The role of arginine in infection and sepsis

Multifactorial etiology of gastric cancer

The prevalence of gastric cancer is associated with several factors including geographical location, diet, and genetic background of the host. However, it is evident that infection with Helicobacter pylori (H. pylori) is crucial for the development of the disease. Virulence of the bacteria is also important in modulating the risk of the disease. After infection, H. pylori gains access to the gastric mucosa and triggers the production of cytokines that promote recruitment of inflammatory cells, probably involved in tissue damage. Once the infection is established, a cascade of inflammatory steps associated with changes in the gastric epithelia that may lead to cancer is triggered. H. pylori-induced gastritis and H. pylori-associated gastric cancer have been the focus of extensive research aiming to discover the underlying mechanisms of gastric tissue damage. This research has led to the association of host genetic components with the risk of the disease. Among these is the presence of single nucleotide polymorphisms (SNPs) in several genes, including cytokine genes, which are able to differentially modulate the production of inflammatory cytokines and then modulate the risk of gastric cancer. Interestingly, the frequency of some of these SNPs is different among populations and may serve as a predictive factor for gastric cancer risk within that specific population. However, the role played by other genetic modifications should not be minimized. Methylation of gene promoters has been recognized as a major mechanism of gene expression regulation without changing the primary structure of the DNA. Most DNA methylation occurs in cytosine residues in CpG dinucleotide, but it can also be found in other DNA bases. DNA methyltransferases add methyl groups to the CpG dinucleotide, and when this methylation level is too high, the gene expression is turned off. In H. pylori infection as well as in gastric cancer, hypermethylation of promoters of genes involved in cell cycle control, metabolism of essential nutrients, and production of inflammatory mediators, among others, has been described. Interestingly, DNA changes like SNPs or mutations can create CpG sites in sequences where transcription factors normally sit, affecting transcription.In this chapter, we review the literature about the role of SNPs and methylation on H. pylori infection and gastric cancer, with big emphasis to the H. pylori role in the development of the disease due to the strong association between both.

Safety, efficacy and physiological actions of a lysine-free, arginine-rich formula to treat glutaryl-CoA dehydrogenase deficiency: focus on cerebral amino acid influx

Striatal degeneration from glutaryl-CoA dehydrogenase deficiency (glutaric aciduria type 1, GA1) is associated with cerebral formation and entrapment of glutaryl-CoA and its derivatives that depend on cerebral lysine influx. In 2006 we designed a lysine-free study formula enriched with arginine to selectively block lysine transport across cerebral endothelia and thereby limit glutaryl-CoA production by brain. Between 2006 and present, we treated twelve consecutive children with study formula (LYSx group) while holding all other treatment practices constant. Clinical and biochemical outcomes were compared to 25 GA1 patients (PROx group) treated between 1995 and 2005 with natural protein restriction (dietary lysine/arginine ratio of 1.7±0.3 mg:mg). We used published kinetic parameters of the y+and LAT1 blood-brain barrier transporters to model the influx of amino acids into the brain. Arginine fortification to achieve a mean dietary lysine/arginine ratio of 0.7±0.2 mg:mg was neuroprotective. All 12 LYSx patients are physically and neurologically healthy after 28 aggregate patient-years of follow up (current ages 28±21 months) and there were no adverse events related to formula use. This represents a 36% reduction of neurological risk (95% confidence interval 14-52%, p=0.018) that we can directly attribute to altered amino acid intake. During the first year of life, 20% lower lysine intake and two-fold higher arginine intake by LYSx patients were associated with 50% lower plasma lysine, 3-fold lower plasma lysine/arginine concentration ratio, 42% lower mean calculated cerebral lysine influx, 54% higher calculated cerebral arginine influx, 15-26% higher calculated cerebral influx of several anaplerotic precursors (isoleucine, threonine, methionine, and leucine), 50% less 3-hydroxyglutarate excretion, and a 3-fold lower hospitalization rate (0.8 versus 2.3 hospitalizations per patient per year). The relationship between arginine fortification and plasma lysine indicates that transport competition exists at both cerebrovascular and gastrointestinal barriers, suggesting their co-administration is key to efficacy. Monitoring the ratio between lysine and arginine in diet and plasma may prove a useful strategy for treating children with GA1.

