2004 to 30 July 2005, 28 patients referred to our unit with colon disease (neoplasms and diverticular disease) amenable to laparoscopic surgery were prospectively randomized into two groups of 14 patients each. For 6 days preoperatively, the patients in group 1 were given 750 ml/day of a diet enriched with arginine, omega-3 fatty acids, and ribonucleic acid (RNA) associated with low-fiber foods. They had 1 day of intestinal preparation with 3 l of iso-osmotic laxative. On postoperative day 2, they were fed orally with the same diet. The patients in group 2 preoperatively received a low-fiber diet. They had 2 days of preparation with iso-osmotic laxative (3 l/day). On postoperative day 3, oral nutrition was restored. Intraoperatively, we evaluated loop relaxation and intestinal cleanliness. Clinical trends were monitored in both groups, as well as adverse reactions to early nutrition. The nutritional (albumin, prealbumin) and immunologic (lymphocyte subpopulations, immunoglobulins) biohumoral parameters were evaluated at the first visit, on the day before surgery, on postoperative day 7, and 1 month after surgery.

RESULTS

The two groups did not differ in terms of age, gender, distribution of disease, or baseline anthropometric, biohumoral, or immunologic parameters. There was a significant increase in CD4 lymphocytes on the day before surgery as compared with baseline parameters (p < 0.05) in group 1, but not in group 2. There was no statistically significant difference between the two groups in intestinal loop relaxation or cleanliness or in postoperative infectious complications.

CONCLUSIONS

Perioperative immunonutrition proved to be safe and useful in increasing the perioperative immunologic cell response. It may contribute toward improving the preparation and relaxation of the intestinal loops despite the shorter intestinal preparation.

Effects of arginine-containing total parenteral nutrition on N balance and phagocytic activity in rats undergoing a partial gastrectomy

The present study investigated the effect of arginine (Arg)-containing parenteral nutrition on phagocytic activity to elucidate the possible roles of Arg in the secretion of anabolic hormones and N balance in rats undergoing gastrectomy. Rats were divided into two experimental groups and received total parenteral nutrition (TPN). The TPN solutions were isonitrogenous and identical in nutrient compositions except for differences in amino acid content. One group received conventional TPN, the other group replaced 2 % of the total energy as Arg. After receiving TPN for 3 d, one-third of the rats in each experimental group were killed as the baseline group. The remaining rats underwent a partial gastrectomy and were killed 1 or 3 d after surgery. The results showed that there were no differences in N balance, plasma growth hormone and insulin-like growth factor-1 levels between the two groups before or after surgery. The phagocytic activity of peritoneal macrophages was higher in the Arg group than in the control group 1 d after surgery. There were no differences in the phagocytic activities of blood polymorphonuclear neutrophils between the two groups at various time points. TNF-α levels in peritoneal lavage fluid were lower in the Arg group than in the control group on post-operative day 3. These results suggest that parenterally infused Arg enhances phagocytic activity and reduces the production of inflammatory mediators at the site of injury. However, Arg supplementation did not influence the secretion of anabolic hormones nor N balance in rats with a partial gastrectomy.

L-Arginine supplementation in sepsis: beneficial or harmful?

PURPOSE OF REVIEW

Recent results are reviewed on the effects of L-arginine supplements in excess of standard nutritional practices during severe sepsis and septic shock.

RECENT FINDINGS

Septic shock has been alternatively viewed as an L-arginine-deficient state or as a syndrome caused by excess nitric oxide, a vasoactive product of L-arginine metabolism. L-Arginine has many physiologic and pharmacologic effects that indicate its potential to affect survival in septic patients. Animal studies have documented immunologic effects of L-arginine and of commercial 'immune-enhancing' diets. However, survival studies in small animals have not consistently favored L-arginine. L-Arginine monotherapy in a canine model of septic shock found significant harm at infusion rates of less than twice that administered in standard formulations of total parenteral nutrition. Meanwhile, clinical studies have suffered from lack of statistical power, patient heterogeneity, randomization failures, and use of complex nutritional formulas. Meta-analyses have noted heterogeneity between the effects of immune-enhancing diets in surgical versus medical patients and mixed critically ill populations that include subjects with sepsis, indicating that these results may not be reliably pooled.

SUMMARY

To date, published evidence has not established the safety and efficacy of L-arginine at doses above standard dietary practices in severe sepsis or septic shock.

