High arginine levels in intravenous hyperalimentation abrogate post-traumatic immune suppression

Quantitative proteomic analysis of hepatic tissue in allotetraploid hybridized from red crucian carp and common carp identified crucial proteins and pathways associated with metabolism and growth rate

Allotetraploid is a new species produced by distant hybridization between red crucian carp (Carassius auratus red var., abbreviated as RCC) and common carp (Cyprinus carpio L., abbreviated as CC). There is a significant difference in growth rate between allotetraploid and its parents. However, the underlying molecular mechanism is largely unknown. In this study, to find direct evidence associated with metabolism and growth rate in protein level, we performed quantitative proteomics analysis on liver tissues between allotetraploid and its parents. A total of 2502 unique proteins were identified and quantified by SWATH-MS in our proteomics profiling. Subsequently, comprehensive bioinformatics analyses including gene ontology enrichment analysis, pathway and network analysis, and protein-protein interaction analysis (PPI) were conducted based on differentially expressed proteins (DEPs) between allotetraploid and its parents. The results revealed several significant DEPs involved in metabolism pathways in liver. More specifically, the integrative analysis highlighted that the DEPs ACSBG1, OAT, and LDHBA play vital roles in metabolism pathways including "pentose phosphate pathway," "TCA cycle," and "glycolysis and gluconeogenesis." These could directly affect the growth rate in fresh water fishes by regulating the metabolism, utilization, and exchange of substance and energy. Since the liver is the central place for metabolism activity in animals, we firstly established the comprehensive and quantitative proteomics knowledge base for liver tissue from freshwater fishes, our study may serve as an irreplaceable reference for further studies regarding fishes' culture and growth.

Mitochondrial arginase-2 is a cell‑autonomous regulator of CD8+ T cell function and antitumor efficacy

As sufficient extracellular arginine is crucial for T cell function, depletion of extracellular arginine by elevated arginase 1 (Arg1) activity has emerged as a hallmark immunosuppressive mechanism. However, the potential cell-autonomous roles of arginases in T cells have remained unexplored. Here, we show that the arginase isoform expressed by T cells, the mitochondrial Arg2, is a cell-intrinsic regulator of CD8+ T cell activity. Both germline Arg2 deletion and adoptive transfer of Arg2-/- CD8+ T cells significantly reduced tumor growth in preclinical cancer models by enhancing CD8+ T cell activation, effector function, and persistence. Transcriptomic, proteomic, and high-dimensional flow cytometry characterization revealed a CD8+ T cell-intrinsic role of Arg2 in modulating T cell activation, antitumor cytoxicity, and memory formation, independently of extracellular arginine availability. Furthermore, specific deletion of Arg2 in CD8+ T cells strongly synergized with PD-1 blockade for the control of tumor growth and animal survival. These observations, coupled with the finding that pharmacologic arginase inhibition accelerates activation of ex vivo human T cells, unveil Arg2 as a potentially new therapeutic target for T cell-based cancer immunotherapies.

Acquired Amino Acid Deficiencies: A Focus on Arginine and Glutamine

Nonessential amino acids are synthesized de novo and therefore not diet dependent. In contrast, essential amino acids must be obtained through nutrition since they cannot be synthesized internally. Several nonessential amino acids may become essential under conditions of stress and catabolic states when the capacity of endogenous amino acid synthesis is exceeded. Arginine and glutamine are 2 such conditionally essential amino acids and are the focus of this review. Low arginine bioavailability plays a pivotal role in the pathogenesis of a growing number of varied diseases, including sickle cell disease, thalassemia, malaria, acute asthma, cystic fibrosis, pulmonary hypertension, cardiovascular disease, certain cancers, and trauma, among others. Catabolism of arginine by arginase enzymes is the most common cause of an acquired arginine deficiency syndrome, frequently contributing to endothelial dysfunction and/or T-cell dysfunction, depending on the clinical scenario and disease state. Glutamine, an arginine precursor, is one of the most abundant amino acids in the body and, like arginine, becomes deficient in several conditions of stress, including critical illness, trauma, infection, cancer, and gastrointestinal disorders. At-risk populations are discussed together with therapeutic options that target these specific acquired amino acid deficiencies.

Metabolomic analysis of human plasma reveals that arginine is depleted in knee osteoarthritis patients

OBJECTIVE

To identify novel biomarker(s) for knee osteoarthritis (OA) using a metabolomics approach.

METHOD

We utilized a two-stage case-control study design. Plasma samples were collected from knee OA patients and healthy controls after 8-h fasting and metabolically profiled using a targeted metabolomics assay kit. Linear regression was used to identify novel metabolic markers for OA. Receiver operating characteristic (ROC) analysis was used to examine diagnostic values. Gene expression analysis was performed on human cartilage to explore the potential mechanism for the novel OA marker(s).

RESULTS

Sixty-four knee OA patients and 45 controls were included in the discovery stage and 72 knee OA patients and 76 age and sex matched controls were included in the validation stage. We identified and confirmed six metabolites that were significantly associated with knee OA, of which arginine was the most significant metabolite (P < 3.5 × 10(-13)) with knee OA patients having on average 69 μM lower than that in controls. ROC analysis showed that arginine had the greatest diagnostic value with area under the curve (AUC) of 0.984. The optimal cutoff of arginine concentration was 57 μM with 98.3% sensitivity and 89% specificity. The depletion of arginine in OA patients was most likely due to the over activity of arginine to ornithine pathway, leading to imbalance between cartilage repair and degradation.

CONCLUSION

Arginine is significantly depleted in refractory knee OA patients. Further studies within a longitudinal setting are required to examine whether arginine can predict early OA changes.

"Immunonutrition" Has Failed to Improve Peritonitis-Induced Septic Shock in Rodents

BACKGROUND

Immunonutrition in sepsis, including n-3 poly-unsaturated fatty acids (PUFAs) or L-arginine supplementation, is a controversial issue that has yielded a great number of studies for the last thirty-five years, and the conclusions regarding the quantity and quality of this support in patients are deceiving. The aim of the present experimental study is to investigate the effects of a pretreatment with enteral nutrition enriched with n-3 PUFAs or L-arginine on vascular dysfunctions, inflammation and oxidative stress during septic shock in rats.

