The relationship between plasma taurine and other amino acid levels in human sepsis

Taurine in Septic Critically Ill Patients: Plasma versus Blood

Purpose: Sepsis and systemic inflammatory response syndrome (SIRS) encompass various problems throughout the body, and two of its major problems are the creation of oxidative substances in the body and decrease of the body's antioxidant capacity to deal with the stress and organ damage. Optimal enteral nutrition fortified with antioxidant or immunomodulator amino acid is a hot topic concerning sepsis in the critical care setting. Taurine plays a protective role as an antioxidant in cells that is likely to have a protective role in inflammation and cytotoxicity. Methods: In the present study, 20 septic patients and 20 healthy volunteers were enrolled. The blood and plasma taurine levels of the patients on days 1, 3 and 7 were measured. Blood and plasma taurine level and the correlation between them, organ failure, and severity of the disease were assessed. Results: Taurine concentrations in the plasma of the septic patients were significantly lower than control group, and the whole blood concentrations were significantly higher than those of the control group (P<0.001). There was not a significant correlation between the blood and plasma taurine levels in control and septic patients. In addition, there was not any correlation between the severity of the disease, organ failure, mortality, and plasma as well as the blood concentration of taurine. Conclusion: In septic patients, taurine concentration in plasma and blood are low and high, respectively. These concentrations are not linked to each other and not associated with the patients' outcome, and the disease severity, and organ failure.

Taurine Supplementation as a Neuroprotective Strategy upon Brain Dysfunction in Metabolic Syndrome and Diabetes

Obesity, type 2 diabetes, and their associated comorbidities impact brain metabolism and function and constitute risk factors for cognitive impairment. Alterations to taurine homeostasis can impact a number of biological processes, such as osmolarity control, calcium homeostasis, and inhibitory neurotransmission, and have been reported in both metabolic and neurodegenerative disorders. Models of neurodegenerative disorders show reduced brain taurine concentrations. On the other hand, models of insulin-dependent diabetes, insulin resistance, and diet-induced obesity display taurine accumulation in the hippocampus. Given the possible cytoprotective actions of taurine, such cerebral accumulation of taurine might constitute a compensatory mechanism that attempts to prevent neurodegeneration. The present article provides an overview of brain taurine homeostasis and reviews the mechanisms by which taurine can afford neuroprotection in individuals with obesity and diabetes. We conclude that further research is needed for understanding taurine homeostasis in metabolic disorders with an impact on brain function.

Amino acid-mediated negatively charged surface improve antifouling and tribological characteristics for medical applications

To prevent infections associated with biomedical catheters, various antimicrobial coatings have been investigated. However, those materials do not provide consistent antibacterial effects or biocompatibility, generally, due to degradation of the coating materials, in vivo. Additionally, biomedical catheters must have low surface friction to reduce tribological damage. In this study, we developed an antifouling surface composed of biocompatible amino acids (leucine, taurine, and aspartic acid) on polyimide, via modification using a series of facile immersion steps with waterborne reactions. The naturally derived amino acid could be formed highly biostable amide bonds on the polyimide surface like peptides. The amino acid-modified surface formed a water layer with antifouling performance through the hydrophilic properties of amino acids. Amino acid-mediated modification reduced adhesion up to 84.45% and 94.81% against Escherichia coli and Staphylococcus epidermidis, respectively, and exhibited an excellent prevention to adhesion against the proteins, albumin and fibrinogen. Evaluation of the surface friction of the catheter revealed a dramatic reduction in the tribological force after amino acid modification on polyimide that of 0.81 N to aspartic acid of 0.44 N. These results clearly demonstrate a reduced occurrence of infections, thrombi and tribological damage following the relatively facile surface modification of catheters. The proposed modification method can be used in a continuous manufacturing process via using the same time of modification steps for the easy producing the product. Moreover, the method uses biocompatible naturally derived materials and can be applied to medical equipment that requires biocompatibility and biofunctionality with polyimide surfaces.

Past Experiences for Future Applications of Metabolomics in Critically Ill Patients with Sepsis and Septic Shocks

A disruption of several metabolic pathways in critically ill patients with sepsis indicates that metabolomics might be used as a more precise tool for sepsis and septic shock when compared with the conventional biomarkers. This article provides information regarding metabolomics studies in sepsis and septic shock patients. It has been shown that a variety of metabolomic pathways are altered in sepsis and septic shock, including amino acid metabolism, fatty acid oxidation, phospholipid metabolism, glycolysis, and tricarboxylic acid cycle. Based upon this comprehensive review, here, we demonstrate that metabolomics is about to change the world of sepsis biomarkers, not only for its utilization in sepsis diagnosis, but also for prognosticating and monitoring the therapeutic response. Additionally, the future direction regarding the establishment of studies integrating metabolomics with other molecular modalities and studies identifying the relationships between metabolomic profiles and clinical characteristics to address clinical application are discussed in this article. All of the information from this review indicates the important impact of metabolomics as a tool for diagnosis, monitoring therapeutic response, and prognostic assessment of sepsis and septic shock. These findings also encourage further clinical investigations to warrant its use in routine clinical settings.