Effects of L-arginine pretreatment on nitric oxide metabolism and hepatosplanchnic perfusion during porcine endotoxemia

BACKGROUND

Sepsis is accompanied by an increased need for and a decreased supply of arginine, reflecting a condition of arginine deficiency.

OBJECTIVE

The objective was to evaluate the effects of l-arginine pretreatment on arginine-nitric oxide (NO) production and hepatosplanchnic perfusion during subsequent endotoxemia.

DESIGN

In a randomized controlled trial, pigs (20-25 kg) received 3 μg . kg(-1) . min(-1) lipopolysaccharide (LPS; 5 endotoxin units/ng) intravenously and saline resuscitation. l-Arginine (n = 8; 5.3 μmol . kg(-1) . min(-1)) or saline (n = 8) was infused starting 12 h before LPS infusion and continued for 24 h after the endotoxin infusion ended. Whole-body appearance rates, portal-drained viscera (PDV), and liver fluxes of arginine, citrulline, NO, and arginine de novo synthesis were measured by using stable-isotope infusion of [(15)N(2)]arginine and [(13)C-(2)H(2)]citrulline. Hepatosplanchnic perfusion was assessed by using a primed continuous infusion of para-aminohippuric acid and jejunal intramucosal partial pressure of carbon dioxide and was related to systemic hemodynamics.

RESULTS

Arginine supplementation before LPS increased whole-body NO production in the PDV but not in the liver. Furthermore, it increased blood flow in the portal vein but not in the aorta and hepatic artery. During endotoxin infusion, arginine pretreatment was associated with an increased whole-body arginine appearance and NO production in the gut. Additional effects included a preserved mean arterial pressure, the prevention of an increase in pulmonary arterial pressure, an attenuated metabolic acidosis, and an attenuated increase in the intramucosal partial pressure of carbon dioxide.

CONCLUSION

Arginine treatment starting before endotoxemia appears to be beneficial because it improves hepatosplanchnic perfusion and oxygenation during prolonged endotoxemia, probably through an enhancement in NO synthesis, without causing deleterious systemic side effects.

Dose effects of chronically infused nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester on anabolic response and arginine metabolism in rats with subacute peritonitis

Nitric oxide synthase (NOS) inhibitors alleviate the adverse effects of nitric oxide (NO) overproduction that occurs during peritonitis, a clinical condition that is accompanied by arginine deficiency. However, the variations in the disease severity and the dosage, route, and period of NOS inhibitor administration are debatable. Therefore, we investigated the dose effects of chronically infused NOS inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME) on the anabolism, inflammatory responses, and arginine metabolism in parenterally fed rats with cecal puncture-induced subacute peritonitis. Male Wistar rats were divided into 4 groups and were administered total parenteral nutrition solutions with 0, 5 (low dose), 25 (medium dose), or 50 (high dose) mg·kg(-1)·d(-1) of L-NAME for 7 d. Sham-operated rats administered total parenteral nutrition solution and normal healthy rats fed chow diet were also included. Our results showed that parenteral infusion significantly decreased body weight gain and plasma citrulline concentrations. In rats with subacute peritonitis, the parenteral infusion-induced increases in circulating white blood cells and NO were significantly decreased, whereas the decrease in serum albumin levels was significantly increased. Rats with subacute peritonitis that were administered chronic infusion of L-NAME had a significantly reduced nitrogen balance. In addition, rats administered the medium dose of L-NAME had significantly increased plasma arginine, ornithine, glutamate, and proline. In conclusion, chronic infusion of NOS inhibitors may not alter systemic NO homeostasis and inflammatory response but may facilitate the production of arginine-associated amino acids and nitrogen excretion in cases of subacute peritonitis.

Is plasma arginine concentration decreased in patients with sepsis? A systematic review and meta-analysis

INTRODUCTION

L-arginine is a conditionally essential amino acid that plays an important role in immune and vascular function in sepsis. Plasma concentrations of L-arginine are decreased after trauma or surgery but have been variably reported to be normal or decreased in patients with sepsis.

METHODS

We searched MEDLINE and Embase from database inception until January 2010 for the MESH terms "arginine," "amino acids," and "sepsis" and reviewed all studies that reported plasma arginine concentrations in humans with sepsis. Studies were grouped according to the presence or absence of trauma and surgery. We performed a pooled quantitative analysis on the subset of studies that reported appropriate data.