DESIGN

Rats were fed with enteral Peptamen® HN (HN group), Peptamen® AF containing n-3 PUFAs (AF group) or Peptamen® AF enriched with L-arginine (AFA group). On day 4, peritonitis by cecal ligation and puncture (CLP) was performed. Rats were resuscitated (H18) once septic shock was established. After a 4-hour resuscitation, vessels and organs were harvested to assess inflammation, superoxide anion, nitric oxide and prostacyclin levels. Ex-vivo vascular reactivity was also performed.

RESULTS

Compared to CLP-AF or CLP-HN groups, 47.6% of CLP-AFA rats died before the beginning of hemodynamic measurements (vs. 8.0% and 20.0% respectively, p<0.05). AF and AFA rats required significantly increased norepinephrine infusion rates to reach the mean arterial pressure objective, compared to CLP-HN rats. Both CLP-AF and CLP-AFA reduced mesenteric resistance arterial contractility, decreased vascular oxidative stress, but increased NF-κB (0.40±0.15 in CLP-AF and 0.69±0.06 in CLP-AFA vs. 0.09±0.03 in SHAM rats and 0.30±0.06 in CLP-HN, ß-actin ratio, p<0.05) and pIκB expression (0.60±0.03 in CLP-AF and 0.94±0.15 in CLP-AFA vs. 0.04±0.01 in SHAM rats and 0.56±0.07 in CLP-HN, ß-actin ratio, p<0.05), nitric oxide and prostacyclin production in septic rats.

CONCLUSIONS

Although n-3 PUFAs or L-arginine supplementation exhibited an antioxidant effect, it worsened the septic shock-induced vascular dysfunction. Furthermore, mortality was higher after L-arginine supplementation.

Amino acid and vitamin supplementation improved health conditions in elderly participants

The purpose of this study was to investigate the effects of supplementation with amino acids and vitamins on health conditions in unhealthy older people. One bedridden inpatient group (n = 10; mean age, 79.8 ± 8.5 y) and one outpatient group (n = 9; mean age, 72.9 ± 12.2 y) participated in this study. A mixture supplementation with amino acids containing arginine (500 mg/day), glutamine (600 mg/day), and leucine (1200 mg/day), and 11 kinds of vitamins was daily administrated for 8 weeks. In both groups, general blood biomarkers such as white blood cell count, natural killer cell activity, and C-reactive protein levels were measured. All measurements were taken before (baseline), at 4 weeks (mid-point), and after each trial (post-point). At mid-point, natural killer cell activity in the outpatient group increased significantly compared to baseline. At post-point, natural killer cell activity in the outpatient and inpatient groups increased significantly compared to baseline. The other blood biomarkers did not show any significant change throughout the trial. This pilot study suggested that a mixture of arginine, glutamine, leucine, and vitamins is useful to support innate immunity in unhealthy older people, even if their diseases, symptoms, and prescribed medicines are different.

L-arginine deprivation regulates cyclin D3 mRNA stability in human T cells by controlling HuR expression

Myeloid-derived suppressor cells are a major mechanism of tumor-induced immune suppression in cancer. Arginase I-producing myeloid-derived suppressor cells deplete l-arginine (L-Arg) from the microenvironment, which arrests T cells in the G(0)-G(1) phase of the cell cycle. This cell cycle arrest correlated with an inability to increase cyclin D3 expression resulting from a decreased mRNA stability and an impaired translation. We sought to determine the mechanisms leading to a decreased cyclin D3 mRNA stability in activated T cells cultured in medium deprived of L-Arg. Results show that cyclin D3 mRNA instability induced by L-Arg deprivation is dependent on response elements found in its 3'-untranslated region (UTR). RNA-binding protein HuR was found to be increased in T cells cultured in medium with L-Arg and bound to the 3'-untranslated region of cyclin D3 mRNA in vitro and endogenously in activated T cells. Silencing of HuR expression significantly impaired cyclin D3 mRNA stability. L-Arg deprivation inhibited the expression of HuR through a global arrest in de novo protein synthesis, but it did not affect its mRNA expression. This alteration is dependent on the expression of the amino acid starvation sensor general control nonderepressible 2 kinase. These data contribute to an understanding of a central mechanism by which diseases characterized by increased arginase I production may cause T cell dysfunction.

Arginine-enriched total parenteral nutrition improves survival in peritonitis by normalizing NFkappaB activation in peritoneal resident and exudative leukocytes

BACKGROUND

Enteral nutrition maintains peritoneal defense more effectively than parenteral nutrition, at least partly by preserving NFkappaB activation in peritoneal cells. We hypothesized that arginine (ARG)-enriched parenteral nutrition would normalize NFkappaB activation in peritoneal leukocytes, thereby improving the survival of peritonitis models.

METHODS

A total of 105 ICR mice were randomized to chow (n=33), IV feeding of a standard (STD) total parenteral nutrition (STD-TPN) solution (ARG 0.3%) (n=35), or 1% ARG-TPN solution (n=37), and fed accordingly for 5 days.Experiment 1: Thirty mice were used for intranuclear NFkappaB measurement in peritoneal resident cells (PRCs). After incubation with lipopolysaccharide (LPS: 0, 1, 10 microg/mL) for 30 minutes, intranuclear NFkappaB activity was examined by laser scanning cytometry.Experiment 2: Fifty-one mice were injected with 2 mL of 1% glycogen intraperitoneally. Peritoneal exudative cells (PECs) were obtained at 2 or 4 hours after glycogen administration for NFkappaB measurement. Cytokine (TNFalpha, IL-10) levels in peritoneal lavage fluid were also determined by ELISA.Experiment 3: After 5 days of feeding, 24 mice underwent cecal ligation and puncture. Survival was observed up to 5 days.

RESULTS

Experiment 1: Intranuclear NFkappaB levels in the ARG-TPN and chow groups increased dose-dependently after LPS stimulation, while the level in the STD-TPN group was unchanged.Experiment 2: Intranuclear NFkappaB level was significantly higher at 2 hours in the chow than in the STD-TPN group, whereas in the ARG-TPN mice the level was midway between those of the chow and STD-TPN groups. TNFalpha and IL-10 levels of the chow group were significantly higher than those of STD-TPN mice at 2 hours. TNFalpha was significantly higher in the ARG-TPN group than in the STD-TPN group, but the IL-10 level showed no recovery.Experiment 3: Survival times were significantly reduced in the STD-TPN as compared with the chow group, though ARG-TPN improved survival.