Evaluation of Antibacterial Effects of Matrix-Induced Silver Ions against Antibiotic-Resistant ESKAPE Pathogens

Recently, drug-resistant bacterial infections, especially ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.), have become a critical health issue worldwide, highlighting the emerging need for novel antibacterial agents. In this study, silver nanoparticles were extracted from silver-containing mesoporous bioactive glass (MBG-Ag) using four different matrixes, including water, phosphate buffer saline (PBS), tryptic soy broth (TSB), and taurine (Tau). The inductively coupled plasma-mass spectrometer (ICP-MS) results demonstrated that the silver concentration of Tau-Ag was the highest among the four matrixes. The Tau-Ag was also observed to have 87.35% silver ions in its X-ray photoelectron spectrometer (XPS) spectra. The micrograph of transmission electron microscope (TEM) displayed a uniform distribution of silver nanoparticles, which was confined in a smaller size compared to that in TSB-Ag. Moreover, the peak shifts observed in the Fourier-transform infrared spectrometer (FTIR) spectrum implied that the -SO₃²⁻ and -NH groups in taurine may interact with silver. A low cytotoxicity was noted for Tau-Ag, with approximately 70% of cells surviving at 0.63 mg/mL. Compared to the other three matrix-induced silver agents, Tau-Ag represented a better antibacterial effect against methicillin-resistant Staphylococcus aureus, with a minimum inhibitory concentration (MIC) value of 0.63 mg/mL and a postponed growth of 0.31 mg/mL observed. Further antibacterial examinations illustrated the presence of remarkable antibacterial activities against vancomycin-resistant Enterococcus feacium, carbapenem-resistant Klebsiella pneumoniae, carbapenem-resistant Acinetobacter baumannii, and carbapenem-resistant Pseudomonas aeruginosa. Given our observations and multiple bioactive functions of taurine (prevent patients from inflammation and oxidative-stress injuries), we anticipate that taurine matrix-induced silver ions would be a biomedical material with a high potential for combatting drug-resistant ESKAPE pathogens.

Supplementation of taurine improves ionic homeostasis and mitochondrial function in the rats exhibiting post-traumatic stress disorder-like symptoms

RATIONALE

Current pharmacotherapy for post-traumatic stress disorder (PTSD) is limited to few antidepressants. Mitochondrial dysfunction is observed in PTSD, along with altered potassium homeostasis. Nutritional supplementation of taurine can improve ionic homeostasis and thereby treat PTSD-like symptoms in rats.

AIM

The purpose is to study the pharmacological effect of taurine in stress re-stress-induced PTSD in rats.

METHODS

As per protocol, animals were restrained for 2 h then exposed to footshock (FS) (2 mA/10 s) followed by halothane-induced anesthesia. Behavioral assessments such as elevated plus maze (EPM) and Y-maze tests were performed on days 2, 8, and 32 of experimental protocol after re-stress. In addition, daily oral administration of taurine (100, 200, and 300 mg/kg) and paroxetine (PAX) (10 mg/kg) was done from D-8 to D-32 followed by re-stress. The plasma concentration of taurine, corticosterone, and potassium was measured on Day-32 along with mitochondrial function in discrete brain regions.

RESULTS

Sub-chronic administration of taurine in high and medium doses significantly ameliorated PTSD-like symptoms such as hyperarousal, anxiety, and improved spatial recognition memory. Taurine in all doses restored the plasma concentration of corticosterone and potassium. SRS-induced alterations in mitochondrial bioenergetics, complex enzyme activities, and reduced mitochondrial membrane potential in different brain regions were ameliorated by taurine.

CONCLUSION

Nutritional supplementation of taurine improves potassium ionic homeostasis, mitochondrial function, and attenuated PTSD-like symptoms in SRS subjected rats.

Association of Taurine with In-Hospital Mortality in Patients after Out-of-Hospital Cardiac Arrest: Results from the Prospective, Observational COMMUNICATE Study

Background: Studies have suggested that taurine may have neuro- and cardio-protective functions, but there is little research looking at taurine levels in patients after out-of-hospital cardiac arrest (OHCA). Our aim was to evaluate the association of taurine with mortality and neurological deficits in a well-defined cohort of OHCA patients. Methods: We prospectively measured serum taurine concentration in OHCA patients upon admission to the intensive care unit (ICU) of the University Hospital Basel (Switzerland). We analyzed the association of taurine levels and in-hospital mortality (primary endpoint). We further evaluated neurological outcomes assessed by the cerebral performance category scale. We calculated logistic regression analyses and report odds ratios (OR) and 95% confidence intervals (CI). We calculated different predefined multivariable regression models including demographic variables, comorbidities, initial vital signs, initial blood markers and resuscitation measures. We assessed discrimination by means of area under the receiver operating curve (ROC). Results: Of 240 included patients, 130 (54.2%) survived until hospital discharge and 110 (45.8%) had a favorable neurological outcome. Taurine levels were significantly associated with higher in-hospital mortality (adjusted OR 4.12 (95%CI 1.22 to 13.91), p = 0.02). In addition, a significant association between taurine concentration and a poor neurological outcome was observed (adjusted OR of 3.71 (95%CI 1.13 to 12.25), p = 0.03). Area under the curve (AUC) suggested only low discrimination for both endpoints (0.57 and 0.57, respectively). Conclusion: Admission taurine levels are associated with mortality and neurological outcomes in OHCA patients and may help in the risk assessment of this vulnerable population. Further studies are needed to assess whether therapeutic modulation of taurine may improve clinical outcomes after cardiac arrest.