Bacterial translocation as a source of Dacron-graft contamination in experimental aortic operation: the importance of controlling SIRS

BACKGROUND

Several experimental studies have shown the beneficial effects of nitric oxide (NO) in the modulation of the systemic inflammatory response syndrome (SIRS). Nitric oxide is involved in and affects almost all stages in the development of inflammation. We have attempted to ascertain whether the nitric oxide donor molsidomine prevents aortic graft contamination through control of the SIRS and a decrease in bacterial translocation (BT).

METHODS

Twenty-four mini-pigs were divided into 4 groups. The animals were subjected to suprarenal aortic/iliac cross-clamping (for 30 minutes) and by-pass with a Dacron-collagen prosthetic graft impregnated in rifampicin. Groups: 1) sham (aortic dissection alone); 2) cross-clamping and bypass; 3) hemorrhage of 40% of total blood volume before cross-clamping and by-pass; and 4) the same as in group 3 but also including the administration of the NO donor molsidomine (4 mg/kg) 5 minutes before cross-clamping.

VARIABLES

1) bacteriology of mesenteric lymph nodes (MLN), kidney, blood, and prosthesis; 2) serum TNF-alpha (ELISA); and 3) iNOS expression in kidney and liver (Western blot).

RESULTS

Aortic cross-clamping with or without hemorrhage was associated with BT in 80% and 100% of the animals, respectively. About 86% of the bacteria isolated in the graft were also present in MLN. This contamination coincided with an increase in TNF-alpha and with a greater expression of iNOS. Molsidomine administration decreased TNF-alpha and iNOS, decreased BT (from 100% to 20% of the animals), and decreased graft contamination (from 83% to 20%).

CONCLUSIONS

The present model induces high levels of BT and SIRS, both acted as sources of contamination for the implanted Dacron graft. Molsidomine administration decreased the presence of bacteria in the graft by controlling BT and modulating SIRS.

Controlled study of enteral arginine supplementation in burned children: impact on immunologic and metabolic status

OBJECTIVE

We compared the effects of an arginine-supplemented diet with those of an isocaloric isonitrogenous diet on immune and metabolic response of children with burns.

METHODS

This was a double-blind, randomized, placebo-controlled trial in a burn treatment center of a pediatric hospital in Santiago, Chile. All children (1-5 y of age) admitted within 48 h of a moderate to deep burn injury covering 10% to 40% of total body surface area were evaluated. Twenty-eight children met the criteria and were randomly assigned to receive an arginine-supplemented diet (AG; n = 14) or an isocaloric isonitrogenous diet (CG; control, n = 14) for 14 d. Samples were collected at admission (baseline) and on days 7 and 14 for lymphoproliferative response to mitogens, plasma interleukins (interleukin-1, interleukin-6, tumor necrosis factor-alpha), plasma arginine and ornithine levels, serum C-reactive protein, prealbumin, albumin, glucose, and total urinary nitrogen.

RESULTS

The AG enhanced lymphoproliferative responses (analysis of variance, P < 0.05), which were 72% of normal at baseline in both groups; by day 7 responses increased to 144% in the AG group and decreased to 56% in the CG group; both groups returned to normal by day 14. Baseline interleukin-6 was significantly increased in all children. There were no differences in plasma concentrations of interleukin-1, interleukin-6, tumor necrosis factor-alpha, C-reactive protein, prealbumin, albumin, or glucose between the AG and CG groups. On day 7 plasma ornithine levels increased significantly in the AG versus CG group (P < 0.05); arginine levels showed no change.

CONCLUSIONS

An exclusively AG improves mitogen-stimulated lymphocyte proliferation in burned children. The benefits of arginine for the immune system do not appear to be related to a metabolic response. The biological significance of this finding remains to be determined.

Preoperative oral immune-enhancing nutritional supplementation corrects TH1/TH2 imbalance in patients undergoing elective surgery for colorectal cancer

PURPOSE

Recent studies have shown that the type 1/2 CD4+ T cell (Th1/Th2) balance shifts toward Th2 dominance in cancer-bearing state or by surgical stress. Perioperative immunonutrition is reported to improve the outcome in patients with gastrointestinal cancer. This study was designed to investigate whether preoperative immunonutrition corrects the impaired Th1/Th2 balance in the perioperative period.

METHODS

Thirty-six patients with colorectal cancer were prospectively divided into two groups as follows: preoperative oral intake supplementation with a formula enriched with arginine, omega-3 fatty acids and ribonucleic acid for five days (supplemented group; n = 19); and (control group; n = 17). Blood sampling was performed before supplementation, on the morning of surgery, and 3, 7, and 14 days postoperatively. The proportions of CD4+ T cells producing intracellular cytokines (interferon-gamma and interleukin-4) were measured by flow cytometry.