CONCLUSION

ARG-enriched TPN is a surrogate for enteral feeding which maintains peritoneal defense by preserving NFkappaB activation in peritoneal resident and exudative leukocytes.

Glucose transport in fibroblasts is unaffected by polyamines

OBJECTIVE

Wound healing is characterized by a net increase in glucose utilization in wound tissues. The mediators involved in this process remain largely unknown. Because polyamines are known to stimulate d-glucose uptake in brush-border membrane vesicles, we investigated whether or not they stimulated sugar uptake in confluent cultured fibroblasts.

METHODS

Cells (at a quiescent or growing state) were incubated for 1 h with various concentrations (0.5-4 mM) of putrescine, spermine, or spermidine or for a range of times (30 min to 3 h) with 2 mM of these same polyamines. Cultures were then incubated for 5 min at +37 degrees C with 2-deoxy-d-[1-(3)H] glucose.

RESULTS

Polyamines were found to have no action on sugar uptake in any of the experimental configurations.

CONCLUSION

These data suggest that polyamines have no effect in cell types in which glucose uptake is mediated by a passive facilitated diffusion process (energy independent). This contrasts with results obtained with cells in which sugar uptake is dependent on adenosine triphosphate. Even if this model does not reflect the complexity of wound healing, these negative results are nevertheless important because they suggest that the arginine- and ornithine-mediated effects on wound healing are not related to a polyamine-mediated increase in glucose transport in fibroblasts.

EFFECT OF ARGININE ON CELLULAR ADHESION MOLECULE EXPRESSION AND LEUKOCYTE TRANSMIGRATION IN ENDOTHELIAL CELLS STIMULATED BY BIOLOGICAL FLUID FROM SURGICAL PATIENTS

This study investigated the effect of different arginine (Arg) concentrations on adhesion molecule expression on endothelial cells (ECs) and leukocytes and the transendothelial migration of polymorphonuclear neutrophils (PMNs) through ECs stimulated by plasma or peritoneal drain fluid (PDF) from surgical patients. Human umbilical vein ECs (HUVECs) and PMNs from healthy subjects were treated with different concentrations (0, 50, 100, and 1000 micromol/L) of Arg for 24 h. After that, HUVECs were stimulated for 3 h with plasma or PDF from patients who underwent abdominal surgery, and PMNs were allowed to transmigrate through ECs for 2 h. The HUVEC expression of cellular adhesion molecules (CAMs) and integrin (CD11b) and the interleukin (IL) 8 receptor expression on PMNs were measured by flow cytometry. The PMNs transmigrating through ECs were also analyzed. The results showed that CAM and integrin expressions in PDF groups were higher than those in control groups. Among the PDF groups, IL-8 secretions from ECs and PMNs were lower with 100 and 1000 micromol/L Arg than with 0 and 50 micromol/L Arg, and this was consistent with the expression of the IL-8 receptor on PMNs. In addition, CAM expressions on ECs and CD11b expression on PMNs, as well as PMN transmigration, were lower with 100 and 1000 micromol/L Arg than with 0 and 50 micromol/L Arg. The HUVECs stimulated by plasma from surgical patients had similar effects on surface molecule expression as PDF; however, as shown in PDF stimulation, the effects were not so obvious. Inhibition of nitric oxide production results in high CAM and IL-8 expressions comparable with groups with low Arg administration. The results of this in vitro study suggest that ECs and PMNs were activated after patients' plasma or PDF stimulation. A low Arg concentration comparable with catabolic conditions resulted in higher adhesion molecule expression and greater transendothelial migration of neutrophils. Arginine administration at levels similar to or higher than physiological concentrations reduced IL-8 and CAM expression, and PMN transmigration was also decreased after stimulation with plasma or PDF from surgical patients. Inactivation of NO results in high CAM and IL-8 expression. This finding indicated that NO may be an important endogenous inhibitor for EC-PMN interaction and neutrophil transmigration.

Arginine and immunity

For many years, dietary arginine supplementation, often combined with other substances, has been used as a mechanism to boost the immune system. Considerable controversy, however, exists as to the benefits and indications of dietary arginine due in part to a poor understanding of the role played by this amino acid in maintaining immune function. Emerging knowledge promises to clear this controversy and allow for arginine's safe use. In myeloid cells, arginine is mainly metabolized either by inducible nitric oxide (NO) synthases (iNOS) or by arginase 1, enzymes that are stimulated by T helper 1 or 2 cytokines, respectively. Thus, activation of iNOS or arginase (or both) reflects the type of inflammatory response in a specific disease process. Myeloid suppressor cells (MSC) expressing arginase have been described in trauma (in both mice and humans), intra-abdominal sepsis, certain infections, and prominently, cancer. Myeloid cells expressing arginase have been shown to accumulate in patients with cancer. Arginase 1 expression is also detected in mononuclear cells after trauma or surgery. MSC efficiently deplete arginine and generate ornithine. Through arginine depletion, MSC may control NO production and regulate other arginine-dependent biological processes. Low circulating arginine has been documented in trauma and cancer, suggesting that MSC may exert a systemic effect and cause a state of arginine deficiency. Simultaneously, T lymphocytes depend on arginine for proliferation, zeta-chain peptide and T-cell receptor complex expression, and the development of memory. T-cells cocultured with MSC exhibit the molecular and functional effects associated with arginine deficiency. Not surprisingly, T-cell abnormalities, including decreased proliferation and loss of the zeta-chain, are observed in cancer and after trauma.

Effect of an immune-enhancing diet on lymphocyte in head-injured rats: What is the role of arginine?

OBJECTIVE

The benefit of immune-enhancing diets (IEDs) in the intensive care unit remains controversial. Considering their complexity, the role of each component, in particular arginine (Arg), in their properties is largely unknown. The aim of this study was to determine the role of arginine in the immunomodulatory effects of an IED (Crucial) in head-injured rats.