Arginine, ornithine and citrulline supplementation in rainbow trout: Free amino acid dynamics and gene expression responses to bacterial infection

Supplementing the diet with functional ingredients is a key strategy to improve fish performance and health in aquaculture. The amino acids of the urea and nitric oxide (NO) cycles - arginine, ornithine and citrulline - perform crucial roles in the immune response through the generation of NO and the synthesis of polyamine used for tissue repair. We previously found that citrulline supplementation improves and maintains circulating free arginine levels in rainbow trout more effectively than arginine supplementation. Here, to test whether supplementation of urea cycle amino acids modulates the immune response in rainbow trout (Oncorhynchus mykiss), we supplemented a commercial diet with high levels (2% of total diet) of either arginine, ornithine or citrulline during a 7-week feeding trial, before challenging fish with the bacterium Aeromonas salmonicida. We carried out two separate experiments to investigate fish survival and 24 h post-infection to investigate the immediate response of free amino acid levels, and transcriptional changes in genes encoding urea cycle, NO cycle and polyamine synthesis enzymes. There were no differences in percentage fish mortality between diets, however there were numerous highly significant changes in free amino acid levels and gene expression to both dietary supplementation and infection. Out of 26 amino acids detected in blood plasma, 8 were significantly changed by infection and 9 by dietary supplementation of either arginine, ornithine or citrulline. Taurine, glycine and aspartic acid displayed the largest decreases in circulating levels in infected fish, while ornithine and isoleucine were the only amino acids that increased in concentration. We investigated transcriptional responses of the enzymes involved in arginine metabolism in liver and head kidney; transcripts for polyamine synthesis enzymes showed highly significant increases in both tissues across all diets following infection. The paralogous arginase-encoding genes, Arg1a, Arg1b, Arg2a and Arg2b, displayed complex responses across tissues and also due to diet and infection. Overall, these findings improve our understanding of amino acid metabolism following infection and suggests new potential amino acid targets for improving the immune response in salmonids.

Research progress on Traditional Chinese Medicine syndromes of diabetes mellitus

With the improvement of people's living standard and the changes of environment, the incidence of diabetes mellitus (DM) is on the rise day by day, while clinical treatment mainly aims at lowering blood glucose, instead of fundamental prevention and treatment. What's worse, the measures of prevention and treatment of DM complications remain inadequate. Both Chinese and modern medicine have advantages and disadvantages in treating DM, therefore, it would be a worthy attempt to break through the bottleneck of DM treatment by combining the advantages of both, and explore the new measures to prevent and deal with DM from the perspective of the combination of Traditional Chinese Medicine (TCM) syndrome and modern medicine. In this paper, modern research methods and possible indicators of TCM syndromes of DM were expounded from clinical and basic research aspects, aiming to find specific biomarkers of TCM syndromes, and providing experimental supports for the diagnosis and treatment of DM and the verification of TCM theory.

Taurine administration ablates sepsis induced diaphragm weakness

Infection induced diaphragm weakness is a major contributor to death and prolonged mechanical ventilation in critically ill patients. Infection induced muscle dysfunction is associated with activation of muscle proteolytic enzymes, and taurine is known to suppress proteolysis. We therefore postulated that taurine administration may prevent infection induced diaphragm dysfunction. The purpose of this study was to test this hypothesis using a clinically relevant animal model of infection, i.e. cecal ligation puncture induced sepsis (CLP). Studies were performed on (n = 5-7 mice/group): (a) sham operated controls, (b) animals with sepsis induced by CLP, (c) sham operated animals given taurine (75 mg/kg/d, intraperitoneally), and (d) CLP animals given taurine. At intervals after surgery animals were euthanized, diaphragm force generation measured in vitro, and diaphragm calpain, caspase and proteasomal activity determined. CLP elicited a large reduction in diaphragm specific force generation at 24 h (1-150 Hz, p < 0.001) and taurine significantly attenuated CLP induced diaphragm weakness at all stimulation frequencies (p < 0.001). CLP induced significant increases in diaphragm calpain, caspase and proteasomal activity; taurine administration prevented increases in the activity of all three pathways. In additional time course experiments, diaphragm force generation remained at control levels over 72 h in CLP animals treated with daily taurine administration, while CLP animals demonstrated severe, sustained reductions in diaphragm strength (p < 0.01 for all time points). Our results indicate that taurine administration prevents infection induced diaphragm weakness and reduces activation of three major proteolytic pathways. Because this agent is has been shown to be safe, non-toxic when administered to humans, taurine may have a role in treating infection induced diaphragm weakness. Future clinical studies will be needed to assess this possibility.

Metabolomics based predictive biomarker model of ARDS: A systemic measure of clinical hypoxemia

Despite advancements in ventilator technologies, lung supportive and rescue therapies, the outcome and prognostication in acute respiratory distress syndrome (ARDS) remains incremental and ambiguous. Metabolomics is a potential insightful measure to the diagnostic approaches practiced in critical disease settings. In our study patients diagnosed with mild and moderate/severe ARDS clinically governed by hypoxemic P/F ratio between 100-300 but with indistinct molecular phenotype were discriminated employing nuclear magnetic resonance (NMR) based metabolomics of mini bronchoalveolar lavage fluid (mBALF). Resulting biomarker prototype comprising six metabolites was substantiated highlighting ARDS susceptibility/recovery. Both the groups (mild and moderate/severe ARDS) showed distinct biochemical profile based on 83.3% classification by discriminant function analysis and cross validated accuracy of 91% using partial least squares discriminant analysis as major classifier. The predictive performance of narrowed down six metabolites were found analogous with chemometrics. The proposed biomarker model consisting of six metabolites proline, lysine/arginine, taurine, threonine and glutamate were found characteristic of ARDS sub-stages with aberrant metabolism observed mainly in arginine, proline metabolism, lysine synthesis and so forth correlating to diseased metabotype. Thus NMR based metabolomics has provided new insight into ARDS sub-stages and conclusively a precise biomarker model proposed, reflecting underlying metabolic dysfunction aiding prior clinical decision making.