RESULTS

We identified 285 citations, of which 16 met inclusion criteria and 10 were included in the quantitative analysis. Plasma arginine concentration was lower in sepsis patients compared with concurrent or historical controls in three of four studies of surgical sepsis, one of four of sepsis after trauma, and all eight studies of predominantly medical sepsis. In the quantitative analysis, mean plasma L-arginine concentration was 33.9 μmol/L (95% confidence interval, 41.2-26.6) lower in sepsis patients than in concurrent nonseptic controls (p < .001), which is a relative decrease of 41%.

CONCLUSION

Plasma concentrations of plasma L-arginine are substantially decreased in patients with sepsis in the absence of trauma or surgery. There are not enough studies of sufficient quality to determine whether this is also the case for trauma-associated or surgery-associated sepsis.

Does pharmacological dose of parenteral arginine have beneficial effect in rats with sub-acute peritonitis?

PURPOSE

Peritonitis is a life-threatening condition that may occur as a sequela of intra-abdominal infection. The management of peritonitis includes surgical intervention, antimicrobial therapy, and nutritional support. Arginine has been reported to have beneficial and adverse effects in subjects with inflammation, which might be related to the dose, time, and route of supplementation and the disease severity. So far, the optimal doses of parenteral arginine are not known. In this study, we investigated dose effects of parenterally supplemented arginine on anabolism and arginine-derived metabolites in sub-acute inflammation.

METHODS AND MATERIALS

Male Wistar rats underwent modified cecal puncture procedure for induction of peritonitis were infused with total parenteral nutrition solutions for 7 days, which contained conventional, low, medium, and high doses of arginine, i.e., 1.61, 2.85, 4.08, and 6.54% of calories from arginine. Healthy, orally fed rats were included as references.

RESULTS

On day 7, peritonitic rats had significantly decreased body weight, declined serum albumin, and increased serum nitric oxide (NO) and tumor-necrosis factor-alpha compared to references (ANOVA, P < 0.05). There were no dose effects of parenteral arginine on body weight, nitrogen retention, and serum blood urea nitrogen and creatinine in peritonitic rats. In contrast, plasma arginine, proline, and ornithine, and urinary urea nitrogen were significantly increased, whereas serum NO and plasma glutamine were significantly decreased in dose-dependent manners with parenteral arginine. Pharmacological dose of parenteral arginine may increase the synthesis of ornithine, urea, and proline instead of citrulline and NO in peritonitic rats.

CONCLUSION

These results suggest that high dose of parenteral arginine may facilitate ureagenesis and proline conversion without causing augmentation of NO production in sub-acute inflammation. Therefore, pharmacological dose of parenteral arginine may not have benefits in anabolism but does not cause adverse effect in rats with sub-acute inflammation.

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.

Reduced caloric intake during endotoxemia reduces arginine availability and metabolism

BACKGROUND

Inadequate caloric intake increases the risk of sepsis-induced complications. Metabolic changes during sepsis indicate that the availability of the amino acid l-arginine decreases. Availability of arginine may further decrease during reduced caloric intake, which thereby limits the adaptive response of arginine-nitric oxide metabolism during sepsis.

OBJECTIVE

We tested the hypothesis that reduced caloric intake during endotoxemia, as an experimental model for sepsis, further reduces arginine availability.

DESIGN

In a randomized trial, a 7-d reduced caloric intake feed regimen (RE; n = 9) was compared with a normal control feed regimen (CE; n = 9), before 24 h of endotoxemia, as a model for sepsis. Whole-body arginine-nitric oxide metabolism and protein metabolism were measured by using a stable-isotope infusion of [(15)N(2)]arginine, [(13)C-(2)H(2)]citrulline, [(2)H(5)]phenylalanine, and [(2)H(2)]tyrosine. Plasma pyruvate and lactate concentrations were determined by fully automated HPLC.

RESULTS

Pre-endotoxin arginine appearance was significantly lower in the RE group than in the CE group (P = 0.002). During endotoxemia, arginine appearance increased in the CE animals but not in the RE animals (P = 0.04). In addition, nitric oxide production was significantly lower in the RE animals (P < 0.0001). Protein synthesis was significantly lower at the start of endotoxin infusion (P < 0.05) and remained lower during endotoxemia in the RE group than in the CE group (P < 0.001). The lactate:pyruvate ratio was not higher in the RE group than in the CE group before endotoxemia but increased significantly during endotoxemia in the RE group (P = 0.04).