DESIGN

Thirty-four rats were randomized into five groups: AL (ad libitum), HI (head-injured), HI-STD (HI + standard enteral nutrition, EN), HI-STD-Arg (HI + standard EN + Arg in equimolar concentration to Arg in IED), and HI-IED (HI + IED). These isocaloric and isonitrogenous diets were administered over 4 days. After death, the thymus was removed and weighed. The density of CD25, CD4 and CD8 on lymphocytes from blood and from Peyer patches was evaluated. Mesenteric lymph nodes, liver and spleen were cultured for analysis of enterobacterial translocation and dissemination.

MEASUREMENTS AND RESULTS

HI induced an atrophy of the thymus which was not corrected by the standard diet (HI 0.27 +/- 0.03, HI-STD 0.35 +/- 0.03 vs. AL 0.49 +/- 0.02 g; p < 0.05). However, the standard diet supplemented with arginine limited the thymic atrophy and the IED restored thymus weight. CD25 density and interleukin-2 production were increased only in the HI-STD-Arg and HI-IED groups (p < 0.05). Head injury induced enterobacterial translocation and dissemination which were blunted only in the HI-STD-Arg group (p < 0.05).

CONCLUSIONS

In this rat HI model, arginine appears to be safe, contributes to a large extent to the immunomodulatory effects of the IED, and seems to limit enterobacterial translocation and dissemination more efficiently alone than in an IED.

Arginase, prostaglandins, and myeloid-derived suppressor cells in renal cell carcinoma

Tumor-induced tolerance is a well-established phenomenon in cancer patients that can severely impair the therapeutic efficacy of immunotherapy. One mechanism leading to T-cell tolerance is the generation of myeloid-derived suppressor cells (MDSC) by soluble factors produced by the tumor. MDSC express CD11b(+) as a common marker but may vary in their stage of maturation, depending on the tumor factors being produced. Arginase production by MDSC depletes arginine from the tumor microenvironment and impairs T-cell signal transduction and function. We studied whether an increase in MDSC could explain the molecular alterations and dysfunction found in T cells of patients with renal cell carcinoma (RCC). Arginase activity in the peripheral blood mononuclear cells of 117 RCC patients was increased between 6- to 8-fold compared with normal controls. The increased arginase activity was limited to the CD11b(+)CD14(-) myeloid cells and resulted in significantly decreased serum levels of arginine and increased ornithine in patients. Depletion of MDSC restored IFN-gamma production and T-cell proliferation. Preliminary data suggest that prostaglandin E(2) produced by the tumor induces arginase I expression in MDSC. Therefore, blocking MDSC activity may enhance the therapeutic efficacy of immunotherapy in RCC.

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.

Nutrition and Wound Healing

The relationship between nutrition and wound healing--after injury or surgical intervention--has been recognized for centuries. There is no doubt that adequate carbohydrate, fat, and protein intake is required for healing to take place, but research in the laboratory has suggested that other specific nutritional interventions can have significant beneficial effects on wound healing. Successful translation into the clinical arena, however, has been rare. A review of normal metabolism as it relates to wound healing in normoglycemic and diabetic individuals is presented. This is followed by an assessment of the current literature and the data that support and refute the use of specialized nutritional support in postoperative and wounded patients. The experimental evidence for the use of arginine, glutamine, vitamins, and micronutrient supplementation is described. Most of the experimental evidence in the field supporting the use of specialized nutritional support has not been borne out by clinical investigation. A summary of the clinical implications of the data is presented, with the acknowledgment that each patient's plan of care must be individualized to optimize the relationship between nutrition and wound healing.

Impairment of lymphocyte function in head-injured rats: effects of standard and immune-enhancing diets for enteral nutrition

BACKGROUND

The metabolic response to head injury (HI) is characterized by a dysimmunity which may be a risk factor of a septic state. The use of immune enhancing diets (IEDs) could be a promising approach to improve immune functions. The aim of the study was to investigate the consequences of HI on lymphocyte function and to determine the effects of an enteral IED comparatively to a standard enteral nutrition.

METHOD

A rat model of HI by fluid percussion was used. Twenty-five male Sprague-Dawley rats were randomized into 4 groups: rats receiving standard chow diet ad libitum (AL), rats sustaining HI and receiving standard chow diet and enteral saline (HI), rats receiving the enteral standard diet Sondalis HP (HIS), and rats receiving the IED Crucial (HIC). The two enteral diets were infused continuously during 4 days after the HI and were isocaloric, isonitrogenous and isovolumic.

RESULTS

HI induced a thymus atrophy (HI vs. AL, P<0.05), and an impairment in lymphocyte CD25 receptor density responsiveness to stimulation. The IED blunted thymus atrophy and allowed to preserve the stimulation of blood and Peyer patches lymphocytes (HIC: Stimulated vs. Basal, P<0.05).

CONCLUSION

IED seems more adapted for preserving lymphocyte function than standard diet in HI patients.

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.

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.

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.

Potential ergogenic effects of arginine and creatine supplementation

The rationale for the use of nutritional supplements to enhance exercise capacity is based on the assumption that they will confer an ergogenic effect above and beyond that afforded by regular food ingestion alone. The proposed or advertised ergogenic effect of many supplements is based on a presumptive metabolic pathway and may not necessarily translate to quantifiable changes in a variable as broadly defined as exercise performance. L-arginine is a conditionally essential amino acid that has received considerable attention due to potential effects on growth hormone secretion and nitric oxide production. In some clinical circumstances (e.g., burn injury, sepsis) in which the demand for arginine cannot be fully met by de novo synthesis and normal dietary intake, exogenous arginine has been shown to facilitate the maintenance of lean body mass and functional capacity. However, the evidence that supplemental arginine may also confer an ergogenic effect in normal healthy individuals is less compelling. In contrast to arginine, numerous studies have reported that supplementation with the arginine metabolite creatine facilitates an increase in anaerobic work capacity and muscle mass when accompanied by resistance training programs in both normal and patient populations. Whereas improvement in the rate of phosphocreatine resynthesis is largely responsible for improvements in acute work capacity, the direct effect of creatine supplementation on skeletal muscle protein synthesis is less clear. The purpose of this review is to summarize the role of arginine and its metabolite creatine in the context of a nutrition supplement for use in conjunction with an exercise stimulus in both healthy and patient populations.

l-Arginine modulates CD3ζ expression and T cell function in activated human T lymphocytes