Anti-Inflammatory Effect of Taurine in Burned Patients

PURPOSE

Burn induced inflammatory response can be mediated by reactive oxygen metabolites and accompanied by multiple organ dysfunction. Taurine has protective effects against various inflammatory conditions. The aim of this study was to determine the effect of Taurine supplement in thermal burn victims.

METHODS

Thirty patients with severe thermal burns were enrolled in this randomized double-blinded clinical trial. These patients were randomly divided into two equal groups (namely Control and Taurine groups), where both received isocaloric and isonitrogenous formula. One group was supplemented with 50 mg/kg of Taurine per day for a duration of 10 days. Blood samples were obtained to measure Interleukin-10 (IL-10), high-sensitivity C-reactive protein (hs-CRP), and Tumor Necrosis Factor alpha (TNF-α) levels at the beginning and the end of the study.

RESULTS

Change in serum level of IL-10 in Taurine group was more than Control group [-13.60(-31.40, -10.40) compared to -4.00(-20.00, -0.20) respectively; P = 0.030]. This change was significant in patients with more than 30% TBSA of burn [-14.20(-31.40, -10.40) compared to -2.40(-9.60, 0.40) respectively; P = 0.013]. As for the hs-CRP and TNF-α levels, the difference between the two groups were not significant.

CONCLUSION

Based on the results obtained, Taurine supplement showed a positive outcome on anti-inflammatory cytokine IL-10 in all burn patients. This effect was even more significant in patients with higher percentage of burn area. Taurine had no significant effect on the inflammatory marker hs-CRP and the pro-inflammatory cytokine TNF-α level. For a more thorough verification, measurement of a wider range of inflammatory cytokines in more frequent time intervals are suggested.

An integrated metabonomic and proteomic study on Kidney-Yin Deficiency Syndrome patients with diabetes mellitus in China

AIM

To investigate specific changes in metabolites and proteins of Kidney-Yin Deficiency Syndrome (KYDS) patients with diabetes mellitus (DM) in China.

METHODS

KYDS (n=29) and non-KYDS (n=23) patients with DM were recruited for this study. The KYDS was diagnosed by two senior TCM clinicians separately. The metabonomic and proteomic profiles of the patients were assessed using a metabonomic strategy based on NMR with multivariate analysis and a proteomic strategy based on MALDI-TOF-MS, respectively.

RESULTS

Eighteen upregulated peptides and thirty downregulated peptides were observed in the plasma of the KYDS patients. Comparing the proteomic profiles of the KYDS and non-KYDS groups, however, no significantly differentially expressed peptides were found. At the same time, major metabolic alterations were found to distinguish the two groups, including eight significantly changed metabolites (creatinine, citrate, TMAO, phenylalanine, tyrosine, alanine, glycine and taurine). The levels of creatinine, citrate, TMAO, phenylalanine and tyrosine were decreased, whereas the levels of alanine, glycine and taurine were increased in the KYDS patients. These biochemical changes were found to be associated with alterations in amino acid metabolism, energy metabolism and gut microflora.

CONCLUSION

The identification of distinct expression profiles of metabolites and signaling pathways in KYDS patients with DM suggests that there are indeed molecular signatures underlying the principles of 'Syndrome Differentiation' in traditional Chinese medicine.

Dynamic changes in amino acid concentration profiles in patients with sepsis

Objectives

The goal of this work was to explore the dynamic concentration profiles of 42 amino acids and the significance of these profiles in relation to sepsis, with the aim of providing guidance for clinical therapies.

Methods

Thirty-five critically ill patients with sepsis were included. These patients were further divided into sepsis (12 cases) and severe sepsis (23 cases) groups or survivor (20 cases) and non-survivor (15 cases) groups. Serum samples from the patients were collected on days 1, 3, 5, 7, 10, and 14 following intensive care unit (ICU) admission, and the serum concentrations of 42 amino acids were measured.

Results

The metabolic spectrum of the amino acids changed dramatically in patients with sepsis. As the disease progressed further or with poor prognosis, the levels of the different amino acids gradually increased, decreased, or fluctuated over time. The concentrations of sulfur-containing amino acids (SAAs), especially taurine, decreased significantly as the severity of sepsis worsened or with poor prognosis of the patient. The serum concentrations of SAAs, especially taurine, exhibited weak negative correlations with the Sequential Organ Failure Assessment (SOFA) (r=-0.319) and Acute Physiology and Chronic Health Evaluation (APACHE) II (r=-0.325) scores. The areas under the receiver operating characteristic curves of cystine, taurine, and SAA levels and the SOFA and APACHE II scores, which denoted disease prognosis, were 0.623, 0.674, 0.678, 0.86, and 0.857, respectively.

Conclusions

Critically ill patients with disorders of amino acid metabolism, especially of SAAs such as cystine and taurine, may provide an indicator of the need for the nutritional support of sepsis in the clinic.

Trial Registration

ClinicalTrial.gov identifier NCT01818830.

Integration of metabolic and inflammatory mediator profiles as a potential prognostic approach for septic shock in the intensive care unit

INTRODUCTION

Septic shock is a major life-threatening condition in critically ill patients and it is well known that early recognition of septic shock and expedient initiation of appropriate treatment improves patient outcome. Unfortunately, to date no single compound has shown sufficient sensitivity and specificity to be used as a routine biomarker for early diagnosis and prognosis of septic shock in the intensive care unit (ICU). Therefore, the identification of new diagnostic tools remains a priority for increasing the survival rate of ICU patients. In this study, we have evaluated whether a combined nuclear magnetic resonance spectroscopy-based metabolomics and a multiplex cytokine/chemokine profiling approach could be used for diagnosis and prognostic evaluation of septic shock patients in the ICU.