CONCLUSION

A well-nourished condition before prolonged endotoxemia results in a better ability to adapt to endotoxin-induced metabolic deterioration of arginine-nitric oxide metabolism than does reduced caloric intake before endotoxemia.

Nutrition in Trauma and Critically Ill Patients

Despite significant improvements in the practice of metabolic support of critically ill patients in recent years, malnutrition continues to be common among surgical patients, adding significantly to complications, infections, length of stay, costs, and increased mortality. Furthermore, hypercatabolism is the major metabolic response after major trauma and emergency surgery, making this patient population a unique subgroup of critically ill patients vulnerable to further decline in nutritional status. Many questions have already been answered, such as whether critically ill patients should be fed, when they should be fed, and how nutrients should be delivered. What is not entirely clear is what we should feed critically ill patients at different phases of specific diseases and disorders, as well as whether or not we should enhance and/or modulate patients' immunity.

Bone marrow cell derived arginase I is the major source of allergen-induced lung arginase but is not required for airway hyperresponsiveness, remodeling and lung inflammatory responses in mice

Background

Arginase is significantly upregulated in the lungs in murine models of asthma, as well as in human asthma, but its role in allergic airway inflammation has not been fully elucidated in mice.

Results

In order to test the hypothesis that arginase has a role in allergic airway inflammation we generated arginase I-deficient bone marrow (BM) chimeric mice. Following transfer of arginase I-deficient BM into irradiated recipient mice, arginase I expression was not required for hematopoietic reconstitution and baseline immunity. Arginase I deficiency in bone marrow-derived cells decreased allergen-induced lung arginase by 85.8 ± 5.6%. In contrast, arginase II-deficient mice had increased lung arginase activity following allergen challenge to a similar level to wild type mice. BM-derived arginase I was not required for allergen-elicited sensitization, recruitment of inflammatory cells in the lung, and proliferation of cells. Furthermore, allergen-induced airway hyperresponsiveness and collagen deposition were similar in arginase-deficient and wild type mice. Additionally, arginase II-deficient mice respond similarly to their control wild type mice with allergen-induced inflammation, airway hyperresponsiveness, proliferation and collagen deposition.

Conclusion

Bone marrow cell derived arginase I is the predominant source of allergen-induced lung arginase but is not required for allergen-induced inflammation, airway hyperresponsiveness or collagen deposition.

Nitric oxide and arginine dysregulation: a novel pathway to pulmonary hypertension in hemolytic disorders

Secondary pulmonary hypertension (PH) is emerging as one of the leading causes of mortality and morbidity in patients with hemolytic anemias such as sickle cell disease (SCD) and thalassemia. Impaired nitric oxide (NO) bioavailability represents the central feature of endothelial dysfunction, and is a major factor in the pathophysiology of PH. Inactivation of NO correlates with hemolytic rate and is associated with the erythrocyte release of cell-free hemoglobin, which consumes NO directly, and the simultaneous release of the arginine-metabolizing enzyme arginase, which limits bioavailability of the NO synthase substrate arginine during the process of intravascular hemolysis. Rapid consumption of NO is accelerated by oxygen radicals that exists in both SCD and thalassemia. A dysregulation of arginine metabolism contributes to endothelial dysfunction and PH in SCD, and is strongly associated with prospective patient mortality. The central mechanism responsible for this metabolic disorder is enhanced arginine turnover, occurring secondary to enhanced plasma arginase activity. This is consistent with a growing appreciation of the role of excessive arginase activity in human diseases, including asthma and pulmonary arterial hypertension. New treatments aimed at improving arginine and NO bioavailability through arginase inhibition, suppression of hemolytic rate, oral arginine supplementation, or use of NO donors represent potential therapeutic strategies for this common pulmonary complication of hemolytic disorders.

Effect of citrulline and glutamine on nitric oxide production in RAW 264.7 cells in an arginine-depleted environment

BACKGROUND

Nitric oxide (NO) is a highly reactive free radical essential for antimicrobial and tumor immunity as well as endothelial function. Arginine is a limiting factor in NO synthesis. Citrulline can be converted to arginine and might restore NO production when arginine availability is limited, while glutamine may competitively inhibit citrulline availability. We aimed to assess how these amino acids interact to generate NO using an in vitro model.