Engagement of the T cell receptor (TCR) by antigen or anti-CD3 antibody results in a cycle of internalization and re-expression of the CD3zeta. Following internalization, CD3zeta is degraded and replaced by newly synthesized CD3zeta on the cell surface. Here, we provide evidence that availability of the amino acid L-arginine modulates the cycle of internalization and re-expression of CD3zeta and cause T cell dysfunction. T cells stimulated and cultured in presence of L-arginine, undergo the normal cycle of internalization and re-expression of CD3zeta. In contrast, T cells stimulated and cultured in absence of L-arginine, present a sustained down-regulation of CD3zeta preventing the normal expression of the TCR, exhibit a decreased proliferation, and a significantly diminished production of IFNgamma, IL5, and IL10, but not IL2. The replenishment of L-arginine recovers the expression of CD3zeta. The decreased expression of CD3zeta is not caused by a decreased CD3zeta mRNA, an increased CD3zeta degradation or T cell apoptosis.

High plasma arginine concentrations in critically ill patients suffering from hepatic failure

OBJECTIVE

In physiological conditions, the liver plays an important role in the regulation of plasma arginine concentrations by taking up large amounts of arginine from the hepatic circulation. When hepatic failure is present, arginine metabolism may be disturbed. Therefore, we hypothesized high arginine plasma concentrations in critically ill patients suffering from hepatic failure.

DESIGN

We prospectively collected blood samples from a cross-section of intensive care unit patients.

SETTING

Surgical intensive care unit of a Dutch university medical center.

SUBJECTS

A total of 52 critically ill patients with clinical evidence of dysfunction of more than two organs were recruited.

MEASUREMENTS

Plasma arginine concentrations were determined by HPLC. We identified correlations of arginine concentrations with organ failure scores and laboratory variables by univariate and multiple regression analyses.

RESULTS

High plasma arginine concentrations were found in critically ill patients developing organ failure. Patients who were in the highest quartile of plasma arginine concentrations had significantly lower fibrinogen concentrations, higher lactic acid concentrations, and longer prothrombin time. Stepwise multiple regression analysis showed that concentrations of arginine were independently associated with the presence of hepatic failure (P=0.03) and renal failure (P=0.048). In addition, lactic acid proved to be an independent determinant of plasma arginine concentration (P=0.014).

CONCLUSIONS

Critically ill patients who suffer from hepatic failure have elevated plasma arginine concentrations. Additional arginine in the treatment of these patients can be harmful, and therefore should not be used as a standard nutritional regimen until further evaluation.

L-arginine consumption by macrophages modulates the expression of CD3 zeta chain in T lymphocytes

L-Arginine plays a central role in the normal function of several organs including the immune system. It is metabolized in macrophages by inducible nitric oxide synthase to produce nitric oxide, important in the cytotoxic mechanisms, and by arginase I (ASE I) and arginase II (ASE II) to synthesize L-ornithine and urea, the first being the precursor for the production of polyamines needed for cell proliferation. L-Arginine availability can modulate T cell function. Human T cells stimulated and cultured in the absence of L-arginine lose the expression of the TCR zeta-chain (CD3zeta) and have an impaired proliferation and a decreased cytokine production. The aim of this work was to test whether activated macrophages could modulate extracellular levels of L-arginine and alter T cell function, and to determine which metabolic pathway was responsible for this event. The results show that macrophages stimulated with IL-4 + IL-13 up-regulate ASE I and cationic amino acid transporter 2B, causing a rapid reduction of extracellular levels of L-arginine and inducing decreased expression of CD3zeta and diminished proliferation in normal T lymphocytes. Competitive inhibitors of ASE I or the addition of excess L-arginine lead to the re-expression of CD3zeta and recovery of T cell proliferation. In contrast, inducible nitric oxide synthase or ASE II failed to significantly reduce the extracellular levels of L-arginine and modulate CD3zeta expression. These results may provide new insights into the mechanisms leading to T cell dysfunction and the down-regulation of CD3zeta in cancer and chronic infectious diseases.

Nutrition and wound healing

The relationship between host nutrition and wound healing has been the subject of study and experimentation for centuries. Despite the many years of study and a substantial knowledge base of the specific processes and factors involved, wound healing remains enigmatic. There is still much to learn about the wound-specific nutritional interventions that are available to improve wound healing. Nutrition profoundly influences the process of wound healing. Nutritional depletion exerts an inhibitory effect, and nutritional supplementation with such positive effectors as arginine can stimulate wound healing. Within this paradigm, the physician should be able to recognize patients who may be expected to have wound healing difficulties and offer early intervention to avoid wound failure.

Effects of arginine-enriched total parenteral nutrition on inflammatory-related mediator and T-cell population in septic rats

OBJECTIVES

Previous reports have shown that oral arginine (Arg) has immune-enhancing properties in injury. However, the effects of parenterally infused Arg on sepsis are not well understood. We used a septic rat model to study Arg infusion in inflammatory-related cytokines and blood T lymphocyte population in vivo.

METHODS

Rats with internal jugular catheters were assigned to one of two groups. Both groups received isonitrogenous total parenteral nutrition (TPN) supplemented with 270 mg of nitrogen per kilogram per day as Arg or glycine (Gly). TPN provided 270 kcal/kg of body weight, and the kilocalorie:nitrogen ratio was 143:1. TPN was maintained for 5 d plus 2, 4, or 6 h or 6 d, according to the scheduled deaths of the rats. On day 5, sepsis was induced by cecal ligation and puncture (CLP). After CLP for 2, 4, 6, and 24 h, rats were killed.

RESULTS

The results showed that interleukin-1beta and tumor necrosis factor-alpha concentrations in peritoneal lavage fluid at 6 h and interleukin-6 levels at 24 h after CLP in the Gly group were significantly higher than those in the Arg group. The T-lymphocyte population in blood showed that CD8(+) suppressor T-cell number was significantly higher in the Gly group than in the Arg group at 6 h after CLP. The blood CD4(+):CD8(+) ratio was significantly higher in the Arg group than in the Gly group at 24 h after CLP. A negative nitrogen balance was observed in the Arg and Gly groups after CLP; there was no significant difference in nitrogen balance between the septic groups. No difference in survival rate at 24 h after CLP was observed between the groups.