METHODS

Serum and plasma samples were collected from septic shock patients and ICU controls (ICU patients with the systemic inflammatory response syndrome but not suspected of having an infection). (1)H Nuclear magnetic resonance spectra were analyzed and quantified using the targeted profiling methodology. The analysis of the inflammatory mediators was performed using human cytokine and chemokine assay kits.

RESULTS

By using multivariate statistical analysis we were able to distinguish patient groups and detect specific metabolic and cytokine/chemokine patterns associated with septic shock and its mortality. These metabolites and cytokines/chemokines represent candidate biomarkers of the human response to septic shock and have the potential to improve early diagnosis and prognosis of septic shock.

CONCLUSIONS

Our findings show that integration of quantitative metabolic and inflammatory mediator data can be utilized for the diagnosis and prognosis of septic shock in the ICU.

Taurine Concentrations Decrease in Critically Ill Patients With Shock Given Enteral Nutrition

BACKGROUND

Nutrition studies in the intensive care unit (ICU) have shown that adequate enteral nutrition (EN) support has clinical benefits. However, the course of amino acid concentrations in plasma has never been investigated in patients admitted with shock receiving EN. We hypothesized that plasma concentrations, when deficit, increase during EN and that persistent deficiency is associated with poor outcome.

METHODS

In 33 septic or cardiogenic shock patients receiving EN, plasma amino acid concentrations were measured during 5 days. Changes in amino acid concentrations, correlations with clinical outcome variables, and regression analyses were studied.

RESULTS

On ICU admission, several plasma concentrations were deficient. Plasma concentrations of almost all amino acids increased. In contrast, taurine decreased by >50%, from 47.6 µmol/L on admission to 20.0 µmol/L at day 1, and remained low at day 5. Taurine (admission) correlated with time on mechanical ventilation (R = -0.42, P = .015). Taurine decrease within 24 hours correlated with Acute Physiology and Chronic Health Evaluation II predicted mortality (R = 0.43, P = .017) and Sequential Organ Failure Assessment score (R = 0.36, P = .05). Regression analyses confirmed correlations.

CONCLUSIONS

Several amino acids were deficient in plasma on ICU admission but increased during EN. Taurine concentrations declined and were associated with longer periods of mechanical ventilation and ICU support. Fast taurine decline correlated with severity of organ failure. These findings support the role of taurine during ischemia, reperfusion, and inflammation. Taurine may be an essential candidate to enrich nutrition support for critically ill patients, although more research is required.

The importance and dosage of amino acids in nutritional support of various pathological conditions in ICU patients

BACKGROUND

Normal adults require twenty L-amino acids (AA) for protein synthesis. Functional AA regulate key metabolic pathways that are necessary for maintenance, growth, reproduction and immunity. Dietary supplementation with one or a mixture of these AA may be beneficial for ameliorating health problems at various stages of the life cycle and for optimizing of the efficiency of metabolic transformations. During disease, other amino acids also become essential. The principal goal of protein/amino acid administration in various pathological conditions in intensive care unit (ICU) patients is to provide the precursors of protein synthesis in tissues with high turnover and to protect skeletal muscle mass and function. Amino acid requirements in parenteral nutrition (PN) are higher when the patient is stressed/traumatized/infected than in the unstressed state. In severely ill ICU patients a higher provision of protein and amino acids has been associated with a lower mortality.

METHODS AND RESULTS

An overview of the effects and dosage of amino acids in nutritional support of various pathological conditions in ICU patients is presented.

CONCLUSION

It was demonstrated that 2.0-2.5 g protein substrate/kg normal body weight/day is safe and could be optimal for the most critically ill adults to decrease the risk of morbidity and mortality in some pathological conditions.

Metabolic profiling of serum samples by 1H nuclear magnetic resonance spectroscopy as a potential diagnostic approach for septic shock

OBJECTIVES

To determine whether a nuclear magnetic resonance-based metabolomics approach can be useful for the early diagnosis and prognosis of septic shock in ICUs.

DESIGN

Laboratory-based study.

SETTING

University research laboratory.

SUBJECTS

Serum samples from septic shock patients and ICU controls (ICU patients with systemic inflammatory response syndrome but not suspected of having an infection) were collected within 24 hours of admittance to the ICU.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

H nuclear magnetic resonance spectra of septic shock and ICU control samples were analyzed and quantified using a targeted profiling approach. By applying multivariate statistical analysis (e.g., orthogonal partial least squares discriminant analysis), we were able to distinguish the patient groups and detect specific metabolic patterns. Some of the metabolites were found to have a significant impact on the separation between septic shock and control samples. These metabolites could be interpreted in terms of a biological human response to septic shock and they might serve as a biomarker pattern for septic shock in ICUs. Additionally, nuclear magnetic resonance-based metabolomics was evaluated in order to detect metabolic variation between septic shock survivors and nonsurvivors and to predict patient outcome. The area under the receiver operating characteristic curve indicated an excellent predictive ability for the constructed orthogonal partial least squares discriminant analysis models (septic shock vs ICU controls: area under the receiver operating characteristic curve = 0.98; nonsurvivors vs survivors: area under the receiver operating characteristic curve = 1).