METHODS

RAW 264.7 cells were exposed to various amino acid concentrations before and after lipopolysaccharide (LPS) stimulation, and NO production was assessed.

RESULTS

NO production directly correlated up to 200 microM with arginine available after LPS stimulation (R(2) = 0.99). Provided the same arginine concentrations following LPS stimulation, low arginine precultured cells produced significantly less NO than high arginine precultured cells (P < .01). Citrulline added to low arginine preculture significantly increased NO production compared to cells in low arginine alone (P < .01). When glutamine was withdrawn before and after LPS stimulation, cells precultured in low arginine and citrulline produced NO equivalent to that of high arginine precultured cells. Additional citrulline provided after LPS stimulation additionally improved NO production beyond that observed in cells precultured in high arginine (P < .01), and NO production became less dependent on arginine availability (R(2) = 0.78).

CONCLUSION

Arginine availability is a limiting factor for NO production. Citrulline is a potential substitute to restore NO production when arginine availability is limited. Glutamine appears to be an important modulator that interferes with citrulline-mediated NO production.

Obesity, inflammation, and the potential application of pharmaconutrition

Obesity is an emerging problem worldwide. Hospitalized obese patients often have a worse outcome than patients of normal weight, particularly in the setting of trauma and critical care. Obesity creates a low-grade systemic inflammatory response syndrome (SIRS) that is similar (but on a much smaller scale) to gram-negative sepsis. This process involves up-regulation of systemic immunity, is characterized clinically by insulin resistance and the metabolic syndrome, and puts the patient at increased risk for organ failure, infectious morbidity, and mortality. Through lipotoxicity and cytokine dysregulation, obesity may act to prime the immune system, predisposing to an exaggerated subsequent immune response when a second clinical insult occurs (such as trauma, burns, or myocardial infarction). Specialized nutrition therapy for such patients currently consists of a hypocaloric, high-protein diet. However, this approach does not address the putative pathophysiologic mechanisms of inflammation and altered metabolism associated with obesity. A number of dietary agents such as arginine, fish oil, and carnitine may correct these problems at the molecular level. Pharmaconutrition formulas may provide exciting innovations for the nutrition therapy of the obese patient.

Elevated plasma arginase-1 does not affect plasma arginine in patients undergoing liver resection

Arginine is an important substrate in health and disease. It is a commonly held view that arginase-1 release from injured erythrocytes and hepatocytes leads to arginine breakdown; however, the true relationship between plasma arginase-1 concentration and activity has remained unaddressed. In the present study, blood was sampled from patients undergoing liver resection, a known cause of hepatocyte injury and arginase-1 release, to determine arginase-1, arginine and ornithine plasma levels. Arginase activity was assessed in vitro by measuring changes in arginine and ornithine plasma levels during incubation of plasma and whole-blood samples at 37 degrees C. Arginase-1 plasma levels increased 8-10-fold during liver resection, whereas arginine and ornithine levels remained unchanged. In accordance with these in vivo findings, arginine and ornithine levels remained unchanged in plasma incubated at 37 degrees C irrespective of the arginase-1 concentration. In contrast, arginine plasma levels in whole blood decreased significantly during incubation, with ornithine increasing stoichiometrically. These changes were irrespective of arginase-1 plasma levels and were explained by arginase activity present in intact erythrocytes. Next, plasma samples with 1000-fold normal arginase-1 concentrations were obtained from patients undergoing cadaveric liver transplantation. A significant decrease in arginine plasma levels occurred in vivo and in vitro. In contrast with commonly held views, moderately increased arginase-1 plasma levels do not affect plasma arginine. Very high plasma arginase-1 levels are required to induce potential clinically relevant effects.

Specific amino acids in the critically ill patient--exogenous glutamine/arginine: a common denominator?

OBJECTIVE

Glutamine and arginine are both used as nutritional supplements in critically ill patients. Although glutamine has been shown to be beneficial for the metabolically stressed patient, considerations about arginine supplementation are not unanimously determined. Our aim is to review the current knowledge on the possible interplay between glutamine and arginine generation in the stressed patient and to elaborate on whether these amino acids may function as a common denominator. Because glutamine can be given by the parenteral and enteral routes, possible different actions on the metabolic fate (e.g., generation of citrulline) with both routes are analyzed.