RESULTS

In the preoperative period, the proportions of CD4+ T cells producing interleukin-4 significantly decreased and Th1/Th2 ratio significantly increased on the morning of surgery compared with those before supplementation. In the postoperative period, the proportions of CD4+ T cells producing interferon-gamma in both groups maintained the preoperative level. The proportions of CD4+ T cells producing interleukin-4 in the control group showed a gradual increase from the preoperative level, which implies Th2 dominant shift. In contrast, the supplemented group maintained the preoperative level of Th1/Th2 ratio.

CONCLUSIONS

Preoperative immunonutrition corrects impaired Th1/Th2 balance in both cancer-bearing state and the postoperative period. This correction may be one of the important determinants of the clinical benefits of immunonutrition.

Effects of arginine supplementation on splenocyte cytokine mRNA expression in rats with gut-derived sepsis

AIM

To investigate the effects of arginine (Arg)-enriched diets before sepsis and/or Arg-containing total parenteral nutrition (TPN) after sepsis or both on cytokine mRNA expression levels in splenocytes of rats with gut-derived sepsis.

METHODS

Rats were assigned to four experimental groups. Groups 1 and 2 were fed with a semipurified diet, while groups 3 and 4 had part of the casein replaced by Arg which provided 2% of the total calories. After the rats were fed with these diets for 10 d, sepsis was induced by cecal ligation and puncture (CLP), at the same time an internal jugular vein was cannulated. All rats were maintained on TPN for 3 d. Groups 1 and 3 were infused with conventional TPN, while groups 2 and 4 were supplemented with Arg which provided 2% of the total calories in the TPN solution. All rats were killed 3 d after CLP to examine their splenocyte subpopulation distribution and cytokine expression levels.

RESULTS

Plasma interleukin (IL)-2, IL-4, tumor necrosis factor-alpha (TNF-alpha) and interferon (IFN-gamma) were not detectable 3 d after CLP. There were no differences in the distributions of CD45Ra(+), CD3(+), CD4(+), and CD8(+) cells in whole blood and splenocytes among the four groups. The splenocyte IL-2 mRNA expression in the Arg-supplemented groups was significantly higher than that in group 1. IL-4 mRNA expression in groups 3 and 4 was significantly higher than that in groups 1 and 2. The mRNA expression of IL-10 and IFN-gamma was significantly higher in group 4 than in the other three groups. There was no difference in TNF-alpha mRNA expression among the four groups.

CONCLUSION

The influence of Arg on the whole blood and splenic lymphocyte subpopulation distribution is not obvious. However, Arg administration, especially before and after CLP, significantly enhances the mRNA expression levels of Th1 and Th2 cytokines in the spleen of rats with gut-derived sepsis.

Does Pharmaconutrition with L-Arginine and/or α-Tocopherol Improve the Gut Barrier in Bile Duct Ligated Rats?

BACKGROUND/AIM

Nitric oxide supplementation and antioxidant therapy modulate gut barrier function, but the relationships between enhanced nitric oxide production, antioxidant administration, and biliary obstruction remain unclear. We evaluated the role of nitric oxide and alpha-tocopherol supplementation in bile duct ligated rats.

METHODS

Fifty male Wistar albino rats underwent sham operation (group I; control animals) or bile duct ligation (groups II, III, IV, and V). The ligation groups received the following regimens: standard pellet diet (group II), pellet diet plus intramuscularly administered alpha-tocopherol (group III), and L-arginine-enriched pellet diet without (group IV) or with (group V) alpha-tocopherol. Nitric oxide, malondialdehyde, and alpha-tocopherol concentrations were assessed at the end of 3 weeks. Liver and intestinal samples were scored histologically. Mesenteric lymph node and liver cultures were assessed for bacterial translocation.

RESULTS

The liver malondialdehyde concentration was highest in group III. The nitric oxide content in the liver was higher in groups III and V, as were the blood alpha-tocopherol levels. Bacterial translocation was evident following bile duct ligation, but did not differ among the treatment groups. Intestinal histology revealed that group III had the lowest villus height, that group V had the least villus count, and that group II had the highest mucous cell count. The fibrosis scores were higher in groups IV and V.