CONCLUSIONS

Our results indicate that nuclear magnetic resonance-based metabolic profiling could be used for diagnosis and mortality prediction of septic shock in the ICU.

A proton nuclear magnetic resonance metabonomics approach for biomarker discovery in nonalcoholic fatty liver disease

This study was undertaken to discover novel biomarkers for the noninvasive early diagnosis of nonalcoholic fatty liver disease (NAFLD). A methionine and choline deficient (MCD) diet was used to represent different stages of NAFLD in male C57BL/6 mice. (1)H NMR spectroscopy and principal components analysis (PCA) were used to investigate the time-related biochemical changes in mice sera induced by the MCD diet. Many serum metabolites' concentrations changed between control and MCD-fed mice. Hierarchical cluster analysis (HCA) and artificial neural networks (ANNs) were used to select the least number of metabolites to be used for the noninvasive diagnosis of various stages of NAFLD; four potential biomarkers, serum glucose, lactate, glutamate/glutamine, and taurine were selected. To verify the diagnostic accuracy of these selected metabolites, their serum concentrations were measured in healthy controls (n = 28), NAFLD patients with steatosis (n = 15), steatosis patients with necro-inflammatory disease (n = 11), and NASH patients (n = 6). On the basis of results from MCD-fed mice model, clinical tests, and previous reports, we propose using the levels of the four metabolites for diagnosing NAFLD at various stages. Furthermore, the probability of developing NAFLD at a particular stage was assessed by multinomial logistic regression (MLR) based on the clinical results of the four serum metabolites.

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.

Sepsis biomarkers: a review

INTRODUCTION

Biomarkers can be useful for identifying or ruling out sepsis, identifying patients who may benefit from specific therapies or assessing the response to therapy.

METHODS

We used an electronic search of the PubMed database using the key words "sepsis" and "biomarker" to identify clinical and experimental studies which evaluated a biomarker in sepsis.

RESULTS

The search retrieved 3370 references covering 178 different biomarkers.

CONCLUSIONS

Many biomarkers have been evaluated for use in sepsis. Most of the biomarkers had been tested clinically, primarily as prognostic markers in sepsis; relatively few have been used for diagnosis. None has sufficient specificity or sensitivity to be routinely employed in clinical practice. PCT and CRP have been most widely used, but even these have limited ability to distinguish sepsis from other inflammatory conditions or to predict outcome.

Sepsis-associated microvascular dysfunction measured by peripheral arterial tonometry: an observational study

Introduction

Sepsis has a high mortality despite advances in management. Microcirculatory and endothelial dysfunction contribute to organ failure, and better tools are needed to assess microcirculatory responses to adjunctive therapies. We hypothesised that peripheral arterial tonometry (PAT), a novel user-independent measure of endothelium-dependent microvascular reactivity, would be impaired in proportion to sepsis severity and related to endothelial activation and plasma arginine concentrations.

Methods

Observational cohort study in a 350-bed teaching hospital in tropical Australia. Bedside microvascular reactivity was measured in 85 adults with sepsis and 45 controls at baseline and 2-4 days later by peripheral arterial tonometry. Microvascular reactivity was related to measures of disease severity, plasma concentrations of L-arginine (the substrate for nitric oxide synthase), and biomarkers of endothelial activation.

Results

Baseline reactive hyperaemia index (RH-PAT index), measuring endothelium-dependent microvascular reactivity; (mean [95% CI]) was lowest in severe sepsis (1.57 [1.43-1.70]), intermediate in sepsis without organ failure (1.85 [1.67-2.03]) and highest in controls (2.05 [1.91-2.19]); P < 0.00001. Independent predictors of baseline RH-PAT index in sepsis were APACHE II score and mean arterial pressure, but not plasma L-arginine or markers of endothelial activation. Low baseline RH-PAT index was significantly correlated with an increase in SOFA score over the first 2-4 days (r = -0.37, P = 0.02).

Conclusions

Endothelium-dependent microvascular reactivity is impaired in proportion to sepsis severity and suggests decreased endothelial nitric oxide bioavailability in sepsis. Peripheral arterial tonometry may have a role as a user-independent method of monitoring responses to novel adjunctive therapies targeting endothelial dysfunction in sepsis.

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.

Taurine status and response to intravenous taurine supplementation in adults with short-bowel syndrome undergoing long-term parenteral nutrition: a pilot study

Taurine deficiency in patients on long-term parenteral nutrition may be involved in cholestasis. We aimed to assess plasma taurine and tauro-conjugated bile acids in adults with short-bowel syndrome and their response to intravenous taurine. Thirty-two adult patients, who had been on taurine-free parenteral nutrition for a mean of 59(SE14) months for short-bowel syndrome, were studied retrospectively. In a second study, a subgroup of ten patients with chronic cholestasis received taurine-enriched (6·0(SE0·6)mg/kg per d) parenteral nutrition for 55(SE13) months. Post-absorptive plasma taurine and bile acid concentrations were measured and liver function tests routinely sampled. At baseline, plasma taurine was lower in patients with a jejunal length of less than 35cm (group A,n16) than in those with a jejunal length of 35cm or more (group B,n16): 43(SE3)v. 58(SE4)μmol/l (P=0·01). The groups were no different in terms of chronic cholestasis (1/6v.1/6 patients), total bile acids (26(SE13)v.14(SE5)μmol/l) or the ratio of tauro-conjugated:glyco-conjugated bile acids (5(SE2)v.8(SE 4)%, usual range 30–60%). After supplementation, there was an increase in plasma taurine level (63(SE8)v. 43(SE4),P=0·007) but was no change in either total bile acids or the ratio of tauro-conjugated: glyco-conjugated bile acids. There was a significant decrease in aspartate aminotransferase level. Long-term parenteral nutrition for short-bowel syndrome is associated with an impaired tauro-conjugation of bile acids (enterohepatic pool), irrespective of plasma taurine level (systemic pool) and despite long-term taurine intravenous supplementation.