DATA SOURCE

A summary of data on the clinical effect of glutamine and arginine metabolism is given, incorporating data on glutamine and arginine supplementation. Differences between the route of administration, parenteral or enteral, and the molecular form of supplied glutamine, free or as dipeptide, on citrulline generation by the gut and production of arginine are discussed.

RESULTS

Glutamine and arginine influence similar organ systems; however, they differ in their targets. For example, glutamine serves as fuel for the immune cells, increases human leukocyte antigen-DR expression on monocytes, enhances neutrophil phagocytosis, and increases heat shock protein expression. Arginine affects the immune system by stimulating direct or indirect proliferation of immune cells. This indirect effect is possibly mediated by nitric oxide, which also enhances macrophage cytotoxicity. Furthermore, glutamine serves as a precursor for the de novo production of arginine through the citrulline-arginine pathway. Glutamine has shown to be beneficial in the surgical and critically ill patient, whereas arginine supplementation is still under debate. The route of glutamine administration (parenteral or enteral) determines the effect on citrulline and on the de novo arginine generation. There is a marked difference between the administration of free glutamine and dipeptide enterally or parenterally. Splanchnic extraction of the hydrolyzed glutamine in mice when administering the dipeptide enterally is higher compared with administering free glutamine from the enteral site. In patients, splanchnic extraction of the dipeptide given enterally is 100% when comparing supplementation of the dipeptide intravenously.

CONCLUSIONS

The beneficial effects of free glutamine or dipeptide may depend on the route of administration but also on the metabolic fate of amino acids generated (e.g., citrulline, arginine). Glutamine serves as a substrate for de novo citrulline and arginine synthesis. More research needs to be done to establish the direct clinical relevance of the different metabolic pathways. Future perspectives might include combining enteral and parenteral routes of administrating free glutamine or dipeptide.

Clinical differences between children and adults with pulmonary hypertension and sickle cell disease

Pulmonary hypertension (PHT) is an important co-morbidity in sickle cell disease (SCD). Despite increasing research in adults, the prevalence and implication of this condition in children is unknown. Charts of 362 SCD patients followed at the Children's Hospital & Research Center Oakland were reviewed to determine clinical variables associated with obtaining echocardiographic screening for PHT, clinical associations of PHT, and associated mortality following diagnosis in adults and children with SCD. In this cohort, patients with underlying lung abnormalities or those on chronic transfusions were more likely to have echocardiograms, however the diagnosis of PHT was often unrecognized. A different clinical phenotype for PHT in adults versus children was identified. Associations with PHT for adults included age, renal and lung disease, hepatitis C, chronic transfusions, and a history of acute chest syndrome (ACS), with ACS being protective. Surprisingly, for children, a history of sepsis, along with a history of ACS, or obstructive lung disease were associated with PHT. Survival analysis found significant mortality for PHT, with a hazard ratio of 17.3 (95% confidence interval 4.9-60.4). The divergent clinical spectrum for PHT between adults and children may point to different age-specific mechanisms or biological expression of PHT.

Plasma citrulline concentration: a reliable marker of small bowel absorptive capacity independent of intestinal inflammation

OBJECTIVES

Postabsorptive plasma citrulline concentration has been proposed as a reliable marker of small bowel absorptive capacity in short bowel patients. The aim of this study was to address the potentially confounding impact of intestinal inflammation.

METHODS

Fifty-five patients were selected according to diagnosis, small bowel length, and degree of bowel inflammation. (a) Crohn's disease (CD) with massive small bowel resection leaving </=50 cm (N = 6), (b) CD with 50-150 cm remaining (N = 9), (c) CD with no resection but active inflammation (high C-reactive protein [CRP] and Crohn's Disease Activity Index [CDAI] >220) (N = 7), (d) CD without resection or active inflammation (normal CRP and CDAI <150) (N = 9), (e) mesenteric infarction (MI) with resection leaving </=50 cm (N = 6), (f) MI leaving 50-150 cm (N = 6), (g) active celiac disease (N = 6), (h) healthy volunteers (N = 6). Postabsorptive fasting plasma citrulline was measured using reverse-phase, high performance liquid chromatography. Absorptive capacity and permeability were also measured after oral sugar-mix ingestion (5 g lactulose, 1 g L-rhamnose, 0.5 g D-xylose).