CONCLUSIONS

The results showed that, compared with the Gly group, TPN preinfused with Arg reduces the production of inflammatory mediators at the site of injury and that cellular immunity is enhanced at 24 h after CLP. Parenterally administered Arg had no beneficial effect in preventing nitrogen loss and improving survival in septic rats. Whether Gly has specific effects that reduce the effects of Arg require further investigation.

Supplemental dietary arginine enhances wound healing in normal but not inducible nitric oxide synthase knockout mice

BACKGROUND

Although generation of nitric oxide (NO) from inducible nitric oxide synthase (iNOS) has been shown to be required for cutaneous wound healing, no differences have been noted in incisional healing between iNOS knockout (iNOS-KO) and wild type (WT) mice. Because supplemental dietary arginine enhances cutaneous healing in normal rodents and is the sole substrate for NO synthesis, we studied whether arginine can enhance cutaneous wound healing in iNOS-KO mice.

METHODS

Twenty iNOS-KO and 20 WT mice, all on a C57BL/6 background, were divided into 4 groups of 10 animals each. Ten animals with each trait were randomized to receive either normal food and tap water or food and water each supplemented with 0.5% arginine (w/w). All animals underwent a 2.5-cm dorsal skin incision with implantation of four 20-mg polyvinyl alcohol sponges into subcutaneous pockets. On postoperative day 14 the animals were killed. The dorsal wound was harvested for breaking strength determination and the wound sponges were assayed for hydroxyproline content and total wound fluid nitrite/nitrate concentration.

RESULTS

Dietary arginine supplementation enhanced both wound breaking strength and collagen deposition in WT but not iNOS-KO mice. Wound fluid nitrite/nitrate levels were higher in WT than iNOS-KO animals but were not significantly influenced by additional arginine.

CONCLUSIONS

These data demonstrate that supplemental dietary arginine enhances wound healing in normal mice. The loss of a functional iNOS gene abrogates the beneficial effect of arginine in wound healing. This suggests that the metabolism of arginine via the NO pathway is one mechanism by which arginine enhances wound healing.

Effects of dietary arginine supplementation on protein turnover and tissue protein synthesis in scald-burn rats

We assessed the effects of dietary arginine supplementation on protein turnover and organ protein synthesis in burned rats. Male Wistar rats weighing about 200 g underwent catheter jejunostomy and received scald burns covering 30% of the whole-body surface area. Animals were divided into a control group (n = 9) and an arginine group (n = 9) and continuously received total enteral nutrition for 7 d (250 kcal.kg-1.d-1, 1.72 gN.kg-1.d-1). Changes in body weight, plasma total protein, plasma albumin, urinary excretion of polyamines, nitrogen balance, whole-body protein kinetics, and tissue protein synthesis rates were determined. Whole-body protein kinetics and tissue fractional protein synthetic rates (Ks, percent/d) were estimated using a 24-h constant enteral infusion of 15N glycine on the last day. The changes in body weight were not different between the control and arginine groups. The urinary excretion of polyamines was higher in the arginine group than in the control group (P < 0.01). Burned rats enterally fed arginine-supplemented diet yielded significantly greater cumulative and daily nitrogen balance on days 3 and 5 than those fed a control diet (cumulative, P < 0.05; day 3, P < 0.01; day 5, P < 0.01). Whole-body protein turnover rate was significantly elevated in the arginine group as compared to that in the control group (P < 0.05). The Ks of rectus abdominis muscles were significantly increased in the arginine group in comparison to the control group (P < 0.01). We have shown that dietary arginine supplementation improved protein anabolism and attenuated muscle protein catabolism after thermal injury.

Early enteral nutrition in surgical patients

There is increasing evidence that delivery of nutrients via the gastrointestinal tract reduces the septic morbidity in severely injured patients. This article reviews the most current data and also reviews the importance of the gut-associated lymphoid tissue as an important factor in maintaining the host defenses.

Oral arginine supplementation in acute liver injury

Acute liver failure is accompanied by a high rate of bacterial and septic complications. Arginine has a potent effect on the immune system and modulates bacterial clearance in septic models. We studied the effect of oral arginine supplementation on the extent of liver injury and the associated bacterial translocation in an acute liver injury model in rats. Sprague-Dawley rats were divided into normal, liver injury, and arginine supplemented groups. In the arginine group, 2% arginine was supplemented daily through a nasogastric tube for 8 d. Acute liver injury was induced on the eighth day by intraperitoneal injection of D-galactosamine (1.1 g/kg body wt). Samples were collected 24 h after the liver injury. In the arginine-supplemented group, alkaline phosphatase, bilirubin, and aspartate aminotransferase were reduced significantly compared with the acute liver injury control group. The results of bacterial translocation in the arginine-supplemented group showed a significantly reduced number of translocated bacteria to the liver and mesenteric lymph nodes than occurred in the acute liver injury group. The histological study of the liver in arginine-supplemented group showed scattered areas of hepatocellular necrosis and inflammatory cell infiltration, and in the acute liver injury group there were more and widespread hepatocellular necrosis and inflammatory cell infiltration. Oral supplementation of arginine in an acute liver injury model improves significantly the state of the liver injury and reduces bacterial translocation to the liver and mesenteric lymph nodes.

Problems and priorities for controlling opportunistic pathogens with new antimicrobial strategies; an overview of current literature

An International Study Group on New Antimicrobial Strategies (ISGNAS) has been formed in response to the recognition that development of microbial resistance to antibiotics is becoming a serious, world-wide problem. The group met in 1993 for the first time to discuss the feasibility of developing rational alternatives to the use of antibiotics and prepared, as a result, a comprehensive overview of normal (physiological) mechanisms involved in the control of potentially pathogenic (oppotunistic) microorganisms. One objective of ISGNAS is to understand the conditions which allow opportunistic microbes present among the symbionts to cause an infection. There is a need for more coherent information concerning the habitat, growth requirements and host and pathogen properties which allow opportunistic pathogens to cause life-threatening infections. In particular, information is urgently being sought to understand the complexity of the interactions between the vast number of microbial species, and the interactions between the microbes and their host. Another goal is to inspire and enable basic and clinical research that will lead to the development of new therapies for regulating colonization, translocation and infection by opportunistic micro-organisms in patients during periods of decreased resistance. With a sufficient amount of knowledge of how healthy individuals keep opportunistic micro-organisms under control, it may become feasible for physicians to maintain host resistance and inter-microbial factors involved in the containment of opportunistic microbes. Therapies aimed at boostering natural resistance mechanisms will be of critical importance to individuals whose resistance has been compromised as a result of another clinical condition.