The relationship between albumin, other plasma proteins and variables, and age in the acute phase response after liver resection in man

A large series of plasma albumin (ALB, g/dl) and simultaneous blood and clinical measurements were prospectively performed on 92 liver resection patients, and processed to assess the correlations between ALB, other plasma proteins, additional variables and clinical events. The measurements were performed preoperatively and at postoperative day 1, 3 and 7 in all patients, and subsequently only in those who developed complications or died. In patients who recovered normally ALB was 4.3 +/- 0.4 g/dl (mean +/- SD) preoperatively, 3.7 +/- 0.7 at day 1 and 3, and 3.9 +/- 0.4 at day 7. In patients with complications its decrease was more prolonged. In non-survivors it was 3.4 +/- 0.4 preoperatively, 3.0 +/- 0.4 at day 1, and then decreased further. Regression analysis showed direct correlations between ALB and pseudo-cholinesterase (CHE, U/l, nv 5300-13000), cholesterol (CHOL, mg/dl), iron binding capacity (IBC, mg/dl), prothrombin activity (PA, % of standard reference) and fibrinogen, an inverse correlation with blood urea nitrogen (BUN, mg/dl) for any given creatinine level (CREAT, mg/dl), and weaker direct correlations with hematocrit, other variables and dose of exogenous albumin. An inverse relationship found between ALB and age (AGE, years) became postoperatively (POSTOP) also a function of outcome, showing larger age-related decreases in ALB associated with complications (COMPL: sepsis, liver insufficiency) or death (DEATH). Main overall correlations: CHE = 287.4(2.014)(ALB), r = 0.73; CHOL = 16.5(1.610)(ALB) (1.001)(ALKPH), r = 0.71; IBC = 68.6(1.391)(ALB), r = 0.64; PA = 13.8 + 16.0(ALB), r = 0.51; BUN = 21.3 + 20.2(CREAT) - 6.2(ALB), r = 0.91; ALB = 5.0-0.013(AGE) - {0.5 + 0.003(AGE)( COMPL ) + 0.012(AGE)( DEATH )}( POSTOP ), r = 0.74 [p < 0.001 for each regression and each coefficient; ALKPH = alkaline phosphatase, U/l, nv 98-279, independent determinant of CHOL; discontinuous variables in italics label the change in regression slope or intercept associated with the corresponding condition]. These results suggest that altered albumin synthesis (or altered synthesis unable to compensate for albumin loss, catabolism or redistribution) is an important determinant of hypoalbuminemia after hepatectomy. The correlations with age and postoperative outcome support the concept that hypoalbuminemia is a marker of pathophysiologic frailty associated with increasing age, and amplified by the challenges of postoperative illness.

Relationship of taurine and other amino acids in plasma and in neutrophils of septic trauma patients

Recently, an interdependency of plasma taurine and other amino acids as well as metabolic and clinical variables implicating therapeutic options was reported. This result may be an indication that plasma taurine levels are directly related to intracellular levels. Therefore, the aim of this study was to analyse the possible relationship between taurine levels in plasma and in neutrophils, the relationship to other amino acids, and variables quantifying metabolic impairment and severity of sepsis in multiple trauma patients developing sepsis. After multiple trauma taurine decreased significantly in plasma in thirty-two patients as well as within the neutrophil and does not recover in sepsis. Lower individual levels in the neutrophil did not follow lower individual levels in plasma and no correlation of taurine in plasma and in the neutrophils could be observed. In sepsis, only plasma showed an interdependency of taurine, aspartate, and glutamate. No association between taurine plasma or intracellular levels and SOFA score as indicator for severity of sepsis or metabolic variables was observed. After multiple trauma and in sepsis, taurine uptake in cells (which is regulated in different ways), and intracellular taurine (which serves e.g. as an osmolyte) can be influenced. Therefore a prediction of the neutrophil taurine pool seems not fully possible from taurine plasma levels. Intracellular taurine has some unique properties explaining the missing interdependency despite some similarities in osmoregulation and metabolic interactions to other amino acids. The association of taurine, aspartate, and glutamate in plasma cannot be simply transferred to the neutrophils intracellular level. The clinical meaning of the plasma correlation remains unclear. A dependency of plasma and neutrophil taurine to severity of sepsis and to metabolic variables seems not possible because of the multifactorial pathophysiology of sepsis.

Classic dengue fever affects levels of circulating antioxidants

OBJECTIVE

We studied alterations of circulating antioxidant nutrients in patients with classic dengue fever in the tropical lowlands of Guatemala.

METHODS

In nine patients with dengue fever and 12 healthy Guatemalan control subjects, we assessed plasma concentrations of retinol, alpha-tocopherol, beta-carotene, glutathione, taurine, thiobarbituric acid-reactive species, and total antioxidant status. Control subjects were assessed twice within 48 h to account for day-to-day variations. Febrile patients with dengue fever were examined on the day of admission to the hospital, at discharge after defervescence (approximately 5 d after admission), and 7 d thereafter.