RESULTS

The plasma citrulline strongly correlated with small bowel length (P < 0.0001) and xylose absorption (P < 0.001). No correlation was found with CDAI, permeability, CRP, albumin, sedimentation rate, white cell count, or platelet count. Citrulline was significantly higher (P < 0.0004) in CD and MI patients with a remnant small bowel length of 50-150 cm (mean 21.0 micromol/L) than in those with length </=50 cm (mean 9.2 micromol/L).

CONCLUSIONS

Plasma citrulline concentration is a simple and reliable surrogate for small bowel absorptive capacity and is not influenced by intestinal inflammation.

Pharmacological Treatment of Geriatric Cachexia: Evidence and Safety in Perspective

Anticachexic or antisarcopenic medications are prescribed worldwide for geriatric patients with poor appetite and associated weight loss. They represent a valuable treatment option for managing cachexia. However, the well-publicized adverse reports about these medications in acquired immunodeficiency syndrome (AIDS) and in the cancer population has led to some concern and much subsequent discussion over the safety of these medications being used in geriatric population. This review looks at the evidence in relation to the benefits and risks of these medications and discusses what we know about their use in the geriatric population.

Enteral nutrition affects nitric oxide production in peripheral blood and liver after a postoperative lipopolysaccharide-induced endotoxemia in rats

OBJECTIVES

Sepsis is a common complication in the early postoperative period, leading to the augmentation of oxidative and nitrosative stresses. The present study investigated the role of enteral nutrition on nitric oxide (NO) production after a lipopolysaccharide (LPS)-induced endotoxemia as an index of nitrosative stress.

METHODS

Fifty rats were subjected to midline laparotomy and feeding gastrostomy. Ten rats served as controls after recovering from operative stress. The remaining rats received, through gastrostomy, enteral nutrition or placebo feeding for 24 h, after which they were injected intraperitoneally with LPS or equal volume of saline. Two hours later blood and liver tissue were collected. NO production was quantified in serum samples and homogenates of liver tissue by a modification of Griess's reaction. NO synthase (NOS) mRNA expression was examined in homogenate of liver tissue by reverse transcription-polymerase chain reaction.

RESULTS

The operation significantly increased basal NO production in rat serum. LPS induced a further significant increase of NO levels. Enteral feeding of rats significantly decreased NO levels in both groups. In contrast, enteral nutrition was found to increase significantly NO levels in liver homogenates from rats treated with LPS. A constitutive endothelial NOS mRNA expression was found in liver tissue, whereas LPS administration induced inducible NOS mRNA expression in liver tissue regardless of enteral feeding.

CONCLUSION

These findings indicate that early enteral feeding leads to a reduction in circulating NO levels induced by operation and endotoxemia, but increases hepatic NO levels in endotoxemia probably by the effect of LPS-induced inducible NOS on the increased L-arginine uptake.

Which mechanisms are involved in taurine-dependent granulocytic immune response or amino- and α-keto acid homeostasis?

We examined the effects of beta-alanine (taurine analogue and taurine transport antagonist), taurine (regarding its role in neutrophil (PMN) immunonutrition) and taurine combined either with L-NAME (inhibitor of *NO-synthase), SNAP (*NO donor), DON (glutamine-analogue and inhibitor of glutamine-requiring enzymes), DFMO (inhibitor of ornithine-decarboxylase) and beta-alanine on neutrophil amino- and alpha-keto acid profiles or important PMN immune functions in order to establish whether taurine transport-, nitric oxide-, glutamine- or ornithine-dependent mechanisms are involved in any of the taurine-induced effects. According to the present findings, the taurine-mediated effect appears to be based primarily on a modulation of important transmembraneous transport mechanisms and only secondarily on directly or indirectly induced modifications in intragranulocytic amino- and alpha-keto acid homoeostasis or metabolism. Although a direct relation to the parallel observed immunological modifications can only be presumed, these results show very clearly that compositional modifications in the free intragranulocytic amino- and alpha keto-acid pools coinciding with changes in intragranulocytic taurine levels are relevant metabolic determinants that can significantly influence the magnitude and quality of the granulocytic immune response.

Management of perioperative nutrition support

PURPOSE OF REVIEW

Perioperative nutrition has been extensively studied, but numerous questions remain unanswered. This review focuses on new developments in nutrient delivery in the immediate perioperative period. Issues specifically addressed include which patients are most likely to benefit from perioperative nutritional supplementation, and the optimal route, timing, and quantity of nutrient delivery.