Manipulation of the L-arginine-nitric oxide pathway in experimental colitis

The role of the L-arginine-nitric oxide pathway in the pathogenesis of colonic inflammation was assessed using L-arginine and its competitive analogue N omega-nitro-L-arginine methyl ester (L-NAME) in a rat model of colitis. In the first study oral L-arginine 2 per cent (control: 3.4 per cent L-glycine) was administered with and without L-NAME 100 mg/l. Orally administered L-arginine increased colonic inflammation (P = 0.004) and decreased thymic weight (P = 0.0007). Addition of L-NAME reduced the colonic inflammation and prevented loss of body-weight (P < 0.04). In the second study L-NAME was administered orally in concentrations of 100, 200 and 500 mg/l (control: no L-NAME). L-NAME 500 mg/l reduced colonic inflammation and increased thymic weight and body-weight (P < 0.01). Thymic weight and body-weight correlated positively with the concentration of L-NAME administered orally (rs > or = 0.3, P = 0.04). L-NAME l g/l was administered topically as an enema (control: suspension agent). Topical L-NAME reduced colonic inflammation and increased thymic weight (P < 0.05). These results suggest that the L-arginine-nitric oxide pathway mediates colonic inflammation in this model.

Metabolic effects of arginine in a healthy elderly population

Recently there has been much interest in the use of arginine to stimulate immune responses and to promote wound healing. In the present study, the effect of an oral supplementation with arginine on the metabolism of 45 healthy, nonsmoking, elderly volunteers was investigated. Subjects were divided into two groups that received either arginine aspartate (17 g free arginine) (n = 30) or a placebo (n = 15). The supplements were taken for a period of 14 days. Dietary intake of food was not controlled. Blood chemistry, lipid profiles, and as an index of nutritional status, serum insulin-like growth factor-1 levels and nitrogen balance were compared before and after supplementation. Two weeks of arginine supplementation led to a significant elevation of serum insulin-like growth factor concentrations and an improved and positive nitrogen balance (2.0 +/- 0.41 g N) when compared with controls (0.11 +/- 0.47 g N; p = 0.0114). In addition the arginine-supplemented group demonstrated a decreased total serum cholesterol with a reduction in the low-density lipoprotein but not the high-density lipoprotein fraction resulting in a increase in the ratio of low- to high-density lipoprotein fraction. No adverse effects were observed at this dosage of arginine. The data suggest that oral arginine supplementation may be used safely in elderly humans.

Nutritional support in critically ill patients

OBJECTIVE

The author reviews the newer nutritional substrates in use or under investigation for enteral and parenteral nutrition. Management of the critically ill patient remains a significant challenge to clinicians, and it is hoped that dietary manipulations, such as those outlined, may augment host barriers and immune function and improve survival.

SUMMARY BACKGROUND DATA

The role of nutrition in patient well-being has long been recognized, but until the past 25 years, the technology to artificially provide nutrients when patients could not eat was not developed. With current, new methods for enteral and vascular access, patients can be fed nonvolitionally with little difficulty. Continued efforts have been directed toward identifying optimal feeding formulations, which have resulted in a multitude of commercially available products. In the past several years, attention has been turned to evaluation of four specialized nutrients and the use of other substrates as pharmacologic agents.

METHODS

Pertinent laboratory and clinical data were reviewed to present the pros and cons for each nutritive substrate.

CONCLUSIONS

Medium-chain fatty acids, branched-chain amino acids, and glutamine have been shown to be of clinical benefit and should be in common use in the near future. Short-chain fatty acids still are under investigation. Albumin, vitamins E and C, arginine, glutamine, and omega-3 fatty acids show great promise as pharmacologic agents to manipulate the stress response. Nucleotides remain investigational. CONTENTS SUMMARY: The application of some new nutritional substrates for use in critically ill patients, both as caloric sources and as pharmacologic agents, are reviewed.

Rationale and efficacy of specialized enteral nutrition

Enteral nutrition, whenever feasible, is the preferred route of nutrition support. There has been a tremendous increase in the number of enteral products available on the market. Many of these are designed for use in specific disease states. This review will summarize the scientific rationale and supporting research for specialized enteral nutrition.

Supplemental arginine and ornithine do not affect splenocyte proliferation in surgically treated rats

The present study was designed to determine whether arginine or ornithine supplementation enhanced immune responsiveness in surgically stressed rats. Young rats (130 to 150 g; n = 72) were fed one of three nonpurified diets: control, arginine-supplemented (30 g/kg of diet), or supplemented with ornithine on an equimolar basis to supplemental arginine. Control and ornithine-supplemented diets were made isonitrogenous to the arginine-supplemented diet with alanine. Food intake and body weight were monitored throughout the experimental period. Eight days after initiation of dietary treatments, 36 rats were given dorsal skin wounds. Rats were killed 7 days later. Blood was collected, spleen and thymus were weighed, and splenocytes were isolated to measure proliferation in response to mitogens and interleukin-2 production. Food intake, body weight gain, and thymus weight were lower in rats subjected to surgery than in controls rats (p < .01). Neither supplemental dietary arginine nor ornithine affected food intake, body weight gain, thymus weight, splenocyte proliferation, or splenocyte interleukin-2 production in any treatment group (p < .1). These data suggest that low-level dietary supplementation of arginine and ornithine did not ameliorate detrimental effects of minor surgery in rats.

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

OBJECTIVE

The effect of arginine on survival rates and host defense mechanisms was studied using two clinically relevant models of infection that included transfusion-induced immunosuppression.

SUMMARY BACKGROUND DATA

Dietary arginine will improve resistance to infection but its role in transfusion-induced immunosuppression and bacterial translocation (gut-derived sepsis) has not been defined.