RESULTS

In patients with dengue fever, increases in plasma concentrations of retinol and beta-carotene were seen, whereas decreases were observed for glutathione and total antioxidant status. As compared with the reference group, patients with dengue fever had lower retinol concentrations in the acute phase of the disease and lower glutathione concentrations 7 d after discharge. Further, thiobarbituric acid-reactive species levels were higher in the dengue fever patients as analyzed by unpaired t test.

CONCLUSION

Using dengue fever as a model for the metabolic response to an acute, self-limited tropical viral infection, the present findings suggest slight turbulence of the antioxidant system that may be a response to or a consequence of the viral inflammatory process.

Glutamine: recent developments in research on the clinical significance of glutamine

PURPOSE OF REVIEW

The aim of this review is to describe the clinical relevance of supplementation of glutamine from the recent literature. First, new basic research is examined and subsequently recent clinical trials and a metaanalysis are illustrated.

RECENT FINDINGS

Glutamine has a major impact on the functionality of the immune system. It has recently been established that glutamine not only has a protective effect on cells of the immune system, but also on other cells of the body, for instance cardiomyocytes. Evidence is accumulating for an effect of glutamine via glutathione, heat shock proteins as well as taurine. Another area of interest is the way glutamine enhances gut barrier function. More and more research is concentrating on the positive effect of glutamine on the gut-associated lymphoid tissue.

SUMMARY

Based on a recent meta-analysis and up-to-date clinical trials, we may conclude that glutamine has a beneficial effect on infectious complications and reduces hospital stay. In critically ill patients glutamine supplementation may reduce morbidity and mortality. The greatest effect was observed in patients receiving high dose parenteral glutamine. A recent study with high dose enteral glutamine demonstrated a reduced mortality in the glutamine supplemented group. In the future more trials with larger numbers of participants are needed, especially with high dose enteral glutamine in the perioperatively and the intensive care unit setting.

Taurine: new implications for an old amino acid

Taurine is a semi-essential amino acid and is not incorporated into proteins. In mammalian tissues, taurine is ubiquitous and is the most abundant free amino acid in the heart, retina, skeletal muscle, brain, and leukocytes. In fact, taurine reaches up to 50 mM concentration in leukocytes. Taurine has been shown to be tissue-protective in many models of oxidant-induced injury. One possibility is that taurine reacts with hypochlorous acid, produced by the myeloperoxidase pathway, to produce the more stable but less toxic taurine chloramine (Tau-Cl). However, data from several laboratories demonstrate that Tau-Cl is a powerful regulator of inflammation. Specifically, Tau-Cl has been shown to down-regulate the production of pro-inflammatory mediators in both rodent and human leukocytes. Taurolidine, a derivative of taurine, is commonly used in Europe as an adjunctive therapy for various infections as well as for tumor therapy. Recent molecular studies on the function of taurine provide evidence that taurine is a constituent of biologic macromolecules. Specifically, two novel taurine-containing modified uridines have been found in both human and bovine mitochondria. Studies investigating the mechanism of action of Tau-Cl have shown that it inhibits the activation of NF-kappaB, a potent signal transducer for inflammatory cytokines, by oxidation of IkappaB-alpha at Met45. Key enzymes for taurine biosynthesis have recently been cloned. Cysteine sulfinic acid decarboxylase, a rate-limiting enzyme for taurine biosynthesis, has been cloned and sequenced in the mouse, rat and human. Another key enzyme for cysteine metabolism, cysteine dioxygenase (CDO), has also been cloned from rat liver. CDO has a critical role in determining the flux of cysteine between cysteine catabolism/taurine synthesis and glutathione synthesis. Taurine transporter knockout mice show reduced taurine, reduced fertility, and loss of vision due to severe apoptotic retinal degeneration. Apoptosis induced by amino chloramines is a current and important finding since oxidants derived from leukocytes play a key role in killing pathogens. The fundamental importance of taurine in adaptive and acquired immunity will be unveiled using genetic manipulation.

Plasma taurine concentrations increase after enteral glutamine supplementation in trauma patients and stressed rats

BACKGROUND

Taurine is a unique amino acid with antioxidant and osmolytic properties. Glutamine serves as the preferred fuel for the gut, liver, and immune cells and as a precursor for antioxidants. Trauma patients have low glutamine concentrations.

OBJECTIVES

We investigated the effect of glutamine-enriched enteral nutrition on plasma taurine concentrations in patients with severe trauma (injury severity score >20). Additionally, plasma taurine concentrations and organ fluxes were studied in a stressed rat model.

DESIGN

Twenty-nine patients with multiple trauma received glutamine-enriched nutrition and 31 patients received isocaloric, isonitrogenous control solution for 5 d. Plasma taurine and glutamine concentrations were measured. Male Wistar rats (250-300 g) received a glutamine-enriched diet (12%, by wt) or a control solution for 2 wk. Plasma taurine concentrations were measured. Taurine fluxes and fractional extraction rates in the liver, kidneys, and gut were assessed with a radioactive microsphere technique.

RESULTS

Both patient groups had low taurine concentrations on day 1. From day 3 onward, the glutamine-fed patients had significantly higher taurine concentrations. Rats fed a glutamine-enriched diet had significantly higher plasma taurine concentrations than did the controls. A high taurine uptake was found in the liver, kidneys, and gut of the glutamine-fed rats. Fractional extraction rates were not significantly different between the rat groups.

CONCLUSIONS

Glutamine enrichment increases plasma taurine in trauma patients and in stressed rats. Because of increased availability, organ fluxes showed a higher taurine uptake in the liver, kidneys, and gut. The reduction in morbidity with glutamine enrichment could be explained in part by increased taurine availability.