CONCLUSIONS

An obvious effect of alpha-tocopherol (with or without L-arginine) on the gut barrier could not be demonstrated. Moreover, the L-arginine-enriched diet promoted fibrosis in the liver. Thus, while biliary duct obstruction triggers bacterial translocation, nitric oxide and/or alpha-tocopherol supplementation did not seem to improve the gut barrier in our model.

DIETARY ARGININE ENHANCES ADHESION MOLECULE AND T HELPER 2 CYTOKINE EXPRESSION IN MICE WITH GUT-DERIVED SEPSIS

This study investigated the effects of arginine (Arg) on cellular adhesion molecules and intracellular Th1/Th2 cytokine expressions in mice with polymicrobial sepsis. Myeloperoxidase activity in organs was also analyzed to identify the extent of tissue injury resulting from neutrophil infiltration. Mice were randomly assigned to a normal group (NC), a control group, or an Arg group. The NC group was fed a standard chow diet. The control group was fed a common semipurified diet, and in the Arg group, part of the casein was replaced by Arg, which provided 2% of the total calories. After 3 weeks, sepsis was induced by cecal ligation and puncture (CLP) in the control and Arg groups. Mice in the experimental groups were sacrificed at 0, 6, 12, and 24 h after CLP, whereas mice in the NC group were sacrificed when the CLP was performed. Blood and organ samples were immediately collected for further analysis. Results showed that compared with the control group, plasma intracellular adhesion molecule-1 levels were significantly higher in the Arg group 12 and 24 h after CLP. Lymphocyte interferon-gamma expression in the Arg groups was significantly lower, whereas interleukin (IL)-4 expression was higher than the control group at various time points after CLP. The expression of lymphocyte CD11a/CD18 was significantly higher in the Arg group 6, 12, and 24 h after CLP than those of the corresponding control group and the NC group. PMN expressions of CD11b/CD18 in the Arg groups were higher than those in the control group at 12 and 24 h after CLP. The Arg group had higher IL-6 levels at 6 and 12 h in the kidney and intestine and 12 h in the lung after CLP. Higher myeloperoxidase activities were observed in the Arg groups at 24 h after CLP than those in the control group in various organs. These findings suggest that pretreatment with an Arg-supplemented diet enhances adhesion molecule and inflammatory cytokine expression during sepsis, which may aggravate the inflammatory reaction and increase neutrophil infiltration into tissues. In addition, Arg supplementation reduced intracellular interferon-gamma and enhanced IL-4 expression. This change may promote the Th2-type response and suppress the cellular immune response in gut-derived sepsis.

Influence of preoperative administration of omega-3 fatty acid-enriched supplement on inflammatory and immune responses in patients undergoing major surgery for cancer

OBJECTIVE

Polyunsaturated fatty acid supplementation may produce beneficial effects after surgery. We investigated the influence of preoperative administration of a supplement rich in arginine, omega-3 fatty acids, and RNA, Impact (Japan), on inflammatory and immune responses in patients undergoing major surgery for cancer.

METHODS

Patients in the supplement group (n = 12) received 1 L/d of Impact (Japan) for 5 d before surgery, and those in the control group (n = 14) received an ordinary diet without Impact (Japan) before surgery. Plasma levels of omega-3 and omega-6 fatty acids, thromboxane B(2), prostaglandin E(2), inflammatory markers, nutritional markers, cytokines, and cytokine receptors were obtained 5 d before the operation at the starting point of supplementation in the supplement group. Samples were collected on postoperative days (PODs) 0, 1, 3, and 7.

RESULTS

After taking the supplement, significant increases in omega-3 fatty acids and rapid turnover proteins were found the day after ending supplementation (POD-0), whereas thromboxane B(2) levels and the ratio of omega-6 fatty acids to omega-3 fatty acids were significantly lower than before supplementation (P < 0.001). On POD-0 only, inflammatory markers and cytokine receptors in the supplement group showed low levels in comparison with the control group (P < 0.05). On POD-1 and POD-3, remarkable decreases in polymorphonuclear leukocyte-elastase and interleukin-8 in the supplement group were observed.

CONCLUSION

Our findings suggest that oral administration of a supplement rich in omega-3 fatty acids for 5 d before surgery may improve not only preoperative nutritional status but also preoperative and postoperative inflammatory and immune responses in patients who have cancer.

Effect of early postoperative enteral immunonutrition on wound healing in patients undergoing surgery for gastric cancer

BACKGROUND & AIMS

One of the most frequent complications in patients with cancer and malnutrition is the surgical wound healing delay or failure. Some studies have shown that arginine improves wound healing in rodents and in healthy human beings. The main objective of this study was to assess the effect of early postoperative enteral immunonutrition on the wound healing process in patients undergoing surgery for gastric cancer.