RECENT FINDINGS

Visceral proteins, particularly albumin, play an important role in nutritional and perioperative risk assessment. Although the recommendation to use the enteral route for delivery of nutrition whenever possible is clear, the cautious introduction of enteral feeds in the labile group of patients with circulatory failure is essential. Preoperative use of immune-modulating enteral formulas, preoperative carbohydrate loading, and the concept of early enteral feeding are important developments. Supplementary arginine, glutamine, and omega-3 fats play a potential role in nutritional management, as does 'permissive' hypocaloric feeding.

SUMMARY

The particulars of nutritional support for perioperative and critically ill patients remain controversial. Recent studies addressing specific issues in this diverse discipline perhaps raise more questions than are answered. However, each new contribution to the literature brings us closer to an understanding of optimal nutritional management in the metabolically stressed patient.

Nutrition and Immune Function

The complexity of the immune system allows for a multitude of potential avenues for nutrient modulation, but this also increase the challenge of producing a predictable in vivo response. Because the immune response is a cascade of biologic events, development of nutritional support paradigms cannot and should not be made in a vacuum or with the expectation of a singular response. It is absolutely imperative that the clinician/nutritionist understand the differences in metabolIc and physiologic responses to disease states (ie, shock, trauma, organ-specific dysfunction) so as to maximize immunocompetence through specialized feeding practices. This level of understanding is invaluable, especially when considering the possible benefit of nutrient combinations for immunomodualtion.

Oxidants and antioxidants in disease: oxidative stress in farm animals

Important infectious diseases in farm animals, such as pneumonia and enteritis, are thought to be associated with the so-called oxidative stress, i.e. a chemical phenomenon involving an imbalance in the redox status of the individual animal. The specifics of oxidative stress and how it may result in disease or be prevented are complex questions with no simple answers. However, the considerable literature on the subject suggests that many researchers consider oxidative stress-related mechanisms to be important early events in disease development. A particularly intriguing aspect is that, at least theoretically, oxidative stress should be easily prevented with antioxidants yet the use of antioxidants as therapy remains controversial. The present knowledge on oxidative stress in farm animals is the topic of this review.

Plasma arginine correlations in trauma and sepsis

Arginine (ARG) is an amino acid (AA) with unique properties and with a key-role in the metabolic, immune and reparative response to trauma and sepsis. This study has been performed to characterize the correlations between plasma levels of ARG, of other AA and of multiple metabolic variables in trauma and sepsis. Two-hundred and sixty-three plasma amino-acidograms with a large series of additional biochemical and blood variables were obtained consecutively in 9 trauma patients who developed sepsis, undergoing total parenteral nutrition with dextrose, fat and a mixed AA solution containing 10.4% arginine. ARG was low soon after trauma, then it increased with increasing distance from trauma and with the development of sepsis. ARG was also directly related to the AA infusion rate (AAIR) and for any given AAIR, was lower after trauma than after the development of sepsis. ARG was also related directly to the plasma levels of most of the other AA, the best correlation being that with lysine (r(2) = 0.81, p < 0.001). These correlations were often shifted downwards (showing lower ARG for any given level of the other AA) in measurements performed after trauma, compared to those performed after development of sepsis; this effect was more pronounced for the correlations with branched chain AA. Correlations between ARG and non-AA variables were not particularly relevant. The best simultaneous correlates of ARG, among variables involved in plasma ARG availability, were citrulline level, AAIR and urinary 3-methylhistidine excretion (accounting for the effect of endogenous proteolysis) (multiple r(2) = 0.70, p < 0.001). Plasma ornithine (ORN), the AA more specifically linked to ARG metabolism, correlated with AAIR better than ARG and, for any given AAIR, was lower after trauma than after the development of sepsis. Correlations of ORN with other AA levels were poorer than those found for ARG, however ORN was directly related to white blood cell and platelet count, fibrinogen, transferrin, cholesterol and many AA clearances. These data show that changes in ARG in trauma and sepsis are correlated with changes in other AA and, within these correlations, reconfirm a tendency to lower ARG in trauma compared to sepsis. The strong correlation with lysine warrants a deeper assessment of the practical implications of interdependency between these two AA. The data also suggest that changes in plasma ORN in trauma and sepsis may reflect adequacy of AA substrate to support acute-phase and other synthetic processes.