METHODS

Balb/c mice were fed for 10 days with either a defined AIN-76A diet, an AIN-76A diet supplemented with 2% arginine, an AIN-76A diet supplemented with 4% glycine, or standard laboratory chow. In most experiments, the mice were then transfused with allogeneic blood and allowed to feed for an additional 5 days before undergoing either cecal ligation and puncture (CLP) or gavage with 10(10) Escherichia coli and a 20% burn injury. Additional animals fed with the arginine supplemented diet were treated with the nitric oxide inhibitor N omega-Nitro-L-arginine (NNA) before gavage and burn. The effect of these diets and NNA on the degree of translocation of 14C-radiolabeled E. coli from the intestine and the ability of the host to kill translocated organisms was also investigated. Mice were fed and received transfusion, gavage, and burn as above. Mesenteric lymph nodes (MLN), liver and spleen were harvested 4 hours postburn.

RESULTS

Survival after CLP was 56% in the arginine-supplemented group versus 28% in the AIN-76A group and 20% in the chow group (p < 0.02). After gavage and burn, survival was 100% in the arginine-supplemented group versus 50% in both the glycine-supplemented and chow groups and 35% in the AIN-76A group (p < 0.01). In animals receiving the arginine-supplemented diet, treatment with NNA decreased survival from 95% to 30.5% (p < 0.0001). Greater translocation, as measured by radionuclide counts, was observed to the MLN of the AIN-76A group. However, there was no difference in translocation to the liver and spleen related to dietary group. Quantitative colony counts and the calculated percentage of remaining viable bacteria showed that the ability to kill translocated organisms was significantly enhanced in animals receiving arginine. Treatment with NNA reversed the beneficial effects of arginine on immune defense.

CONCLUSIONS

The benefit of arginine appears to be mediated by improved bactericidal mechanisms via the arginine-nitric oxide pathway.

The PROEF diet--a new postoperative regimen for oral early feeding

OBJECTIVE

The purpose of this study was to determine if immediate postoperative feeding of a new oral elemental diet (PROEF diet) would be tolerated by patients and to determine its effect on gastrointestinal function after cesarean section.

STUDY DESIGN

One hundred eighteen patients undergoing cesarean section were randomly assigned by a computer-generated list of numbers to receive either the PROEF diet (60 patients) or routine postoperative dietary management (58 patients). Gastrointestinal morbidity was analyzed by an independent-samples t test.

RESULTS

The PROEF diet group has a more rapid return of normal bowel sounds, 10.3 versus 14.5 hours (p = 0.001), and earlier acceptance of a regular diet, 2.0 versus 2.3 days (p = 0.008).

CONCLUSION

The PROEF diet was well tolerated in cesarean section patients with no increase in gastrointestinal morbidity when compared with a control group of patients. This dispels the classic teaching that postoperative patients may not have oral intake until the return of normal bowel function. Further study is necessary to support the theoretic benefits that may accrue from early feeding of an elemental diet.

Harry M. Vars Research Award. Arginine supplementation improves histone and acute-phase protein synthesis during gram-negative sepsis in the rat

Mechanisms of nutrient alteration of hepatic protein synthesis during sepsis are unclear. In vitro, arginine downregulates endotoxin-stimulated hepatocyte protein synthesis but in vivo effects are unknown. This study evaluated the effects of supplemental arginine or glycine on fibrinogen (acute-phase protein), histone, albumin, and liver protein synthesis after Gram-negative sepsis in the rat. Adult rats (225 g, n = 36) were randomized to receive isonitrogenous isocaloric total parenteral nutrition supplemented with 264 mg of N per kilogram per day as either arginine or glycine. On day 5, each group was further randomized to control or sepsis. Sepsis was induced by injection of 8 x 10(7) Escherichia coli per 100 g body weight, and then a continuous infusion of [1-14C]leucine was started. The rats were sacrificed 4 hours later. The fractional protein synthesis rates (percent per day) of histone, fibrinogen, albumin, and liver were determined. Supplemental arginine led to significantly increased histone (p less than 0.05, analysis of variance) and fibrinogen (p less than 0.01, analysis of variance) synthesis in the septic rats compared with all other groups. Histone and albumin synthesis were also significantly increased (p less than 0.05) in the arginine-supplemented control group compared with the glycine-supplemented control group. Arginine supplementation during sepsis significantly increased (p less than 0.05) albumin and liver protein synthesis compared with controls. Histones which are involved in DNA synthesis and are rich in arginine may play a role in the host response to stress and sepsis. These in vivo results appear to contradict hepatocyte-Kupffer cell coculture studies perhaps because of the hormonal and cytokine responses to nutrient substrate and acute septicemia.

The effects of an arginine-free enteral diet on wound healing and immune function in the postsurgical rat

Critically ill patients have increased rates of sepsis partly due to a down-regulated immune system. Nutrients may modulate the immune system. The following studies were performed to determine whether arginine is one of these "essential" nutrients for the immune system. Thirty-two male Sprague-Dawley rats (weighing 175 g) were divided into two groups that were pair-fed with either an elemental, arginine-supplemented enteral diet, or the same diet with arginine removed and replaced with glycine. Both diets were isocaloric, isoosmolar, and isonitrogenous. After 6 days on the diet, animals underwent testing. There were no significant differences between the arginine-supplemented and the arginine-free diet groups in blood glucose or hematocrit. The arginine-supplemented animals had higher serum albumin (4.1 +/- 0.1 mg/dL v 3.6 +/- 0.1 mg/dL; P = .035) and serum protein levels (5.2 +/- 0.1 mg/dL v 4.3 +/- 0.1 mg/dL; P = .041); and had higher thymus gland (0.53 +/- 0.03 g v 0.44 +/- 0.02 g; P less than .0001) and spleen weights (0.66 +/- 0.01 g v 0.57 +/- 0.01 g; P less than .01). Daily total urinary nitrogen excretion, nitrogen balance, and weight gain showed a tendency for the arginine-supplemented animals to retain more of their nitrogen calories. There was no difference in the amount of hydroxyproline (OHP) found in the wound cylinders of either group (both 25.6 micrograms OHP/cm polytetrafluoroethylene) but the arginine-supplemented group's wounds had greater wound bursting strengths (429 +/- 3 g/cm v 350 +/- 7 g/cm; P = .044).(ABSTRACT TRUNCATED AT 250 WORDS)