METHODS

Sixty six patients with gastric cancer were randomized to receive early postoperative enteral immunonutrition (formula supplemented with arginine, omega-3 fatty acids and ribonucleic acid (RNA)) or an isocaloric-isonitrogenous control. Assessment of wound healing process: (1) Quantification of hydroxyproline deposition in a subcutaneously placed catheter, (2) occurrence of surgical wound healing complications.

RESULTS

Sixty patients were analyzed. Patients fed with immunonutrition (n=30) showed higher local hydroxyproline levels (59.7 nmol (5.0-201.8), vs. 28.0 nmol (5.8-89.6) P=0.0018) and significantly lower episodes of surgical wound healing complications (0 vs. 8 (26.7%) P=0.005) when compared to patients fed with the control formula (n=30).

CONCLUSIONS

Early postoperative enteral nutrition with a formula supplemented with arginine, omega 3 fatty acids and RNA increased hydroxyproline synthesis and improved surgical wound healing in patients undergoing gastrectomy for gastric cancer.

Effects of arginine supplementation on mucosal immunity in rats with septic peritonitis

BACKGROUND

Supplemental Arginine (Arg) has been demonstrated to improve the immunologic response and reduce mortality in rodents with sepsis. However, the effects of Arg on gut-associated lymphoid tissue function after infection and sepsis are not clear. The aim of this study was to study the effect of Arg-supplemented diets before and Arg-enriched total parenteral nutrition (TPN) after sepsis or both on the intestinal immunity of rats with septic peritonitis.

METHODS

Rats were assigned to four groups. Groups 1 and 2 were fed a semipurified diet, while in the diets of groups 3 and 4, part of the casein was replaced with Arg. After feeding the experimental diets for 10 days, sepsis was induced by cecal ligation and puncture (CLP); at the same time, the internal jugular vein was cannulated. All rats were maintained on TPN for 3 days. Groups 1 and 3 were infused with conventional TPN, while groups 2 and 4 were given a TPN solution supplemented with Arg, which replaced 10% of the total amino acids. All rats were sacrificed 3 days after CLP. Intestinal immunoglobin (Ig) A levels, total lymphocyte yields, and lymphocyte subpopulations in Peyer's patches were analyzed. In vitro cytokine secretion by splenocytes and Peyer's patch lymphocytes were also measured.

RESULTS

Total lymphocyte yields in Peyer's patches, and small intestinal immunoglobulin A (IgA) secretion in group 4 were significantly higher than the groups 1 and 2. No differences were observed between groups 3 and 4. There were no differences in the interleukin (IL)-2 and interferon- gamma levels among all groups when splenocytes were stimulated with mitogen. However, in vitro splenocyte IL-10 production in group 4 was significantly higher than those of groups 1 and 2, and had no difference from group 3. There were no differences in the ratios of B and T lymphocyte subpopulations in Peyer's patches among all groups.

CONCLUSIONS

Enteral Arg supplementation before sepsis tended to enhance total lymphocyte yields in Peyer's patches and intestinal IgA secretion. Arg administered both before and after CLP had a synergistic effect on improving intestinal immunity, possibly by enhancing systemic IL-10 secretion. However, intravenous Arg administration after CLP had no favorable effects on mucosal immunity in rats with septic peritonitis.

Potentiation by amino acid of the therapeutic effect of highly purified vitamin B2 in mice with lipopolysaccharide-induced shock

The aim of this experiment was to clarify whether an amino acid supplement could enhance the therapeutic effect of vitamin B2 (riboflavin 5'-sodium phosphate; purity > 97%) in mice with lipopolysaccharide-induced shock. Six hours after injection of a lethal dose of lipopolysaccharide, treatment (6-h i.v. infusion) was commenced. All mice died in the groups treated with saline or aminolevane (an amino acids mixture used to treat hepatopathy); however, the survival rates in the vitamin B2 (10 mg/kg/6 h) and vitamin B2 plus aminolevane groups were 45% (P < 0.05) and 80% (P < 0.05), respectively. Valine (200 mg/kg/6 h) alone had little effect on the survival rate (10%), but the combination of vitamin B2 (10 mg/k/g/6 h) and valine was highly effective (80%, P < 0.05). Clinical trials of vitamin B2 plus amino acids for the treatment of patients with sepsis would appear to be warranted.

Epidermal growth factor and interleukin-1beta synergistically stimulate the production of nitric oxide in rat intestinal epithelial cells

Epidermal growth factor (EGF) is one of the trophic factors for intestinal adaptation after small bowel transplantation (SBT). A recent report indicates that nitric oxide (NO) has cytoprotective effects on bacterial translocation (BT) after SBT. We hypothesized that EGF stimulates the expression of the inducible NO synthase (iNOS) gene in the graft after SBT, followed by increased production of NO, resulting in the decrease of BT. Intestinal epithelial cells (IEC)-6 were treated with EGF and/or IL-1beta in the presence and absence of phosphatidylinositol 3-kinase (PI3-kinase) and EGF receptor kinase inhibitors (LY-294002 and tyrphostin A25). The induction of NO production and iNOS and its signal molecules, including the inhibitory protein of NF-kappaB (IkappaB), NF-kappaB, and Akt, were analyzed. IL-1beta stimulated the degradation of IkappaB and the activation of NF-kappaB but had no effect on iNOS induction. EGF, which had no effect on the NF-kappaB activation and iNOS induction, stimulated the upregulation of type 1 IL-1 receptor (IL-1R1) through PI3-kinase/Akt. Simultaneous addition of EGF and IL-1beta stimulated synergistically the induction of iNOS, leading to the increased production of NO. Our results indicate that EGF and IL-1beta stimulate two essential signals for iNOS induction in IEC-6 cells: the upregulation of IL-1R1 through PI3-kinase/Akt and the activation of NF-kappaB through IkappaB kinase, respectively. Simultaneous addition of EGF and IL-1beta can enhance the production of NO, which may contribute to the cytoprotective effect of EGF against intestinal injury.

Trophic and cytoprotective nutrition for intestinal adaptation, mucosal repair, and barrier function

Intestinal epithelial cell turnover (proliferation, migration, differentiation, and apoptosis) and gut barrier functions are dynamic processes that are markedly affected by nutritional status, the route of feeding, and the adequacy of specific nutrients in the diet. Emerging studies are defining potential therapeutic roles for specific nutrients and diet-derived compounds (including arginine, glutamate, glutamine, glutathione, glycine, vitamin A, zinc, and specific lipids) in gut mucosal turnover, repair, adaptation after massive bowel resection, and barrier function. The role and regulation of endogenous bowel flora in generating short-chain fatty acids from diet-derived fiber and other diet-derived compounds and the effects of these agents on gut function are increasingly being elucidated. Results of these investigations should define new nutritional methods for trophic and cytoprotective effects on the intestine in conditions such as inflammatory bowel disease, malnutrition, and short bowel syndrome.

Dietary fructo-oligosaccharides and lactulose inhibit intestinal colonisation but stimulate translocation of salmonella in rats

BACKGROUND AND AIMS

It is frequently assumed that dietary non-digestible carbohydrates improve host resistance to intestinal infections by stimulating the protective gut microflora. However, compelling scientific evidence from in vivo infection studies is lacking. Therefore, we studied the effect of several non-digestible carbohydrates on the resistance of rats to Salmonella enteritidis infection.

METHODS

Rats (n=8 per group) were fed "humanised" purified diets containing 4% lactulose, fructo-oligosaccharides (FOS), resistant starch, wheat fibre, or cellulose. After an adaptation period of 2 weeks the animals were orally infected with S enteritidis. Supplement induced changes in faecal biochemical and microbiological parameters were studied before infection. Colonisation of salmonella was determined by studying the faecal excretion of this pathogen and translocation by analysis of urinary nitric oxide metabolites over time and classical organ cultures. Intestinal mucosal myeloperoxidase activity was determined to quantify intestinal inflammation after infection.

RESULTS

Despite stimulation of intestinal lactobacilli and bifidobacteria and inhibition of salmonella colonisation, FOS and lactulose significantly enhanced translocation of this pathogen. These supplements also increased cytotoxicity of faecal water and faecal mucin excretion, which may reflect mucosal irritation. In addition, caecal and colonic, but not ileal, mucosal myeloperoxidase activity was increased in infected rats fed FOS and lactulose. In contrast, cellulose, wheat fibre, and resistant starch did not affect the resistance to salmonella.

CONCLUSIONS

In contrast to most expectations, FOS and lactulose impair the resistance of rats to intestinal salmonella infection. Obviously, stimulation of the endogenous lactobacilli and bifidobacteria is no guarantee of improved host defence against intestinal infections.